[gnome-builder/gnome-builder-41] flatpak: set cargo buildsystem

[Christian Hergert <chergert src gnome org>]

commit c4db5cd181ae29ba07fe3dd47ebbd0667d25080b
Author: Günther Wagner <info gunibert de>
Date:   Sun Oct 3 18:27:09 2021 +0200

    flatpak: set cargo buildsystem
    
    In case the rust-stable sdk extension is set and we didn't found a fitting buildsystem besides the 
generic 'directory' we set the cargo buildsystem in order to allow language server features kick in.

 .../flatpak/gbp-flatpak-build-system-discovery.c     | 20 +++++++++++++++++++-
 1 file changed, 19 insertions(+), 1 deletion(-)
---
diff --git a/src/plugins/flatpak/gbp-flatpak-build-system-discovery.c 
b/src/plugins/flatpak/gbp-flatpak-build-system-discovery.c
index a94328c25..4308f9aaf 100644
--- a/src/plugins/flatpak/gbp-flatpak-build-system-discovery.c
+++ b/src/plugins/flatpak/gbp-flatpak-build-system-discovery.c
@@ -205,7 +205,25 @@ gbp_flatpak_build_system_discovery_discover (IdeBuildSystemDiscovery  *discovery
           if (dzl_str_equal0 (buildsystem, "cmake-ninja"))
             buildsystem = "cmake";
           else if (dzl_str_equal0 (buildsystem, "simple"))
-            buildsystem = "directory";
+            {
+              JsonNode *sdk_extensions;
+              JsonArray *sdk_extensions_array;
+
+              buildsystem = "directory";
+
+              /* Check for a cargo project */
+              sdk_extensions = json_object_get_member (root_object, "sdk-extensions");
+              sdk_extensions_array = json_node_get_array (sdk_extensions);
+              len = json_array_get_length (sdk_extensions_array);
+              for (guint j = 0; j < len; j++)
+                {
+                  const gchar *extension;
+                  extension = json_array_get_string_element (sdk_extensions_array, j);
+                  if (ide_str_equal0 (extension, "org.freedesktop.Sdk.Extension.rust-stable") ||
+                      ide_str_equal0 (extension, "org.freedesktop.Sdk.Extension.rust-nightly"))
+                      buildsystem = "cargo_plugin";
+                }
+            }
 
           /* Set priority higher than normal discoveries */
           if (priority != NULL)