Read an admin dependency as admin2 on Grav 2

A plugin declaring support for both 1.7 and 2.0 and asking for
`admin >= 1.10.x` is saying it needs the admin panel. On Grav 2 that is
admin2, so the requirement is met rather than unsatisfiable, and dropping it
outright (as the previous commit did) threw away the intent.

The version constraint is deliberately not carried over: 1.10.x describes the
classic admin's numbering and says nothing about admin2's, so comparing them
would be comparing unrelated version lines. Without a constraint the
requirement reads "the admin panel is present", which is true on any Grav 2
site that has one, and installable when it is not.

Mirrors the `replaced_by` record the compatibility registry already holds for
admin. It is repeated in core because dependency resolution must not depend on
a network lookup.

[getgrav/grav-premium-issues#618]

Author: rhukster

CHANGELOG.md

@@ -3,7 +3,8 @@
 
 1. [](#bugfix)
     * Installing a package whose dependency is not in the GPM index now says so and carries on, instead of stopping the command with a PHP fatal error. A plugin that still asks for the Grav 1.7 admin plugin was enough to trigger it [getgrav/grav-premium-issues#618](https://github.com/getgrav/grav-premium-issues/issues/618)
-    * A dependency that cannot be installed on this generation of Grav is now ignored rather than attempted. A plugin that works on both 1.7 and 2.0 has no way to say "the admin plugin, but only on 1.7", so on Grav 2 that requirement is dropped instead of failing the install [getgrav/grav-premium-issues#618](https://github.com/getgrav/grav-premium-issues/issues/618)
+    * A plugin that asks for the `admin` plugin now has that read as Admin 2 on Grav 2, so a plugin written for both 1.7 and 2.0 installs instead of failing on a dependency that cannot exist there. The version it asks for is not carried over, because it describes the old admin's numbering [getgrav/grav-premium-issues#618](https://github.com/getgrav/grav-premium-issues/issues/618)
+    * Any other dependency that cannot be installed on this generation of Grav is now left out of the install rather than attempted and failed
 
 # v2.0.24
 ## 09/03/2026

system/src/Grav/Common/GPM/GPM.php

@@ -1083,6 +1083,43 @@ public static function declaresGravCompatibility($compatibility): bool
      * @param  string $slug
      * @return bool
      */
+    /**
+     * Rewrite dependencies that name the admin panel under the slug the running
+     * generation of Grav actually ships.
+     *
+     * A plugin that supports both 1.7 and 2.0 and asks for `admin >= 1.10.x` is
+     * saying "I need the admin panel". On Grav 2 that is `admin2`, so the
+     * requirement is met by admin2 rather than being unsatisfiable. The version
+     * constraint is deliberately dropped: 1.10.x describes the classic admin's
+     * numbering and says nothing about admin2's, so carrying it over would
+     * compare two unrelated version lines. Without a constraint the requirement
+     * is simply "the admin panel is present", which is true on any Grav 2 site
+     * that has one — and installable when it is not
+     * (getgrav/grav-premium-issues#618).
+     *
+     * This mirrors the `replaced_by` record the compatibility registry already
+     * holds for `admin`; it is repeated here because dependency resolution must
+     * not depend on a network lookup.
+     *
+     * @param  array $dependencies slug => version-constraint
+     * @return array
+     */
+    protected function remapGenerationDependencies(array $dependencies): array
+    {
+        if (self::gravGeneration() !== '2.0' || !isset($dependencies['admin'])) {
+            return $dependencies;
+        }
+
+        unset($dependencies['admin']);
+
+        // Already required in its own right, or already there: nothing to add.
+        if (!isset($dependencies['admin2']) && !$this->isPluginInstalled('admin2')) {
+            $dependencies['admin2'] = '*';
+        }
+
+        return $dependencies;
+    }
+
     public function dependencyIsInstallable(string $slug): bool
     {
         $package = $this->findPackage($slug, true);
@@ -1112,6 +1149,7 @@ public function dependencyIsInstallable(string $slug): bool
     public function getDependencies($packages)
     {
         $dependencies = $this->calculateMergedDependenciesOfPackages($packages);
+        $dependencies = $this->remapGenerationDependencies($dependencies);
         foreach ($dependencies as $dependency_slug => $dependencyVersionWithOperator) {
             $dependency_slug = (string)$dependency_slug;
             if (in_array($dependency_slug, $packages, true)) {

tests/unit/Grav/Common/GPM/GPMTest.php

@@ -351,6 +351,65 @@ public function testDeclaresGravCompatibility(): void
         self::assertSame($isGrav2 ? '2.0' : '1.7', GPM::gravGeneration());
     }
 
+    /**
+     * A plugin supporting both generations that asks for `admin` means "the
+     * admin panel". On Grav 2 that is admin2, so the requirement is met there
+     * rather than being unsatisfiable, and the classic admin's version
+     * constraint is dropped because it describes a different version line.
+     */
+    public function testAdminDependencyResolvesToAdmin2OnGrav2(): void
+    {
+        if (((int)GRAV_VERSION) < 2) {
+            self::markTestSkipped('Behaviour is specific to Grav 2.');
+        }
+
+        $this->gpm->data = [
+            'dual-compat-plugin' => (object)[
+                'dependencies' => [
+                    ['name' => 'admin', 'version' => '>=1.10.49'],
+                ]
+            ],
+            'admin2' => (object)[],
+        ];
+
+        $dependencies = $this->gpm->getDependencies(['dual-compat-plugin']);
+
+        self::assertArrayNotHasKey('admin', $dependencies, 'the classic admin slug never survives on Grav 2');
+        // admin2 is not installed in the test environment, so it is offered.
+        self::assertSame('install', $dependencies['admin2'] ?? null, 'the requirement is carried over to admin2');
+    }
+
+    /**
+     * The same requirement is simply satisfied when admin2 is already there,
+     * which is every real Grav 2 site with an admin.
+     */
+    public function testAdminDependencySatisfiedWhenAdmin2Installed(): void
+    {
+        if (((int)GRAV_VERSION) < 2) {
+            self::markTestSkipped('Behaviour is specific to Grav 2.');
+        }
+
+        $gpm = new class extends GpmStub {
+            public function isPluginInstalled($slug): bool
+            {
+                return $slug === 'admin2';
+            }
+        };
+        $gpm->data = [
+            'dual-compat-plugin' => (object)[
+                'dependencies' => [
+                    ['name' => 'admin', 'version' => '>=1.10.49'],
+                ]
+            ],
+            'admin2' => (object)[],
+        ];
+
+        $dependencies = $gpm->getDependencies(['dual-compat-plugin']);
+
+        self::assertArrayNotHasKey('admin', $dependencies);
+        self::assertArrayNotHasKey('admin2', $dependencies, 'nothing to do when the admin panel is already installed');
+    }
+
     /**
      * A dependency is uninstallable both when the repository does not serve it
      * and when it serves it declaring another generation.