feat(buffer-file): make the disk-changed diff review navigable

Pressing d in the C-x C-s conflict menu (and the save-some loop) now enters a modal review instead of a peek-and-return toggle: point lands on the first hunk, arrows and TAB move through the changes, and the menu keys act from inside the diff. difftastic gets --context 1 and an explicit --width, since as a subprocess it can't detect the terminal and wrapped at 80 columns. A new m choice resolves the conflict in ediff. I kept the post-merge save re-asking once, so an abandoned merge can't silently overwrite the disk version.

1 files changed, 261 insertions, 0 deletions

diff --git a/tests/test-custom-buffer-file--diff-review.el b/tests/test-custom-buffer-file--diff-review.el
new file mode 100644
index 00000000..5418638d
--- /dev/null
+++ b/tests/test-custom-buffer-file--diff-review.el
@@ -0,0 +1,261 @@
+;;; test-custom-buffer-file--diff-review.el --- navigable diff review pieces -*- lexical-binding: t; -*-
+
+;;; Commentary:
+;; Pure-logic tests for the navigable diff review added to the disk-changed save
+;; prompts: the diff command argument builders (context + width), first-hunk
+;; positioning, the generated review keymap (menu keys act inside the diff, q
+;; goes back, TAB/S-TAB navigate), the merge menu entry, and the reworked
+;; read-choice loop (d enters the review; a review choice terminates the
+;; prompt).  The recursive-edit itself and the live window interaction are
+;; exercised manually, not here.
+
+;;; Code:
+
+(require 'ert)
+(require 'cl-lib)
+(add-to-list 'load-path (expand-file-name "modules" user-emacs-directory))
+(require 'custom-buffer-file)
+
+(declare-function cj/--difft-args "custom-buffer-file" (file1 file2 context width))
+(declare-function cj/--unified-diff-args "custom-buffer-file" (file1 file2 context))
+(declare-function cj/--diff-review-keymap "custom-buffer-file" (choices))
+(declare-function cj/--diff-review-back "custom-buffer-file" ())
+(declare-function cj/--diff-section-next "custom-buffer-file" ())
+(declare-function cj/--diff-section-prev "custom-buffer-file" ())
+(declare-function cj/--diff-review "custom-buffer-file" (diff-buffer choices))
+(declare-function cj/--diff-with-regular-diff "custom-buffer-file" (file1 file2 buffer))
+(declare-function cj/--diff-with-difftastic "custom-buffer-file" (file1 file2 buffer))
+(declare-function cj/--buffer-differs-choices "custom-buffer-file" ())
+(declare-function cj/--buffer-differs-action "custom-buffer-file" (key))
+(declare-function cj/--buffer-differs-dispatch "custom-buffer-file" (buffer action))
+(declare-function cj/--save-some-buffers-choices "custom-buffer-file" ())
+(declare-function cj/--read-choice-with-diff "custom-buffer-file" (prompt choices show-diff-fn))
+
+(defvar cj/--diff-review-choice)
+(defvar cj/diff-context-lines)
+
+;;; ------------------------------ arg builders --------------------------------
+
+(ert-deftest test-cbf-difft-args-context-and-width ()
+  "Normal: difft args carry the context and width knobs plus both files."
+  (let ((args (cj/--difft-args "/a.el" "/b.el" 1 143)))
+    (should (member "--context" args))
+    (should (member "1" args))
+    (should (member "--width" args))
+    (should (member "143" args))
+    (should (member "/a.el" args))
+    (should (member "/b.el" args))))
+
+(ert-deftest test-cbf-difft-args-color-and-display ()
+  "Normal: difft args keep forced color and the side-by-side display."
+  (let ((args (cj/--difft-args "/a" "/b" 3 80)))
+    (should (member "--color" args))
+    (should (member "always" args))
+    (should (member "side-by-side-show-both" args))))
+
+(ert-deftest test-cbf-difft-args-zero-context ()
+  "Boundary: context 0 is passed through, not dropped."
+  (let ((args (cj/--difft-args "/a" "/b" 0 80)))
+    (should (member "--context" args))
+    (should (member "0" args))))
+
+(ert-deftest test-cbf-unified-diff-args-context ()
+  "Normal: unified diff args use -U<context> and both files, in order."
+  (should (equal (cj/--unified-diff-args "/a" "/b" 1) '("-U1" "/a" "/b"))))
+
+(ert-deftest test-cbf-unified-diff-args-zero-context ()
+  "Boundary: context 0 produces -U0."
+  (should (equal (car (cj/--unified-diff-args "/a" "/b" 0)) "-U0")))
+
+;;; ------------------------- first-hunk positioning ---------------------------
+
+(defun test-cbf-review--two-files (line-changed body-fn)
+  "Make two 60-line temp files differing at LINE-CHANGED; call BODY-FN with both."
