powershell: escape all five single-quote characters

[dylanpulver]

PowerShell closes a verbatim string literal on any of five characters — U+0027, U+2018, U+2019, U+201A and U+201B (Language Specification 3.0, §2.3.5.1.1 single-quote-character). _powershell_escape doubles only the first three, so help text, an option string or a command name containing U+201A or U+201B emits a script PowerShell cannot parse.

U+201A is the ordinary opening single quote in German, Czech, Slovak, Polish and Hungarian typography, so this is reachable from plain help= text.

Measured with pwsh 7.6.5, parsing the output of shtab.complete(parser, "powershell") via [Parser]::ParseFile — same script, same binary, before and after:

help text contains       before          after
U+0027  it's fine        0 errors        0 errors
U+2018  a 'quoted' word  0 errors        0 errors
U+201A  German ,quoted'  5 errors        0 errors   <- Unexpected token ... in expression or statement
U+201B  odd 'quoted'     5 errors        0 errors
no quote characters      0 errors        0 errors

Doubling is the right remedy for all five, not just a workaround: 'x<C><C>y' evaluates to x<C>y with the original codepoint preserved, confirmed in pwsh for each of the five (8218 and 8219 come back intact).

How this was found: not from a bug report — a systematic pass over escaping/quoting tables in CLI tooling, checking each against the grammar it claims to implement. This one is a hand-written character set with no test covering it, so a character the grammar lists and the set omits cannot fail anything.

_powershell_escape currently has no test at all; the new one is parametrized over all five characters so the set can't silently fall behind again.

Verified: pytest tests/, pwsh on PATH for every run — 100 passed / 56 skipped before, 105 passed / 56 skipped after (the 5 new parametrized cases). Reverting only shtab/__init__.py and keeping the test: 2 failed / 103 passed / 56 skipped. Two naive alternatives also fail it — normalising all five to an ASCII apostrophe (4 failed; it parses but corrupts the text) and adding only U+201A (1 failed). pre-commit run on both changed files: all 22 hooks pass.

Not tested: only pwsh 7.6.5 on macOS/arm64. Windows PowerShell 5.1 was not available to me; the grammar is the same but I did not confirm it there.

AI assistance: this change was written with Claude Code (model Claude Opus 5). I reviewed the diff and ran everything reported above.

[casperdcl]

Thanks!

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 87.83%. Comparing base (2c51f5e) to head (0d60059).

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #258   +/-   ##
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  Coverage   87.83%   87.83%           
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  Files           4        4           
  Lines         666      666           
  Branches      138      138           
=======================================
  Hits          585      585           
  Misses         43       43           
  Partials       38       38           

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