Re: [openstack-dev] [Mistral] Changing "expression" delimiters in Mistral DSL
Ok, we will proceed with <% %> option. --- Best Regards, Nikolay @Mirantis Inc. __ OpenStack Development Mailing List (not for usage questions) Unsubscribe: openstack-dev-requ...@lists.openstack.org?subject:unsubscribe http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev
Re: [openstack-dev] [Mistral] Changing "expression" delimiters in Mistral DSL
Folks, one more thing to consider: the next big release of yaql (1.0,
coming really soon) will get support of curly braces (by default - to
initialise dictionaries in the following way:
v0.2/v0.3 syntax: dict(key1=>value1, key2=>value2)
v1 syntax: {key1=>value1, key2=>value2} (the old syntax works in v1 as well)
So, {} will become a valid yaql expression (empty dict). I believe it is
not a big deal to parse that correctly and differentiate between outer
markup and an expression contained within, however statements like <{{}}>
may be a little ugly.
--
Regards,
Alexander Tivelkov
On Thu, Feb 19, 2015 at 1:13 PM, Nikolay Makhotkin
wrote:
> Hi !
>
> From those three I'd choose only <{ ... }>, it looks better for YAML while
> '%' sign looks foreign for YAML. Moreover, it needs extra spaces for
> writing expressions:
>
> Compare:
> 1. <%$.var + 1%>
> 2. <% $.var + 1 %>
> 3. <{$.var + 1}>
>
> One more point from me: We can't do things just beacuse it is familiar
> with N things and it should be so.
>
>
> Best Regards,
> Nikolay
>
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Re: [openstack-dev] [Mistral] Changing "expression" delimiters in Mistral DSL
Hi !
>From those three I'd choose only <{ ... }>, it looks better for YAML while
'%' sign looks foreign for YAML. Moreover, it needs extra spaces for
writing expressions:
Compare:
1. <%$.var + 1%>
2. <% $.var + 1 %>
3. <{$.var + 1}>
One more point from me: We can't do things just beacuse it is familiar with
N things and it should be so.
Best Regards,
Nikolay
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Re: [openstack-dev] [Mistral] Changing "expression" delimiters in Mistral DSL
On Thu, Feb 19, 2015 at 12:24:14PM +0600, Renat Akhmerov wrote: >Guys, >I really appreciate the input of you all. >We decided that ideally we need to agree on that syntax within days, not >weeks or months. But anyway, since we started this discussion yesterday I >just want to give us extra 1-2 days to play with all these thoughts in our >heads. >Just one additional maybe a little bit crazy idea to the pile wea**ve >already made: >What if we officially allow more than one delimiter syntax? Why stick to >just one? Because consistency is a good thing, it aids readability, reduces developer confusion, encourages consistent style, etc, etc. If you've ever worked on a perl codebase of any size, I'm sure you'll appreciate the zen of python: "There should be one, and preferably only one obvious way to do it" My 0.02 :) Steve __ OpenStack Development Mailing List (not for usage questions) Unsubscribe: openstack-dev-requ...@lists.openstack.org?subject:unsubscribe http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev
Re: [openstack-dev] [Mistral] Changing "expression" delimiters in Mistral DSL
bers we came to the following things:
>>>
>>> Syntax options that we’d like to discuss further
>>>
>>> <% 1 + 1 %> # pro- ruby/js/puppet/chef familiarity con - spaces, and % is
>>> too large symbol
>>> <{1 + 1}> # pro - less spaces, con - no familiarity
>>> # php familiarity, need spaces
>>>
>>> The primary criteria to select these 3 options is that they are YAML
>>> compatible. Technically they all would solve our problems (primarily no
>>> embracing quotes needed like in Ansible so no ambiguity on data types).
>>>
>>> The secondary criteria is syntax symmetry. After all I agree with Patrick's
>>> point about better readability when we have opening and closing sequences
>>> alike.
>>>
>>> Some additional details can be found in [0]
>>>
>>>
>>> [0] https://etherpad.openstack.org/p/mistral-YAQL-delimiters
>>> <https://etherpad.openstack.org/p/mistral-YAQL-delimiters>
>>>
>>> Renat Akhmerov
>>> @ Mirantis Inc.
>>>
>>>
>>>> On 18 Feb 2015, at 07:37, Patrick Hoolboom >>> <mailto:patr...@stackstorm.com>> wrote:
>>>>
>>>> My main concern with the {} delimiters in YAQL is that the curly brace
>>>> already has a defined use within YAML. We most definitely will eventually
>>>> run in to parsing errors with whatever delimiter we choose but I don't
>>>> feel that it should conflict with the markup language it is directly
>>>> embedded in. It gets quite difficult to, at a glance, identify YAQL
>>>> expressions. <% %> may appear ugly to some but I feel that it works as a
>>>> clear delimiter of both the beginning AND the end of the YAQL query. The
>>>> options that only escape the beginning look fine in small examples like
>>>> this but the workflows that we have written or seen in the wild tend to
>>>> have some fairly large expressions. If the opening and closing delimiters
>>>> don't match, it gets quite difficult to read.
>>>>
>>>>> From: Anastasia Kuznetsova >>>> <mailto:akuznets...@mirantis.com>>
>>>>> Subject: Re: [openstack-dev] [Mistral] Changing "expression" delimiters
>>>>> in Mistral DSL
>>>>> Date: February 17, 2015 at 8:28:27 AM PST
>>>>> To: "OpenStack Development Mailing List (not for usage questions)"
>>>>> >>>> <mailto:openstack-dev@lists.openstack.org>>
>>>>> Reply-To: "OpenStack Development Mailing List \(not for usage
>>>>> questions\)" >>>> <mailto:openstack-dev@lists.openstack.org>>
>>>>>
>>>>> As for me, I think that <% ... %> is not an elegant solution and looks
>>>>> massive because of '%' sign. Also I agree with Renat, that <% ... %>
>>>>> reminds HTML/Jinja2 syntax.
>>>>>
>>>>> I am not sure that similarity with something should be one of the main
>>>>> criteria, because we don't know who will use Mistral.
>>>>>
>>>>> I like:
>>>>> - <{1 + $.var}> Renat's example
>>>>> - variant with using some functions (item 2 in Dmitry's list): { yaql:
>>>>> “1+1+$.my.var < 100” } or
>>>>> - my two cents, maybe we can use something like: result: -< "Hello" +
>>>>> $.name >-
>>>>>
>>>>>
>>>>> Regards,
>>>>> Anastasia Kuznetsova
>>>>>
>>>>> On Tue, Feb 17, 2015 at 1:17 PM, Nikolay Makhotkin
>>>>> mailto:nmakhot...@mirantis.com>> wrote:
>>>>> Some suggestions from me:
>>>>>
>>>>> 1. # (short from yaql).
>>>>> 2. <{ 1 + $.var }> # as for me, looks more elegant than <% %>. And
>>>>> visually it is more strong
>>>>>
>>>>> A also like p7 and p8 suggested by Renat.
>>>>>
>>>>> On Tue, Feb 17, 2015 at 11:43 AM, Renat Akhmerov >>>> <mailto:rakhme...@mirantis.com>> wrote:
>>>>> One more:
>>>>>
>>>>> p9: \{1 + $.var} # That’s pretty much what
>>>>> https://review.openstack.org/#/c/155348/
>>>>> <https://review.openstack.org/#/c/155348/> addresses but it’s not exac
Re: [openstack-dev] [Mistral] Changing "expression" delimiters in Mistral DSL
gt;>> expressions. <% %> may appear ugly to some but I feel that it works as a
>>>> clear delimiter of both the beginning AND the end of the YAQL query. The
>>>> options that only escape the beginning look fine in small examples like
>>>> this but the workflows that we have written or seen in the wild tend to
>>>> have some fairly large expressions. If the opening and closing delimiters
>>>> don't match, it gets quite difficult to read.
