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Get mypy itself type-checking cleanly under --strict-optional #1955
Description
One necessary milestone toward making --strict-optional a recommended thing to use; the default; and ultimately the only mode (following what PEP 484 already says) will be for the mypy implementation itself to pass type-checking under --strict-optional. This is a tracking task for that goal.
Activity
gnprice commentedon Jul 29, 2016
As of a version from master yesterday (commit
67d89b9e7from 2016-07-27), this produced 480 error messages (counted withmypy -p mypy --strict-optional 2>&1 | grep -cP '^\S*:\d+: ') and 728 total lines of output. So there's some work to do.I went through these errors to try to sort out which ones are bugs in mypy in its role as the type-checker, either in the
--strict-optionalcode or exposed here by--strict-optional, and which ones are bugs in mypy as a statically-typed Python codebase.Detailed notes here:
https://paper.dropbox.com/doc/Mypy-strict-optional-issues-UQPcKDn5VDdSXQme37o1G
and data here:
https://gist.github.com/gnprice/6d0413f022ca2a17d3d2bb1d4b96fbae
Short summary:
None/Optional-related type errors in a codebase.subprocessstub causes 2 messages.I'll locate or file individual issues for the bugs in mypy-as-type-checker.
I think a lot of the 334 lines of issues in mypy-as-target-codebase will be straightforward to fix, many of them in large swaths, by adding
Optionalin appropriate places andis Nonechecks in others. These often have the effect that addingOptionalin one place causes a new error to show up in another place, so it can be hard to track progress. Probably we should fix the bugs in mypy-as-type-checker first, though, and work around any we don't yet fix, before making a big push to sort out the types.gnprice commentedon Jul 29, 2016
Two of the issues are
Optional[t]#1734 -- one error, easy to work around locallyI think the other issues are as yet unfiled -- I'll start filing them.
gnprice commentedon Jul 29, 2016
Filed also #1956, #1957, and #1958.
The three issues that cause errors in many places are #1956, #1957, #1820.
There are four more issues (in addition to #1734 and #1958) that cause an error in just one place each and probably aren't hard to just work around where they occur. Should definitely be filed and fixed, but I'm going AFK just now -- so as a temporary breadcrumb, here they are by the shorthand titles I gave them in my notes:
ddfisher commentedon Aug 9, 2016
FYI, for counting error messages, instead of piping mypy's output through grep you can use
--suppress-error-context.Last strict optional fixes (#4070)
Last strict optional fixes (#4070)