Use custom require hook to strip Flow types from NativeModule spec pa…

…rser

Summary:
## Context
We currently run ESLint using `flow-node`. This is a very recent change that was introduced in these two diffs:
- Switch VSCode ESLint plugin using flow-node: D24454702.
- Switch all ESLint scripts to use flow-node: D24379783 (facebook@ad5802c).

## Problem
Because `react-native/eslint-plugin-codegen` (written in vanilla JavaScript) requires two files from `react-native-codegen` (written with Flow typings), we force all requires executed while initializing ESLint to compile out Flow types. Issues:
- In the grand scheme of things, this is such a tiny and isolated problem. It shouldn't be the reason why we switch over to using flow node. That's a larger decision that should be discussed outside of this diff.
- On VSCode cold start, in D24454702, I measured that using flow-node adds approximately 320ms to JavaScript file lint time. So, this is just slow.

## Solution
- Switch ESLint back to using regular node:
   - Revert the changes to VSCode's ESLint plugin: D24454702
   - Revert the changes to the internal ESLint scripts: D24379783 (facebook@ad5802c).
- Inside the ESLint plugin, register a temporary require hook to remove Flow types from the NativeModule spec parser, before we require it. We de-register this hook after the requires finish.

## Implementation Notes:
- The `with-babel-register/` is a fork of `babel/register`, except I simplified the implementation based on the assumption that we're using it literally to only compile `react-native-codegen`.
- `with-babel-register/` uses a disk cache, so we only call transformSync when a the input file (1) hasn't been transformed before, or (2) the cache entry was created before the file was last modified.
- I ported over the source-map logic, so that when the NativeModule spec parser throws non-parsing errors, we get the correct stack trace. **Note:** I'm not sure if the source maps will work if there's a babel/register earlier during initialization. However, I don't think this will pose an actual problem, since we don't use a babel/register hook earlier. So, I think we should punt on this investigation.

## Alternative: Why aren't we using babel/register?
Every time you call babel/register, it replaces the last registered hook. We don't want the ESLint plugin to be changing any existing require hooks that people have set up. Abandoned diff with babel/register: D24519349.

Changelog: [Internal]

Reviewed By: cpojer

Differential Revision: D24551549

fbshipit-source-id: bbd7c5be44f74c0e9adbb20fe86e09802410b123

packages/eslint-plugin-codegen/package.json

@@ -9,8 +9,13 @@
     "directory": "packages/eslint-plugin-codegen"
   },
   "dependencies": {
+    "@babel/core": "^7.0.0",
+    "@babel/plugin-transform-flow-strip-types": "^7.0.0",
     "flow-parser": "^0.121.0",
-    "react-native-codegen": "*"
+    "make-dir": "^2.1.0",
+    "pirates":"^4.0.1",
+    "react-native-codegen": "*",
+    "source-map-support": "0.5.0"
   },
   "license": "MIT"
 }

packages/eslint-plugin-codegen/react-native-modules.js

@@ -11,6 +11,7 @@
 'use strict';
 
 const path = require('path');
+const withBabelRegister = require('./with-babel-register');
 
 const ERRORS = {
   misnamedHasteModule(hasteModuleName) {
@@ -38,6 +39,28 @@ const ERRORS = {
   },
 };
 
+let RNModuleParser;
+let RNParserUtils;
+
+function requireModuleParser() {
+  if (RNModuleParser == null || RNParserUtils == null) {
+    const config = {
+      only: [/react-native-codegen\/src\//],
+      plugins: [require('@babel/plugin-transform-flow-strip-types').default],
+    };
+
+    withBabelRegister(config, () => {
+      RNModuleParser = require('react-native-codegen/src/parsers/flow/modules');
+      RNParserUtils = require('react-native-codegen/src/parsers/flow/utils');
+    });
+  }
+
+  return {
+    buildModuleSchema: RNModuleParser.buildModuleSchema,
+    createParserErrorCapturer: RNParserUtils.createParserErrorCapturer,
+  };
+}
+
 const VALID_SPEC_NAMES = /^Native\S+$/;
 
 function isModuleRequire(node) {
@@ -121,25 +144,12 @@ function rule(context) {
         });
       }
 
