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Diffstat (limited to 'docs')
| -rw-r--r-- | docs/mvzr-group-backtrack.md | 22 |
1 files changed, 22 insertions, 0 deletions
diff --git a/docs/mvzr-group-backtrack.md b/docs/mvzr-group-backtrack.md index d074af62..867336a3 100644 --- a/docs/mvzr-group-backtrack.md +++ b/docs/mvzr-group-backtrack.md @@ -62,3 +62,25 @@ string end at `e`, so a group ending in either can accept a cut the full string would not; a continuation-passing matcher (each repeat trying the rest of the whole pattern) would be the full fix. `hasAlt` returning false at the group's own `)` is worth fixing too. + +# mvzr: `$` before `|` is a bad pattern + +A second report, same trunk. `compile` refuses `$` anywhere but at the +very end of the pattern, so an anchored alternative must come last: + +```zig +std.debug.assert(mvzr.compile("zz|h$") != null); +std.debug.assert(mvzr.compile("h$|zz") == null); // expected a regex +std.debug.assert(mvzr.compile("(h$|zz)") == null); // likewise +``` + +The parser's check is `if (i + 1 < in.len) bad_string = true`. The +matcher already handles `.end` inside an alternative: `matchAlt` and +`matchGroup` hand `matchPattern` each alternative as its own slice, and +`.end` returns an empty rest, which ends that slice. So `$` can stand +before `|` or `)` as well as last; pardes's patch: + +```zig +'$' => { + if (i + 1 < in.len and in[i + 1] != '|' and in[i + 1] != ')') { +``` |