test(compiler-cli): log unexpected compilation errors in compliance test runner (#39862)

If the testcase has not specified that errors were expected, then any
errors that have occurred should be reported. These errors may have
prevented an output file from being generated, which resulted in hard
to debug test failures due to missing files.

PR Close #39862

packages/compiler-cli/test/compliance/test_helpers/check_errors.ts

@@ -22,3 +22,11 @@ export function checkErrors(
     }
   }
 }
+
+export function checkNoUnexpectedErrors(testPath: string, actualErrors: string[]): void {
+  if (actualErrors.length > 0) {
+    throw new Error(
+        `Unexpected errors occurred for test case at "${testPath}"\n` +
+        `Errors: ${inspect(actualErrors)}.`);
+  }
+}

packages/compiler-cli/test/compliance/test_helpers/test_runner.ts

@@ -9,7 +9,7 @@ import {FileSystem} from '../../../src/ngtsc/file_system';
 import {checkExpectations} from '../test_helpers/check_expectations';
 import {CompileResult, initMockTestFileSystem} from '../test_helpers/compile_test';
 import {ComplianceTest, getAllComplianceTests} from '../test_helpers/get_compliance_tests';
-import {checkErrors} from './check_errors';
+import {checkErrors, checkNoUnexpectedErrors} from './check_errors';
 
 /**
  * Set up jasmine specs for each of the compliance tests.
@@ -46,6 +46,7 @@ export function runTests(
                   test.relativePath, expectation.failureMessage, expectation.expectedErrors,
                   errors);
             } else {
+              checkNoUnexpectedErrors(test.relativePath, errors);
               checkExpectations(
                   fs, test.relativePath, expectation.failureMessage, expectation.files,
                   expectation.extraChecks);