fix(@angular-devkit/build-angular): avoid CommonJS warnings for relative imports with esbuild builders

When using the esbuild-based browser application builder, CommonJS file warnings were incorrectly being
issued for relative file imports. The CommonJS warnings are only intended to be generated for node module
imports.

Author: clydin

packages/angular_devkit/build_angular/src/builders/browser-esbuild/commonjs-checker.ts

@@ -75,8 +75,11 @@ export function checkCommonJSModules(
         continue;
       }
 
-      // Check if the import is ESM format and issue a diagnostic if the file is not allowed
-      if (metafile.inputs[imported.path].format !== 'esm') {
+      // Check if non-relative import is ESM format and issue a diagnostic if the file is not allowed
+      if (
+        !isPotentialRelative(imported.original) &&
+        metafile.inputs[imported.path].format !== 'esm'
+      ) {
         const request = imported.original;
 
         let notAllowed = true;
@@ -119,6 +122,23 @@ function isPathCode(name: string): boolean {
   return /\.[cm]?[jt]sx?$/.test(name);
 }
 
+/**
+ * Test an import module specifier to determine if the string potentially references a relative file.
+ * npm packages should not start with a period so if the first character is a period than it is not a
+ * package. While this is sufficient for the use case in the CommmonJS checker, only checking the
+ * first character does not definitely indicate the specifier is a relative path.
+ *
+ * @param specifier An import module specifier.
+ * @returns True, if specifier is potentially relative; false, otherwise.
+ */
+function isPotentialRelative(specifier: string): boolean {
+  if (specifier[0] === '.') {
+    return true;
+  }
+
+  return false;
+}
+
 /**
  * Creates an esbuild diagnostic message for a given non-ESM module request.
  *

packages/angular_devkit/build_angular/src/builders/browser-esbuild/tests/options/allowed-common-js-dependencies_spec.ts

@@ -159,5 +159,25 @@ describeBuilder(buildEsbuildBrowser, BROWSER_BUILDER_INFO, (harness) => {
         }),
       );
     });
+
+    it('should not show warning for relative imports', async () => {
+      await harness.appendToFile('src/main.ts', `import './abc';`);
+      await harness.writeFile('src/abc.ts', 'console.log("abc");');
+
+      harness.useTarget('build', {
+        ...BASE_OPTIONS,
+        allowedCommonJsDependencies: [],
+        optimization: true,
+      });
+
+      const { result, logs } = await harness.executeOnce();
+
+      expect(result?.success).toBe(true);
+      expect(logs).not.toContain(
+        jasmine.objectContaining<logging.LogEntry>({
+          message: jasmine.stringMatching(/CommonJS or AMD dependencies/),
+        }),
+      );
+    });
   });
 });