IronLanguages / IronLanguages/ironpython3

Update WithStatement ast to match CPython

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CPython compatibility What's New In Python 3.3
Dominant language
C#
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Description

Currently, with statements get unwrapped. For example:

with a as b, c as d:
    pass

becomes

with a as b:
    with c as d:
        pass

in the AST.

Since Python 3.3, the AST has been changed to use a list of "withitem" instead.

While the two are functionally equivalent it would be nice to remove the unwrapping from the parser and update IronPython.Compiler.Ast.WithStatement to match (e.g. use a list of items).

Related to: https://github.com/IronLanguages/ironpython3/pull/744

Contributor guide

Open the contributing guide

First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

Start by reading the parser code that unwraps multiple with items and the IronPython.Compiler.Ast.WithStatement implementation. Review the related pull request 744 for context. Done means preserving multiple with items in the AST as a list, matching CPython's structure instead of nested WithStatement nodes.

Written by the indexing model from the issue text.

Assessment

Tech stack
csharp, python
Domain
compilers
Issue type
Refactor
Difficulty
4/5
Estimated time
3-5 days
Activity status
Stale
Clarity
Mostly clear
Newbie friendliness
45/100

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