[gnome-software: 3/9] download-utils: Return new NOT_MODIFIED error if ETags match

[Milan Crha <mcrha src gnome org>]

commit 56a9d3b4239c0841c3be5bc3b49db3d86321adbd
Author: Georges Basile Stavracas Neto <georges stavracas gmail com>
Date:   Mon Sep 12 13:56:35 2022 -0300

    download-utils: Return new NOT_MODIFIED error if ETags match
    
    The downloading routines of GNOME Software treat matching ETags
    as not errors, however, there are circumstances where it'll be
    important to react to this result differently from other error
    paths.
    
    Add the GS_DOWNLOAD_ERROR quark, and GS_DOWNLOAD_ERROR_NOT_MODIFIED
    to represent that case. Next commits will adjust the error paths of
    consumers of this API to not do anything, or react appropriately,
    if that error is reported.

 lib/gs-download-utils.c | 18 +++++++++++++++---
 lib/gs-download-utils.h | 15 +++++++++++++++
 2 files changed, 30 insertions(+), 3 deletions(-)
---
diff --git a/lib/gs-download-utils.c b/lib/gs-download-utils.c
index 0a0a316a1..494906483 100644
--- a/lib/gs-download-utils.c
+++ b/lib/gs-download-utils.c
@@ -28,6 +28,8 @@
 #include "gs-download-utils.h"
 #include "gs-utils.h"
 
+G_DEFINE_QUARK (gs-download-error-quark, gs_download_error)
+
 /**
  * gs_build_soup_session:
  *
@@ -348,7 +350,11 @@ open_input_stream_cb (GObject      *source_object,
                        data->discard_output_stream = TRUE;
                        data->new_etag = g_strdup (data->last_etag);
                        data->new_last_modified_date = (data->last_modified_date != NULL) ? g_date_time_ref 
(data->last_modified_date) : NULL;
-                       finish_download (task, NULL);
+                       finish_download (task,
+                                        g_error_new (GS_DOWNLOAD_ERROR,
+                                                     GS_DOWNLOAD_ERROR_NOT_MODIFIED,
+                                                     "Skipped downloading ‘%s’: %s",
+                                                     data->uri, soup_status_get_phrase (status_code)));
                        return;
                } else if (status_code != SOUP_STATUS_OK) {
                        g_autoptr(GString) str = g_string_new (NULL);
@@ -491,6 +497,12 @@ write_bytes_cb (GObject      *source_object,
        }
 }
 
+static inline gboolean
+is_not_modidifed_error (GError *error)
+{
+       return g_error_matches (error, GS_DOWNLOAD_ERROR, GS_DOWNLOAD_ERROR_NOT_MODIFIED);
+}
+
 /* error is (transfer full) */
 static void
 finish_download (GTask  *task,
@@ -500,7 +512,7 @@ finish_download (GTask  *task,
        GCancellable *cancellable = g_task_get_cancellable (task);
 
        /* Final progress update. */
-       if (error == NULL) {
+       if (error == NULL || is_not_modidifed_error (error)) {
                data->expected_stream_size_bytes = data->total_read_bytes;
                download_progress (task);
        }
@@ -520,7 +532,7 @@ finish_download (GTask  *task,
                 * output stream (perhaps because of a cache hit), close the
                 * output stream but cancel the close operation so that the old
                 * output file is not overwritten. */
-               if (data->error != NULL || data->discard_output_stream) {
+               if ((data->error != NULL && !is_not_modidifed_error (data->error)) || 
data->discard_output_stream) {
                        output_cancellable = g_cancellable_new ();
                        g_cancellable_cancel (output_cancellable);
                } else if (g_task_get_cancellable (task) != NULL) {
diff --git a/lib/gs-download-utils.h b/lib/gs-download-utils.h
index 6ab568579..cd9dd46cd 100644
--- a/lib/gs-download-utils.h
+++ b/lib/gs-download-utils.h
@@ -40,6 +40,21 @@ typedef void (*GsDownloadProgressCallback) (gsize    bytes_downloaded,
                                             gsize    total_download_size,
                                             gpointer user_data);
 
+/**
+ * GsExternalAppstreamError:
+ * @GS_DOWNLOAD_ERROR_NOT_MODIFIED: The ETag matches that of the server file.
+ *
+ * Error codes for download operations.
+ *
+ * Since: 44
+ */
+typedef enum {
+       GS_DOWNLOAD_ERROR_NOT_MODIFIED,
+} GsDownloadError;
+
+#define GS_DOWNLOAD_ERROR gs_download_error_quark ()
+GQuark          gs_download_error_quark (void);
+
 void           gs_download_stream_async        (SoupSession                *soup_session,
                                                 const gchar                *uri,
                                                 GOutputStream              *output_stream,