> 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
> <? 1 + 1 ?> # 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 <[email protected]> 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
> <? 1 + 1 ?> # 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 <[email protected]> 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 <[email protected]>
>>> 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)"
>>> <[email protected]>
>>> Reply-To: "OpenStack Development Mailing List \(not for usage questions\)"
>>> <[email protected]>
>>>
>>> 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 <yaql: 'Hello' + $.name >
>>> - 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
>>> <[email protected]> wrote:
>>> Some suggestions from me:
>>>
>>> 1. <y 1 + $.var > # (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 <[email protected]>
>>> 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 <[email protected]> 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 <[email protected]> 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 <[email protected]> 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.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: [email protected]?subject:unsubscribe
>>> http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev
>>>
>>>
>>>
>>>
>>> --
>>> Best Regards,
>>> Nikolay
>>>
>>> __________________________________________________________________________
>>> OpenStack Development Mailing List (not for usage questions)
>>> Unsubscribe: [email protected]?subject:unsubscribe
>>> http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev
>>>
>>>
>>> __________________________________________________________________________
>>> OpenStack Development Mailing List (not for usage questions)
>>> Unsubscribe: [email protected]?subject:unsubscribe
>>> http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev
>>
>>
>> __________________________________________________________________________
>> OpenStack Development Mailing List (not for usage questions)
>> Unsubscribe: [email protected]?subject:unsubscribe
>> http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev
>
> __________________________________________________________________________
> OpenStack Development Mailing List (not for usage questions)
> Unsubscribe: [email protected]?subject:unsubscribe
> http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev
__________________________________________________________________________
OpenStack Development Mailing List (not for usage questions)
Unsubscribe: [email protected]?subject:unsubscribe
http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev
