[jackielii]

Problem

camelToKebab lowercased every rune with r | 0x20, which is only correct for ASCII capitals:

Name	Id before	Id now
Row_Edit	row\x7f-edit (DEL control character)	row-edit
row_edit	row\x7fedit	row-edit
Größe	gröÿe	größe
pageÜber	pageüber	page-über
ui-Kit (an import path element)	ui--kit	ui-kit

It also compared bytes rather than runes around multi-byte letters. These strings end up in every generated id (ID, IDTarget, and the htmx selectors' name matching), so a page field or component method named with an underscore got an id containing a control character.

Fix

• Runes and Unicode case: walk runes, lowercase with unicode.ToLower, and find word starts with unicode.IsUpper/IsLower.
• Separators: underscores and hyphens separate words. The result never starts or ends with a hyphen and never holds two in a row. That also covers a function's hyphenated package path element, so a generated id can't contain the -- that jackielii/structpages#41 uses as the keyed-id separator.

Compatibility

• Unchanged: ids of names made of ASCII letters and digits. A test checks this against the old function over 100,000 random names.
• Changed: names with underscores or non-ASCII letters. Latin-1 capitals happened to come out right before, so the difference shows outside that range and in where words split (pageÜber). A function's package path element also changes if it has leading, trailing or doubled hyphens, or a hyphen before a capital.
• Collisions: two names that now kebab-case alike in one tree (RowEdit and Row_Edit) are reported by Mount's existing id uniqueness check. There's a test for it.

Testing

• Root suite: passes. New tests in case_folding_test.go:
  • underscores, hyphens and non-ASCII cases;
  • the ASCII-unchanged comparison;
  • an end-to-end Row_Edit id selected by HTMXRenderTarget;
  • the Mount collision error.
• Performance: about 15 ns slower per call for a short name, with the same single allocation.

Interaction with #41

Rebased onto main after jackielii/structpages#41 merged. #41's idSegment, which collapsed hyphen runs after camelToKebab, is now the same as camelToKebab, so this PR removes it. Its test cases moved to case_folding_test.go.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 96.09%. Comparing base (e26ca64) to head (8562fb1).

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #42      +/-   ##
==========================================
+ Coverage   95.72%   96.09%   +0.37%     
==========================================
  Files          20       20              
  Lines        1870     1869       -1     
==========================================
+ Hits         1790     1796       +6     
+ Misses         48       43       -5     
+ Partials       32       30       -2     

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