fix(compiler-cli): do not lower expressions in non-modules (#21649)

Fixes: #21651

PR Close #21649

packages/compiler-cli/src/transformers/lower_expressions.ts

@@ -325,13 +325,14 @@ export class LowerMetadataCache implements RequestsMap {
     };
 
     // Do not validate or lower metadata in a declaration file. Declaration files are requested
-    // when we need to update the version of the metadata to add informatoin that might be missing
+    // when we need to update the version of the metadata to add information that might be missing
     // in the out-of-date version that can be recovered from the .d.ts file.
     const declarationFile = sourceFile.isDeclarationFile;
+    const moduleFile = ts.isExternalModule(sourceFile);
 
     const metadata = this.collector.getMetadata(
         sourceFile, this.strict && !declarationFile,
-        declarationFile ? undefined : substituteExpression);
+        moduleFile && !declarationFile ? substituteExpression : undefined);
 
     return {metadata, requests};
   }

packages/compiler-cli/test/transformers/lower_expressions_spec.ts

@@ -99,7 +99,17 @@ describe('Expression lowering', () => {
           .toBeTruthy('did not find the data field');
     });
 
-    it('should throw a validation execption for invalid files', () => {
+    it('should not lower a non-module', () => {
+      const collected = collect(`
+          declare const global: any;
+          const ngDevMode: boolean = (function(global: any) {
+            return global.ngDevMode = true;
+          })(typeof window != 'undefined' && window || typeof self != 'undefined' && self || typeof global != 'undefined' && global);
+       `);
+      expect(collected.requests.size).toBe(0, 'unexpected rewriting');
+    });
+
+    it('should throw a validation exception for invalid files', () => {
       const cache = new LowerMetadataCache({}, /* strict */ true);
       const sourceFile = ts.createSourceFile(
           'foo.ts', `