-      let buildModuleSchema = null;
-      let createParserErrorCapturer = null;
-      try {
-        /**
-         * The following files are written with Flow typings.
-         * Unless the typings are stripped at compile-time or run-time,
-         * the following requires fill fail. Hence, the try/catch.
-         */
-        ({
-          buildModuleSchema,
-        } = require('react-native-codegen/src/parsers/flow/modules'));
-        ({
-          createParserErrorCapturer,
-        } = require('react-native-codegen/src/parsers/flow/utils'));
-      } catch (ex) {
-        return;
-      }
-
+      const {
+        buildModuleSchema,
+        createParserErrorCapturer,
+      } = requireModuleParser();
       const flowParser = require('flow-parser');
+
       const [parsingErrors, guard] = createParserErrorCapturer();
 
       const sourceCode = context.getSourceCode().getText();

packages/eslint-plugin-codegen/with-babel-register/disk-cache.js

@@ -0,0 +1,131 @@
+/**
+ * Copyright (c) Facebook, Inc. and its affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @emails react_native
+ * @format
+ */
+
+const path = require('path');
+const fs = require('fs');
+const os = require('os');
+const {sync: makeDirSync} = require('make-dir');
+
+const packageJson = JSON.parse(
+  fs.readFileSync(require.resolve('../package.json'), 'utf8'),
+);
+
+/**
+ * This file is a fork of
+ * https://github.com/babel/babel/blob/2782a549e99d2ef1816332d23d7dfd5190f58a0f/packages/babel-register/src/cache.js#L1
+ */
+
+const FILENAME = path.join(
+  os.tmpdir(),
+  `.eslint-plugin-codegen.${packageJson.version}.disk-cache.json`,
+);
+
+let data = {};
+
+let cacheDisabled = process.env.NODE_ENV === 'test';
+
+function isCacheDisabled() {
+  return cacheDisabled;
+}
+
+/**
+ * Write stringified cache to disk.
+ */
+function save() {
+  if (isCacheDisabled()) {
+    return;
+  }
+
+  let serialised = '{}';
+
+  try {
+    serialised = JSON.stringify(data, null, '  ');
+  } catch (err) {
+    if (err.message === 'Invalid string length') {
+      err.message = "Cache too large so it's been cleared.";
+      console.error(err.stack);
+    } else {
+      throw err;
+    }
+  }
+
+  try {
+    makeDirSync(path.dirname(FILENAME));
+    fs.writeFileSync(FILENAME, serialised);
+  } catch (e) {
+    switch (e.code) {
+      // workaround https://github.com/nodejs/node/issues/31481
+      // todo: remove the ENOENT error check when we drop node.js 13 support
+      case 'ENOENT':
+      case 'EACCES':
+      case 'EPERM':
+        console.warn(
+          `Could not write cache to file: ${FILENAME} due to a permission issue. Cache is disabled.`,
+        );
+        cacheDisabled = true;
+        break;
+      case 'EROFS':
+        console.warn(
+          `Could not write cache to file: ${FILENAME} because it resides in a readonly filesystem. Cache is disabled.`,
+        );
+        cacheDisabled = true;
+        break;
+      default:
+        throw e;
+    }
+  }
+}
+
+/**
+ * Load cache from disk and parse.
+ */
+
+function load() {
+  if (isCacheDisabled()) {
+    data = {};
+    return;
+  }
+
+  process.on('exit', save);
+  process.nextTick(save);
+
+  let cacheContent;
+
+  try {
+    cacheContent = fs.readFileSync(FILENAME);
+  } catch (e) {
+    switch (e.code) {
+      // check EACCES only as fs.readFileSync will never throw EPERM on Windows
+      // https://github.com/libuv/libuv/blob/076df64dbbda4320f93375913a728efc40e12d37/src/win/fs.c#L735
+      case 'EACCES':
+        console.warn(
+          `Babel could not read cache file: ${FILENAME} due to a permission issue. Cache is disabled.`,
+        );
+        cacheDisabled = true;
+      /* fall through */
+      default:
+        return;
+    }
+  }
+
+  try {
+    data = JSON.parse(cacheContent);
+  } catch {}
+}
+
+/**
+ * Retrieve data from cache.
+ */
+
+function get() {
+  return data;
+}
+
+module.exports = {load, get};

