[libpeas/meson.msvc: 5/12] peas-object-module.c: Add fallback module search for Windows

[Chun-wei Fan <fanchunwei src gnome org>]

commit 99d0bdb7153a5a463d8d06970ca0122af04858a3
Author: Chun-wei Fan <fanchunwei src gnome org>
Date:   Tue Nov 19 16:34:49 2019 +0800

    peas-object-module.c: Add fallback module search for Windows
    
    When we specify the plugin module name via a plugin file,
    g_module_build_path() will append a 'lib' prefix to the final filename
    of the module DLL, which may cause the module load to fail because the
    module DLL is not built with the 'lib' prefix for its filename, which
    is often the case for Meson builds with Visual Studio and also likely
    in other scenarios.
    
    Fix this by adding a fallback check for Windows, that we look for the
    module DLL without the 'lib' prefix by appending '.dll' to the module
    name that we pass into g_module_build_path(), if we can't find the
    module DLL with the 'lib' prefix.

 libpeas/peas-object-module.c | 29 ++++++++++++++++++++++++++++-
 1 file changed, 28 insertions(+), 1 deletion(-)
---
diff --git a/libpeas/peas-object-module.c b/libpeas/peas-object-module.c
index 10e7d82..d48b6fb 100644
--- a/libpeas/peas-object-module.c
+++ b/libpeas/peas-object-module.c
@@ -108,8 +108,23 @@ peas_object_module_load (GTypeModule *gmodule)
     {
       gchar *path;
       GModuleFlags flags = 0;
+      gchar *fallback_path = NULL;
 
-      path = g_module_build_path (priv->path, priv->module_name);
+#ifdef G_OS_WIN32
+      if (!g_str_has_suffix (priv->module_name, "." G_MODULE_SUFFIX))
+        {
+          /* On Windows, g_module_build_path() will add a "lib" prefix,
+           * to the module_name unless a ".dll" suffix is appended to the
+           * module_name. So, we also try to look for a DLL whose filename
+           * is the module name in the case that lib<module_name>.dll is
+           * not found, as it is commonly the case on Meson builds and
+           * also likely in other cases.
+           */
+          gchar *mod_file = g_strconcat (priv->module_name, "." G_MODULE_SUFFIX, NULL);
+          fallback_path = g_module_build_path (priv->path, mod_file);
+          g_free (mod_file);
+        }
+#endif
 
       /* g_module_build_path() will add G_MODULE_SUFFIX to the path,
        * however g_module_open() will only try to load the libtool archive
@@ -117,6 +132,8 @@ peas_object_module_load (GTypeModule *gmodule)
        * which allows uninstalled builds to load plugins as well, as there
        * is only the .la file in the build directory.
        */
+      path = g_module_build_path (priv->path, priv->module_name);
+
       if (G_MODULE_SUFFIX[0] != '\0' && g_str_has_suffix (path, "." G_MODULE_SUFFIX))
         path[strlen (path) - strlen (G_MODULE_SUFFIX) - 1] = '\0';
 
@@ -125,6 +142,16 @@ peas_object_module_load (GTypeModule *gmodule)
 
       /* Bind symbols immediately to avoid errors long after loading */
       priv->library = g_module_open (path, flags);
+
+      /* Windows case if lib<module_name>.dll cannot be found */
+      if (fallback_path != NULL)
+        {
+          if (priv->library == NULL)
+            priv->library = g_module_open (fallback_path, flags);
+
+          g_free (fallback_path);
+        }
+
       g_free (path);
     }