Syntax error output if a field is named 'from'

[gaggle]

This tool generates .pyi files with syntax error when parsing a proto-file with a field named from. E.g. foo.proto:

message FooRequest {
	int64 from = 5;
}

Running mypy on a project with this kind of autogenerated files results in syntax error:

$ mypy
package/schemas/foo_pb2.pyi:356: error: invalid syntax

This is because the foo_pb2.pyi file has this in it:

class FooRequest(google___protobuf___message___Message):
    from = ... # type: int

The from = ... is invalid syntax, and so we have a problem.

Just to say I've set up my mypy to ignore these files, mypy.ini:

[mypy]

[mypy-package.schemas.*]
ignore_errors = True

But this doesn't ignore syntax errors. As per python/mypy#6897 mypy can't ignore syntax errors. It would be favorable if this project did not generate syntax-invalid output.

I'm using versions:

$ python --version Python 3.6.7
mypy==0.701
mypy-protobuf==1.10

And here is a gist with the entire contents of the .proto file, the generated .py file (which does not have syntax errors and the problematic and unexcludable .pyi file:
https://gist.github.com/gaggle/8aef6102d314936c9eb33724194682b0

[nipunn1313]

Great bugreport! Thanks.

I don't know offhand how we're supposed to type a variable with a reserved keyword name. Will look into it w/ mypy docs / folks. Thanks for reporting!

[gvanrossum]

It looks like the .py file generator sidesteps the issue by not generating Python code but some meta thing. So at runtime you'd have to write getattr(thing, 'from'). (And add # noqa :-)

Since there can't be any code that writes thing.from, maybe the simplest thing would be to just not emit the field at all? Or perhaps emit it with a # in front of it?

[ikonst]

I'd not emit them. See also https://developers.google.com/protocol-buffers/docs/reference/python-generated#keyword-conflicts