[ci] In check_todo.sh, permit disabling check (#2839)

* [ci] In check_todo.sh, permit disabling check

Support `TODO-check-disable` and `TODO-check-enable` to toggle the check
within a particular file.

gherrit-pr-id: I0ca32fb0b6e87d3be51ff69487a4f221c0a9ee45

* Apply suggestion from @gemini-code-assist[bot]

Co-authored-by: gemini-code-assist[bot] <176961590+gemini-code-assist[bot]@users.noreply.github.com>

---------

Co-authored-by: gemini-code-assist[bot] <176961590+gemini-code-assist[bot]@users.noreply.github.com>

Author: joshlf

ci/check_todo.sh

@@ -23,12 +23,53 @@ rg --version >/dev/null
 # -H: Print filename (default for multiple files/recursive)
 # -n: Print line number
 # -w: Match whole words
-output=$(rg -H -n -w "$KEYWORD" || true)
-
-if [ -n "$output" ]; then
-  echo "Found $KEYWORD markers in the codebase." >&2
-  echo "$KEYWORD is used for tasks that should be done before merging a PR; if you want to leave a message in the codebase, use FIXME." >&2
-  echo "" >&2
-  echo "$output" >&2
-  exit 1
+# Match TODO, TODO-check-disable, and TODO-check-enable
+output=$(rg -H -n -w "$KEYWORD|$KEYWORD-check-disable|$KEYWORD-check-enable" "$@" || true)
+
+if [ -z "$output" ]; then
+  exit 0
 fi
+
+# Track the disabled state for each file. Since we process lines in order for
+# each file, we can maintain state. However, rg output might interleave files if
+# not sorted, but usually it's grouped. To be safe, we sort the output by
+# filename and line number.
+sorted_output=$(echo "$output" | sort -t: -k1,1 -k2,2n)
+
+exit_code=0
+current_file=""
+disabled=0
+
+while IFS= read -r line; do
+  if [[ "$line" =~ ^(.*):([0-9]+):(.*)$ ]]; then
+    file="${BASH_REMATCH[1]}"
+    content="${BASH_REMATCH[3]}"
+  else
+    echo "Error: could not parse rg output line: $line" >&2
+    exit 1
+  fi
+
+  if [ "$file" != "$current_file" ]; then
+    current_file="$file"
+    disabled=0
+  fi
+
+  if [[ "$content" == *"$KEYWORD-check-disable"* ]]; then
+    disabled=1
+  elif [[ "$content" == *"$KEYWORD-check-enable"* ]]; then
+    disabled=0
+  elif [[ "$content" == *"$KEYWORD"* ]]; then
+    if [ "$disabled" -eq 0 ]; then
+      if [ "$exit_code" -eq 0 ]; then
+        echo "Found $KEYWORD markers in the codebase." >&2
+        echo "$KEYWORD is used for tasks that should be done before merging a PR; if you want to leave a message in the codebase, use FIXME." >&2
+        echo "If you need to allow a $KEYWORD, wrap it in $KEYWORD-check-disable and $KEYWORD-check-enable." >&2
+        echo "" >&2
+        exit_code=1
+      fi
+      echo "$line" >&2
+    fi
+  fi
+done <<< "$sorted_output"
+
+exit $exit_code