[issue32911] Doc strings no longer stored in body of AST

[Matthias Bussonnier]

Matthias Bussonnier <bussonniermatthias at gmail.com> added the comment:

Łukasz Langa wrote:

> Inadasan, I think what we should do is to amend `ast.parse()` and `compile()` docs that mode="exec" treats given code as a module, we should even give the docstring handling as an example.

That is what I proposed in https://bugs.python.org/issue33477
and in PR https://github.com/python/cpython/pull/6973

The other surprise, is that even is I  knew AST were change and had a docstring field I was not expecting `compile()` to be affected.


I think that the change for ast to have a docstring field is a good one from an API point of view for ast nodes. But It should probably be opt-in, at least with a deprecation period to make it the default. The other issue is that as it affect only sequence of statement where the first node is (was) a string, it can lead to really subtle difference in execution. 



MinRk said:
> The only affected case for us is interactively typed string literals in single statement cells not displaying themselves as results

It might affect our downstream consumers that have syntax/ast transformation like sage, sympy on top of IPython. I doubt we have any but it's a possibility. 

While I would prefer (B) as well, I see how the new behavior can be useful in some case, and strongly also support the addition of a `multiline` mode, which correspond to what 3.6 and before were doing with `exec`. The other possibility is to leave `exec` and `ast.parse` with 3.6 behavior, and include a `'module'` mode that does reflect current 3.7 behavior.

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nosy: +mbussonn

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