+  (let ((f1 (make-temp-file "cbf-rev-a-" nil ".txt"))
+        (f2 (make-temp-file "cbf-rev-b-" nil ".txt")))
+    (unwind-protect
+        (progn
+          (with-temp-file f1
+            (dotimes (i 60) (insert (format "line %d stays the same\n" (1+ i)))))
+          (with-temp-file f2
+            (dotimes (i 60)
+              (insert (if (= (1+ i) line-changed)
+                          (format "line %d CHANGED in buffer\n" (1+ i))
+                        (format "line %d stays the same\n" (1+ i))))))
+          (funcall body-fn f1 f2))
+      (when (file-exists-p f1) (delete-file f1))
+      (when (file-exists-p f2) (delete-file f2)))))
+
+(ert-deftest test-cbf-regular-diff-lands-on-first-hunk ()
+  "Normal: after rendering a unified diff, point sits on the first @@ hunk line."
+  (test-cbf-review--two-files
+   30
+   (lambda (f1 f2)
+     (with-temp-buffer
+       (cj/--diff-with-regular-diff f1 f2 (current-buffer))
+       (should (looking-at "@@"))))))
+
+(ert-deftest test-cbf-difftastic-lands-past-headers ()
+  "Normal: after rendering difftastic output, point sits on hunk content, not the headers."
+  (skip-unless (executable-find "difft"))
+  (test-cbf-review--two-files
+   30
+   (lambda (f1 f2)
+     (with-temp-buffer
+       (cj/--diff-with-difftastic f1 f2 (current-buffer))
+       (should (> (line-number-at-pos) 2))          ; past our two-line header
+       (should-not (looking-at-p ".* --- "))         ; past difft's file header
+       (should-not (eolp))))))                       ; on a content line, not a blank
+
+;;; ------------------------------ review keymap -------------------------------
+
+(ert-deftest test-cbf-review-keymap-binds-menu-keys ()
+  "Normal: every buffer-differs menu key except d becomes a review binding."
+  (let ((map (cj/--diff-review-keymap (cj/--buffer-differs-choices))))
+    (dolist (key '(?s ?w ?r ?m ?c))
+      (should (commandp (lookup-key map (vector key)))))
+    (should-not (lookup-key map (vector ?d)))))
+
+(ert-deftest test-cbf-review-keymap-q-goes-back-when-free ()
+  "Normal: q maps to back-to-menu when the menu does not claim q."
+  (let ((map (cj/--diff-review-keymap (cj/--buffer-differs-choices))))
+    (should (eq (lookup-key map "q") #'cj/--diff-review-back))))
+
+(ert-deftest test-cbf-review-keymap-q-stays-menu-key-when-claimed ()
+  "Boundary: in the save-some loop q is a menu action, not back-to-menu."
+  (let ((map (cj/--diff-review-keymap (cj/--save-some-buffers-choices))))
+    (should (commandp (lookup-key map "q")))
+    (should-not (eq (lookup-key map "q") #'cj/--diff-review-back))))
+
+(ert-deftest test-cbf-review-keymap-navigation-bound ()
+  "Normal: TAB and S-TAB navigate hunks in every review."
+  (let ((map (cj/--diff-review-keymap (cj/--buffer-differs-choices))))
+    (should (eq (lookup-key map (kbd "TAB")) #'cj/--diff-section-next))
+    (should (eq (lookup-key map (kbd "<backtab>")) #'cj/--diff-section-prev))))
+
+(ert-deftest test-cbf-review-keymap-np-navigate-when-free ()
+  "Normal: n/p navigate hunks when the menu does not claim them."
+  (let ((map (cj/--diff-review-keymap (cj/--buffer-differs-choices))))
+    (should (eq (lookup-key map "n") #'cj/--diff-section-next))
+    (should (eq (lookup-key map "p") #'cj/--diff-section-prev))))
+
+(ert-deftest test-cbf-review-keymap-n-stays-menu-key-when-claimed ()
+  "Boundary: in the save-some loop n is the skip action, not navigation."
+  (let ((map (cj/--diff-review-keymap (cj/--save-some-buffers-choices))))
+    (should (commandp (lookup-key map "n")))
+    (should-not (eq (lookup-key map "n") #'cj/--diff-section-next))))
+
+(ert-deftest test-cbf-review-keymap-escape-always-back ()
+  "Normal: ESC goes back to the menu even when the menu claims q (save-some loop)."
+  (let ((map (cj/--diff-review-keymap (cj/--save-some-buffers-choices))))
+    (should (eq (lookup-key map (kbd "<escape>")) #'cj/--diff-review-back))))
+
+(ert-deftest test-cbf-review-choice-command-records-key ()
+  "Normal: a review action command records its key and exits the review."
+  (let ((map (cj/--diff-review-keymap (cj/--buffer-differs-choices)))
+        (cj/--diff-review-choice nil)
+        (exited nil))
+    (cl-letf (((symbol-function 'exit-recursive-edit)
+               (lambda (&rest _) (setq exited t))))
+      (funcall (lookup-key map "s"))
+      (should (eq cj/--diff-review-choice ?s))
+      (should exited))))
+
+(ert-deftest test-cbf-review-back-leaves-choice-nil ()
+  "Normal: back-to-menu exits the review without recording a choice."