>>>>
>>>>> From: Anastasia Kuznetsova
>>>>> Subject: Re: [openstack-dev] [Mistral] Changing "expression" delimiters
>>>>> in Mistral DSL
>>>>> Date: February 17, 2015 at 8:28:27 AM PST
>>>>> To: "OpenStack Development Mailing List (not for usage questions)"
>>>>>
>>>>> Reply-To: "OpenStack Development Mailing List \(not for usage
>>>>> questions\)"
>>>>>
>>>>> As for me, I think that <% ... %> is not an elegant solution and looks
>>>>> massive because of '%' sign. Also I agree with Renat, that <% ... %>
>>>>> reminds HTML/Jinja2 syntax.
>>>>>
>>>>> I am not sure that similarity with something should be one of the main
>>>>> criteria, because we don't know who will use Mistral.
>>>>>
>>>>> I like:
>>>>> - <{1 + $.var}> Renat's example
>>>>> - variant with using some functions (item 2 in Dmitry's list): { yaql:
>>>>> “1+1+$.my.var < 100” } or
>>>>> - my two cents, maybe we can use something like: result: -< "Hello" +
>>>>> $.name >-
>>>>>
>>>>>
>>>>> Regards,
>>>>> Anastasia Kuznetsova
>>>>>
>>>>>> On Tue, Feb 17, 2015 at 1:17 PM, Nikolay Makhotkin
>>>>>> wrote:
>>>>>> Some suggestions from me:
>>>>>>
>>>>>> 1. # (short from yaql).
>>>>>> 2. <{ 1 + $.var }> # as for me, looks more elegant than <% %>. And
>>>>>> visually it is more strong
>>>>>>
>>>>>> A also like p7 and p8 suggested by Renat.
>>>>>>
>>>>>> On Tue, Feb 17, 2015 at 11:43 AM, Renat Akhmerov
>>>>>> wrote:
>>>>>>> One more:
>>>>>>>
>>>>>>> p9: \{1 + $.var}# That’s pretty much what
>>>>>>> https://review.openstack.org/#/c/155348/ addresses but it’s not exactly
>>>>>>> that. Note that we don’t have to put it in quotes in this case to deal
>>>>>>> with YAML {} semantics, it’s just a string
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> Renat Akhmerov
>>>>>>> @ Mirantis Inc.
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>> On 17 Feb 2015, at 13:37, Renat Akhmerov
>>>>>>>> wrote:
>>>>>>>>
>>>>>>>> Along with <% %> syntax here are some other alternatives that I
>>>>>>>> checked for YAML friendliness with my short comments:
>>>>>>>>
>>>>>>>> p1: ${1 + $.var} # Here it’s bad that $ sign is used for two
>>>>>>>> different things
>>>>>>>> p2: ~{1 + $.var} # ~ is easy to miss in a text
>>>>>>>> p3: ^{1 + $.var} # For someone may be associated with regular
>>>>>>>> expressions
>>>>>>>> p4: ?{1 + $.var}
>>>>>>>> p5: <{1 + $.var}> # This is kinda crazy
>>>>>>>> p6: e{1 + $.var} # That looks a pretty interesting option to me,
>>>>>>>> “e” could mean “expression” here.
>>>>>>>> p7: yaql{1 + $.var}# This is interesting because it would give a
>>>>>>>> clear and easy mechanism to plug in other expression languages, “yaql”
>>>>>>>> here is a used dialect for the following expression
>>>>>>>> p8: y{1 + $.var} # “y” here is just shortened “yaql"
>>>>>>>>
>>>>>>>>
>>>>>>>> Any ideas and thoughts would be really appreciated!
>
Re: [openstack-dev] [Mistral] Changing "expression" delimiters in Mistral DSL
As a user of Mistral pretty regularly these days, I certainly prefers <% %>. I agree with the other comments on devops familiarity. And looking this from another angle, it's certainly easier to type <% %> then the other options, especially if you have to do this over and over again. LOL Although, I am interested in the security concerns of this use in Jinja2. __ OpenStack Development Mailing List (not for usage questions) Unsubscribe: openstack-dev-requ...@lists.openstack.org?subject:unsubscribe http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev
Re: [openstack-dev] [Mistral] Changing "expression" delimiters in Mistral DSL
Out of those three I still prefer <% %>. The main reason I like it is
familiarity. Also the question mark makes me think of a wildcard, and I
don't want to use curly braces because of all the aforementioned reasons
(already has a meaning in YAML).
On Wed, Feb 18, 2015 at 3:07 PM, Dmitri Zimine
wrote:
> *Syntax options that we’d like to discuss **further *
>
> <% 1 + 1 %> # pro- ruby/js/puppet/chef familiarity con - spaces, and % is
> too large symbol
> <{1 + 1}> # pro - less spaces, con - no familiarity
> # php familiarity, need spaces
>
> The primary criteria to select these 3 options is that they are YAML
> compatible. Technically they all would solve our problems (primarily no
> embracing quotes needed like in Ansible so no ambiguity on data types).
>
> The secondary criteria is syntax symmetry. After all I agree with
> Patrick's point about better readability when we have opening and closing
> sequences alike.
>
>
> To me, another critical criteria is familiarity: target users - openstack
> developers and devops, familiar with the delimiters.
>
> That is why of the three above I prefer <% %> .
>
> It is commonly used in Puppet/Chef [1], Ruby, Javascript. One won’t be
> surprised to see it and won’t need to change the muscle memory to type
> open/closed characters especially when working on say Puppet and Mistral at
> the same time (not unlikely).
>
>
> [1]
> https://docs.puppetlabs.com/guides/templating.html#erb-is-plain-text-with-embedded-ruby
>
>
>
> On Feb 18, 2015, at 3:20 AM, Renat Akhmerov
> wrote:
>
> Hi again,
>
> Sorry, I started writing this email before Angus replied so I will shoot
> it as is and then we can continue…
>
>
> So after discussing all the options again with a small group of team
> members we came to the following things:
>
> *Syntax options that we’d like to discuss **further *
>
> <% 1 + 1 %> # pro- ruby/js/puppet/chef familiarity con - spaces, and % is
> too large symbol
> <{1 + 1}> # pro - less spaces, con - no familiarity
> # php familiarity, need spaces
>
> The primary criteria to select these 3 options is that they are YAML
> compatible. Technically they all would solve our problems (primarily no
> embracing quotes needed like in Ansible so no ambiguity on data types).
>
> The secondary criteria is syntax symmetry. After all I agree with
> Patrick's point about better readability when we have opening and closing
> sequences alike.
>
> Some additional details can be found in [0]
>
>
> [0] https://etherpad.openstack.org/p/mistral-YAQL-delimiters
>
> Renat Akhmerov
> @ Mirantis Inc.
>
>
> On 18 Feb 2015, at 07:37, Patrick Hoolboom wrote:
>
> My main concern with the {} delimiters in YAQL is that the curly brace
> already has a defined use within YAML. We most definitely will eventually
> run in to parsing errors with whatever delimiter we choose but I don't feel
> that it should conflict with the markup language it is directly embedded
> in. It gets quite difficult to, at a glance, identify YAQL expressions.
> <% %> may appear ugly to some but I feel that it works as a clear
> delimiter of both the beginning AND the end of the YAQL query. The options
> that only escape the beginning look fine in small examples like this but
> the workflows that we have written or seen in the wild tend to have some
> fairly large expressions. If the opening and closing delimiters don't
> match, it gets quite difficult to read.
>
>>
>> *From: *Anastasia Kuznetsova
>> *Subject: **Re: [openstack-dev] [Mistral] Changing "expression"
>> delimiters in Mistral DSL*
>> *Date: *February 17, 2015 at 8:28:27 AM PST
>> *To: *"OpenStack Development Mailing List (not for usage questions)" <
>> openstack-dev@lists.openstack.org>
>> *Reply-To: *"OpenStack Development Mailing List \(not for usage
>> questions\)"
>>
>> As for me, I think that <% ... %> is not an elegant solution and looks
>> massive because of '%' sign. Also I agree with Renat, that <% ... %>
>> reminds HTML/Jinja2 syntax.
>>
>> I am not sure that similarity with something should be one of the main
>> criteria, because we don't know who will use Mistral.
