CS/check thresholds: require exact match for thresholds

This changes the implementation of the coding standards threshold check to require that both the `YOASTCS_THRESHOLD_ERRORS` environment variable, as well as the `YOASTCS_THRESHOLD_WARNINGS` environment variable match the current status exactly.

This prevents PR A fixing some issues and forgetting to update the threshold, which then would allow PR B to introduce new issues.

.github/workflows/cs.yml

@@ -109,15 +109,23 @@ jobs:
           custom-cache-suffix: $(date -u "+%Y-%m")
 
       # Check the codestyle of the files against a threshold of expected errors and warnings.
+      # Keep track of the exit code as it determines whether to run the branch check or not.
+      # Exit code 128 means the thresholds needs to be lowered. Other exit codes imply CS errors.
       - name: Check PHP code style against the thresholds
-        run: composer check-cs-thresholds
+        id: thresholds
+        run: |
+          set +e
+          composer check-cs-thresholds
+          exitcode="$?"
+          echo "EXITCODE=$exitcode" >> $GITHUB_OUTPUT
+          exit "$exitcode"
 
       # Check the codestyle only of the files which were changed in the current branch.
       # This step will only be executed if the threshold check exited with a failure status.
       # The results of this CS check will be shown inline in the PR via the CS2PR tool.
       # @link https://github.com/staabm/annotate-pull-request-from-checkstyle/
       - name: Check PHP code style for the changes made in the branch only
-        if: ${{ failure() }}
+        if: ${{ failure() && steps.thresholds.outputs.EXITCODE != 128 }}
         id: phpcs
         run: composer check-branch-cs -- ${{ steps.base_branch.outputs.REF }}
 

config/composer/actions.php

@@ -153,6 +153,11 @@ public static function check_cs_thresholds() {
 			$above_threshold = false;
 		}
 
+		$threshold_exact = true;
+		if ( \strpos( $phpcs_output, ' than the threshold, great job!' ) !== false ) {
+			$threshold_exact = false;
+		}
+
 		/*
 		 * Don't run the branch check in CI/GH Actions as it prevents the errors from being shown inline.
 		 * The GH Actions script will run this via a separate script step.
@@ -167,7 +172,15 @@ public static function check_cs_thresholds() {
 			@\passthru( 'composer check-branch-cs' );
 		}
 
-		exit( ( $above_threshold === true || $return > 2 ) ? $return : 0 );
+		$exit_code = 0;
+		if ( $above_threshold === true || $return > 2 ) {
+			$exit_code = $return;
+		}
+		elseif ( $threshold_exact === false ) {
+			$exit_code = 128;
+		}
+
+		exit( $exit_code );
 	}
 
 	/**