feat: support shell-style # comments#182
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Recognize `#` as a comment delimiter at word boundaries (start of a line/command or following whitespace or a metacharacter), matching POSIX shell behavior. Everything from the `#` to the end of the line is ignored. A `#` in the middle of a word (`foo#bar`) or inside quotes (`'# x'`, `"# x"`) remains a literal character. Closes denoland/deno#27644
dsherret
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Jun 4, 2026
| loop { | ||
| let (rest, _) = skip_whitespace(current)?; | ||
| let rest = skip_comment(rest); | ||
| if rest == current { |
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Nitpick: This could instead do rest.len() == current.len() for a faster comparison
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Good call — switched to a length comparison in 7323235.
The `or(tag(">"), tag(">|"))` ordering let `>` match the prefix of
`>|`, leaving the `|` to be misparsed as a pipe. Try `>|` first so the
clobber operator parses as an overwrite redirect (noclobber is not
modeled, so `>|` behaves identically to `>`).
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Implements shell-style
#comments in task commands, requested indenoland/deno#27644. Previously a command like
echo foo # commentexecuted the entire string literally instead of stopping at
#.A
#now begins a comment wherever a shell would recognize one: at thestart of a line or command, or following whitespace or a metacharacter.
Everything from the
#to the end of the line is ignored. A#in themiddle of a word (
foo#bar) or inside single/double quotes ('# x',"# x") stays a literal character, so existing commands are unaffected.The implementation keeps comment handling at the parser's existing word
boundaries.
skip_inline_whitespacenow also consumes a trailing#-comment up to the next newline, and a new comment-awareskip_whitespace_and_commentsreplaces the plain whitespace skip at theremaining boundary positions: the start of a sequential list, after a
newline separator, after
&&/||, after|/|&, and at the start of asubshell. This covers trailing comments, whole comment lines interspersed
with commands, and comments following operator continuations and inside
subshells.
Note the
\#"Unsupported reserved word" error mentioned in the issue nolonger applies, since real comment support removes the need to escape
#.While adding comment support surfaced two adjacent redirect-parsing bugs,
both are fixed here:
echo foo >,cat <, ora comment beginning right after the operator as in
echo foo > #c) nowfails with
Expected redirect path.instead of silently producing aredirect with an empty target word that only errored later at runtime.
>|(clobber) now parses. Theor(tag(">"), tag(">|"))ordering let>match the prefix first, leaving the|to be misparsed as a pipe;>|is now tried first and, since noclobber is not modeled, behavesidentically to
>.Tests are added at both layers: parser unit tests asserting the parsed
AST for each case (comments, the missing-path error, and
>|), and anintegration test verifying end-to-end stdout for the comment cases.