Inline flags such as (?i) in one -e pattern leak into the other patterns, and indexed and scanned results disagree #182

Summary

When several patterns are given with -e (or -f), an inline flag group such as (?i) or (?-i) at the start of one pattern also applies to the patterns after it. ripgrep scopes inline flags to the pattern they appear in.

The index planner parses each pattern on its own, so it and the matcher disagree: the same query can give different results with and without the index.

Reproduce

mkdir repro && cd repro
printf 'bar\n' > bar.txt
tgrep index .

tgrep            -i -e '(?-i)foo' -e 'BAR' .
tgrep --no-index -i -e '(?-i)foo' -e 'BAR' .
tgrep               -e '(?i)foo'  -e 'BAR' .
tgrep --no-index    -e '(?i)foo'  -e 'BAR' .

• In the first query, (?-i) from foo turns -i off for BAR too, so bar is missed everywhere.
• In the second, (?i) from foo makes BAR match bar during a scan. The index planned BAR case-sensitively and drops the file, so the indexed result differs from the scan.

With -w or -x the queries behave like ripgrep, because each pattern is then wrapped in its own group.

Environment

• tgrep 1.1.0, built from 1120aca (current main) with rustc 1.95.0 (59807616e 2026-04-14)
• Windows 11 Pro (build 28000); the code involved is platform-independent
• The indexed result is the same with a local index and through tgrep serve

Cause

combine_patterns only wraps a pattern in a group for -w/-x. Otherwise it joins the raw patterns as alternatives of one group:

-e '(?i)foo' -e 'BAR' becomes (?:(?i)foo|BAR). In regex syntax a bare flag group applies until the end of the enclosing group, so it reaches BAR too. build_multi_pattern_plan plans each pattern separately, where the flag does not leak.

Possible fix

Wrap every pattern in its own non-capturing group before joining, for example (?:(?i)foo)|(?:BAR), whether or not -w/-x is set. Flags then stay inside their pattern, which is also how the planner already reads them. The fancy-regex path is built from the same combined string, so it would be covered too.

A regression test could compare both queries above across --no-index, a local index and serve.