packages/eslint-plugin-codegen/with-babel-register/index.js

@@ -0,0 +1,110 @@
+/**
+ * Copyright (c) Facebook, Inc. and its affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @emails react_native
+ * @format
+ */
+
+const babel = require('@babel/core');
+const {OptionManager, DEFAULT_EXTENSIONS} = require('@babel/core');
+const sourceMapSupport = require('source-map-support');
+const {addHook} = require('pirates');
+const path = require('path');
+const fs = require('fs');
+const diskCache = require('./disk-cache');
+
+function compile(sourceMapManager, cache, options, code, filename) {
+  const opts = new OptionManager().init({
+    sourceRoot: path.dirname(filename) + path.sep,
+    ...options,
+    filename,
+  });
+
+  // Bail out ASAP if the file has been ignored.
+  if (opts === null) {
+    return code;
+  }
+
+  let output = cache[filename];
+
+  if (!output || output.mtime !== mtime(filename)) {
+    output = babel.transformSync(code, {
+      ...opts,
+      sourceMaps: opts.sourceMaps === undefined ? 'both' : opts.sourceMaps,
+      ast: false,
+    });
+
+    cache[filename] = output;
+    output.mtime = mtime(filename);
+  }
+
+  if (!sourceMapManager.isInstalled) {
+    sourceMapManager.install();
+  }
+
+  if (output.map) {
+    sourceMapManager.maps[filename] = output.map;
+  }
+
+  return output.code;
+}
+
+function mtime(filename) {
+  return +fs.statSync(filename).mtime;
+}
+
+function withBabelRegister(options, fn) {
+  let revertHook;
+  /**
+   * TODO: Do source maps break when we use a require hook
+   * to before we initialize the ESLint plugin?
+   */
+  const sourceMapManager = {
+    isInstalled: false,
+    maps: {},
+    install() {
+      if (sourceMapManager.isInstalled) {
+        return;
+      }
+      sourceMapManager.isInstalled = true;
+      sourceMapSupport.install({
+        handleUncaughtExceptions: true,
+        environment: 'node',
+        retrieveSourceMap(filename) {
+          const map = sourceMapManager.maps && sourceMapManager.maps[filename];
+          if (map) {
+            return {
+              url: null,
+              map: map,
+            };
+          } else {
+            return null;
+          }
+        },
+      });
+    },
+  };
+
+  diskCache.load();
+  const cache = diskCache.get();
+
+  try {
+    revertHook = addHook(
+      (code, filename) => {
+        return compile(sourceMapManager, cache, options, code, filename);
+      },
+      {
+        exts: DEFAULT_EXTENSIONS,
+        ignoreNodeModules: false,
+      },
+    );
+    return fn();
+  } finally {
+    revertHook();
+  }
+}
+
+module.exports = withBabelRegister;

yarn.lock

@@ -6480,6 +6480,13 @@ source-map-resolve@^0.5.0:
     source-map-url "^0.4.0"
     urix "^0.1.0"
 
+source-map-support@0.5.0:
+  version "0.5.0"
+  resolved "https://registry.yarnpkg.com/source-map-support/-/source-map-support-0.5.0.tgz#2018a7ad2bdf8faf2691e5fddab26bed5a2bacab"
+  integrity sha512-vUoN3I7fHQe0R/SJLKRdKYuEdRGogsviXFkHHo17AWaTGv17VLnxw+CFXvqy+y4ORZ3doWLQcxRYfwKrsd/H7Q==
+  dependencies:
+    source-map "^0.6.0"
+
 source-map-support@^0.5.16, source-map-support@^0.5.6:
   version "0.5.16"
   resolved "https://registry.yarnpkg.com/source-map-support/-/source-map-support-0.5.16.tgz#0ae069e7fe3ba7538c64c98515e35339eac5a042"