bug#29007: 25.3; [PATCH] Make filecache use extended completion

[Andreas Politz]

Eli Zaretskii <eliz@gnu.org> writes:

> Thanks.  I think your patch is good for the master branch, but I think
> it should include a NEWS entry about the change.

Take a look and see if it's OK.

diff --git a/etc/NEWS b/etc/NEWS
index 0dd6e36c70..c47ca42d27 100644
--- a/etc/NEWS
+++ b/etc/NEWS
@@ -103,6 +103,12 @@ less verbose by removing non-essential information.
 dimensions, instead of always using 16 pixels. As a result, Tetris,
 Snake and Pong are more playable on HiDPI displays.
 
+** Filecache
+
+---
+*** Completing filenames in the minibuffer via 'C-TAB' now uses the
+styles as configured by the variable 'completion-styles'.
+
 
 * New Modes and Packages in Emacs 27.1
 
diff --git a/lisp/filecache.el b/lisp/filecache.el
index 38a434b11b..aac4f488cd 100644
--- a/lisp/filecache.el
+++ b/lisp/filecache.el
@@ -566,68 +566,67 @@ file-cache-minibuffer-complete
 the name is considered already unique; only the second substitution
 \(directories) is done."
   (interactive "P")
-  (let*
-      (
-       (completion-ignore-case file-cache-completion-ignore-case)
-       (case-fold-search       file-cache-case-fold-search)
-       (string                 (file-name-nondirectory (minibuffer-contents)))
-       (completion-string      (try-completion string file-cache-alist))
-       (completion-list)
-       (len)
-       (file-cache-string))
+  (let* ((completion-ignore-case file-cache-completion-ignore-case)
+         (case-fold-search       file-cache-case-fold-search)
+         (string                 (file-name-nondirectory 
(minibuffer-contents)))
+         (completion             (completion-try-completion
+                                  string file-cache-alist nil 0)))
     (cond
      ;; If it's the only match, replace the original contents
-     ((or arg (eq completion-string t))
-      (setq file-cache-string (file-cache-file-name string))
-      (if (string= file-cache-string (minibuffer-contents))
-         (minibuffer-message file-cache-sole-match-message)
-       (delete-minibuffer-contents)
-       (insert file-cache-string)
-       (if file-cache-multiple-directory-message
-           (minibuffer-message file-cache-multiple-directory-message))))
+     ((or arg (eq completion t))
+      (let ((file-name (file-cache-file-name string)))
+        (if (string= file-name (minibuffer-contents))
+            (minibuffer-message file-cache-sole-match-message)
+          (delete-minibuffer-contents)
+          (insert file-name)
+          (if file-cache-multiple-directory-message
+              (minibuffer-message file-cache-multiple-directory-message)))))
 
      ;; If it's the longest match, insert it
-     ((stringp completion-string)
-      ;; If we've already inserted a unique string, see if the user
-      ;; wants to use that one
-      (if (and (string= string completion-string)
-              (assoc-string string file-cache-alist
-                            file-cache-ignore-case))
-         (if (and (eq last-command this-command)
-                  (string= file-cache-last-completion completion-string))
-             (progn
-               (delete-minibuffer-contents)
-               (insert (file-cache-file-name completion-string))
-               (setq file-cache-last-completion nil))
-           (minibuffer-message file-cache-non-unique-message)
-           (setq file-cache-last-completion string))
-       (setq file-cache-last-completion string)
-       (setq completion-list (all-completions string file-cache-alist)
-             len             (length completion-list))
-       (if (> len 1)
-           (progn
-             (goto-char (point-max))
-             (insert
-              (substring completion-string (length string)))
-             ;; Add our own setup function to the Completions Buffer
-             (let ((completion-setup-hook
-                     (append completion-setup-hook
-                             (list 'file-cache-completion-setup-function))))
-               (with-output-to-temp-buffer file-cache-completions-buffer
-                 (display-completion-list
-                   (completion-hilit-commonality completion-list
-                                                 (length string))))))
-         (setq file-cache-string (file-cache-file-name completion-string))
-         (if (string= file-cache-string (minibuffer-contents))
-             (minibuffer-message file-cache-sole-match-message)
-           (delete-minibuffer-contents)
-           (insert file-cache-string)
-           (if file-cache-multiple-directory-message
-               (minibuffer-message file-cache-multiple-directory-message)))
-         )))
+     ((consp completion)
+      (let ((newstring (car completion))
+            (newpoint  (cdr completion)))
+        ;; If we've already inserted a unique string, see if the user
+        ;; wants to use that one
+        (if (and (string= string newstring)
+                 (assoc-string string file-cache-alist
+                               file-cache-ignore-case))
+            (if (and (eq last-command this-command)
+                     (string= file-cache-last-completion newstring))
+                (progn
+                  (delete-minibuffer-contents)
+                  (insert (file-cache-file-name newstring))
+                  (setq file-cache-last-completion nil))
+              (minibuffer-message file-cache-non-unique-message)
+              (setq file-cache-last-completion string))
+          (setq file-cache-last-completion string)
+          (let* ((completion-list (completion-all-completions
+                                   newstring file-cache-alist nil newpoint))
+                 (base-size       (cdr (last completion-list))))
+            (when base-size
+              (setcdr (last completion-list) nil))
+            (if (> (length completion-list) 1)
+                (progn
+                  (delete-region (- (point-max) (length string)) (point-max))
+                  (save-excursion (insert newstring))
+                  (forward-char newpoint)
+                  ;; Add our own setup function to the Completions Buffer
+                  (let ((completion-setup-hook
+                         (append completion-setup-hook
+                                 (list 
'file-cache-completion-setup-function))))
+                    (with-output-to-temp-buffer file-cache-completions-buffer
+                      (display-completion-list
+                       (completion-hilit-commonality completion-list 
newpoint)))))
+              (let ((file-name (file-cache-file-name newstring)))
+                (if (string= file-name (minibuffer-contents))
+                    (minibuffer-message file-cache-sole-match-message)
+                  (delete-minibuffer-contents)
+                  (insert file-name)
+                  (if file-cache-multiple-directory-message
+                      (minibuffer-message 
file-cache-multiple-directory-message)))))))))
 
      ;; No match
-     ((eq completion-string nil)
+     ((eq completion nil)
       (minibuffer-message file-cache-no-match-message)))))
 
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-ap