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Hacking on zsh-syntax-highlighting itself

This document includes information for people working on z-sy-h itself: on the core driver (zsh-syntax-highlighting.zsh), on the highlighters in the distribution, and on the test suite. It does not target third-party highlighter authors (although they may find it an interesting read).

The `main` highlighter

The following function pz is useful when working on the main highlighting:

pq() {
  (( $#argv )) || return 0
  print -r -l -- ${(qqqq)argv}
}
pz() {
  local arg
  for arg; do
    pq ${(z)arg}
  done
}

It prints, for each argument, its token breakdown, similar to how the main loop of the main highlighter sees it.

Testing the `brackets` highlighter

Since the test harness empties ZSH_HIGHLIGHT_STYLES and the brackets highlighter interrogates ZSH_HIGHLIGHT_STYLES to determine how to highlight, tests must set the bracket-level-# keys themselves. For example:

ZSH_HIGHLIGHT_STYLES[bracket-level-1]=
ZSH_HIGHLIGHT_STYLES[bracket-level-2]=

BUFFER='echo ({x})'

expected_region_highlight=(
  "6  6  bracket-level-1" # (
  "7  7  bracket-level-2" # {
  "9  9  bracket-level-2" # }
  "10 10 bracket-level-1" # )
)

Testing the `pattern` and `regexp` highlighters

Because the pattern and regexp highlighters modifies region_highlight directly instead of using _zsh_highlight_add_highlight, the test harness cannot get the ZSH_HIGHLIGHT_STYLES keys. Therefore, when writing tests, use the style itself as third word (cf. the documentation for expected_region_highlight). For example:

ZSH_HIGHLIGHT_PATTERNS+=('rm -rf *' 'fg=white,bold,bg=red')

BUFFER='rm -rf /'

expected_region_highlight=(
  "1 8 fg=white,bold,bg=red" # rm -rf /
)

Memos and commas

We append to region_highlight as follows:

region_highlight+=("$start $end $spec, memo=zsh-syntax-highlighting")

That comma is required to cause zsh 5.8 and older to ignore the memo without ignoring the $spec. It's a hack, but given that no further 5.8.x patch releases are planned, it's been deemed acceptable. See issue #418 and the cross-referenced issues.

Miscellany

If you work on the driver (zsh-syntax-highlighting.zsh), you may find the following zstyle useful:

zstyle ':completion:*:*:*:*:globbed-files' ignored-patterns {'*/',}zsh-syntax-highlighting.plugin.zsh

IRC channel

We're on #zsh-syntax-highlighting on Libera.Chat.

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