>>
>> I like:
>> - <{1 + $.var}> Renat's example
>> - variant with using some functions (item 2 in Dmitry's list): { yaql:
>> “1+1+$.my.var < 100” } or
>> - my two cents, maybe we can use something like: result: -< "Hello" +
>> $.name >-
>>
>>
>> Regards,
>> Anastasia Kuznetsova
>>
>> On Tue, Fe
Re: [openstack-dev] [Mistral] Changing "expression" delimiters in Mistral DSL
> Syntax options that we’d like to discuss further
>
> <% 1 + 1 %> # pro- ruby/js/puppet/chef familiarity con - spaces, and % is too
> large symbol
> <{1 + 1}> # pro - less spaces, con - no familiarity
> # php familiarity, need spaces
>
> The primary criteria to select these 3 options is that they are YAML
> compatible. Technically they all would solve our problems (primarily no
> embracing quotes needed like in Ansible so no ambiguity on data types).
>
> The secondary criteria is syntax symmetry. After all I agree with Patrick's
> point about better readability when we have opening and closing sequences
> alike.
To me, another critical criteria is familiarity: target users - openstack
developers and devops, familiar with the delimiters.
That is why of the three above I prefer <% %> .
It is commonly used in Puppet/Chef [1], Ruby, Javascript. One won’t be
surprised to see it and won’t need to change the muscle memory to type
open/closed characters especially when working on say Puppet and Mistral at the
same time (not unlikely).
[1]
https://docs.puppetlabs.com/guides/templating.html#erb-is-plain-text-with-embedded-ruby
On Feb 18, 2015, at 3:20 AM, Renat Akhmerov wrote:
> Hi again,
>
> Sorry, I started writing this email before Angus replied so I will shoot it
> as is and then we can continue…
>
>
> So after discussing all the options again with a small group of team members
> we came to the following things:
>
> Syntax options that we’d like to discuss further
>
> <% 1 + 1 %> # pro- ruby/js/puppet/chef familiarity con - spaces, and % is too
> large symbol
> <{1 + 1}> # pro - less spaces, con - no familiarity
> # php familiarity, need spaces
>
> The primary criteria to select these 3 options is that they are YAML
> compatible. Technically they all would solve our problems (primarily no
> embracing quotes needed like in Ansible so no ambiguity on data types).
>
> The secondary criteria is syntax symmetry. After all I agree with Patrick's
> point about better readability when we have opening and closing sequences
> alike.
>
> Some additional details can be found in [0]
>
>
> [0] https://etherpad.openstack.org/p/mistral-YAQL-delimiters
>
> Renat Akhmerov
> @ Mirantis Inc.
>
>
>> On 18 Feb 2015, at 07:37, Patrick Hoolboom wrote:
>>
>> My main concern with the {} delimiters in YAQL is that the curly brace
>> already has a defined use within YAML. We most definitely will eventually
>> run in to parsing errors with whatever delimiter we choose but I don't feel
>> that it should conflict with the markup language it is directly embedded in.
>> It gets quite difficult to, at a glance, identify YAQL expressions. <% %>
>> may appear ugly to some but I feel that it works as a clear delimiter of
>> both the beginning AND the end of the YAQL query. The options that only
>> escape the beginning look fine in small examples like this but the workflows
>> that we have written or seen in the wild tend to have some fairly large
>> expressions. If the opening and closing delimiters don't match, it gets
>> quite difficult to read.
>>
>>> From: Anastasia Kuznetsova
>>> Subject: Re: [openstack-dev] [Mistral] Changing "expression" delimiters in
>>> Mistral DSL
>>> Date: February 17, 2015 at 8:28:27 AM PST
>>> To: "OpenStack Development Mailing List (not for usage questions)"
>>>
>>> Reply-To: "OpenStack Development Mailing List \(not for usage questions\)"
>>>
>>>
>>> As for me, I think that <% ... %> is not an elegant solution and looks
>>> massive because of '%' sign. Also I agree with Renat, that <% ... %>
>>> reminds HTML/Jinja2 syntax.
>>>
>>> I am not sure that similarity with something should be one of the main
>>> criteria, because we don't know who will use Mistral.
>>>
>>> I like:
>>> - <{1 + $.var}> Renat's example
>>> - variant with using some functions (item 2 in Dmitry's list): { yaql:
>>> “1+1+$.my.var < 100” } or
>>> - my two cents, maybe we can use something like: result: -< "Hello" +
>>> $.name >-
>>>
>>>
>>> Regards,
>>> Anastasia Kuznetsova
>>>
>>> On Tue, Feb 17, 2015 at 1:17 PM, Nikolay Makhotkin
>>> wrote:
>>> Some suggestions from me:
>>>
>>> 1. # (short from yaql).
>>> 2. <{ 1 + $.var }> # as for me, looks more elegant than <% %>. An
Re: [openstack-dev] [Mistral] Changing "expression" delimiters in Mistral DSL
Zane, Angus, thanks for your input!
This functional based syntax is consisted for dev use. The trouble is it ITSELF
needs to be delimited. Without pissing off the users :) Consider two key usage:
input parameters and shorthand syntax for action input. That’s why we are
looking for two-char symmetric (opening + closing) delimiters.
task_with_full_syntax_input:
action: std.ssh
input:
cmd = awk '{ print "<% $.my_var %>" }' /etc/passwd
task_with_shorthand_action_input:
action: std.ssh cmd="awk '{ print \”<% $.my_var %>\" }' /etc/passwd”
using function-like we still will have to do
action: std.ssh cmd=“awk '{ print \”<% yaql {$.my_var} %>\" }' /etc/passwd”
that only adds confusion IMO.
The full set of usages for YAQL in DSL is here:
https://etherpad.openstack.org/p/mistral-YAQL-delimiters
DZ.
On Feb 18, 2015, at 7:22 AM, Zane Bitter wrote:
> On 16/02/15 16:06, Dmitri Zimine wrote:
>> 2) Use functions, like Heat HOT or TOSCA:
>>
>> HOT templates and TOSCA doesn’t seem to have a concept of typed
>> variables to borrow from (please correct me if I missed it). But they
>> have functions: function: { function_name: {foo: [parameter1, parameter
>> 2], bar:"xxx”}}. Applied to Mistral, it would look like:
>>
>> publish:
>> - bool_var: { yaql: “1+1+$.my.var < 100” }
>>
>> Not bad, but currently rejected as it reads worse than delimiter-based
>> syntax, especially in simplified one-line action invocation.
>
> Note that you don't actually need the quotes there, so this would be
> equivalent:
>
>publish:
> - bool_var: {yaql: 1+1+$.my.var < 100}
>
> FWIW I am partial to this or to Renat's p7 suggestion:
>
>publish:
> - bool_var: yaql{1+1+$.my.var < 100}
>
> Both offer the flexibility to introduce new syntax in the future without
> breaking backwards compatibility.
>
> cheers,
> Zane.
>
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Re: [openstack-dev] [Mistral] Changing "expression" delimiters in Mistral DSL
On 16/02/15 16:06, Dmitri Zimine wrote:
2) Use functions, like Heat HOT or TOSCA:
HOT templates and TOSCA doesn’t seem to have a concept of typed
variables to borrow from (please correct me if I missed it). But they
have functions: function: { function_name: {foo: [parameter1, parameter
2], bar:"xxx”}}. Applied to Mistral, it would look like:
publish:
- bool_var: { yaql: “1+1+$.my.var < 100” }
Not bad, but currently rejected as it reads worse than delimiter-based
syntax, especially in simplified one-line action invocation.
Note that you don't actually need the quotes there, so this would be
equivalent:
publish:
- bool_var: {yaql: 1+1+$.my.var < 100}
FWIW I am partial to this or to Renat's p7 suggestion:
publish:
- bool_var: yaql{1+1+$.my.var < 100}
Both offer the flexibility to introduce new syntax in the future without
breaking backwards compatibility.
cheers,
Zane.
