fixed rub out of file writes to non-existing symlinks

* teco_file_get_absolute_path() does not currently guarantee to resolve
  non-existent parts of the path.
  When opening a symbolic link to a non-existing file, it would only
  be created when writing out the file.
  The undo token to remove it, however would remove the original
  unresolved path.
  When rubbing out the EW, the symlink would get removed instead
  of the newly written file.
* We now resolve/canonicalize the path again immediately after
  opening the new file, which should ensure that it resolves.
* As an alternative, we might have also tried to reliably canonicalize
  non-existent symlinks. This however is tricky and there would have
  to be a break condition to guard against cyclic symlinke.
  In the end there is no guarantee to be able to resolve a path
  exactly like the OS does.
  Therefore, teco_file_get_absolute_path() was not touched,
  not even on UNIX.
* A test case was not added since it would rely on creating real symlinks.
  It wouldn't work on MSYS when `ln -s` falls back to hardlinks.
  Perhaps other non-UNIX platforms would have similar restrictions.

1 files changed, 16 insertions, 3 deletions

diff --git a/src/view.c b/src/view.c
index 702c5b6..53199bd 100644
--- a/src/view.c
+++ b/src/view.c
@@ -550,16 +550,16 @@ teco_view_save_to_file(teco_view_t *ctx, const gchar *filename, GError **error)
 	file_stat.st_gid = -1;
 #endif
 	teco_file_attributes_t attributes = TECO_FILE_INVALID_ATTRIBUTES;
+	gboolean undo_remove_file = FALSE;
 
 	if (teco_undo_enabled) {
-		if (g_file_test(filename, G_FILE_TEST_IS_REGULAR)) {
+		undo_remove_file = !g_file_test(filename, G_FILE_TEST_IS_REGULAR);
+		if (!undo_remove_file) {
 #ifdef G_OS_UNIX
 			g_stat(filename, &file_stat);
 #endif
 			attributes = teco_file_get_attributes(filename);
 			teco_make_savepoint(filename);
-		} else {
-			teco_undo_remove_file_push(filename);
 		}
 	}
 
@@ -568,6 +568,18 @@ teco_view_save_to_file(teco_view_t *ctx, const gchar *filename, GError **error)
 	if (!channel)
 		return FALSE;
 
+	if (undo_remove_file) {
+		/*
+		 * The file is new, so has to be removed on undo.
+		 * If `filename` is a symlink, it's crucial to resolve it now,
+		 * since early canonicalization may have failed (for non-existent
+		 * path segments).
+		 * Now, `filename` is guaranteed to exist.
+		 */
+		g_autofree gchar *filename_canon = teco_file_get_absolute_path(filename);
+		teco_undo_remove_file_push(filename_canon);
+	}
+
 	/*
 	 * teco_view_save_to_channel() expects a buffered and blocking channel
 	 */
@@ -576,6 +588,7 @@ teco_view_save_to_file(teco_view_t *ctx, const gchar *filename, GError **error)
 
 	if (!teco_view_save_to_channel(ctx, channel, error)) {
 		g_prefix_error(error, "Error writing file \"%s\": ", filename);
+		/* file might also be removed (in interactive mode) */
 		return FALSE;
 	}