Crash (assertion location != NULL) when browsing a folder through favorites:/// and a file needs a thumbnail

[armint]

Distribution / versions

• Arch Linux, Cinnamon session on X11
• nemo 6.6.4, xapp 3.2.3, glib2 2.88.3, gtk3 3.24.52, cinnamon-desktop 6.6.2, glycin 2.1.5
• The code path is unchanged on current master.

Issue

Nemo aborts when it shows the contents of a favorited folder through its favorites:///<name> location, and that folder contains a file that has no cached thumbnail yet. The same folder opens without problems through its normal file:// path.

(nemo): Nemo-WARNING **: File has symlink target, but  is not marked as symlink
(nemo): GLib-GIO-CRITICAL **: g_file_new_for_uri: assertion 'uri != NULL' failed
**
Nemo:ERROR:../nemo/libnemo-private/nemo-file.c:679:nemo_file_get_internal: assertion failed: (location != NULL)
Bail out! Nemo:ERROR:../nemo/libnemo-private/nemo-file.c:679:nemo_file_get_internal: assertion failed: (location != NULL)

Steps to reproduce

1. Add a folder that contains images (e.g. PNG/JPG/SVG) to Favorites, for example ~/tmp.
2. Make sure those images have no thumbnails yet. For a clean test, run nemo with an empty cache: XDG_CACHE_HOME=$(mktemp -d) nemo favorites:///tmp
3. Nemo crashes with SIGABRT as soon as the list view renders the icons.

Control test: XDG_CACHE_HOME=$(mktemp -d) nemo ~/tmp works and creates the thumbnails.

Expected behaviour

Nemo shows the folder contents and creates thumbnails (or just shows the generic icons). It does not crash.

Stack trace (main thread)

#4  g_assertion_message_expr            (libglib-2.0)
#5  nemo_file_get_internal              nemo-file.c:679  (via nemo_file_get_by_uri)
#6  nemo_create_thumbnail               nemo-thumbnails.c
#7  nemo_file_get_icon                  nemo-file.c
#8  nemo_list_model_get_value           nemo-list-model.c
#17 gtk_cell_area_apply_attributes      (libgtk-3)
...
#25 g_application_run

(Frames 5–8 were mapped against the 6.6.4 source. The binary has no symbols, but the assertion message and the call chain match.)

Analysis

In libnemo-private/nemo-thumbnails.c, nemo_create_thumbnail() does:

if (nemo_file_is_in_favorites (file)) {
    uri = nemo_file_get_symbolic_link_target_uri (file);
    real_file = nemo_file_get_by_uri (uri);   /* uri can be NULL */
    ...
}

nemo_file_is_in_favorites() → nemo_directory_is_in_favorites() only checks whether the parent directory has the favorites URI scheme. That is true for the top-level items in favorites:///, which XApp exposes as symlinks. It is also true for every file inside a favorited folder opened as favorites:///<folder>. Those files are not symlinks, so symlink_name is NULL and nemo_file_get_symbolic_link_target_uri() returns NULL. That produces the "is not marked as symlink" warning. Then nemo_file_get_by_uri (NULL) → g_file_new_for_uri (NULL) returns NULL → g_assert (location != NULL) aborts.

Possible fix

At a minimum, only follow the link when there is one, for example:

if (nemo_file_is_in_favorites (file) && nemo_file_is_symbolic_link (file)) {

or check uri != NULL before calling nemo_file_get_by_uri(). A complete fix also needs to resolve the real file:// location for files below a favorited folder, so that they get thumbnails too.

[mtwebster]

I can reproduce this only if I launch nemo directly at favorites:///folder. If I navigate to it via the sidebar, there's no issue. Can you confirm the same behavior?