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Re: [openstack-dev] [Mistral] Changing "expression" delimiters in Mistral DSL
Hi again,
Sorry, I started writing this email before Angus replied so I will shoot it as
is and then we can continue…
So after discussing all the options again with a small group of team members we
came to the following things:
Syntax options that we’d like to discuss further
<% 1 + 1 %> # pro- ruby/js/puppet/chef familiarity con - spaces, and % is too
large symbol
<{1 + 1}> # pro - less spaces, con - no familiarity
# php familiarity, need spaces
The primary criteria to select these 3 options is that they are YAML
compatible. Technically they all would solve our problems (primarily no
embracing quotes needed like in Ansible so no ambiguity on data types).
The secondary criteria is syntax symmetry. After all I agree with Patrick's
point about better readability when we have opening and closing sequences alike.
Some additional details can be found in [0]
[0] https://etherpad.openstack.org/p/mistral-YAQL-delimiters
<https://etherpad.openstack.org/p/mistral-YAQL-delimiters>
Renat Akhmerov
@ Mirantis Inc.
> On 18 Feb 2015, at 07:37, Patrick Hoolboom wrote:
>
> My main concern with the {} delimiters in YAQL is that the curly brace
> already has a defined use within YAML. We most definitely will eventually
> run in to parsing errors with whatever delimiter we choose but I don't feel
> that it should conflict with the markup language it is directly embedded in.
> It gets quite difficult to, at a glance, identify YAQL expressions. <% %>
> may appear ugly to some but I feel that it works as a clear delimiter of both
> the beginning AND the end of the YAQL query. The options that only escape the
> beginning look fine in small examples like this but the workflows that we
> have written or seen in the wild tend to have some fairly large expressions.
> If the opening and closing delimiters don't match, it gets quite difficult to
> read.
>
>> From: Anastasia Kuznetsova > <mailto:akuznets...@mirantis.com>>
>> Subject: Re: [openstack-dev] [Mistral] Changing "expression" delimiters in
>> Mistral DSL
>> Date: February 17, 2015 at 8:28:27 AM PST
>> To: "OpenStack Development Mailing List (not for usage questions)"
>> > <mailto:openstack-dev@lists.openstack.org>>
>> Reply-To: "OpenStack Development Mailing List \(not for usage questions\)"
>> > <mailto:openstack-dev@lists.openstack.org>>
>>
>> As for me, I think that <% ... %> is not an elegant solution and looks
>> massive because of '%' sign. Also I agree with Renat, that <% ... %> reminds
>> HTML/Jinja2 syntax.
>>
>> I am not sure that similarity with something should be one of the main
>> criteria, because we don't know who will use Mistral.
>>
>> I like:
>> - <{1 + $.var}> Renat's example
>> - variant with using some functions (item 2 in Dmitry's list): { yaql:
>> “1+1+$.my.var < 100” } or
>> - my two cents, maybe we can use something like: result: -< "Hello" + $.name
>> >-
>>
>>
>> Regards,
>> Anastasia Kuznetsova
>>
>> On Tue, Feb 17, 2015 at 1:17 PM, Nikolay Makhotkin > <mailto:nmakhot...@mirantis.com>> wrote:
>> Some suggestions from me:
>>
>> 1. # (short from yaql).
>> 2. <{ 1 + $.var }> # as for me, looks more elegant than <% %>. And visually
>> it is more strong
>>
>> A also like p7 and p8 suggested by Renat.
>>
>> On Tue, Feb 17, 2015 at 11:43 AM, Renat Akhmerov > <mailto:rakhme...@mirantis.com>> wrote:
>> One more:
>>
>> p9: \{1 + $.var} # That’s pretty much what
>> https://review.openstack.org/#/c/155348/
>> <https://review.openstack.org/#/c/155348/> addresses but it’s not exactly
>> that. Note that we don’t have to put it in quotes in this case to deal with
>> YAML {} semantics, it’s just a string
>>
>>
>>
>> Renat Akhmerov
>> @ Mirantis Inc.
>>
>>
>>
>>> On 17 Feb 2015, at 13:37, Renat Akhmerov >> <mailto:rakhme...@mirantis.com>> wrote:
>>>
>>> Along with <% %> syntax here are some other alternatives that I checked for
>>> YAML friendliness with my short comments:
>>>
>>> p1: ${1 + $.var}# Here it’s bad that $ sign is used for two
>>> different things
>>> p2: ~{1 + $.var}# ~ is easy to miss in a text
>>> p3: ^{1 + $.var}# For someone may be associated with regular
>>> expressions
>>> p4: ?{1 + $.var}
>>> p5: <{1 + $.var}> # This is kinda crazy
&g
Re: [openstack-dev] [Mistral] Changing "expression" delimiters in Mistral DSL
On Tue, Feb 17, 2015 at 7:06 AM, Dmitri Zimine
wrote:
> SUMMARY:
>
>
> We are changing the syntax for inlining YAQL expressions in Mistral YAML
> from {1+$.my.var} (or “{1+$.my.var}”) to <% 1+$.my.var %>
>
> Below I explain the rationale and the criteria for the choice. Comments
> and suggestions welcome.
>
> DETAILS:
> -
>
> We faced a number of problems with using YAQL expressions in Mistral DSL:
> [1] must handle any YAQL, not only the ones started with $; [2] must
> preserve types and [3] must comply with YAML. We fixed these problems by
> applying Ansible style syntax, requiring quotes around delimiters (e.g.
> “{1+$.my.yaql.var}”). However, it lead to unbearable confusion in DSL
> readability, in regards to types:
>
> publish:
>intvalue1: "{1+1}” # Confusing: you expect quotes to be string.
>intvalue2: "{int(1+1)}” # Even this doestn’ clean the confusion
>whatisthis:"{$.x + $.y}” # What type would this return?
>
> We got a very strong push back from users in the filed on this syntax.
>
> The crux of the problem is using { } as delimiters YAML. It is plain wrong
> to use the reserved character. The clean solution is to find a delimiter
> that won’t conflict with YAML.
>
> Criteria for selecting best alternative are:
> 1) Consistently applies to to all cases of using YAML in DSL
> 2) Complies with YAML
> 3) Familiar to target user audience - openstack and devops
>
> We prefer using two-char delimiters to avoid requiring extra escaping
> within the expressions.
>
> The current winner is <% %>. It fits YAML well. It is familiar to
> openstack/devops as this is used for embedding Ruby expressions in Puppet
> and Chef (for instance, [4]). It plays relatively well across all cases of
> using expressions in Mistral (see examples in [5]):
>
A really long time ago I posted this patch for Heat:
https://review.openstack.org/#/c/41858/2/doc/source/template_guide/functions.rst
(adds a jinja2 function to Heat http://jinja.pocoo.org/docs/dev/)
I also used <% %>, it seems to be what people use when using jinja2 on yaml.
This was rejected because of security concerns of Jinja2.
>
> ALTERNATIVES considered:
> --
>
> 1) Use Ansible-like syntax:
> http://docs.ansible.com/YAMLSyntax.html#gotchas
> Rejected for confusion around types. See above.
>
> 2) Use functions, like Heat HOT or TOSCA:
>
> HOT templates and TOSCA doesn’t seem to have a concept of typed variables
> to borrow from (please correct me if I missed it). But they have functions:
> function: { function_name: {foo: [parameter1, parameter 2], bar:"xxx”}}.
> Applied to Mistral, it would look like:
>
> publish:
> - bool_var: { yaql: “1+1+$.my.var < 100” }
>
You *could* have the expression as a list, like this (but might not work in
all cases):
{ yaql: [1, +, 1, $.my.var, <, 100] }
Generally in Heat we make the functions and args a natural part of the yaml
so it's not one big string that gets parsed separately.
Tho' it would be nice to have a common approach to this, so I am partial to
the one you have here.
-Angus
>
> Not bad, but currently rejected as it reads worse than delimiter-based
> syntax, especially in simplified one-line action invocation.
