Add test and fix update whitelist feature

src/Composer/Installer.php

@@ -280,9 +280,7 @@ class Installer
         // if the updateWhitelist is enabled, packages not in it are also fixed
         // to their currently installed version
         foreach ($installedRepo->getPackages() as $package) {
-            if ($package->getRepository() === $localRepo
+            if ($package->getRepository() === $localRepo && (!$this->updateWhitelist || $this->isUpdateable($package))) {
-                && (!$this->updateWhitelist || in_array($package->getName(), $this->updateWhitelist))
-            ) {
                 continue;
             }
 
@@ -338,7 +336,7 @@ class Installer
                 // force update to latest on update
                 if ($this->update) {
                     // skip package if the whitelist is enabled and it is not in it
-                    if ($this->updateWhitelist && !in_array($package->getName(), $this->updateWhitelist)) {
+                    if ($this->updateWhitelist && !$this->isUpdateable($package)) {
                         continue;
                     }
 
@@ -452,6 +450,25 @@ class Installer
         return $aliases;
     }
 
+    private function isUpdateable(PackageInterface $package)
+    {
+        if (!$this->updateWhitelist) {
+            throw new \LogicException('isUpdateable should only be called when a whitelist is present');
+        }
+
+        if (in_array($package->getName(), $this->updateWhitelist)) {
+            return true;
+        }
+
+        foreach ($this->package->getRequires() as $link) {
+            if ($link->getTarget() === $package->getName()) {
+                return false;
+            }
+        }
+
+        return true;
+    }
+
     /**
      * Create Installer
      *

tests/Composer/Test/Fixtures/installer/update-whitelist.test

@@ -0,0 +1,33 @@
+--TEST--
+Update with a package whitelist only updates those packages and their dependencies if they are not present in composer.json
+--COMPOSER--
+{
+    "repositories": [
+        {
+            "type": "package",
+            "package": [
+                { "name": "fixed", "version": "1.1.0" },
+                { "name": "fixed", "version": "1.0.0" },
+                { "name": "whitelisted", "version": "1.1.0", "require": { "dependency": "1.1.0" } },
+                { "name": "whitelisted", "version": "1.0.0", "require": { "dependency": "1.0.0" } },
+                { "name": "dependency", "version": "1.1.0" },
+                { "name": "dependency", "version": "1.0.0" }
+            ]
+        }
+    ],
+    "require": {
+        "fixed": "1.*",
+        "whitelisted": "1.*"
+    }
+}
+--INSTALLED--
+[
+    { "name": "fixed", "version": "1.0.0" },
+    { "name": "whitelisted", "version": "1.0.0" },
+    { "name": "dependency", "version": "1.0.0" }
+]
+--RUN--
+update whitelisted
+--EXPECT--
+Updating dependency (1.0.0) to dependency (1.1.0)
+Updating whitelisted (1.0.0) to whitelisted (1.1.0)