[issue32509] doctest syntax ambiguity between continuation line and ellipsis

[Steven D'Aprano]

Steven D'Aprano <steve+python at pearwood.info> added the comment:

Tim Peters said:
> Right, "..." immediately after a ">>>" line is taken to indicate a code continuation line, and there's no way to stop that short of rewriting the parser.


I haven't gone through the source in detail, but it seems to me that we could change OutputChecker.check_output to support this without touching the parser.

Ignoring issues of backwards compatibility for the moment, suppose we accept either '...' or '<ELLIPSIS>' as the wild card in the output section. Jason's example would then become:

	>>> print(res)  # docstring: +ELLIPSIS
	<ELLIPSIS>
	d41d8cd98f00b204e9800998ecf8427e __init__.py
	...

check_output could replace the substring '<ELLIPSIS>' with three dots before doing anything else, and Bob's yer uncle.

Or in this case, Uncle Timmy's yer uncle :-)

There's probably a million details I haven't thought of, but it seems like a promising approach to me. I did a quick hack of doctest, adding

    want = want.replace('<ELLIPSIS>', '...')

to the start of OutputChecker.check_output and it seems to work.

If this is acceptable, we'll probably need a directive to activate it, for the sake of backwards compatibility.

Thoughts?

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