>
> 3) < > paired with other symbols: php-styoe
>
>
> *REFERENCES: *
> --
>
> [1] Allow arbitrary YAQL expressions, not just ones started with $ :
> https://github.com/stackforge/mistral/commit/5c10fb4b773cd60d81ed93aec33345c0bf8f58fd
> [2] Use Ansible-like syntax to make YAQL expressions YAML complient
> https://github.com/stackforge/mistral/commit/d9517333b1fc9697d4847df33d3b774f881a111b
> [3] Preserving types in YAQL
> https://github.com/stackforge/mistral/blob/d9517333b1fc9697d4847df33d3b774f881a111b/mistral/tests/unit/test_expressions.py#L152-L184
> [4]Using <% %> in Puppet
> https://docs.puppetlabs.com/guides/templating.html#erb-is-plain-text-with-embedded-ruby
>
> [5] Etherpad with discussion
> https://etherpad.openstack.org/p/mistral-YAQL-delimiters
> [6] Blueprint
> https://blueprints.launchpad.net/mistral/+spec/yaql-delimiters
>
>
> __
> OpenStack Development Mailing List (not for usage questions)
> Unsubscribe: openstack-dev-requ...@lists.openstack.org?subject:unsubscribe
> http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev
>
>
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Re: [openstack-dev] [Mistral] Changing "expression" delimiters in Mistral DSL
My main concern with the {} delimiters in YAQL is that the curly brace
already has a defined use within YAML. We most definitely will eventually
run in to parsing errors with whatever delimiter we choose but I don't feel
that it should conflict with the markup language it is directly embedded
in. It gets quite difficult to, at a glance, identify YAQL expressions.
<% %> may appear ugly to some but I feel that it works as a clear
delimiter of both the beginning AND the end of the YAQL query. The options
that only escape the beginning look fine in small examples like this but
the workflows that we have written or seen in the wild tend to have some
fairly large expressions. If the opening and closing delimiters don't
match, it gets quite difficult to read.
>
> *From: *Anastasia Kuznetsova
> *Subject: **Re: [openstack-dev] [Mistral] Changing "expression"
> delimiters in Mistral DSL*
> *Date: *February 17, 2015 at 8:28:27 AM PST
> *To: *"OpenStack Development Mailing List (not for usage questions)" <
> openstack-dev@lists.openstack.org>
> *Reply-To: *"OpenStack Development Mailing List \(not for usage
> questions\)"
>
> As for me, I think that <% ... %> is not an elegant solution and looks
> massive because of '%' sign. Also I agree with Renat, that <% ... %>
> reminds HTML/Jinja2 syntax.
>
> I am not sure that similarity with something should be one of the main
> criteria, because we don't know who will use Mistral.
>
> I like:
> - <{1 + $.var}> Renat's example
> - variant with using some functions (item 2 in Dmitry's list): { yaql:
> “1+1+$.my.var < 100” } or
> - my two cents, maybe we can use something like: result: -< "Hello" +
> $.name >-
>
>
> Regards,
> Anastasia Kuznetsova
>
> On Tue, Feb 17, 2015 at 1:17 PM, Nikolay Makhotkin <
> nmakhot...@mirantis.com> wrote:
>
>> Some suggestions from me:
>>
>> 1. # (short from yaql).
>> 2. <{ 1 + $.var }> # as for me, looks more elegant than <% %>. And
>> visually it is more strong
>>
>> A also like p7 and p8 suggested by Renat.
>>
>> On Tue, Feb 17, 2015 at 11:43 AM, Renat Akhmerov
>> wrote:
>>
>>> One more:
>>>
>>> p9: \{1 + $.var} # That’s pretty much what
>>> https://review.openstack.org/#/c/155348/ addresses but it’s not exactly
>>> that. Note that we don’t have to put it in quotes in this case to deal with
>>> YAML {} semantics, it’s just a string
>>>
>>>
>>>
>>> Renat Akhmerov
>>> @ Mirantis Inc.
>>>
>>>
>>>
>>> On 17 Feb 2015, at 13:37, Renat Akhmerov wrote:
>>>
>>> Along with <% %> syntax here are some other alternatives that I checked
>>> for YAML friendliness with my short comments:
>>>
>>> p1: ${1 + $.var} # Here it’s bad that $ sign is used for two
>>> different things
>>> p2: ~{1 + $.var} # ~ is easy to miss in a text
>>> p3: ^{1 + $.var} # For someone may be associated with regular
>>> expressions
>>> p4: ?{1 + $.var}
>>> p5: <{1 + $.var}> # This is kinda crazy
>>> p6: e{1 + $.var} # That looks a pretty interesting option to me, “e”
>>> could mean “expression” here.
>>> p7: yaql{1 + $.var} # This is interesting because it would give a clear
>>> and easy mechanism to plug in other expression languages, “yaql” here is a
>>> used dialect for the following expression
>>> p8: y{1 + $.var} # “y” here is just shortened “yaql"
>>>
>>>
>>> Any ideas and thoughts would be really appreciated!
>>>
>>> Renat Akhmerov
>>> @ Mirantis Inc.
>>>
>>>
>>>
>>> On 17 Feb 2015, at 12:53, Renat Akhmerov wrote:
>>>
>>> Dmitri,
>>>
>>> I agree with all your reasonings and fully support the idea of changing
>>> the syntax now as well as changing system’s API a little bit due to
>>> recently found issues in the current engine design that don’t allow us, for
>>> example, to fully implement ‘with-items’ (although that’s a little bit
>>> different story).
>>>
>>> Just a general note about all changes happening now: *Once we release
>>> kilo stable release our API, DSL of version 2 must be 100% stable*. I
>>> was hoping to stabilize it much earlier but the start of production use
>>> revealed a number of things (I think this is normal) which we need to
>>> address, but not later than the end of Kilo.
>>>
>>> As
Re: [openstack-dev] [Mistral] Changing "expression" delimiters in Mistral DSL
As for me, I think that <% ... %> is not an elegant solution and looks
massive because of '%' sign. Also I agree with Renat, that <% ... %>
reminds HTML/Jinja2 syntax.
I am not sure that similarity with something should be one of the main
criteria, because we don't know who will use Mistral.
I like:
- <{1 + $.var}> Renat's example
- variant with using some functions (item 2 in Dmitry's list): { yaql:
“1+1+$.my.var < 100” } or
- my two cents, maybe we can use something like: result: -< "Hello" +
$.name >-
Regards,
Anastasia Kuznetsova
On Tue, Feb 17, 2015 at 1:17 PM, Nikolay Makhotkin
wrote:
> Some suggestions from me:
>
> 1. # (short from yaql).
> 2. <{ 1 + $.var }> # as for me, looks more elegant than <% %>. And
> visually it is more strong
>
> A also like p7 and p8 suggested by Renat.
>
> On Tue, Feb 17, 2015 at 11:43 AM, Renat Akhmerov
> wrote:
>
>> One more:
>>
>> p9: \{1 + $.var} # That’s pretty much what
>> https://review.openstack.org/#/c/155348/ addresses but it’s not exactly
>> that. Note that we don’t have to put it in quotes in this case to deal with
>> YAML {} semantics, it’s just a string
>>
>>
>>
>> Renat Akhmerov
>> @ Mirantis Inc.
>>
>>
>>
>> On 17 Feb 2015, at 13:37, Renat Akhmerov wrote:
>>
>> Along with <% %> syntax here are some other alternatives that I checked
>> for YAML friendliness with my short comments:
>>
>> p1: ${1 + $.var} # Here it’s bad that $ sign is used for two
>> different things
>> p2: ~{1 + $.var} # ~ is easy to miss in a text
>> p3: ^{1 + $.var} # For someone may be associated with regular
>> expressions
>> p4: ?{1 + $.var}
>> p5: <{1 + $.var}> # This is kinda crazy
>> p6: e{1 + $.var} # That looks a pretty interesting option to me, “e”
>> could mean “expression” here.
>> p7: yaql{1 + $.var} # This is interesting because it would give a clear
>> and easy mechanism to plug in other expression languages, “yaql” here is a
>> used dialect for the following expression
>> p8: y{1 + $.var} # “y” here is just shortened “yaql"
>>
>>
>> Any ideas and thoughts would be really appreciated!
>>
>> Renat Akhmerov
>> @ Mirantis Inc.
>>
>>
>>
>> On 17 Feb 2015, at 12:53, Renat Akhmerov wrote:
>>
>> Dmitri,
>>
>> I agree with all your reasonings and fully support the idea of changing
>> the syntax now as well as changing system’s API a little bit due to
>> recently found issues in the current engine design that don’t allow us, for
>> example, to fully implement ‘with-items’ (although that’s a little bit
>> different story).
