Add environment variables to print Fantom output and buck commands (#48440)

Summary:
Pull Request resolved: https://github.com/facebook/react-native/pull/48440

Changelog: [internal]

Modifies the Fantom runner to read 2 new environment variables to help with debugging:
- `FANTOM_PRINT_OUTPUT`: prints the output of the CLI to the output of the test.
- `FANTOM_LOG_COMMANDS`: logs the buck commands executed by the runner, so they can be re-run outside the runner for debugging, etc.

Reviewed By: rshest

Differential Revision: D67682750

fbshipit-source-id: aff48c4f47078db1be53e0ee105089fbc921768f

packages/react-native-fantom/runner/EnvironmentOptions.js

@@ -0,0 +1,14 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @flow strict
+ * @format
+ * @oncall react_native
+ */
+
+export const printCLIOutput: boolean = Boolean(process.env.FANTOM_PRINT_OUTPUT);
+
+export const logCommands: boolean = Boolean(process.env.FANTOM_LOG_COMMANDS);

packages/react-native-fantom/runner/runner.js

@@ -13,6 +13,7 @@ import type {TestSuiteResult} from '../runtime/setup';
 import type {AsyncCommandResult} from './utils';
 
 import entrypointTemplate from './entrypoint-template';
+import * as EnvironmentOptions from './EnvironmentOptions';
 import getFantomTestConfig from './getFantomTestConfig';
 import {FantomTestConfigMode} from './getFantomTestConfig';
 import {
@@ -43,8 +44,6 @@ const BUILD_OUTPUT_PATH = fs.mkdtempSync(
   path.join(BUILD_OUTPUT_ROOT, `run-${Date.now()}-`),
 );
 
-const PRINT_FANTOM_OUTPUT: false = false;
-
 async function processRNTesterCommandResult(
   result: AsyncCommandResult,
 ): Promise<TestSuiteResult> {
@@ -108,7 +107,7 @@ async function processRNTesterCommandResult(
     throw new Error(getDebugInfoFromCommandResult(getResultWithOutput()));
   }
 
-  if (PRINT_FANTOM_OUTPUT) {
+  if (EnvironmentOptions.printCLIOutput) {
     console.log(getDebugInfoFromCommandResult(getResultWithOutput()));
   }
 
@@ -248,7 +247,7 @@ module.exports = async function runTest(
     '--featureFlags',
     JSON.stringify(testConfig.flags.common),
     '--minLogLevel',
-    PRINT_FANTOM_OUTPUT ? 'info' : 'error',
+    EnvironmentOptions.printCLIOutput ? 'info' : 'error',
   ]);
 
   const processedResult = await processRNTesterCommandResult(

packages/react-native-fantom/runner/utils.js

@@ -9,6 +9,7 @@
  * @oncall react_native
  */
 
+import * as EnvironmentOptions from './EnvironmentOptions';
 import {spawn, spawnSync} from 'child_process';
 import crypto from 'crypto';
 import fs from 'fs';
@@ -66,10 +67,18 @@ export type SyncCommandResult = {
   stderr: string,
 };
 
+function maybeLogCommand(command: string, args: Array<string>): void {
+  if (EnvironmentOptions.logCommands) {
+    console.log(`RUNNING \`${command} ${args.join(' ')}\``);
+  }
+}
+
 export function runCommand(
   command: string,
   args: Array<string>,
 ): AsyncCommandResult {
+  maybeLogCommand(command, args);
+
   const childProcess = spawn(command, args, {
     encoding: 'utf8',
     env: {
@@ -107,6 +116,8 @@ export function runCommandSync(
   command: string,
   args: Array<string>,
 ): SyncCommandResult {
+  maybeLogCommand(command, args);
+
   const result = spawnSync(command, args, {
     encoding: 'utf8',
     env: {