Ok, I would prefer to spend some time and think how to improve the existing reg 
exp that we use to parse key-value pairs. We definitely can’t just drop support 
of this syntax and can’t even change it significantly since people already use 

Renat Akhmerov
@ Mirantis Inc.

> On 17 Dec 2014, at 07:28, Lakshmi Kannan <laks...@lakshmikannan.me> wrote:
> Apologies for the long email. If this fancy email doesn’t render correctly 
> for you, please read it here: 
> https://gist.github.com/lakshmi-kannan/cf953f66a397b153254a 
> <https://gist.github.com/lakshmi-kannan/cf953f66a397b153254a>
> I was looking into fixing bug: 
> https://bugs.launchpad.net/mistral/+bug/1401039 
> <https://bugs.launchpad.net/mistral/+bug/1401039>. My idea was to use shlex 
> to parse the string. This actually would work for anything that is supplied 
> in the linux shell syntax. Problem is this craps out when we want to support 
> complex data structures such as arrays and dicts as arguments. I did not 
> think we supported a syntax to take in complex data structures in a one line 
> format. Consider for example:
>       task7:
>         for-each:
>           vm_info: $.vms
>         workflow: wf2 is_true=true object_list=[1, null, "str"]
>         on-complete:
>           - task9
>           - task10
> Specifically
> wf2 is_true=true object_list=[1, null, "str"]
> shlex will not handle this correctly because object_list is an array. Same 
> problem with dict.
> There are 3 potential options here:
> Option 1
> 1) Provide a spec for specifying lists and dicts like so:
> list_arg=1,2,3 and dict_arg=h1:h2,h3:h4,h5:h6
> shlex will handle this fine but there needs to be a code that converts the 
> argument values to appropriate data types based on schema. (ActionSpec should 
> have a parameter schema probably in jsonschema). This is doable.
> wf2 is_true=true object_list="1,null,"str""
> Option 2
> 2) Allow JSON strings to be used as arguments so we can json.loads them (if 
> it fails, use them as simple string). For example, with this approach, the 
> line becomes
> wf2 is_true=true object_list="[1, null, "str"]"
> This would pretty much resemble 
> http://stackoverflow.com/questions/7625786/type-dict-in-argparse-add-argument 
> <http://stackoverflow.com/questions/7625786/type-dict-in-argparse-add-argument>
> Option 3
> 3) Keep the spec as such and try to parse it. I have no idea how we can do 
> this reliably. We need a more rigorous lexer. This syntax doesn’t translate 
> well when we want to build a CLI. Linux shells cannot support this syntax 
> natively. This means people would have to use shlex syntax and a translation 
> needs to happen in CLI layer. This will lead to inconsistency. CLI uses some 
> syntax and the action input line in workflow definition will use another. We 
> should try and avoid this.
> Option 4
> 4) Completely drop support for this fancy one line syntax in workflow. This 
> is probably the least desired option.
> My preference
> Looking the options, I like option2/option 1/option 4/option 3 in the order 
> of preference.
> With some documentation, we can tell people why this is hard. People will 
> also grok because they are already familiar with CLI limitations in linux.
> Thoughts?
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