LocateUri: implement UriPluginKind::STORAGE properly

This way, URI schemes supported by arbitrary storage plugins are
allowed.

Closes https://github.com/MusicPlayerDaemon/MPD/issues/1270

NEWS

@@ -2,6 +2,7 @@ ver 0.23 (not yet released)
 * protocol
   - new command "getvol"
   - show the audio format in "playlistinfo"
+  - support "listfiles" with arbitrary storage plugins
 * database
   - proxy: require MPD 0.20 or later
   - proxy: require libmpdclient 2.11 or later

src/LocateUri.cxx

@@ -22,6 +22,7 @@
 #include "client/Client.hxx"
 #include "fs/AllocatedPath.hxx"
 #include "ls.hxx"
+#include "storage/Registry.hxx"
 #include "util/ASCII.hxx"
 #include "util/UriExtract.hxx"
 
@@ -67,11 +68,15 @@ LocateAbsoluteUri(UriPluginKind kind, const char *uri
 {
 	switch (kind) {
 	case UriPluginKind::INPUT:
-	case UriPluginKind::STORAGE: // TODO: separate check for storage plugins
 		if (!uri_supported_scheme(uri))
 			throw std::invalid_argument("Unsupported URI scheme");
 		break;
 
+	case UriPluginKind::STORAGE:
+		/* plugin support will be checked after the
+		   Storage::MapToRelativeUTF8() call */
+		break;
+
 	case UriPluginKind::PLAYLIST:
 		/* for now, no validation for playlist URIs; this is
 		   more complicated because there are three ways to
@@ -88,6 +93,10 @@ LocateAbsoluteUri(UriPluginKind kind, const char *uri
 			return LocatedUri(LocatedUri::Type::RELATIVE,
 					  suffix.data());
 	}
+
+	if (kind == UriPluginKind::STORAGE &&
+	    GetStoragePluginByUri(uri) == nullptr)
+		throw std::invalid_argument("Unsupported URI scheme");
 #endif
 
 	return LocatedUri(LocatedUri::Type::ABSOLUTE, uri);