>>
>> Just a general note about all changes happening now: *Once we release
>> kilo stable release our API, DSL of version 2 must be 100% stable*. I
>> was hoping to stabilize it much earlier but the start of production use
>> revealed a number of things (I think this is normal) which we need to
>> address, but not later than the end of Kilo.
>>
>> As far as <% %> syntax. I see that it would solve a number of problems
>> (YAML friendliness, type ambiguity) but my only not strong argument is that
>> it doesn’t look that elegant in YAML as it looks, for example, in ERB
>> templates. It really reminds me XML/HTML and looks like a bear in a grocery
>> store (tried to make it close to one old russian saying :) ). So just for
>> this only reason I’d suggest we think about other alternatives, maybe not
>> so familiar to Ruby/Chef/Puppet users but looking better with YAML and at
>> the same time being YAML friendly.
>>
>> I would be good if we could here more feedback on this, especially from
>> people who started using Mistral.
>>
>> Thanks
>>
>> Renat Akhmerov
>> @ Mirantis Inc.
>>
>>
>>
>> On 17 Feb 2015, at 03:06, Dmitri Zimine wrote:
>>
>> SUMMARY:
>>
>>
>> We are changing the syntax for inlining YAQL expressions in Mistral YAML
>> from {1+$.my.var} (or “{1+$.my.var}”) to <% 1+$.my.var %>
>>
>> Below I explain the rationale and the criteria for the choice. Comments
>> and suggestions welcome.
>>
>> DETAILS:
>> -
>>
>> We faced a number of problems with using YAQL expressions in Mistral DSL:
>> [1] must handle any YAQL, not only the ones started with $; [2] must
>> preserve types and [3] must comply with YAML. We fixed these problems by
>> applying Ansible style syntax, requiring quotes around delimiters (e.g.
>> “{1+$.my.yaql.var}”). However, it lead to unbearable confusion in DSL
>> readability, in regards to types:
>>
>> publish:
>>intvalue1: "{1+1}” # Confusing: you expect quotes to be string.
>>intvalue2: "{int(1+1)}” # Even this doestn’ clean the confusion
>>whatisthis:"{$.x + $.y}” # What type would this return?
>>
>> We got a very strong push back from users in the filed on this syntax.
>>
>> The crux of the problem is using { } as delimiters YAML. It is plain
>> wrong to use the reserved character. The clean solution is to find a
>> delimiter that won’t conflict with YAML.
>>
>> Criteria for selecting best alternative are:
>> 1) Consistently applies to to all cases of using YAML
Re: [openstack-dev] [Mistral] Changing "expression" delimiters in Mistral DSL
Some suggestions from me:
1. # (short from yaql).
2. <{ 1 + $.var }> # as for me, looks more elegant than <% %>. And
visually it is more strong
A also like p7 and p8 suggested by Renat.
On Tue, Feb 17, 2015 at 11:43 AM, Renat Akhmerov
wrote:
> One more:
>
> p9: \{1 + $.var} # That’s pretty much what
> https://review.openstack.org/#/c/155348/ addresses but it’s not exactly
> that. Note that we don’t have to put it in quotes in this case to deal with
> YAML {} semantics, it’s just a string
>
>
>
> Renat Akhmerov
> @ Mirantis Inc.
>
>
>
> On 17 Feb 2015, at 13:37, Renat Akhmerov wrote:
>
> Along with <% %> syntax here are some other alternatives that I checked
> for YAML friendliness with my short comments:
>
> p1: ${1 + $.var} # Here it’s bad that $ sign is used for two
> different things
> p2: ~{1 + $.var} # ~ is easy to miss in a text
> p3: ^{1 + $.var} # For someone may be associated with regular
> expressions
> p4: ?{1 + $.var}
> p5: <{1 + $.var}> # This is kinda crazy
> p6: e{1 + $.var} # That looks a pretty interesting option to me, “e”
> could mean “expression” here.
> p7: yaql{1 + $.var} # This is interesting because it would give a clear
> and easy mechanism to plug in other expression languages, “yaql” here is a
> used dialect for the following expression
> p8: y{1 + $.var} # “y” here is just shortened “yaql"
>
>
> Any ideas and thoughts would be really appreciated!
>
> Renat Akhmerov
> @ Mirantis Inc.
>
>
>
> On 17 Feb 2015, at 12:53, Renat Akhmerov wrote:
>
> Dmitri,
>
> I agree with all your reasonings and fully support the idea of changing
> the syntax now as well as changing system’s API a little bit due to
> recently found issues in the current engine design that don’t allow us, for
> example, to fully implement ‘with-items’ (although that’s a little bit
> different story).
>
> Just a general note about all changes happening now: *Once we release
> kilo stable release our API, DSL of version 2 must be 100% stable*. I was
> hoping to stabilize it much earlier but the start of production use
> revealed a number of things (I think this is normal) which we need to
> address, but not later than the end of Kilo.
>
> As far as <% %> syntax. I see that it would solve a number of problems
> (YAML friendliness, type ambiguity) but my only not strong argument is that
> it doesn’t look that elegant in YAML as it looks, for example, in ERB
> templates. It really reminds me XML/HTML and looks like a bear in a grocery
> store (tried to make it close to one old russian saying :) ). So just for
> this only reason I’d suggest we think about other alternatives, maybe not
> so familiar to Ruby/Chef/Puppet users but looking better with YAML and at
> the same time being YAML friendly.
>
> I would be good if we could here more feedback on this, especially from
> people who started using Mistral.
>
> Thanks
>
> Renat Akhmerov
> @ Mirantis Inc.
>
>
>
> On 17 Feb 2015, at 03:06, Dmitri Zimine wrote:
>
> SUMMARY:
>
>
> We are changing the syntax for inlining YAQL expressions in Mistral YAML
> from {1+$.my.var} (or “{1+$.my.var}”) to <% 1+$.my.var %>
>
> Below I explain the rationale and the criteria for the choice. Comments
> and suggestions welcome.
>
> DETAILS:
> -
>
> We faced a number of problems with using YAQL expressions in Mistral DSL:
> [1] must handle any YAQL, not only the ones started with $; [2] must
> preserve types and [3] must comply with YAML. We fixed these problems by
> applying Ansible style syntax, requiring quotes around delimiters (e.g.
> “{1+$.my.yaql.var}”). However, it lead to unbearable confusion in DSL
> readability, in regards to types:
>
> publish:
>intvalue1: "{1+1}” # Confusing: you expect quotes to be string.
>intvalue2: "{int(1+1)}” # Even this doestn’ clean the confusion
>whatisthis:"{$.x + $.y}” # What type would this return?
>
> We got a very strong push back from users in the filed on this syntax.
>
> The crux of the problem is using { } as delimiters YAML. It is plain wrong
> to use the reserved character. The clean solution is to find a delimiter
> that won’t conflict with YAML.
>
> Criteria for selecting best alternative are:
> 1) Consistently applies to to all cases of using YAML in DSL
> 2) Complies with YAML
> 3) Familiar to target user audience - openstack and devops
>
> We prefer using two-char delimiters to avoid requiring extra escaping
> within the expressions.
>
> The current winner is <% %>. It fits YAML well. It is familiar to
> openstack/devops as this is used for embedding Ruby expressions in Puppet
> and Chef (for instance, [4]). It plays relatively well across all cases of
> using expressions in Mistral (see examples in [5]):
>
> ALTERNATIVES considered:
> --
>
> 1) Use Ansible-like syntax:
> http://docs.ansible.com/YAMLSyntax.html#gotchas
> Rejected for confusion around types. See above.
>
> 2) Use functions, like Heat HOT or TOSCA:
>
> H
Re: [openstack-dev] [Mistral] Changing "expression" delimiters in Mistral DSL
One more:
p9: \{1 + $.var}# That’s pretty much what
https://review.openstack.org/#/c/155348/
> wrote:
>>
>> Dmitri,
>>
>> I agree with all your reasonings and fully support the idea of changing the
>> syntax now as well as changing system’s API a little bit due to recently
>> found issues in the current engine design that don’t allow us, for example,
>> to fully implement ‘with-items’ (although that’s a little bit different
>> story).
