[7.0.0] Only escape standard BRE metacharacters when preparing grep p…

…attern. (#20118)

POSIX specifies1 that grep shall by default interpret patterns as Basic
Regular Expressions2. BREs only have six metacharacters: .[\*^$; all
other characters are interpreted literally. Escaping non-metacharacter
characters (ordinary characters) either has the effect of turning them
into metacharacters3, or the interpretation is left undefined by the
spec.

Because of the potential for unintended interpretations and behaviours,
escaping these ordinary characters before using them in a BRE is
undesirable. Unintended behaviours may range from benign (e.g. warnings
about the invalid escapes) to broken (not matching entries we did intend
and/or matching entries we did not intend).

Punctuation characters incorrectly escaped by the prior implementation
can come from a few different places:

The ~ used by Bzlmod to manage hierarchies.
From the path to the workspace root - caller path may be absolute.
From paths within the workspace - punctuation characters accepted by
Bazel4 for package and target names but are ordinary characters in BREs
include !%@"#&'()-+,;<=>?]{|}~.
A small demonstration of this unnecessary escaping is available at:
https://github.com/plobsing/bzlmod-bash-runfiles-grep-warning-demo/tree/main

In the example, the unnecessary escaping is reported when the script
runs the rlocation function:

grep: warning: stray \ before ~
grep: warning: stray \ before @
Closes #20066.
Commit
8c70d7b

PiperOrigin-RevId: 580820470
Change-Id: I57218d629cc771a00f05c2da06e97fb0b2ca18fd

Co-authored-by: Peter Lobsinger <plobsing@gmail.com>

tools/bash/runfiles/runfiles.bash

@@ -246,7 +246,7 @@ function runfiles_current_repository() {
     # Escape $caller_path for use in the grep regex below. Also replace \ with / since the manifest
     # uses / as the path separator even on Windows.
     local -r normalized_caller_path="$(echo "$caller_path" | sed 's|\\\\*|/|g')"
-    local -r escaped_caller_path="$(echo "$normalized_caller_path" | sed 's/[^-A-Za-z0-9_/]/\\&/g')"
+    local -r escaped_caller_path="$(echo "$normalized_caller_path" | sed 's/[.[\*^$]/\\&/g')"
     rlocation_path=$(__runfiles_maybe_grep -m1 "^[^ ]* ${escaped_caller_path}$" "${RUNFILES_MANIFEST_FILE}" | cut -d ' ' -f 1)
     if [[ -z "$rlocation_path" ]]; then
       if [[ "${RUNFILES_LIB_DEBUG:-}" == 1 ]]; then