From 9ffed112618ba5b1098fdd34caeddf5c55329de8 Mon Sep 17 00:00:00 2001
From: empyrical <empyrical@outlook.com>
Date: Sat, 10 Nov 2018 13:20:17 -0700
Subject: [PATCH] Add (very basic) Yarn Plug 'n Play support

---
 packages/global-cli/index.js                  | 43 ++++++++++++++++---
 .../local-cli/util/findReactNativePath.js     | 11 +++++
 2 files changed, 47 insertions(+), 7 deletions(-)

diff --git a/packages/global-cli/index.js b/packages/global-cli/index.js
index a3f4fcbf0..cb70cbcb2 100755
--- a/packages/global-cli/index.js
+++ b/packages/global-cli/index.js
@@ -45,6 +45,14 @@ var execSync = require('child_process').execSync;
 var chalk = require('chalk');
 var prompt = require('prompt');
 var semver = require('semver');
+var pnp = null;
+
+try {
+  pnp = require('pnpapi');
+} catch(e) {
+  // Not in PnP
+}
+
 /**
  * Used arguments:
  *   -v --version - to print current version of react-native-cli and react-native dependency
@@ -61,17 +69,38 @@ var semver = require('semver');
 
 var options = require('minimist')(process.argv.slice(2));
 
+/**
+ * This function resolves the path to a specified Node module and, and if more
+ * than one argument is specified, a file inside of a Node module.
+ *
+ * If Yarn Plug 'n Play is enabled, it will use `pnpapi` to resolve the module.
+ * If not, it will look in the `node_modules` folder of the current working directory
+ */
+function resolve(...paths) {
+  if (pnp) {
+    try {
+      return pnp.resolveToUnqualified(path.join(...paths), process.cwd());
+    } catch (e) {
+      // If a node_module cannot be resolved, `resolveToUnqualified` throws.
+      // The rest of the codebase just handles non-existance by seeing if the path
+      // exists. `fs.fileExistsSync` will always return `false` for `null`.
+      return null;
+    }
+  } else {
+    return path.resolve(process.cwd(), 'node_modules', ...paths);
+  }
+}
+
 var CLI_MODULE_PATH = function() {
-  return path.resolve(process.cwd(), 'node_modules', 'react-native', 'cli.js');
+  let path = resolve('react-native-local-cli', 'cli.js');
+  if (!fs.existsSync(path)) {
+    path = resolve('react-native', 'cli.js');
+  }
+  return path;
 };
 
 var REACT_NATIVE_PACKAGE_JSON_PATH = function() {
-  return path.resolve(
-    process.cwd(),
-    'node_modules',
-    'react-native',
-    'package.json',
-  );
+  return resolve('react-native', 'package.json');
 };
 
 if (options._.length === 0 && (options.v || options.version)) {
diff --git a/packages/local-cli/util/findReactNativePath.js b/packages/local-cli/util/findReactNativePath.js
index 0e94b3e1e..f92c8ae19 100644
--- a/packages/local-cli/util/findReactNativePath.js
+++ b/packages/local-cli/util/findReactNativePath.js
@@ -12,10 +12,21 @@
 
 const path = require('path');
 const fs = require('fs');
+let pnp = null;
+
+try {
+  pnp = require('pnpapi');
+} catch (e) {
+  // Not in PnP
+}
 
 let reactNativePath = null;
 
 function findReactNativePath(): string {
+  // If in PnP, try that first.
+  if (pnp) {
+    return pnp.resolveToUnqualified('react-native', path.join(process.cwd(), '../'))
+  }
   // By default, CLI lives inside `node_modules` next to React Native as 
   // node dependencies are flattened
   if (fs.existsSync(path.join(__dirname, '../../react-native'))) {