command/storage: automatically scan new mounts

Closes https://github.com/MusicPlayerDaemon/MPD/issues/841

NEWS

@@ -1,6 +1,8 @@
 ver 0.21.25 (not yet released)
 * protocol:
   - fix crash when using "rangeid" while playing
+* database
+  - simple: automatically scan new mounts
 * storage
   - fix disappearing mounts after mounting twice
   - udisks: fix reading ".mpdignore"

src/command/StorageCommands.cxx

@@ -220,8 +220,10 @@ handle_mount(Client &client, Request args, Response &r)
 
 #ifdef ENABLE_DATABASE
 	if (auto *db = dynamic_cast<SimpleDatabase *>(instance.GetDatabase())) {
+		bool need_update;
+
 		try {
-			db->Mount(local_uri, remote_uri);
+			need_update = !db->Mount(local_uri, remote_uri);
 		} catch (...) {
 			composite.Unmount(local_uri);
 			throw;
@@ -230,6 +232,12 @@ handle_mount(Client &client, Request args, Response &r)
 		// TODO: call Instance::OnDatabaseModified()?
 		// TODO: trigger database update?
 		instance.EmitIdle(IDLE_DATABASE);
+
+		if (need_update) {
+			UpdateService *update = client.GetInstance().update;
+			if (update != nullptr)
+				update->Enqueue(local_uri, false);
+		}
 	}
 #endif
 

src/db/plugins/simple/SimpleDatabasePlugin.cxx

@@ -428,7 +428,7 @@ IsUnsafeChar(char ch)
 	return !IsSafeChar(ch);
 }
 
-void
+bool
 SimpleDatabase::Mount(const char *local_uri, const char *storage_uri)
 {
 	if (cache_path.IsNull())
@@ -447,9 +447,11 @@ SimpleDatabase::Mount(const char *local_uri, const char *storage_uri)
 						   compress);
 	db->Open();
 
-	// TODO: update the new database instance?
+	bool exists = db->FileExists();
 
 	Mount(local_uri, std::move(db));
+
+	return exists;
 }
 
 inline DatabasePtr

src/db/plugins/simple/SimpleDatabasePlugin.hxx

@@ -103,9 +103,11 @@ public:
 
 	/**
 	 * Throws #std::runtime_error on error.
+	 *
+	 * @return false if the mounted database needs to be updated
 	 */
 	gcc_nonnull_all
-	void Mount(const char *local_uri, const char *storage_uri);
+	bool Mount(const char *local_uri, const char *storage_uri);
 
 	gcc_nonnull_all
 	bool Unmount(const char *uri) noexcept;