Parse JS dependencies correctly

To correctly parse JS dependencies, we need to:
1. Pass a long enough directory path so that
   enhanced-resolve can find the root node_modules
2. Pass the webpack config

packages/dependency-finder/src/lib/entrypoints/additional.ts

@@ -2,11 +2,12 @@
  * External dependencies
  */
 import globby from 'globby';
+import { resolve } from 'path';
 
 export const findAdditionalEntryPoints = async (
 	additionalEntryPoints: string[]
 ): Promise< string[] > => {
-	return (
-		await Promise.all( additionalEntryPoints.map( ( pattern ) => globby( pattern ) ) )
-	 ).flat();
+	return ( await Promise.all( additionalEntryPoints.map( ( pattern ) => globby( pattern ) ) ) )
+		.flat()
+		.map( ( entry ) => resolve( entry ) );
 };

packages/dependency-finder/src/lib/find-dependencies.ts

@@ -57,6 +57,17 @@ export const findDependencies = async ( {
 		}
 	} )();
 
+	const webpackConfig = ( () => {
+		try {
+			const webpackPath = path.join( pkg, 'webpack.config.js' );
+			fs.accessSync( webpackPath );
+			modules.add( webpackPath );
+			return webpackPath;
+		} catch {
+			return null;
+		}
+	} )();
+
 	const absoluteAdditionalEntryPoints = await findAdditionalEntryPoints( additionalEntryPoints );
 
 	// Handles monorepo and npm results from parsed files.
@@ -77,10 +88,13 @@ export const findDependencies = async ( {
 		return true;
 	};
 
+	// Entrypoints need to be absolute paths at this point so that the webpack resolver
+	// knows to parse up the filesystem further. (Otherwise, it stops short before reaching the root node_modules.)
 	for ( const entrypoint of [ ...entrypoints, ...jestTests, ...absoluteAdditionalEntryPoints ] ) {
 		const tree = dependencyTree.toList( {
 			filename: entrypoint,
 			directory: path.dirname( entrypoint ),
+			webpackConfig: webpackConfig ?? undefined,
 			tsConfig: tsConfig ?? undefined,
 			visited,
 			filter: fileFilter,