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bpo-40334: Support type comments#19780

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gvanrossum merged 12 commits into
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type-comments
Apr 30, 2020
Merged

bpo-40334: Support type comments#19780
gvanrossum merged 12 commits into
masterfrom
type-comments

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@gvanrossum

@gvanrossum gvanrossum commented Apr 29, 2020 •
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This implements full support for # type: <type> comments, # type: ignore <stuff> comments, and the func_type parsing mode for ast.parse() and compile().

Closes we-like-parsers#95

https://bugs.python.org/issue40334

@gvanrossum
First steps towards supporting type comments …
e17bb92 
This does not yet support the "long form" for arguments with type
comments.

We also totally skip `# type: ignore` comments, and there is no
support for func_type_input yet.
@gvanrossum
Support func_type_input in new parser
2e4126c
@gvanrossum
Support '# type: ignore <tag>'
7b446fb
@gvanrossum
Support per-argument type comments ('long form') …
ed95a14 
This involved a complete refactor of the part of the grammar used to
recognise formal parameters in function definitions.  I renamed many
of the rules involved.

The rewrite always includes the comma following a parameter in that
argument, so that we can also include the type comment, if any (which
follows the comma).

The final parameter may not be followed by a comma, so we allow the
comma to be omitted, but only if a close parenthesis follows instead
(preceded by the type comment, if any).

Some additional complications are needed because the code generator
doesn't actually support alternatives that may be empty.

PS. I didn't refactor the corresponding rules for lambdas, since they
don't have type comments.
@gvanrossum gvanrossum requested a review from pablogsal as a code owner April 29, 2020 00:18
@gvanrossum gvanrossum marked this pull request as draft April 29, 2020 00:18
@gvanrossum gvanrossum changed the title bpo-40334: Support type comments Apr 29, 2020
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gvanrossum commented Apr 29, 2020

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Wait, I forgot to un-skip the test for long-form arguments and it segfaults. On it.

@gvanrossum gvanrossum changed the title bpo-40334: Support type comments [WIP] Apr 29, 2020
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gvanrossum commented Apr 29, 2020

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Hm... when parsing something as simple as

def f(a): pass

it seems the end column number for a is two characters too far. I'll investigate tomorrow.

@lysnikolaou lysnikolaou mentioned this pull request Apr 29, 2020
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@gvanrossum gvanrossum marked this pull request as ready for review April 29, 2020 16:00
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gvanrossum commented Apr 29, 2020

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Dang I already have conflicts. Looking...

@gvanrossum gvanrossum requested a review from lysnikolaou April 29, 2020 17:05
lysnikolaou
lysnikolaou reviewed Apr 29, 2020
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Thanks for doing this! Apart from all the TYPE_COMMENTS work, I strongly feel that the arguments improvements made a significant difference in readability.

@lysnikolaou

lysnikolaou commented Apr 29, 2020

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It seems there's a failure in test_type_comments. Was it there before as well?

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gvanrossum commented Apr 29, 2020

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The test_type_comments failure is new, looking now.

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All your other suggestions will appear in the next commit.

@lysnikolaou

lysnikolaou commented Apr 29, 2020

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Also, all the calls to NEW_TYPE_COMMENT should be wrapped with CHECK_CALL_NULL_ALLOWED.

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lysnikolaou commented Apr 30, 2020 •
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To recap, because it might not be clear what my latest reviews are suggesting. I think that the following are needed:

  1. Change the type of the tc argument in _PyPegen_add_type_comment_to_arg and _PyPegen_name_default_pair to Token *.
  2. Wrap calls to NEW_TYPE_COMMENT with CHECK_CALL_NULL_ALLOWED.

I'd also make NEW_TYPE_COMMENT an inline function, but this is certainly not needed.

@gvanrossum

gvanrossum commented Apr 30, 2020

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Got it. I'm putting the CHECK_CALL_NULL_ALLOWED call inside NEW_TYPE_COMMENT -- does that make sense? I don't see that pattern used elsewhere.

lysnikolaou
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One last thing and it's good to go.

@gvanrossum

gvanrossum commented Apr 30, 2020

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@lysnikolaou Thank you so much for all your help on this one! It's been invaluable.

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My pleasure!

@gvanrossum gvanrossum merged commit c001c09 into master Apr 30, 2020
@gvanrossum gvanrossum deleted the type-comments branch April 30, 2020 19:12
@lysnikolaou

lysnikolaou commented May 1, 2020 •
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Currently working on support for feature_version and I just realised that there is no assignment to tok->type_comments in _PyPegen_run_parser_from_file_pointer like the one in _PyPegen_run_parser_from_file_pointer. Is this okay or should it be fixed?

@gvanrossum gvanrossum mentioned this pull request May 1, 2020
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gvanrossum commented May 1, 2020

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Oops. Fixing in #19828

@hauntsaninja

hauntsaninja commented May 4, 2020

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This doesn't seem to be able to handle function type comments where there aren't "normal" argument types preceding the *args and **kwargs types. I've opened #19894 with a fix, but it's my first time working with CPython's grammar, so apologies in advance for any crimes against parsers committed.

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Supporting type_comments=True

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