[tepl] FileMetadata: have a second GFileInfo for the *modified* metadata

[Sébastien Wilmet <swilmet src gnome org>]

commit 0e267b740f0462593c4d00adca0ac140e04cdf64
Author: Sébastien Wilmet <swilmet gnome org>
Date:   Thu Apr 9 14:00:40 2020 +0200

    FileMetadata: have a second GFileInfo for the *modified* metadata
    
    Plus other minor improvements to the code, while I'm at it.
    
    The unit tests succeed now.

 tepl/tepl-file-metadata.c | 86 ++++++++++++++++++++++++++++++++++-------------
 1 file changed, 63 insertions(+), 23 deletions(-)
---
diff --git a/tepl/tepl-file-metadata.c b/tepl/tepl-file-metadata.c
index 650a49a..40ddfdf 100644
--- a/tepl/tepl-file-metadata.c
+++ b/tepl/tepl-file-metadata.c
@@ -63,8 +63,15 @@ typedef struct _TeplFileMetadataPrivate TeplFileMetadataPrivate;
 
 struct _TeplFileMetadataPrivate
 {
-       /* Never NULL */
-       GFileInfo *file_info;
+       /* Never NULL. Contains all metadata that was loaded with
+        * tepl_file_metadata_load_async() or set with tepl_file_metadata_set().
+        */
+       GFileInfo *file_info_all;
+
+       /* Can be NULL. Contains the metadata that has been modified by calling
+        * tepl_file_metadata_set(), but which has not yet been saved.
+        */
+       GFileInfo *file_info_modified;
 
 #if 0
        guint use_gvfs_metadata : 1;
@@ -85,7 +92,7 @@ get_metadata_attribute_key (const gchar *key)
 static void
 print_fallback_to_metadata_store_warning (void)
 {
-       g_warning_once ("GVfs metadata is not supported. Fallback to TeplMetadataStore. "
+       g_warning_once ("GVfs metadata are not supported. Fallback to TeplMetadataStore. "
                        "Either GVfs is not correctly installed or GVfs metadata are "
                        "not supported on this platform. In the latter case, you should "
                        "configure Tepl with -Dgvfs_metadata=false.");
@@ -98,7 +105,8 @@ tepl_file_metadata_finalize (GObject *object)
 
        priv = tepl_file_metadata_get_instance_private (TEPL_FILE_METADATA (object));
 
-       g_object_unref (priv->file_info);
+       g_object_unref (priv->file_info_all);
+       g_clear_object (&priv->file_info_modified);
 
        G_OBJECT_CLASS (tepl_file_metadata_parent_class)->finalize (object);
 }
@@ -116,7 +124,7 @@ tepl_file_metadata_init (TeplFileMetadata *metadata)
 {
        TeplFileMetadataPrivate *priv = tepl_file_metadata_get_instance_private (metadata);
 
-       priv->file_info = g_file_info_new ();
+       priv->file_info_all = g_file_info_new ();
 
 #if 0
 /* TODO change the #ifdef to an #if. */
@@ -168,10 +176,10 @@ tepl_file_metadata_get (TeplFileMetadata *metadata,
 
        attribute_key = get_metadata_attribute_key (key);
 
-       if (g_file_info_has_attribute (priv->file_info, attribute_key) &&
-           g_file_info_get_attribute_type (priv->file_info, attribute_key) == G_FILE_ATTRIBUTE_TYPE_STRING)
+       if (g_file_info_has_attribute (priv->file_info_all, attribute_key) &&
+           g_file_info_get_attribute_type (priv->file_info_all, attribute_key) == 
G_FILE_ATTRIBUTE_TYPE_STRING)
        {
-               value = g_strdup (g_file_info_get_attribute_string (priv->file_info, attribute_key));
+               value = g_strdup (g_file_info_get_attribute_string (priv->file_info_all, attribute_key));
        }
 
        g_free (attribute_key);
@@ -218,18 +226,34 @@ tepl_file_metadata_set (TeplFileMetadata *metadata,
 
        priv = tepl_file_metadata_get_instance_private (metadata);
 