>>
>> Just a general note about all changes happening now: Once we release kilo
>> stable release our API, DSL of version 2 must be 100% stable. I was hoping
>> to stabilize it much earlier but the start of production use revealed a
>> number of things (I think this is normal) which we need to address, but not
>> later than the end of Kilo.
>>
>> As far as <% %> syntax. I see that it would solve a number of problems (YAML
>> friendliness, type ambiguity) but my only not strong argument is that it
>> doesn’t look that elegant in YAML as it looks, for example, in ERB
>> templates. It really reminds me XML/HTML and looks like a bear in a grocery
>> store (tried to make it close to one old russian saying :) ). So just for
>> this only reason I’d suggest we think about other alternatives, maybe not so
>> familiar to Ruby/Chef/Puppet users but looking better with YAML and at the
>> same time being YAML friendly.
>>
>> I would be good if we could here more feedback on this, especially from
>> people who started using Mistral.
>>
>> Thanks
>>
>> Renat Akhmerov
>> @ Mirantis Inc.
>>
>>
>>
>>> On 17 Feb 2015, at 03:06, Dmitri Zimine >> > wrote:
>>>
>>> SUMMARY:
>>>
>>>
>>> We are changing the syntax for inlining YAQL expressions in Mistral YAML
>>> from {1+$.my.var} (or “{1+$.my.var}”) to <% 1+$.my.var %>
>>>
>>> Below I explain the rationale and the criteria for the choice. Comments and
>>> suggestions welcome.
>>>
>>> DETAILS:
>>> -
>>>
>>> We faced a number of problems with using YAQL expressions in Mistral DSL:
>>> [1] must handle any YAQL, not only the ones started with $; [2] must
>>> preserve types and [3] must comply with YAML. We fixed these problems by
>>> applying Ansible style syntax, requiring quotes around delimiters (e.g.
>>> “{1+$.my.yaql.var}”). However, it lead to unbearable confusion in DSL
>>> readability, in regards to types:
>>>
>>> publish:
>>>intvalue1: "{1+1}” # Confusing: you expect quotes to be string.
>>>intvalue2: "{int(1+1)}” # Even this doestn’ clean the confusion
>>>whatisthis:"{$.x + $.y}” # What type would this return?
>>>
>>> We got a very strong push back from users in the filed on this syntax.
>>>
>>> The crux of the problem is using { } as delimiters YAML. It is plain wrong
>>> to use the reserved character. The clean solution is to find a delimiter
>>> that won’t conflict with YAML.
>>>
>>> Criteria for selecting best alternative are:
>>> 1) Consistently applies to to all cases of using YAML in DSL
>>> 2) Complies with YAML
>>> 3) Familiar to target user audience - openstack and devops
>>>
>>> We prefer using two-char delimiters to avoid requiring extra escaping
>>> within the expressions.
>>>
>>> The current winner is <% %>. It fits YAML well. It is familiar to
>>> openstack/devops as this is used for embedding Ruby expressions in Puppet
>>> and Chef (for instance, [4]). It plays relatively well across all cases of
>>> using expressions in Mistral (see examples in [5]):
>>>
>>> ALTERNATIVES considered:
>>> --
>>>
>>> 1) Use Ansible-like syntax: http://docs.ansible.com/YAMLSyntax.html#gotchas
>>>
Re: [openstack-dev] [Mistral] Changing "expression" delimiters in Mistral DSL
Along with <% %> syntax here are some other alternatives that I checked for
YAML friendliness with my short comments:
p1: ${1 + $.var}# Here it’s bad that $ sign is used for two different
things
p2: ~{1 + $.var}# ~ is easy to miss in a text
p3: ^{1 + $.var}# For someone may be associated with regular expressions
p4: ?{1 + $.var}
p5: <{1 + $.var}> # This is kinda crazy
p6: e{1 + $.var}# That looks a pretty interesting option to me, “e”
could mean “expression” here.
p7: yaql{1 + $.var} # This is interesting because it would give a clear and
easy mechanism to plug in other expression languages, “yaql” here is a used
dialect for the following expression
p8: y{1 + $.var}# “y” here is just shortened “yaql"
Any ideas and thoughts would be really appreciated!
Renat Akhmerov
@ Mirantis Inc.
> On 17 Feb 2015, at 12:53, Renat Akhmerov wrote:
>
> Dmitri,
>
> I agree with all your reasonings and fully support the idea of changing the
> syntax now as well as changing system’s API a little bit due to recently
> found issues in the current engine design that don’t allow us, for example,
> to fully implement ‘with-items’ (although that’s a little bit different
> story).
>
> Just a general note about all changes happening now: Once we release kilo
> stable release our API, DSL of version 2 must be 100% stable. I was hoping to
> stabilize it much earlier but the start of production use revealed a number
> of things (I think this is normal) which we need to address, but not later
> than the end of Kilo.
>
> As far as <% %> syntax. I see that it would solve a number of problems (YAML
> friendliness, type ambiguity) but my only not strong argument is that it
> doesn’t look that elegant in YAML as it looks, for example, in ERB templates.
> It really reminds me XML/HTML and looks like a bear in a grocery store (tried
> to make it close to one old russian saying :) ). So just for this only reason
> I’d suggest we think about other alternatives, maybe not so familiar to
> Ruby/Chef/Puppet users but looking better with YAML and at the same time
> being YAML friendly.
>
> I would be good if we could here more feedback on this, especially from
> people who started using Mistral.
>
> Thanks
>
> Renat Akhmerov
> @ Mirantis Inc.
>
>
>
>> On 17 Feb 2015, at 03:06, Dmitri Zimine > > wrote:
>>
>> SUMMARY:
>>
>>
>> We are changing the syntax for inlining YAQL expressions in Mistral YAML
>> from {1+$.my.var} (or “{1+$.my.var}”) to <% 1+$.my.var %>
>>
>> Below I explain the rationale and the criteria for the choice. Comments and
>> suggestions welcome.
>>
>> DETAILS:
>> -
>>
>> We faced a number of problems with using YAQL expressions in Mistral DSL:
>> [1] must handle any YAQL, not only the ones started with $; [2] must
>> preserve types and [3] must comply with YAML. We fixed these problems by
>> applying Ansible style syntax, requiring quotes around delimiters (e.g.
>> “{1+$.my.yaql.var}”). However, it lead to unbearable confusion in DSL
>> readability, in regards to types:
>>
>> publish:
>>intvalue1: "{1+1}” # Confusing: you expect quotes to be string.
>>intvalue2: "{int(1+1)}” # Even this doestn’ clean the confusion
>>whatisthis:"{$.x + $.y}” # What type would this return?
>>
>> We got a very strong push back from users in the filed on this syntax.
>>
>> The crux of the problem is using { } as delimiters YAML. It is plain wrong
>> to use the reserved character. The clean solution is to find a delimiter
>> that won’t conflict with YAML.
>>
>> Criteria for selecting best alternative are:
>> 1) Consistently applies to to all cases of using YAML in DSL
>> 2) Complies with YAML
>> 3) Familiar to target user audience - openstack and devops
>>
>> We prefer using two-char delimiters to avoid requiring extra escaping within
>> the expressions.
>>
>> The current winner is <% %>. It fits YAML well. It is familiar to
>> openstack/devops as this is used for embedding Ruby expressions in Puppet
>> and Chef (for instance, [4]). It plays relatively well across all cases of
>> using expressions in Mistral (see examples in [5]):
>>
>> ALTERNATIVES considered:
>> --
>>
>> 1) Use Ansible-like syntax: http://docs.ansible.com/YAMLSyntax.html#gotchas
>>
>> Rejected for confusion around types. See above.
>>
>> 2) Use functions, like Heat HOT or TOSCA:
>>
>> HOT templates and TOSCA doesn’t seem to have a concept of typed variables to
>> borrow from (please correct me if I missed it). But they have functions:
>> function: { function_name: {foo: [parameter1, parameter 2], bar:"xxx”}}.
