feat(mail): annotate the attachment picker with MIME type and size

cj/mu4e-save-attachment-here now completes through an annotated table (category mu4e-attachment), so marginalia shows each attachment's MIME type and decoded size beside the filename. Unknown candidates annotate as nil. The existing picker test queries the function table via all-completions instead of car-mapping the old alist.

2 files changed, 70 insertions, 3 deletions

diff --git a/modules/mu4e-attachments.el b/modules/mu4e-attachments.el
index 4acdfd6a..6c2be6fb 100644
--- a/modules/mu4e-attachments.el
+++ b/modules/mu4e-attachments.el
@@ -15,6 +15,7 @@
 ;;; Code:
 
 (require 'seq)
+(require 'system-lib)  ;; cj/completion-table-annotated
 
 (defvar mu4e-uniquify-save-file-name-function)
 (defvar-local cj/mu4e-attachment-selection-directory nil
@@ -67,6 +68,19 @@ The result is an alist of display labels to MIME part plists."
               (cons (cj/mu4e--attachment-label part duplicates) part))
             parts)))
 
+(defun cj/mu4e--attachment-annotator (candidates)
+  "Return an annotation function over attachment CANDIDATES.
+CANDIDATES is the label->part alist from `cj/mu4e--attachment-candidates'.
+The annotation shows the part's MIME type and human-readable decoded
+size; an unknown candidate annotates as nil so marginalia shows nothing."
+  (lambda (cand)
+    (when-let* ((part (cdr (assoc cand candidates))))
+      (let ((mime (or (plist-get part :mime-type) ""))
+            (size (if-let* ((bytes (plist-get part :decoded-size-approx)))
+                      (file-size-human-readable bytes)
+                    "")))
+        (format "  %-24s %s" mime size)))))
+
 (defun cj/mu4e--attachment-default-directory (parts)
   "Return a sensible default save directory for attachment PARTS."
   (file-name-as-directory
@@ -126,7 +140,13 @@ The result is an alist of display labels to MIME part plists."
       (user-error "No attachments for this message"))
     (let* ((directory (cj/mu4e--read-attachment-directory parts))
            (candidates (cj/mu4e--attachment-candidates parts))
-           (choice (completing-read "Save attachment: " candidates nil t))
+           (choice (completing-read
+                    "Save attachment: "
+                    (cj/completion-table-annotated
+                     'mu4e-attachment
+                     (cj/mu4e--attachment-annotator candidates)
+                     candidates)
+                    nil t))
            (part (cdr (assoc choice candidates)))
            (path (cj/mu4e--save-attachment-part part directory)))
       (message "Saved attachment to %s" path)
diff --git a/tests/test-mu4e-attachments.el b/tests/test-mu4e-attachments.el
index 21336f75..0a780977 100644
--- a/tests/test-mu4e-attachments.el
+++ b/tests/test-mu4e-attachments.el
@@ -108,8 +108,10 @@ so this fails the same way whether or not mu4e's MIME support is loadable."
               ((symbol-function 'read-directory-name)
                (lambda (&rest _) "/downloads/"))
               ((symbol-function 'completing-read)
-               (lambda (_prompt candidates &rest _)
-                 (should (equal (mapcar #'car candidates)
+               ;; the collection is an annotated function table now, so
+               ;; query it instead of car-mapping an alist
+               (lambda (_prompt collection &rest _)
+                 (should (equal (all-completions "" collection)
                                 '("a.pdf" "b.pdf")))
                  "b.pdf"))
               ((symbol-function 'cj/mu4e--save-attachment-part)
@@ -252,5 +254,50 @@ so this fails the same way whether or not mu4e's MIME support is loadable."
                         :type 'user-error))
       (kill-buffer buffer))))
 
+;; ------------------------- Picker Annotations --------------------------------
+
+(ert-deftest test-mu4e-attachments-annotator-shows-mime-and-size ()
+  "Normal: the annotator yields MIME type and human-readable size."
+  (let* ((part (plist-put (test-mu4e-attachments--part "invoice.pdf" 1)
+                          :decoded-size-approx 2048))
+         (candidates (list (cons "invoice.pdf" part)))
+         (annotate (cj/mu4e--attachment-annotator candidates))
+         (suffix (funcall annotate "invoice.pdf")))
+    (should (stringp suffix))
+    (should (string-match-p "application/pdf" suffix))
+    (should (string-match-p "2k" suffix))))
+
+(ert-deftest test-mu4e-attachments-annotator-no-size ()
+  "Boundary: a part without a decoded size still annotates the MIME type."
+  (let* ((candidates (list (cons "invoice.pdf"
+                                 (test-mu4e-attachments--part "invoice.pdf" 1))))
+         (annotate (cj/mu4e--attachment-annotator candidates))
+         (suffix (funcall annotate "invoice.pdf")))
+    (should (stringp suffix))
+    (should (string-match-p "application/pdf" suffix))))
+
+(ert-deftest test-mu4e-attachments-annotator-unknown-candidate-nil ()
+  "Error: an unknown candidate annotates as nil (marginalia shows nothing)."
+  (let ((annotate (cj/mu4e--attachment-annotator nil)))
+    (should-not (funcall annotate "nope.txt"))))
+
+(ert-deftest test-mu4e-attachments-picker-uses-annotated-category ()
+  "Normal: the save-here picker's collection carries category + annotator."
+  (let ((captured-collection nil))
+    (cl-letf (((symbol-function 'cj/mu4e--attachment-parts)
+               (lambda (&rest _) (list (test-mu4e-attachments--part "a.pdf" 1))))
+              ((symbol-function 'cj/mu4e--read-attachment-directory)
+               (lambda (&rest _) "/tmp/x/"))
+              ((symbol-function 'cj/mu4e--save-attachment-part)
+               (lambda (&rest _) "/tmp/x/a.pdf"))
+              ((symbol-function 'completing-read)
+               (lambda (_prompt collection &rest _)
+                 (setq captured-collection collection)
+                 "a.pdf")))
+      (cj/mu4e-save-attachment-here)
+      (let ((md (funcall captured-collection "" nil 'metadata)))
+        (should (eq (alist-get 'category (cdr md)) 'mu4e-attachment))
+        (should (functionp (alist-get 'annotation-function (cdr md))))))))
+
 (provide 'test-mu4e-attachments)
 ;;; test-mu4e-attachments.el ends here