+       if (priv->file_info_modified == NULL)
+       {
+               priv->file_info_modified = g_file_info_new ();
+       }
+
        attribute_key = get_metadata_attribute_key (key);
 
        if (value != NULL)
        {
-               g_file_info_set_attribute_string (priv->file_info,
+               g_file_info_set_attribute_string (priv->file_info_all,
+                                                 attribute_key,
+                                                 value);
+
+               g_file_info_set_attribute_string (priv->file_info_modified,
                                                  attribute_key,
                                                  value);
        }
        else
        {
-               /* Unset the key */
-               g_file_info_set_attribute (priv->file_info,
+               g_file_info_remove_attribute (priv->file_info_all, attribute_key);
+
+               /* Unset the key. If we call g_file_info_remove_attribute() on
+                * priv->file_info_modified, then when calling
+                * tepl_file_metadata_save_async(), the metadata attribute will
+                * not get removed, it would just be ignored (since it would not
+                * be there in the GFileInfo anymore).
+                */
+               g_file_info_set_attribute (priv->file_info_modified,
                                           attribute_key,
                                           G_FILE_ATTRIBUTE_TYPE_INVALID,
                                           NULL);
@@ -247,37 +271,38 @@ load_metadata_async_cb (GObject      *source_object,
        GTask *task = G_TASK (user_data);
        TeplFileMetadata *metadata;
        TeplFileMetadataPrivate *priv;
-       GFileInfo *file_info;
+       GFileInfo *loaded_file_info;
        GError *error = NULL;
 
        metadata = g_task_get_source_object (task);
        priv = tepl_file_metadata_get_instance_private (metadata);
 
-       file_info = g_file_query_info_finish (location, result, &error);
+       loaded_file_info = g_file_query_info_finish (location, result, &error);
 
        if (g_error_matches (error, G_IO_ERROR, G_IO_ERROR_NOT_SUPPORTED))
        {
                print_fallback_to_metadata_store_warning ();
-               //priv->use_gvfs_metadata = FALSE;
 
                g_clear_error (&error);
-               g_clear_object (&file_info);
-
-               /* TODO: load from TeplMetadataStore. */
-               file_info = NULL;
+               g_clear_object (&loaded_file_info);
        }
 
        if (error != NULL)
        {
                g_task_return_error (task, error);
                g_object_unref (task);
-               g_clear_object (&file_info);
+               g_clear_object (&loaded_file_info);
                return;
        }
 
-       if (file_info != NULL)
+       if (loaded_file_info != NULL)
        {
-               g_set_object (&priv->file_info, file_info);
+               /* FIXME: is it the right thing to do? */
+
+               g_object_unref (priv->file_info_all);
+               priv->file_info_all = loaded_file_info;
+
+               g_clear_object (&priv->file_info_modified);
        }
 
        g_task_return_boolean (task, TRUE);
@@ -298,7 +323,8 @@ load_metadata_async_cb (GObject      *source_object,
  * Loads asynchronously the metadata for @location.
  *
  * If the metadata are loaded successfully, this function deletes all previous
- * metadata stored in the @metadata object memory.
+ * metadata stored in the @metadata object memory. FIXME: is it the right thing
+ * to do?
  *
  * @location must exist on the filesystem, otherwise an error is returned.
  *
@@ -362,8 +388,13 @@ save_metadata_async_cb (GObject      *source_object,
 {
        GFile *location = G_FILE (source_object);
        GTask *task = G_TASK (user_data);
+       TeplFileMetadata *metadata;
+       TeplFileMetadataPrivate *priv;
        GError *error = NULL;
 
+       metadata = g_task_get_source_object (task);
+       priv = tepl_file_metadata_get_instance_private (metadata);
+
        g_file_set_attributes_finish (location, result, NULL, &error);
 
        if (g_error_matches (error, G_IO_ERROR, G_IO_ERROR_NOT_SUPPORTED))
@@ -379,6 +410,8 @@ save_metadata_async_cb (GObject      *source_object,
                return;
        }
 
+       g_clear_object (&priv->file_info_modified);
+
        g_task_return_boolean (task, TRUE);
        g_object_unref (task);
 }
@@ -422,8 +455,15 @@ tepl_file_metadata_save_async (TeplFileMetadata    *metadata,
        task = g_task_new (metadata, cancellable, callback, user_data);
        g_task_set_priority (task, io_priority);
 
+       if (priv->file_info_modified == NULL)
+       {
+               g_task_return_boolean (task, TRUE);
+               g_object_unref (task);
+               return;
+       }
+
        g_file_set_attributes_async (location,
-                                    priv->file_info,
+                                    priv->file_info_modified,
                                     G_FILE_QUERY_INFO_NONE,
                                     io_priority,
                                     cancellable,