Update API Docs: default package source file can have TS extension

bin/api-docs/update-api-docs.js

@@ -43,13 +43,6 @@ const DATA_DOCS_DIR = resolve(
 	'docs/designers-developers/developers/data'
 );
 
-/**
- * Default path to use if the token doesn't include one.
- *
- * @see TOKEN_PATTERN
- */
-const DEFAULT_PATH = 'src/index.js';
-
 /**
  * Pattern matching start token of a README file.
  *
@@ -64,7 +57,6 @@ const DEFAULT_PATH = 'src/index.js';
  * <!-- END TOKEN(Autogenerated actions|src/actions.js) -->
  *
  * @type {RegExp}
- * @see DEFAULT_PATH
  */
 const TOKEN_PATTERN = /<!-- START TOKEN\((.+?(?:\|(.+?))?)\) -->/g;
 
@@ -169,7 +161,7 @@ const filterTokenTransform = new Transform( {
 			const tokens = [];
 
 			for ( const match of content.matchAll( TOKEN_PATTERN ) ) {
-				const [ , token, path = DEFAULT_PATH ] = match;
+				const [ , token, path ] = match;
 				tokens.push( [ token, path ] );
 			}
 
@@ -182,6 +174,23 @@ const filterTokenTransform = new Transform( {
 	},
 } );
 
+/**
+ * Find default source file (`src/index.{js,ts,tsx}`) in a specified package directory
+ *
+ * @param {string} dir Package directory to search in
+ * @return {string} Name of matching file
+ */
+function findDefaultSourcePath( dir ) {
+	const defaultPathMatches = glob.sync( 'src/index.{js,ts,tsx}', {
+		cwd: dir,
+	} );
+	if ( ! defaultPathMatches.length ) {
+		throw new Error( `Cannot find default source file in ${ dir }` );
+	}
+	// @ts-ignore
+	return defaultPathMatches[ 0 ];
+}
+
 /**
  * Optional process arguments for which to generate documentation.
  *
@@ -202,8 +211,11 @@ glob.stream( [
 		// represented by tokens. The docgen script updates one token at a time,
 		// so the tokens must be replaced in sequence to prevent the processes
 		// from overriding each other.
-		for ( const [ token, path ] of tokens ) {
-			try {
+		try {
+			for ( const [
+				token,
+				path = findDefaultSourcePath( dirname( file ) ),
+			] of tokens ) {
 				await execa(
 					`"${ join(
 						__dirname,
@@ -222,9 +234,9 @@ glob.stream( [
 					],
 					{ shell: true }
 				);
-			} catch ( error ) {
-				console.error( error );
-				process.exit( 1 );
 			}
+		} catch ( error ) {
+			console.error( error );
+			process.exit( 1 );
 		}
 	} );