Extract logic to get Fantom test config to a standalone module (#48092)

Summary:
Pull Request resolved: https://github.com/facebook/react-native/pull/48092

Changelog: [internal]

This is just in preparation to expand the scope of that function to include configuration for feature flags.

Reviewed By: javache

Differential Revision: D66760119

fbshipit-source-id: e955e8f596697ac6a0a87013bec3fc3e09caf19d

jest/integration/runner/getFantomTestConfig.js

@@ -0,0 +1,64 @@
+/**
+ * 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-local
+ * @format
+ * @oncall react_native
+ */
+
+import fs from 'fs';
+// $FlowExpectedError[untyped-import]
+import {extract, parse} from 'jest-docblock';
+
+type DocblockPragmas = {[key: string]: string | string[]};
+type FantomTestMode = 'dev' | 'opt';
+type FantomTestConfig = {
+  mode: FantomTestMode,
+};
+
+const DEFAULT_MODE: FantomTestMode = 'dev';
+
+/**
+ * Extracts the Fantom configuration from the test file, specified as part of
+ * the docblock comment. E.g.:
+ *
+ * ```
+ * /**
+ *  * @flow strict-local
+ *  * @fantom mode:opt
+ *  *
+ * ```
+ *
+ * So far the only supported option is `mode`, which can be 'dev' or 'opt'.
+ */
+export default function getFantomTestConfig(
+  testPath: string,
+): FantomTestConfig {
+  const docblock = extract(fs.readFileSync(testPath, 'utf8'));
+  const pragmas = parse(docblock) as DocblockPragmas;
+
+  const config = {
+    mode: DEFAULT_MODE,
+  };
+
+  const maybeMode = pragmas.fantom_mode;
+
+  if (maybeMode != null) {
+    if (Array.isArray(maybeMode)) {
+      throw new Error('Expected a single value for @fantom_mode');
+    }
+
+    const mode = maybeMode;
+
+    if (mode === 'dev' || mode === 'opt') {
+      config.mode = mode;
+    } else {
+      throw new Error(`Invalid Fantom mode: ${mode}`);
+    }
+  }
+
+  return config;
+}

jest/integration/runner/runner.js

@@ -12,10 +12,10 @@
 import type {TestSuiteResult} from '../runtime/setup';
 
 import entrypointTemplate from './entrypoint-template';
+import getFantomTestConfig from './getFantomTestConfig';
 import {
   getBuckModeForPlatform,
   getDebugInfoFromCommandResult,
-  getFantomTestConfig,
   getShortHash,
   runBuck2,
   symbolicateStackTrace,

jest/integration/runner/utils.js

@@ -12,60 +12,10 @@
 import {spawnSync} from 'child_process';
 import crypto from 'crypto';
 import fs from 'fs';
-// $FlowExpectedError[untyped-import]
-import {extract, parse} from 'jest-docblock';
 import os from 'os';
 // $FlowExpectedError[untyped-import]
 import {SourceMapConsumer} from 'source-map';
 
-type DocblockPragmas = {[key: string]: string | string[]};
-type FantomTestMode = 'dev' | 'opt';
-type FantomTestConfig = {
-  mode: FantomTestMode,
-};
-
-const DEFAULT_MODE: FantomTestMode = 'dev';
-
-/**
- * Extracts the Fantom configuration from the test file, specified as part of
- * the docblock comment. E.g.:
- *
- * ```
- * /**
- *  * @flow strict-local
- *  * @fantom mode:opt
- *  *
- * ```
- *
- * So far the only supported option is `mode`, which can be 'dev' or 'opt'.
- */
-export function getFantomTestConfig(testPath: string): FantomTestConfig {
-  const docblock = extract(fs.readFileSync(testPath, 'utf8'));
-  const pragmas = parse(docblock) as DocblockPragmas;
-
-  const config = {
-    mode: DEFAULT_MODE,
-  };
-
-  const maybeMode = pragmas.fantom_mode;
-
-  if (maybeMode != null) {
-    if (Array.isArray(maybeMode)) {
-      throw new Error('Expected a single value for @fantom_mode');
-    }
-
-    const mode = maybeMode;
-
-    if (mode === 'dev' || mode === 'opt') {
-      config.mode = mode;
-    } else {
-      throw new Error(`Invalid Fantom mode: ${mode}`);
-    }
-  }
-
-  return config;
-}
-
 export function getBuckModeForPlatform(enableRelease: boolean = false): string {
   const mode = enableRelease ? 'opt' : 'dev';