Merge branch 'wip/pwithnall/2777-zerosize' into 'main'

gio: Change content type of zero-sized files to application/x-zerosize

Closes #2777

See merge request GNOME/glib!3053

gio/glocalfileinfo.c

@@ -1361,12 +1361,8 @@ get_content_type (const char          *basename,
     {
       /* Don't sniff zero-length files in order to avoid reading files
        * that appear normal but are not (eg: files in /proc and /sys)
-       *
-       * Note that we need to return text/plain here so that
-       * newly-created text files are opened by the text editor.
-       * See https://bugzilla.gnome.org/show_bug.cgi?id=755795
        */
-      return g_content_type_from_mime_type ("text/plain");
+      return g_content_type_from_mime_type ("application/x-zerosize");
     }
 #endif
 #ifdef S_ISSOCK

gio/gosxcontenttype.m

@@ -419,6 +419,12 @@ g_content_type_from_mime_type (const gchar *mime_type)
   if (strcmp (mime_type, "text/plain") == 0)
     return g_strdup ("public.text");
 
+  /* I don’t know of an appropriate equivalent for application/x-zerosize, but
+   * historically GLib has returned public.text for zero-sized files, so let’s
+   * continue doing that. */
+  if (strcmp (mime_type, "application/x-zerosize") == 0)
+    return g_strdup ("public.text");
+
   /* Non standard type */
   if (strcmp (mime_type, "application/x-executable") == 0)
     return g_strdup ("public.executable");

gio/tests/file.c

@@ -3537,10 +3537,14 @@ test_query_zero_length_content_type (void)
   GFileIOStream *iostream;
 
   g_test_bug ("https://bugzilla.gnome.org/show_bug.cgi?id=755795");
-  /* This is historic behaviour. See:
+  /* Historically, GLib used to explicitly consider zero-size files as text/plain,
+   * so they opened in a text editor. In 2.76, we changed that to application/x-zerosize,
+   * because that’s what xdgmime uses:
    * - https://gitlab.gnome.org/GNOME/glib/-/blob/2.74.0/gio/glocalfileinfo.c#L1360-1369
-   * - https://bugzilla.gnome.org/show_bug.cgi?id=755795 */
-  g_test_summary ("empty files should always be considered text/plain");
+   * - https://bugzilla.gnome.org/show_bug.cgi?id=755795
+   * - https://gitlab.gnome.org/GNOME/glib/-/issues/2777
+   */
+  g_test_summary ("empty files should always be considered application/x-zerosize");
 
   empty_file = g_file_new_tmp ("empty-file-XXXXXX", &iostream, &error);
   g_assert_no_error (error);
@@ -3557,7 +3561,7 @@ test_query_zero_length_content_type (void)
   g_assert_no_error (error);
 
 #ifndef __APPLE__
-  g_assert_cmpstr (g_file_info_get_content_type (file_info), ==, "text/plain");
+  g_assert_cmpstr (g_file_info_get_content_type (file_info), ==, "application/x-zerosize");
 #else
   g_assert_cmpstr (g_file_info_get_content_type (file_info), ==, "public.text");
 #endif