Always mark symlinked path packages for update even during partial updates to make sure they always reflect the current state on disk, fixes #9751

src/Composer/DependencyResolver/PoolBuilder.php

@@ -441,6 +441,16 @@ class PoolBuilder
      */
     private function isUpdateAllowed(PackageInterface $package)
     {
+        // Path repo packages are never loaded from lock, to force them to always remain in sync
+        // unless symlinking is disabled in which case we probably should rather treat them like
+        // regular packages
+        if ($package->getDistType() === 'path') {
+            $transportOptions = $package->getTransportOptions();
+            if (!isset($transportOptions['symlink']) || $transportOptions['symlink'] !== false) {
+                return true;
+            }
+        }
+
         foreach ($this->updateAllowList as $pattern => $void) {
             $patternRegexp = BasePackage::packageNameToRegexp($pattern);
             if (preg_match($patternRegexp, $package->getName())) {

tests/Composer/Test/Fixtures/installer/partial-update-always-updates-symlinked-path-repos.test

@@ -0,0 +1,63 @@
+--TEST--
+Partial updates always update path repos which are symlinked, but not those which are not
+
+--COMPOSER--
+{
+    "repositories": [
+        {
+            "type": "path",
+            "url": "Fixtures/functional/installed-versions/plugin-a"
+        },
+        {
+            "type": "path",
+            "url": "Fixtures/functional/installed-versions/plugin-b",
+            "options": {
+                "symlink": false
+            }
+       },
+       {
+            "type": "package",
+            "package": [
+                { "name": "symfony/console", "version": "1.0.0" },
+                { "name": "c/uptodate", "version": "2.0.0" }
+            ]
+        }
+    ],
+    "require": {
+        "plugin/a": "*",
+        "plugin/b": "*",
+        "c/uptodate": "*"
+    }
+}
+
+--LOCK--
+{
+    "packages": [
+        { "name": "plugin/a", "version": "1.0.0", "dist": { "type": "path", "url": "..." }, "transport-options": {} },
+        { "name": "plugin/b", "version": "1.0.0", "dist": { "type": "path", "url": "..." }, "transport-options": {"symlink": false} },
+        { "name": "c/uptodate", "version": "2.0.0" }
+    ],
+    "packages-dev": [],
+    "aliases": [],
+    "minimum-stability": "stable",
+    "stability-flags": {
+    },
+    "prefer-stable": false,
+    "prefer-lowest": false,
+    "platform": [],
+    "platform-dev": []
+}
+
+--INSTALLED--
+[
+    { "name": "plugin/a", "version": "1.0.0" },
+    { "name": "plugin/b", "version": "1.0.0" },
+    { "name": "c/uptodate", "version": "2.0.0" }
+]
+
+--RUN--
+update c/uptodate
+
+--EXPECT--
+Installing symfony/console (1.0.0)
+Upgrading plugin/a (1.0.0 => 1.1.1)