>> Applied to Mistral, it would look like:
>>
>> publish:
>> - bool_var: { yaql: “1+1+$.my.var < 100” }
>>
>> Not bad, but currently rejected as it reads wo
Re: [openstack-dev] [Mistral] Changing "expression" delimiters in Mistral DSL
Dmitri,
I agree with all your reasonings and fully support the idea of changing the
syntax now as well as changing system’s API a little bit due to recently found
issues in the current engine design that don’t allow us, for example, to fully
implement ‘with-items’ (although that’s a little bit different story).
Just a general note about all changes happening now: Once we release kilo
stable release our API, DSL of version 2 must be 100% stable. I was hoping to
stabilize it much earlier but the start of production use revealed a number of
things (I think this is normal) which we need to address, but not later than
the end of Kilo.
As far as <% %> syntax. I see that it would solve a number of problems (YAML
friendliness, type ambiguity) but my only not strong argument is that it
doesn’t look that elegant in YAML as it looks, for example, in ERB templates.
It really reminds me XML/HTML and looks like a bear in a grocery store (tried
to make it close to one old russian saying :) ). So just for this only reason
I’d suggest we think about other alternatives, maybe not so familiar to
Ruby/Chef/Puppet users but looking better with YAML and at the same time being
YAML friendly.
I would be good if we could here more feedback on this, especially from people
who started using Mistral.
Thanks
Renat Akhmerov
@ Mirantis Inc.
> On 17 Feb 2015, at 03:06, Dmitri Zimine wrote:
>
> SUMMARY:
>
>
> We are changing the syntax for inlining YAQL expressions in Mistral YAML from
> {1+$.my.var} (or “{1+$.my.var}”) to <% 1+$.my.var %>
>
> Below I explain the rationale and the criteria for the choice. Comments and
> suggestions welcome.
>
> DETAILS:
> -
>
> We faced a number of problems with using YAQL expressions in Mistral DSL: [1]
> must handle any YAQL, not only the ones started with $; [2] must preserve
> types and [3] must comply with YAML. We fixed these problems by applying
> Ansible style syntax, requiring quotes around delimiters (e.g.
> “{1+$.my.yaql.var}”). However, it lead to unbearable confusion in DSL
> readability, in regards to types:
>
> publish:
>intvalue1: "{1+1}” # Confusing: you expect quotes to be string.
>intvalue2: "{int(1+1)}” # Even this doestn’ clean the confusion
>whatisthis:"{$.x + $.y}” # What type would this return?
>
> We got a very strong push back from users in the filed on this syntax.
>
> The crux of the problem is using { } as delimiters YAML. It is plain wrong to
> use the reserved character. The clean solution is to find a delimiter that
> won’t conflict with YAML.
>
> Criteria for selecting best alternative are:
> 1) Consistently applies to to all cases of using YAML in DSL
> 2) Complies with YAML
> 3) Familiar to target user audience - openstack and devops
>
> We prefer using two-char delimiters to avoid requiring extra escaping within
> the expressions.
>
> The current winner is <% %>. It fits YAML well. It is familiar to
> openstack/devops as this is used for embedding Ruby expressions in Puppet and
> Chef (for instance, [4]). It plays relatively well across all cases of using
> expressions in Mistral (see examples in [5]):
>
> ALTERNATIVES considered:
> --
>
> 1) Use Ansible-like syntax: http://docs.ansible.com/YAMLSyntax.html#gotchas
>
> Rejected for confusion around types. See above.
>
> 2) Use functions, like Heat HOT or TOSCA:
>
> HOT templates and TOSCA doesn’t seem to have a concept of typed variables to
> borrow from (please correct me if I missed it). But they have functions:
> function: { function_name: {foo: [parameter1, parameter 2], bar:"xxx”}}.
> Applied to Mistral, it would look like:
>
> publish:
> - bool_var: { yaql: “1+1+$.my.var < 100” }
>
> Not bad, but currently rejected as it reads worse than delimiter-based
> syntax, especially in simplified one-line action invocation.
>
> 3) < > paired with other symbols: php-styoe
>
>
> REFERENCES:
> --
>
> [1] Allow arbitrary YAQL expressions, not just ones started with $ :
> https://github.com/stackforge/mistral/commit/5c10fb4b773cd60d81ed93aec33345c0bf8f58fd
>
>
> [2] Use Ansible-like syntax to make YAQL expressions YAML complient
> https://github.com/stackforge/mistral/commit/d9517333b1fc9697d4847df33d3b774f881a111b
>
>
> [3] Preserving types in YAQL
> https://github.com/stackforge/mistral/blob/d9517333b1fc9697d4847df33d3b774f881a111b/mistral/tests/unit/test_expressions.py#L152-L184
>
>
> [4]Using <% %> in Puppet
> https://docs.puppetlabs.com/guides/templating.h
[openstack-dev] [Mistral] Changing "expression" delimiters in Mistral DSL
SUMMARY:
We are changing the syntax for inlining YAQL expressions in Mistral YAML from
{1+$.my.var} (or “{1+$.my.var}”) to <% 1+$.my.var %>
Below I explain the rationale and the criteria for the choice. Comments and
suggestions welcome.
DETAILS:
-
We faced a number of problems with using YAQL expressions in Mistral DSL: [1]
must handle any YAQL, not only the ones started with $; [2] must preserve types
and [3] must comply with YAML. We fixed these problems by applying Ansible
style syntax, requiring quotes around delimiters (e.g. “{1+$.my.yaql.var}”).
However, it lead to unbearable confusion in DSL readability, in regards to
types:
publish:
intvalue1: "{1+1}” # Confusing: you expect quotes to be string.
intvalue2: "{int(1+1)}” # Even this doestn’ clean the confusion
whatisthis:"{$.x + $.y}” # What type would this return?
We got a very strong push back from users in the filed on this syntax.
The crux of the problem is using { } as delimiters YAML. It is plain wrong to
use the reserved character. The clean solution is to find a delimiter that
won’t conflict with YAML.
Criteria for selecting best alternative are:
1) Consistently applies to to all cases of using YAML in DSL
2) Complies with YAML
3) Familiar to target user audience - openstack and devops
We prefer using two-char delimiters to avoid requiring extra escaping within
the expressions.
The current winner is <% %>. It fits YAML well. It is familiar to
openstack/devops as this is used for embedding Ruby expressions in Puppet and
Chef (for instance, [4]). It plays relatively well across all cases of using
expressions in Mistral (see examples in [5]):
ALTERNATIVES considered:
--
1) Use Ansible-like syntax: http://docs.ansible.com/YAMLSyntax.html#gotchas
Rejected for confusion around types. See above.
2) Use functions, like Heat HOT or TOSCA:
HOT templates and TOSCA doesn’t seem to have a concept of typed variables to
borrow from (please correct me if I missed it). But they have functions:
function: { function_name: {foo: [parameter1, parameter 2], bar:"xxx”}}.
Applied to Mistral, it would look like:
publish:
- bool_var: { yaql: “1+1+$.my.var < 100” }
Not bad, but currently rejected as it reads worse than delimiter-based syntax,
especially in simplified one-line action invocation.
3) < > paired with other symbols: php-styoe
REFERENCES:
--
[1] Allow arbitrary YAQL expressions, not just ones started with $ :
https://github.com/stackforge/mistral/commit/5c10fb4b773cd60d81ed93aec33345c0bf8f58fd
[2] Use Ansible-like syntax to make YAQL expressions YAML complient
https://github.com/stackforge/mistral/commit/d9517333b1fc9697d4847df33d3b774f881a111b
[3] Preserving types in YAQL
https://github.com/stackforge/mistral/blob/d9517333b1fc9697d4847df33d3b774f881a111b/mistral/tests/unit/test_expressions.py#L152-L184
[4]Using <% %> in Puppet
https://docs.puppetlabs.com/guides/templating.html#erb-is-plain-text-with-embedded-ruby
[5] Etherpad with discussion
https://etherpad.openstack.org/p/mistral-YAQL-delimiters
[6] Blueprint https://blueprints.launchpad.net/mistral/+spec/yaql-delimiters
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