fix(ui-theme): create persist/ before writing the saved theme

cj/theme-write-file-contents guarded on file-writable-p, which returns nil when the target's directory doesn't exist. On a fresh machine persist/ isn't there yet, so the theme write failed silently and the choice never persisted. Create the parent directory first, and still return nil if the path isn't writable.

2 files changed, 21 insertions, 2 deletions

diff --git a/modules/ui-theme.el b/modules/ui-theme.el
index 499e71a4..b3cdc634 100644
--- a/modules/ui-theme.el
+++ b/modules/ui-theme.el
@@ -88,8 +88,14 @@ If FILENAME isn't readable, return nil."
       (string-trim (buffer-string)))))
 
 (defun cj/theme-write-file-contents (content filename)
-  "Write CONTENT to FILENAME.
-If FILENAME isn't writeable, return nil. If successful, return t."
+  "Write CONTENT to FILENAME, creating its parent directory if absent.
+On a fresh machine the `persist/' directory doesn't exist yet, and
+`file-writable-p' returns nil for a file inside a missing directory, so the
+write would silently fail.  If FILENAME still isn't writeable, return nil.
+If successful, return t."
+  (let ((dir (file-name-directory filename)))
+    (when (and dir (not (file-directory-p dir)))
+      (ignore-errors (make-directory dir t))))
   (when (file-writable-p filename)
     (condition-case err
         (progn
diff --git a/tests/test-ui-theme-persistence.el b/tests/test-ui-theme-persistence.el
index 02bb105a..250b606b 100644
--- a/tests/test-ui-theme-persistence.el
+++ b/tests/test-ui-theme-persistence.el
@@ -32,6 +32,19 @@
                          "modus-vivendi")))
       (delete-file file))))
 
+(ert-deftest test-ui-theme-write-file-contents-creates-missing-parent-dir ()
+  "Boundary: writing into a not-yet-existing directory creates it first.
+On a fresh machine `persist/' does not exist, and `file-writable-p' returns nil
+for a file inside a missing directory, so the write must create the parent."
+  (let* ((sandbox (make-temp-file "ui-theme-sandbox-" t))
+         (file (expand-file-name "persist/emacs-theme" sandbox)))
+    (unwind-protect
+        (progn
+          (should-not (file-directory-p (file-name-directory file)))
+          (should (cj/theme-write-file-contents "modus-vivendi" file))
+          (should (equal (cj/theme-read-file-contents file) "modus-vivendi")))
+      (delete-directory sandbox t))))
+
 (ert-deftest test-ui-theme-write-file-contents-uses-write-region ()
   "Theme persistence should write directly instead of visiting the file."
   (let ((file (make-temp-file "ui-theme-write-region-"))