feat: Handle alternate plugin manifest paths (#18182)

Load plugin manifests through a shared discoverable-path helper so
manifest reads, installs, and skill names all see the same alternate
manifest location.

codex-rs/app-server/tests/suite/v2/plugin_list.rs

@@ -34,6 +34,8 @@ use wiremock::matchers::query_param;
 const DEFAULT_TIMEOUT: Duration = Duration::from_secs(60);
 const TEST_CURATED_PLUGIN_SHA: &str = "0123456789abcdef0123456789abcdef01234567";
 const STARTUP_REMOTE_PLUGIN_SYNC_MARKER_FILE: &str = ".tmp/app-server-remote-plugin-sync-v1";
+const ALTERNATE_MARKETPLACE_RELATIVE_PATH: &str = ".claude-plugin/marketplace.json";
+const ALTERNATE_PLUGIN_MANIFEST_RELATIVE_PATH: &str = ".claude-plugin/plugin.json";
 
 fn write_plugins_enabled_config(codex_home: &std::path::Path) -> std::io::Result<()> {
     std::fs::write(
@@ -246,6 +248,138 @@ async fn plugin_list_keeps_valid_marketplaces_when_another_marketplace_fails_to_
     Ok(())
 }
 
+#[tokio::test]
+async fn plugin_list_uses_alternate_discoverable_manifest_and_keeps_undiscoverable_plugins()
+-> Result<()> {
+    let codex_home = TempDir::new()?;
+    let repo_root = TempDir::new()?;
+    let valid_plugin_root = repo_root.path().join("plugins/valid-plugin");
+    std::fs::create_dir_all(repo_root.path().join(".git"))?;
+    std::fs::create_dir_all(
+        repo_root
+            .path()
+            .join(ALTERNATE_MARKETPLACE_RELATIVE_PATH)
+            .parent()
+            .unwrap(),
+    )?;
+    std::fs::create_dir_all(
+        valid_plugin_root
+            .join(ALTERNATE_PLUGIN_MANIFEST_RELATIVE_PATH)
+            .parent()
+            .unwrap(),
+    )?;
+    write_plugins_enabled_config(codex_home.path())?;
+
+    let marketplace_path =
+        AbsolutePathBuf::try_from(repo_root.path().join(ALTERNATE_MARKETPLACE_RELATIVE_PATH))?;
+    let valid_plugin_path = AbsolutePathBuf::try_from(valid_plugin_root.clone())?;
+
+    std::fs::write(
+        marketplace_path.as_path(),
+        r#"{
+  "name": "alternate-marketplace",
+  "plugins": [
+    {
+      "name": "valid-plugin",
+      "source": "./plugins/valid-plugin"
+    },
+    {
+      "name": "missing-plugin",
+      "source": "./plugins/missing-plugin"
+    }
+  ]
+}"#,
+    )?;
+    std::fs::write(
+        valid_plugin_root.join(ALTERNATE_PLUGIN_MANIFEST_RELATIVE_PATH),
+        r#"{
+  "name": "valid-plugin",
+  "interface": {
+    "displayName": "Valid Plugin"
+  }
+}"#,
+    )?;
+
+    let home = codex_home.path().to_string_lossy().into_owned();
+    let mut mcp = McpProcess::new_with_env(
+        codex_home.path(),
+        &[
+            ("HOME", Some(home.as_str())),
+            ("USERPROFILE", Some(home.as_str())),
+        ],
+    )
+    .await?;
+    timeout(DEFAULT_TIMEOUT, mcp.initialize()).await??;
+
+    let request_id = mcp
+        .send_plugin_list_request(PluginListParams {
+            cwds: Some(vec![AbsolutePathBuf::try_from(repo_root.path())?]),
+            force_remote_sync: false,
+        })
+        .await?;
+
+    let response: JSONRPCResponse = timeout(
+        DEFAULT_TIMEOUT,
+        mcp.read_stream_until_response_message(RequestId::Integer(request_id)),
+    )
+    .await??;
+    let response: PluginListResponse = to_response(response)?;
+
+    assert_eq!(
+        response.marketplaces,
+        vec![PluginMarketplaceEntry {
+            name: "alternate-marketplace".to_string(),
+            path: marketplace_path,
+            interface: None,
+            plugins: vec![
+                PluginSummary {
+                    id: "valid-plugin@alternate-marketplace".to_string(),
+                    name: "valid-plugin".to_string(),
+                    source: PluginSource::Local {
+                        path: valid_plugin_path,
+                    },
+                    installed: false,
+                    enabled: false,
+                    install_policy: PluginInstallPolicy::Available,
+                    auth_policy: PluginAuthPolicy::OnInstall,
+                    interface: Some(codex_app_server_protocol::PluginInterface {
+                        display_name: Some("Valid Plugin".to_string()),
+                        short_description: None,
+                        long_description: None,
+                        developer_name: None,
+                        category: None,
+                        capabilities: Vec::new(),
+                        website_url: None,
+                        privacy_policy_url: None,
+                        terms_of_service_url: None,
+                        default_prompt: None,
+                        brand_color: None,
+                        composer_icon: None,
+                        logo: None,
+                        screenshots: Vec::new(),
+                    }),
+                },
+                PluginSummary {
+                    id: "missing-plugin@alternate-marketplace".to_string(),
+                    name: "missing-plugin".to_string(),
+                    source: PluginSource::Local {
+                        path: AbsolutePathBuf::try_from(
+                            repo_root.path().join("plugins/missing-plugin"),
+                        )?,
+                    },
+                    installed: false,
+                    enabled: false,
+                    install_policy: PluginInstallPolicy::Available,
+                    auth_policy: PluginAuthPolicy::OnInstall,
+                    interface: None,
+                },
+            ],
+        }]
+    );
+    assert!(response.marketplace_load_errors.is_empty());
+    Ok(())
+}
+
 #[tokio::test]
 async fn plugin_list_accepts_omitted_cwds() -> Result<()> {
     let codex_home = TempDir::new()?;

codex-rs/app-server/tests/suite/v2/plugin_read.rs

@@ -512,11 +512,7 @@ async fn plugin_read_returns_invalid_request_when_plugin_manifest_is_missing() -
     .await??;
 
     assert_eq!(err.error.code, -32600);
-    assert!(
-        err.error
-            .message
-            .contains("missing or invalid .codex-plugin/plugin.json")
-    );
+    assert!(err.error.message.contains("missing or invalid plugin.json"));
     Ok(())
 }