+  (let ((cj/--diff-review-choice nil)
+        (exited nil))
+    (cl-letf (((symbol-function 'exit-recursive-edit)
+               (lambda (&rest _) (setq exited t))))
+      (cj/--diff-review-back)
+      (should-not cj/--diff-review-choice)
+      (should exited))))
+
+;;; ---------------------------- merge menu entry ------------------------------
+
+(ert-deftest test-cbf-buffer-differs-choices-include-merge ()
+  "Normal: the disk-changed menu offers m for merge, described via ediff."
+  (let ((entry (assq ?m (cj/--buffer-differs-choices))))
+    (should entry)
+    (should (string-match-p "ediff" (or (nth 2 entry) "")))))
+
+(ert-deftest test-cbf-buffer-differs-action-merge ()
+  "Normal: m maps to the merge action."
+  (should (eq (cj/--buffer-differs-action ?m) 'merge)))
+
+(ert-deftest test-cbf-buffer-differs-dispatch-merge-launches-ediff ()
+  "Normal: dispatching merge launches ediff-current-file in the conflicted buffer."
+  (let ((launched-in nil))
+    (cl-letf (((symbol-function 'ediff-current-file)
+               (lambda (&rest _) (setq launched-in (current-buffer)))))
+      (with-temp-buffer
+        (cj/--buffer-differs-dispatch (current-buffer) 'merge)
+        (should (eq launched-in (current-buffer)))))))
+
+(ert-deftest test-cbf-buffer-differs-dispatch-merge-keeps-buffer-modified ()
+  "Boundary: merge neither saves nor reverts -- the buffer's state is untouched."
+  (cl-letf (((symbol-function 'ediff-current-file) (lambda (&rest _) nil)))
+    (with-temp-buffer
+      (insert "content")
+      (set-buffer-modified-p t)
+      (cj/--buffer-differs-dispatch (current-buffer) 'merge)
+      (should (buffer-modified-p)))))
+
+;;; ------------------------- read-choice loop rework --------------------------
+
+(defun test-cbf-review--run-loop (rmc-keys review-results &optional diff-buffer)
+  "Drive cj/--read-choice-with-diff with scripted inputs.
+RMC-KEYS are successive read-multiple-choice answers; REVIEW-RESULTS are
+successive cj/--diff-review returns.  DIFF-BUFFER (or a fresh one) is what the
+show-diff-fn yields.  Returns (RESULT RMC-CALLS REVIEW-CALLS)."
+  (let ((rmc-calls 0) (review-calls 0) (keys rmc-keys) (reviews review-results))
+    (cl-letf (((symbol-function 'read-multiple-choice)
+               (lambda (&rest _)
+                 (setq rmc-calls (1+ rmc-calls))
+                 (list (pop keys))))
+              ((symbol-function 'cj/--diff-review)
+               (lambda (&rest _)
+                 (setq review-calls (1+ review-calls))
+                 (pop reviews))))
+      (let ((result (cj/--read-choice-with-diff
+                     "Prompt" (cj/--buffer-differs-choices)
+                     (lambda () diff-buffer))))
+        (list result rmc-calls review-calls)))))
+
+(ert-deftest test-cbf-read-choice-review-choice-terminates ()
+  "Normal: a key chosen inside the diff review terminates the prompt directly."
+  (with-temp-buffer
+    (pcase-let ((`(,result ,rmc-calls ,review-calls)
+                 (test-cbf-review--run-loop '(?d) '(?s) (current-buffer))))
+      (should (eq result ?s))
+      (should (= rmc-calls 1))
+      (should (= review-calls 1)))))
+
+(ert-deftest test-cbf-read-choice-review-back-reprompts ()
+  "Normal: leaving the review without a choice re-shows the menu prompt."
+  (with-temp-buffer
+    (pcase-let ((`(,result ,rmc-calls ,review-calls)
+                 (test-cbf-review--run-loop '(?d ?c) '(nil) (current-buffer))))
+      (should (eq result ?c))
+      (should (= rmc-calls 2))
+      (should (= review-calls 1)))))
+
+(ert-deftest test-cbf-read-choice-no-diff-skips-review ()
+  "Error: when the diff cannot render (no differences), d re-prompts without a review."
+  (pcase-let ((`(,result ,rmc-calls ,review-calls)
+               (test-cbf-review--run-loop '(?d ?c) '(?s) nil)))
+    (should (eq result ?c))
+    (should (= rmc-calls 2))
+    (should (= review-calls 0))))
+
+(ert-deftest test-cbf-read-choice-plain-key-never-reviews ()
+  "Boundary: a terminating menu key never enters the review."
+  (with-temp-buffer
+    (pcase-let ((`(,result ,rmc-calls ,review-calls)
+                 (test-cbf-review--run-loop '(?s) '() (current-buffer))))
+      (should (eq result ?s))
+      (should (= rmc-calls 1))
+      (should (= review-calls 0)))))
+
+(provide 'test-custom-buffer-file--diff-review)
+;;; test-custom-buffer-file--diff-review.el ends here