[qodelicious]

A pattern with no regex characters goes to the literal matcher. It drops the backslashes first and then looks for ^ and $, so an escaped \^ or \$ turns into an anchor.

$ echo 'a^b$c' | ./target/debug/sed -e 's/\^/X/' -e 's/\$/Y/'
Xa^b$cY
$ echo 'a^b$c' | /usr/bin/sed -e 's/\^/X/' -e 's/\$/Y/'    # GNU sed 4.9
aXbYc

Same thing with -E, and s/^a\$/X/ matched a plain a line as if it were ^a$.

LiteralMatcher::new now takes the raw pattern, picks the anchors off it, and only then removes the escapes. A trailing $ counts as an anchor only when an even number of backslashes comes before it, so b\\$ still means b\ at the end of the line.

Test test_escaped_anchors_in_literal_pattern checks BRE and ERE cases against GNU sed 4.9. It fails on main and passes with the change.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 95.09%. Comparing base (786c87f) to head (f93957b).
⚠️ Report is 3 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #638      +/-   ##
==========================================
+ Coverage   95.07%   95.09%   +0.01%     
==========================================
  Files          14       14              
  Lines        7436     7483      +47     
  Branches      439      440       +1     
==========================================
+ Hits         7070     7116      +46     
- Misses        365      366       +1     
  Partials        1        1              

Flag	Coverage Δ
macos_latest	96.58% <100.00%> (+<0.01%)	⬆️
ubuntu_latest	96.52% <100.00%> (+<0.01%)	⬆️
windows_latest	0.00% <0.00%> (ø)

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[sylvestre]

could you please run the GNU testsuite to check that nothing regresses?
setup: git clone https://github.com/mirror/sed.git ../gnu.sed
run: ./util/run-gnu-testsuite.sh

[qodelicious]

Ran it with ./util/run-gnu-testsuite.sh on main and on this branch and got identical results for every test, so nothing regresses. The GNU testsuite job on the PR also says no new failures vs main.

[sylvestre]

please add a few LiteralMatcher::new unit tests too (\^a, a\$, ^\^, a\\$) :)

[qodelicious]

Added one for each of those, \^a, a\$, ^\^ and a\\$, checking both what matches and where.