Fix PHP coverage mu-plugin loading and graceful exit

Author: priethor

.wp-env.json

@@ -5,7 +5,8 @@
     "tests": {
       "mappings": {
         "wp-content/plugins/secure-custom-fields": ".",
-        "wp-content/plugins/scf-test-plugins": "./tests/e2e/plugins"
+        "wp-content/plugins/scf-test-plugins": "./tests/e2e/plugins",
+        "wp-content/mu-plugins/php-coverage-collector.php": "./tests/e2e/mu-plugins/php-coverage-collector.php"
       }
     }
   }

scripts/merge-php-coverage.js

@@ -50,21 +50,23 @@ function parseArgs() {
 /**
  * Read all coverage JSON files from the coverage directory.
  *
- * @return {Array} Array of coverage data objects.
+ * @return {Array|null} Array of coverage data objects, or null if none found.
  */
 function readCoverageFiles() {
 	if ( ! fs.existsSync( COVERAGE_DIR ) ) {
-		console.error( `Coverage directory not found: ${ COVERAGE_DIR }` );
-		process.exit( 1 );
+		console.log( `No PHP coverage directory found: ${ COVERAGE_DIR }` );
+		console.log( 'Skipping PHP coverage report generation.' );
+		return null;
 	}
 
 	const files = fs
 		.readdirSync( COVERAGE_DIR )
 		.filter( ( f ) => f.endsWith( '.json' ) );
 
 	if ( files.length === 0 ) {
-		console.error( 'No coverage files found.' );
-		process.exit( 1 );
+		console.log( 'No PHP coverage files found.' );
+		console.log( 'Skipping PHP coverage report generation.' );
+		return null;
 	}
 
 	console.log( `Found ${ files.length } coverage files.` );
@@ -307,6 +309,12 @@ function main() {
 	console.log( 'Merging PHP coverage files...' );
 
 	const coverageFiles = readCoverageFiles();
+
+	if ( coverageFiles === null ) {
+		// No coverage files found, exit gracefully.
+		return;
+	}
+
 	const merged = mergeCoverage( coverageFiles );
 	const stats = calculateStats( merged );