refactor: decouple our version checks

There was a single version check that would log an available stable
version of React Native that was greater than the current version in a
project.

The change breaks that up into:
- what is the current version
- what is the next stable upgrade if available
- log any stable upgrade if available

packages/cli-config/src/__tests__/index-test.ts

@@ -162,6 +162,7 @@ test('should merge project configuration with default values', () => {
 test('should load commands from "react-native-foo" and "react-native-bar" packages', () => {
   DIR = getTempDirectory('config_test_packages');
   writeFiles(DIR, {
+    'react-native.config.js': 'module.exports = { reactNativePath: "." }',
     'node_modules/react-native-foo/package.json': '{}',
     'node_modules/react-native-foo/react-native.config.js': `module.exports = {
       commands: [
@@ -220,6 +221,7 @@ test('does not use restricted "react-native" key to resolve config from package.
     'node_modules/react-native-netinfo/package.json': `{
       "react-native": "src/index.js"
     }`,
+    'react-native.config.js': 'module.exports = { reactNativePath: "." }',
     'package.json': `{
       "dependencies": {
         "react-native-netinfo": "0.0.1"

packages/cli-config/src/loadConfig.ts

@@ -1,6 +1,4 @@
 import path from 'path';
-import fs from 'fs';
-import semver from 'semver';
 import {
   UserDependencyConfig,
   ProjectConfig,
@@ -10,7 +8,9 @@ import {
 } from '@react-native-community/cli-types';
 import {
   findProjectRoot,
+  version,
   resolveNodeModuleDir,
+  UnknownProjectError,
 } from '@react-native-community/cli-tools';
 import findDependencies from './findDependencies';
 import resolveReactNativePath from './resolveReactNativePath';
@@ -96,19 +96,16 @@ function loadConfig(projectRoot: string = findProjectRoot()): Config {
   // currently being used to get our deeplinks working, so it's only worried with
   // the major and minor version.
   try {
-    const {version} = JSON.parse(
-      fs.readFileSync(
-        path.join(initialConfig.reactNativePath, 'package.json'),
-        {encoding: 'utf8'},
-      ),
-    );
-    const out = semver.parse(version);
-    if (out) {
+    let semver = version.current(initialConfig.reactNativePath);
+    if (semver) {
       // Retain only these version, since they correspond with our documentation.
-      initialConfig.reactNativeVersion = `${out.major}.${out.minor}`;
+      initialConfig.reactNativeVersion = `${semver.major}.${semver.minor}`;
+    }
+  } catch (e) {
+    // If we don't seem to be in a well formed project, give up quietly.
+    if (!(e instanceof UnknownProjectError)) {
+      throw e;
     }
-  } catch (_) {
-    // We don't seem to be in a well formed project, give up quietly.
   }
 
   const finalConfig = Array.from(

packages/cli-doctor/src/commands/info.ts

@@ -6,7 +6,7 @@
  */
 
 import getEnvironmentInfo from '../tools/envinfo';
-import {logger, releaseChecker} from '@react-native-community/cli-tools';
+import {logger, version} from '@react-native-community/cli-tools';
 import {Config} from '@react-native-community/cli-types';
 
 const info = async function getInfo(_argv: Array<string>, ctx: Config) {
@@ -17,7 +17,7 @@ const info = async function getInfo(_argv: Array<string>, ctx: Config) {
   } catch (err) {
     logger.error(`Unable to print environment info.\n${err}`);
   } finally {
-    await releaseChecker(ctx.root);
+    await version.logIfUpdateAvailable(ctx.root);
   }
 };
 

packages/cli-plugin-metro/src/commands/start/runServer.ts

@@ -18,7 +18,7 @@ import {
 import {Config} from '@react-native-community/cli-types';
 
 import loadMetroConfig from '../../tools/loadMetroConfig';
-import {releaseChecker} from '@react-native-community/cli-tools';
+import {version} from '@react-native-community/cli-tools';
 import enableWatchMode from './watchMode';
 
 export type Args = {
@@ -124,7 +124,7 @@ async function runServer(_argv: Array<string>, ctx: Config, args: Args) {
   //
   serverInstance.keepAliveTimeout = 30000;
 
