* fix(help): preserve multi-letter CTRL modifiers in :help subject
Problem: After PR 39537 normalized `CTRL-U-default` by excluding
`-` from the trigger char class, the regex `(CTRL%-[^{])([^-_\\])`
also fires between `CTRL-S` and the `H` of the `SHIFT` modifier
in tags like `c_CTRL-SHIFT-V`, splitting it into the non-existent
`c_CTRL-S_HIFT-V`.
Solution: Exclude uppercase letters from the char class so a
multi-letter modifier following `CTRL-X` (e.g. `SHIFT`, `ALT`) is
no longer split. The `-` exclusion from 39537 is preserved so
`i_CTRL-U-default` still works.
* fix(help): escape ~ in expr-=~? exception to keep regex valid
Problem: The `expr-=~?` exception in the tag alias table maps to
`=~?`, but in Vim's regex engine `~` refers to the previous
substitute pattern. With no prior substitute the pattern fails to
compile, so `:help expr-=~?` returns E149 even though the tag exists.
Solution: Escape `~` as \\\~` so the alias expands to a valid
regex (`=\\\~?`) that substring-matches the `expr-=~?` tag. Other
`expr-X?` entries are unaffected since they don't contain `~`.
* fix(help): don't insert _ before CTRL- when preceded by -
Problem: The rule `([^_])CTRL%- -> %1_CTRL-` inserts an underscore
between any non-underscore char and `CTRL-`, which wrongly rewrites
tags like `map-CTRL-C` and `telnet-CTRL-]` (where `CTRL-` is
literal text in the tag, not a key chord).
Solution: Exclude `-` from the trigger char class so a hyphen
immediately before `CTRL-` is preserved. The existing behavior for
`iCTRL-GCTRL-J` -> `i_CTRL-G_CTRL-J` is unaffected because the
`G` before `CTRL-J` is not `-`.
* fix(help): only treat ^X as caret notation for valid control chars
Problem: The regex `%^([^_])` converts any `^X` to `CTRL-X`,
including `:set^=` where `^=` is literal text in the tag, not a
caret-notation control character.
Solution: Restrict the transformation to caret-notation chars
(`%a` or one of `?@[\\]^{}`). This matches the C reference
behavior where `^X` is only converted when X is alphanumeric or one
of the control-notation punctuation chars. `{` is retained so
`^{char}` still maps to the `CTRL-{char}` placeholder tag.
Problem:
The argument to `:help` is normalized to fit the general tag format.
I.e. i^U-default, iCTRL-U-default and i_CTRL_U-default should all point
to the i_CTRL_U-default tag. Our normalization adds an underscore around
the CTRL keycode, e.g. iCTRL-GCTRL-J becomes i_CTRL-G_CTRL-J. That's not
necessary if the following part starts with a dash, like the case of
iCTRL-U-default.
Solution:
Do not insert an underscore if the following character is a dash/minus
(-).
Problem:
`K` in help files may fail in some noisy text. Example:
(`fun(config: vim.lsp.ClientConfig): boolean`)
^cursor
Solution:
- `:help!` (bang, no args) activates DWIM behavior: tries `<cWORD>`,
then trims punctuation until a valid tag is found.
- Set `keywordprg=:help!` by default.
- Does not affect `CTRL-]`, that is still fully "tags" based.
Problem:
Descriptions of plugins often contain taglinks which are generally
concealed. This misaligns them by 2 characters with descriptions that
don't have a taglink in them.
Solution:
Don't count "bar" characters (`|`) for the description width.
Example:
Actual buffer content:
```
myplugin.txt |lsp| is cool
myplugin.txt this is a nice plugin
```
Rendered as:
```
myplugin.txt lsp is cool
myplugin.txt this is a nice plugin
```
Problem:
- ~200 line function of hard-to-maintain C code.
- Local Addition section looks messy because of the varying description
formats.
Solution:
- Move code to Lua.
- Have a best-effort approach where short descriptions are right
aligned, giving a cleaner look. Long descriptions are untouched.
Problem:
Escaping logic for {subject} in ex cmd `:help {subject}` is done in a
messy 200+ lines C function which is hard to maintain and improve.
Solution:
Rewrite in Lua. Use `string.gsub()` instead of looping over characters
to improve clarity and add many more tests to be able to confidently
improve current code later on.
