chore: re-enable console output in tests

packages/aws-cdk-lib/jest.config.js

@@ -19,4 +19,6 @@ module.exports = {
       statements: 55,
     },
   },
+
+  testEnvironment: './testhelpers/jest-bufferedconsole.ts',
 };

packages/aws-cdk-lib/package.json

@@ -176,6 +176,7 @@
     "fast-check": "^3.22.0",
     "jest": "^29.7.0",
     "jest-each": "^29.7.0",
+    "jest-environment-node": "^29.7.0",
     "lambda-tester": "^4.0.1",
     "lodash": "^4.17.21",
     "nock": "^13.5.5",

packages/aws-cdk-lib/testhelpers/jest-bufferedconsole.ts

@@ -0,0 +1,75 @@
+/* eslint-disable import/no-extraneous-dependencies */
+/**
+ * A Jest environment that buffers outputs to `console.log()` and only shows it for failing tests.
+ */
+import type { EnvironmentContext, JestEnvironment, JestEnvironmentConfig } from '@jest/environment';
+import { Circus } from '@jest/types';
+import { TestEnvironment as NodeEnvironment } from 'jest-environment-node';
+
+interface ConsoleMessage {
+  type: 'log' | 'error' | 'warn' | 'info' | 'debug';
+  message: string;
+}
+
+export default class TestEnvironment extends NodeEnvironment implements JestEnvironment<unknown> {
+  private log = new Array<ConsoleMessage>();
+  private originalConsole!: typeof console;
+
+  constructor(config: JestEnvironmentConfig, context: EnvironmentContext) {
+    super(config, context);
+
+    // We need to set the event handler by assignment in the constructor,
+    // because if we declare it as an async member TypeScript's type derivation
+    // doesn't work properly.
+    (this as JestEnvironment<unknown>).handleTestEvent = (async (event, _state) => {
+      if (event.name === 'test_done' && event.test.errors.length > 0 && this.log.length > 0) {
+        this.originalConsole.log(`[Console output] ${fullTestName(event.test)}\n`);
+        for (const item of this.log) {
+          this.originalConsole[item.type]('    ' + item.message);
+        }
+        this.originalConsole.log('\n');
+      }
+
+      if (event.name === 'test_done') {
+        this.log = [];
+      }
+    }) satisfies Circus.EventHandler;
+  }
+
+  async setup() {
+    await super.setup();
+
+    this.log = [];
+    this.originalConsole = console;
+
+    this.global.console = {
+      ...console,
+      log: (message) => this.log.push({ type: 'log', message }),
+      error: (message) => this.log.push({ type: 'error', message }),
+      warn: (message) => this.log.push({ type: 'warn', message }),
+      info: (message) => this.log.push({ type: 'info', message }),
+      debug: (message) => this.log.push({ type: 'debug', message }),
+    };
+  }
+
+  async teardown() {
+    this.global.console = this.originalConsole;
+    await super.teardown();
+  }
+}
+
+// DescribeBlock is not exported from `@jest/types`, so we need to build the parts we are interested in
+type TestDescription = PartialBy<Pick<Circus.TestEntry, 'name' | 'parent'>, 'parent'>;
+
+// Utility type to make specific fields optional
+type PartialBy<T, K extends keyof T> = Omit<T, K> & Partial<Pick<T, K>>
+
+function fullTestName(test: TestDescription) {
+  let ret = test.name;
+  while (test.parent != null && test.parent.name !== 'ROOT_DESCRIBE_BLOCK') {
+    ret = test.parent.name + ' › ' + fullTestName;
+    test = test.parent;
+  }
+  return ret;
+}
+

tools/@aws-cdk/cdk-build-tools/config/jest.config.js

@@ -35,10 +35,4 @@ module.exports = {
   ],
   coveragePathIgnorePatterns: ['\\.generated\\.[jt]s$', '<rootDir>/test/', '.warnings.jsii.js$', '/node_modules/'],
   reporters: ['default', ['jest-junit', { suiteName: 'jest tests', outputDirectory: 'coverage' }]],
-  /**
-   * This will still show us helpful information when running tests but remove console statements.
-   * The exception is when we use our custom logger in the CLI or when other processes are spun up
-   * within tests. It has no impact there.
-   */
-  silent: true,
 };