-  await releaseChecker(ctx.root);
+  await version.logIfUpdateAvailable(ctx.root);
 }
 
 function getReporterImpl(customLogReporterPath: string | undefined) {

packages/cli-tools/src/errors.ts

@@ -19,5 +19,10 @@ export class CLIError extends Error {
   }
 }
 
+/**
+ * Raised when we're unable to find a package.json
+ */
+export class UnknownProjectError extends Error {}
+
 export const inlineString = (str: string) =>
   str.replace(/(\s{2,})/gm, ' ').trim();

packages/cli-tools/src/index.ts

@@ -5,7 +5,7 @@ export {fetch, fetchToTemp} from './fetch';
 export {default as launchDefaultBrowser} from './launchDefaultBrowser';
 export {default as launchDebugger} from './launchDebugger';
 export {default as launchEditor} from './launchEditor';
-export {default as releaseChecker} from './releaseChecker';
+export * as version from './releaseChecker';
 export {default as resolveNodeModuleDir} from './resolveNodeModuleDir';
 export {default as hookStdout} from './hookStdout';
 export {getLoader, NoopLoader, Loader} from './loader';

packages/cli-tools/src/releaseChecker/getLatestRelease.ts

@@ -19,7 +19,7 @@ export type Release = {
 export default async function getLatestRelease(
   name: string,
   currentVersion: string,
-): Promise<Release | void> {
+): Promise<Release | undefined> {
   logger.debug('Checking for a newer version of React Native');
   try {
     logger.debug(`Current version: ${currentVersion}`);
@@ -68,6 +68,7 @@ export default async function getLatestRelease(
     );
     logger.debug(e as any);
   }
+  return undefined;
 }
 
 function buildChangelogUrl(version: string) {

packages/cli-tools/src/releaseChecker/index.ts

@@ -1,21 +1,52 @@
 import path from 'path';
+import semver, {SemVer} from 'semver';
+
+import {UnknownProjectError} from '../errors';
 import logger from '../logger';
-// @ts-ignore - JS file
 import resolveNodeModuleDir from '../resolveNodeModuleDir';
-import getLatestRelease from './getLatestRelease';
+import getLatestRelease, {Release} from './getLatestRelease';
 import printNewRelease from './printNewRelease';
 
-export default async function releaseChecker(root: string) {
+const getReactNativeVersion = (projectRoot: string): string | undefined =>
+  require(path.join(
+    resolveNodeModuleDir(projectRoot, 'react-native'),
+    'package.json',
+  ))?.version;
+
+/**
+ * Logs out a message if the user's version is behind a stable version of React Native
+ */
+export async function logIfUpdateAvailable(projectRoot: string): Promise<void> {
+  const hasUpdate = await latest(projectRoot);
+  if (hasUpdate) {
+    printNewRelease(hasUpdate.name, hasUpdate.upgrade, hasUpdate.current);
+  }
+}
+
+type Update = {
+  upgrade: Release;
+  current: string;
+  name: string;
+};
+
+/**
+ * Finds the latest stables version of React Native > current version
+ */
+export async function latest(projectRoot: string): Promise<Update | undefined> {
   try {
-    const {version: currentVersion} = require(path.join(
-      resolveNodeModuleDir(root, 'react-native'),
-      'package.json',
-    ));
-    const {name} = require(path.join(root, 'package.json'));
+    const currentVersion = getReactNativeVersion(projectRoot);
+    if (!currentVersion) {
+      return;
+    }
+    const {name} = require(path.join(projectRoot, 'package.json'));
     const latestRelease = await getLatestRelease(name, currentVersion);
 
     if (latestRelease) {
-      printNewRelease(name, latestRelease, currentVersion);
+      return {
+        name,
+        current: currentVersion,
+        upgrade: latestRelease,
+      };
     }
   } catch (e) {
     // We let the flow continue as this component is not vital for the rest of
@@ -26,4 +57,20 @@ export default async function releaseChecker(root: string) {
     );
     logger.debug(e as any);
   }
+  return undefined;
+}
+
+/**
+ * Gets the current project's version parsed as Semver
+ */
+export function current(projectRoot: string): SemVer | undefined {
+  try {
+    const found = semver.parse(getReactNativeVersion(projectRoot));
+    if (found) {
+      return found;
+    }
+  } catch (_) {
+    throw new UnknownProjectError(projectRoot);
+  }
+  return undefined;
 }