From 4ab455b37d978178885487663acee10addc92646 Mon Sep 17 00:00:00 2001
From: Philipp von Weitershausen <philikon@silklabs.com>
Date: Mon, 12 Sep 2016 15:08:06 -0700
Subject: [PATCH] packager: dedupe symlinks if they point to already covered
 paths

Summary:
If the packager is already watching `/path/to/MyProject`, and it finds symlinks inside `/path/to/MyProject/node_modules` that point to `/path/to/MyProject/path/to/somewhere/else`, there's no need to add the latter to the project roots.

**Test Plan:** replicate an aforementioned project set-up, and verify that only `/path/to/MyProject` is a project root for the packager, while files in `/path/to/MyProject/path/to/somewhere/else` can still be imported so long as they're part of an npm-style package (e.g. `/path/to/MyProject/path/to/somewhere/else/package.json` exists).
Closes https://github.com/facebook/react-native/pull/9819

Differential Revision: D3852591

Pulled By: mkonicek

fbshipit-source-id: 558ab3f835ee3d2bf6174c31595e242992f75601
---
 local-cli/server/findSymlinksPaths.js | 17 +++++++++++++++--
 local-cli/server/server.js            |  2 +-
 2 files changed, 16 insertions(+), 3 deletions(-)

diff --git a/local-cli/server/findSymlinksPaths.js b/local-cli/server/findSymlinksPaths.js
index 804e1d488..af64f2daf 100644
--- a/local-cli/server/findSymlinksPaths.js
+++ b/local-cli/server/findSymlinksPaths.js
@@ -1,12 +1,25 @@
 const path = require('path');
 const fs = require('fs');
 
-module.exports = function findSymlinksPaths(lookupFolder) {
+function isSubPathOfPath(parentPath, subPath) {
+  return !path.relative(parentPath, subPath).startsWith('..' + path.sep);
+}
+
+function isSubPathOfPaths(parentPaths, subPath) {
+  return parentPaths.some(parentPath => isSubPathOfPath(parentPath, subPath));
+}
+
+/**
+ * Find and resolve symlinks in `lookupFolder`, filtering out any
+ * paths that are subpaths of `existingSearchPaths`.
+ */
+module.exports = function findSymlinksPaths(lookupFolder, existingSearchPaths) {
   const timeStart = Date.now();
   const folders = fs.readdirSync(lookupFolder);
   const resolvedSymlinks = folders.map(folder => path.resolve(lookupFolder, folder))
     .filter(folderPath => fs.lstatSync(folderPath).isSymbolicLink())
-    .map(symlink => path.resolve(process.cwd(), fs.readlinkSync(symlink)));
+    .map(symlink => path.resolve(process.cwd(), fs.readlinkSync(symlink)))
+    .filter(symlinkPath => !isSubPathOfPaths(existingSearchPaths, symlinkPath));
   const timeEnd = Date.now();
 
   console.log(`Scanning ${folders.length} folders for symlinks in ${lookupFolder} (${timeEnd - timeStart}ms)`);
diff --git a/local-cli/server/server.js b/local-cli/server/server.js
index ad512509c..a9a11a10c 100644
--- a/local-cli/server/server.js
+++ b/local-cli/server/server.js
@@ -21,7 +21,7 @@ const NODE_MODULES = path.resolve(__dirname, '..', '..', '..');
 function server(argv, config, args) {
   args.projectRoots = args.projectRoots.concat(
     args.root,
-    findSymlinksPaths(NODE_MODULES)
+    findSymlinksPaths(NODE_MODULES, args.projectRoots)
   );
 
   console.log(formatBanner(