Implemented command to download the Hermes Sampling Profiler to a local machine

.vscode/settings.json

@@ -1,7 +1,5 @@
 {
-  "editor.rulers": [
-    80
-  ],
+  "editor.rulers": [80],
   "files.exclude": {
     "**/.git": true,
     "**/node_modules": true,

packages/cli/src/commands/index.ts

@@ -11,6 +11,7 @@ import info from './info/info';
 import config from './config/config';
 import init from './init';
 import doctor from './doctor';
+import profile from './profile';
 
 export const projectCommands = [
   start,
@@ -24,6 +25,7 @@ export const projectCommands = [
   info,
   config,
   doctor,
+  profile,
 ] as Command[];
 
 export const detachedCommands = [init, doctor] as DetachedCommand[];

packages/cli/src/commands/profile/downloadProfile.ts

@@ -0,0 +1,101 @@
+import {Config} from '@react-native-community/cli-types';
+import {execSync} from 'child_process';
+import {logger, CLIError} from '@react-native-community/cli-tools';
+import chalk from 'chalk';
+import fs from 'fs';
+
+/**
+ * get the last modified hermes profile
+ */
+function getLatestFile(packageName: string): string {
+  try {
+    const file = execSync(`adb shell run-as ${packageName} ls cache/ -tp | grep -v /$ | head -1
+        `);
+
+    return file.toString().trim();
+  } catch (e) {
+    throw new Error(e);
+  }
+}
+/**
+ * get the package name of the running React Native app
+ */
+function getPackageName(config: Config) {
+  const androidProject = config.project.android;
+
+  if (!androidProject) {
+    throw new CLIError(`
+  Android project not found. Are you sure this is a React Native project?
+  If your Android files are located in a non-standard location (e.g. not inside \'android\' folder), consider setting
+  \`project.android.sourceDir\` option to point to a new location.
+`);
+  }
+  const {manifestPath} = androidProject;
+  const androidManifest = fs.readFileSync(manifestPath, 'utf8');
+
+  let packageNameMatchArray = androidManifest.match(/package="(.+?)"/);
+  if (!packageNameMatchArray || packageNameMatchArray.length === 0) {
+    throw new CLIError(
+      'Failed to build the app: No package name found. Found errors in /src/main/AndroidManifest.xml',
+    );
+  }
+
+  let packageName = packageNameMatchArray[1];
+
+  if (!validatePackageName(packageName)) {
+    logger.warn(
+      `Invalid application's package name "${chalk.bgRed(
+        packageName,
+      )}" in 'AndroidManifest.xml'. Read guidelines for setting the package name here: ${chalk.underline.dim(
+        'https://developer.android.com/studio/build/application-id',
+      )}`,
+    );
+  }
+  return packageName;
+}
+/** Validates that the package name is correct
+ *
+ */
+
+function validatePackageName(packageName: string) {
+  return /^[a-z][a-z0-9_]*(\.[a-z][a-z0-9_]*)+$/.test(packageName);
+}
+
+/**
+ * Executes the commands to pull a hermes profile
+ * Commands:
+ * adb shell run-as com.rnhermesapp cp cache/sampling-profiler-trace1502707982002849976.cpuprofile /sdcard/latest.cpuprofile
+ * adb pull /sdcard/latest.cpuprofile
+ */
+export async function downloadProfile(
+  ctx: Config,
+  dstPath?: string,
+  fileName?: string,
+) {
+  try {
+    const packageName = getPackageName(ctx);
+
+    const file = fileName || (await getLatestFile(packageName));
+    if (!file) {
+      logger.error(
+        'There is no file in the cache/ directory. Did you record a profile from the developer menu?',
+      );
+      process.exit(1);
+    }
+    logger.info(`File to be pulled: ${file}`);
+    execSync(`adb shell run-as ${packageName} cp cache/${file} /sdcard`);
+
+    //if not specify destination path, pull to the current directory
+    if (dstPath === undefined) {
+      execSync(`adb pull /sdcard/${file} ${ctx.root}`);
+      console.log(`Successfully pulled the file to ${ctx.root}/${file}`);
+    }
+    //if specified destination path, pull to that directory
+    else {
+      execSync(`adb pull /sdcard/${file} ${dstPath}`);
+      console.log(`Successfully pulled the file to ${dstPath}/${file}`);
+    }
+  } catch (e) {
+    throw new Error(e.message);
+  }
+}

packages/cli/src/commands/profile/index.ts

@@ -0,0 +1,50 @@
+// @ts-ignore untyped
+import {logger} from '@react-native-community/cli-tools';
+import {Config} from '@react-native-community/cli-types';
+import {downloadProfile} from './downloadProfile';
+
+type Options = {
+  fileName?: string;
+};
+
+async function profile(
+  [dstPath]: Array<string>,
+  ctx: Config,
+  options: Options,
+) {
+  try {
+    logger.info(
+      'Downloading a Hermes Sampling Profiler from your Android device...',
+    );
+
+    if (options.fileName) {
+      await downloadProfile(ctx, dstPath, options.fileName);
+    } else {
+      logger.info('No filename is provided, pulling latest file');
+      await downloadProfile(ctx, dstPath, undefined);
+    }
+  } catch (err) {
+    logger.error(`Unable to download the Hermes Sampling Profiler.\n${err}`);
+  }
+}
+
+export default {
+  name: 'profile-hermes [destinationDir]',
+  description:
+    'Download the Hermes Sampling Profiler to the directory <destinationDir> of the local machine',
+  func: profile,
+  options: [
+    //options: download the latest or fileName
+    {
+      name: '--fileName [string]',
+      description: 'Filename of the profile to be downloaded',
+    },
+  ],
+  examples: [
+    {
+      desc:
+        'Download the Hermes Sampling Profiler to the directory <destinationDir> of the local machine',
+      cmd: 'profile-hermes /Users/phuonganh/Desktop',
+    },
+  ],
+};

tsconfig.json

@@ -2,7 +2,7 @@
   "compilerOptions": {
     "target": "es2017",
     "module": "commonjs",
-    "lib": ["es2017"],
+    "lib": ["es2017", "esnext.asynciterable"],
     "declaration": true,
     "declarationMap": true,
     "composite": true,