LocateUri: pass URI plugin kind, optionally disables plugin verify

Commit b3a458338a added a LocateUri()
call to several playlist commands, which applied InputPlugin URI
scheme verification to playlist URIs.  This broke the SoundCloud
playlist plugin which uses "soundcloud://" URIs for which no input
plugin exists.

This commit allows the caller to specify the kind of plugin which
shall be used to verify the URI.  Right now, only "input" is
implemented; "storage" uses the "input" verification for now; and
"playlist" has no verification at all (for now).

Closes https://github.com/MusicPlayerDaemon/MPD/issues/528

NEWS

@@ -2,6 +2,8 @@ ver 0.21.8 (not yet released)
 * output
   - httpd: add missing mutex lock
   - httpd: fix use-after-free bug
+* playlist
+  - soundcloud: fix "Unsupported URI scheme" (0.21.6 regression)
 * fix Bonjour bug
 * fix build failure with GCC 9
 * fix build failure with -Ddatabase=false

src/LocateUri.cxx

@@ -55,14 +55,26 @@ LocateFileUri(const char *uri, const Client *client
 }
 
 static LocatedUri
-LocateAbsoluteUri(const char *uri
+LocateAbsoluteUri(UriPluginKind kind, const char *uri
 #ifdef ENABLE_DATABASE
 		  , const Storage *storage
 #endif
 		  )
 {
+	switch (kind) {
+	case UriPluginKind::INPUT:
+	case UriPluginKind::STORAGE: // TODO: separate check for storage plugins
 		if (!uri_supported_scheme(uri))
 			throw std::runtime_error("Unsupported URI scheme");
+		break;
+
+	case UriPluginKind::PLAYLIST:
+		/* for now, no validation for playlist URIs; this is
+		   more complicated because there are three ways to
+		   identify which plugin to use: URI scheme, filename
+		   suffix and MIME type */
+		break;
+	}
 
 #ifdef ENABLE_DATABASE
 	if (storage != nullptr) {
@@ -76,7 +88,8 @@ LocateAbsoluteUri(const char *uri
 }
 
 LocatedUri
-LocateUri(const char *uri, const Client *client
+LocateUri(UriPluginKind kind,
+	  const char *uri, const Client *client
 #ifdef ENABLE_DATABASE
 	  , const Storage *storage
 #endif
@@ -100,7 +113,7 @@ LocateUri(const char *uri, const Client *client
 #endif
 				     );
 	else if (uri_has_scheme(uri))
-		return LocateAbsoluteUri(uri
+		return LocateAbsoluteUri(kind, uri
 #ifdef ENABLE_DATABASE
 					 , storage
 #endif

src/LocateUri.hxx

@@ -41,6 +41,12 @@ class Client;
 class Storage;
 #endif
 
+enum class UriPluginKind {
+	INPUT,
+	STORAGE,
+	PLAYLIST,
+};
+
 struct LocatedUri {
 	enum class Type {
 		/**
@@ -84,7 +90,8 @@ struct LocatedUri {
  * that feature is disabled if this parameter is nullptr
  */
 LocatedUri
-LocateUri(const char *uri, const Client *client
+LocateUri(UriPluginKind kind,
+	  const char *uri, const Client *client
 #ifdef ENABLE_DATABASE
 	  , const Storage *storage
 #endif

src/SongLoader.cxx

@@ -94,7 +94,8 @@ SongLoader::LoadSong(const char *uri_utf8) const
 	assert(uri_utf8 != nullptr);
 #endif
 
-	const auto located_uri = LocateUri(uri_utf8, client
+	const auto located_uri = LocateUri(UriPluginKind::INPUT,
+					   uri_utf8, client
 #ifdef ENABLE_DATABASE
 					   , storage
 #endif

src/command/FileCommands.cxx

@@ -218,7 +218,7 @@ handle_read_comments(Client &client, Request args, Response &r)
 
 	const char *const uri = args.front();
 
-	const auto located_uri = LocateUri(uri, &client
+	const auto located_uri = LocateUri(UriPluginKind::INPUT, uri, &client
 #ifdef ENABLE_DATABASE
 					   , nullptr
 #endif
@@ -331,7 +331,7 @@ handle_album_art(Client &client, Request args, Response &r)
 	const char *uri = args.front();
 	size_t offset = args.ParseUnsigned(1);
 
-	const auto located_uri = LocateUri(uri, &client
+	const auto located_uri = LocateUri(UriPluginKind::INPUT, uri, &client
 #ifdef ENABLE_DATABASE
 					   , nullptr
 #endif

src/command/OtherCommands.cxx

@@ -99,7 +99,7 @@ handle_listfiles(Client &client, Request args, Response &r)
 	/* default is root directory */
 	const auto uri = args.GetOptional(0, "");
 
-	const auto located_uri = LocateUri(uri, &client
+	const auto located_uri = LocateUri(UriPluginKind::STORAGE, uri, &client
 #ifdef ENABLE_DATABASE
 					   , nullptr
 #endif
@@ -219,7 +219,7 @@ handle_lsinfo(Client &client, Request args, Response &r)
 		   compatibility, work around this here */
 		uri = "";
 
-	const auto located_uri = LocateUri(uri, &client
+	const auto located_uri = LocateUri(UriPluginKind::INPUT, uri, &client
 #ifdef ENABLE_DATABASE
 					   , nullptr
 #endif

src/command/PlaylistCommands.cxx

@@ -69,7 +69,8 @@ handle_save(Client &client, Request args, gcc_unused Response &r)
 CommandResult
 handle_load(Client &client, Request args, gcc_unused Response &r)
 {
-	const auto uri = LocateUri(args.front(), &client
+	const auto uri = LocateUri(UriPluginKind::PLAYLIST, args.front(),
+				   &client
 #ifdef ENABLE_DATABASE
 					   , nullptr
 #endif
@@ -99,7 +100,8 @@ handle_load(Client &client, Request args, gcc_unused Response &r)
 CommandResult
 handle_listplaylist(Client &client, Request args, Response &r)
 {
-	const auto name = LocateUri(args.front(), &client
+	const auto name = LocateUri(UriPluginKind::PLAYLIST, args.front(),
+				    &client
 #ifdef ENABLE_DATABASE
 					   , nullptr
 #endif
@@ -115,7 +117,8 @@ handle_listplaylist(Client &client, Request args, Response &r)
 CommandResult
 handle_listplaylistinfo(Client &client, Request args, Response &r)
 {
-	const auto name = LocateUri(args.front(), &client
+	const auto name = LocateUri(UriPluginKind::PLAYLIST, args.front(),
+				    &client
 #ifdef ENABLE_DATABASE
 					   , nullptr
 #endif

src/command/QueueCommands.cxx

@@ -83,7 +83,8 @@ handle_add(Client &client, Request args, Response &r)
 		   here */
 		uri = "";
 
-	const auto located_uri = LocateUri(uri, &client
+	const auto located_uri = LocateUri(UriPluginKind::INPUT, uri,
+					   &client
 #ifdef ENABLE_DATABASE
 					   , nullptr
 #endif