master 7aaffe25eb 1/2: Use base prefix and suffix instead of completion-base-position (bug#49931)

[Juri Linkov]

branch: master
commit 7aaffe25eb178f69027fb0af844a89a86db4b1f2
Author: Juri Linkov <juri@linkov.net>
Commit: Juri Linkov <juri@linkov.net>

    Use base prefix and suffix instead of completion-base-position (bug#49931)
    
    * lisp/minibuffer.el (minibuffer-completion-help):
    Set completion-base-affixes from base-prefix and base-suffix.
    In completion-list-insert-choice-function handle
    string values of start/end as prefix/suffix.
    
    * lisp/simple.el (completion-base-affixes)
    (completion-use-base-affixes): New variables.
    (choose-completion): Let-bind base-affixes to completion-base-affixes.
    Use base-affixes when completion-use-base-affixes is non-nil.
    (completion-setup-function): Sync values of base-affixes and
    completion-base-affixes.
---
 lisp/minibuffer.el | 29 ++++++++++++++++++++---------
 lisp/simple.el     | 16 +++++++++++++++-
 2 files changed, 35 insertions(+), 10 deletions(-)

diff --git a/lisp/minibuffer.el b/lisp/minibuffer.el
index 5ad44a7a2d..393555fc62 100644
--- a/lisp/minibuffer.el
+++ b/lisp/minibuffer.el
@@ -2284,6 +2284,9 @@ variables.")
       (let* ((last (last completions))
              (base-size (or (cdr last) 0))
              (prefix (unless (zerop base-size) (substring string 0 base-size)))
+             (base-prefix (buffer-substring (minibuffer--completion-prompt-end)
+                                            (+ start base-size)))
+             (base-suffix (buffer-substring (point) (point-max)))
              (all-md (completion--metadata (buffer-substring-no-properties
                                             start (point))
                                            base-size md
@@ -2375,20 +2378,28 @@ variables.")
                                    ;; completion-all-completions does not give 
us the
                                    ;; necessary information.
                                    end))
+                        (setq-local completion-base-affixes
+                                    (list base-prefix base-suffix))
                         (setq-local completion-list-insert-choice-function
                              (let ((ctable minibuffer-completion-table)
                                    (cpred minibuffer-completion-predicate)
                                    (cprops completion-extra-properties))
                                (lambda (start end choice)
-                                 (unless (or (zerop (length prefix))
-                                             (equal prefix
-                                                    
(buffer-substring-no-properties
-                                                     (max (point-min)
-                                                          (- start (length 
prefix)))
-                                                     start)))
-                                   (message "*Completions* out of date"))
-                                 ;; FIXME: Use `md' to do quoting&terminator 
here.
-                                 (completion--replace start end choice)
+                                 (if (and (stringp start) (stringp end))
+                                     (progn
+                                       (delete-minibuffer-contents)
+                                       (insert start choice)
+                                       ;; Keep point after completion before 
suffix
+                                       (save-excursion (insert end)))
+                                   (unless (or (zerop (length prefix))
+                                               (equal prefix
+                                                      
(buffer-substring-no-properties
+                                                       (max (point-min)
+                                                            (- start (length 
prefix)))
+                                                       start)))
+                                     (message "*Completions* out of date"))
+                                   ;; FIXME: Use `md' to do quoting&terminator 
here.
+                                   (completion--replace start end choice))
                                  (let* ((minibuffer-completion-table ctable)
                                         (minibuffer-completion-predicate cpred)
                                         (completion-extra-properties cprops)
diff --git a/lisp/simple.el b/lisp/simple.el
index e49a0ff0f6..5bf1c32e1d 100644
--- a/lisp/simple.el
+++ b/lisp/simple.el
@@ -9119,6 +9119,16 @@ Its value is a list of the form (START END) where START 
is the place
 where the completion should be inserted and END (if non-nil) is the end
 of the text to replace.  If END is nil, point is used instead.")
 
+(defvar completion-base-affixes nil
+  "Base context of the text corresponding to the shown completions.
+This variable is used in the *Completions* buffer.
+Its value is a list of the form (PREFIX SUFFIX) where PREFIX is the text
+before the place where completion should be inserted, and SUFFIX is the text
+after the completion.")
+
+(defvar completion-use-base-affixes nil
+  "Non-nil means to restore original prefix and suffix in the minibuffer.")
+
 (defvar completion-list-insert-choice-function #'completion--replace
   "Function to use to insert the text chosen in *Completions*.
 Called with three arguments (BEG END TEXT), it should replace the text
@@ -9245,6 +9255,7 @@ minibuffer, but don't quit the completions window."
   (with-current-buffer (window-buffer (posn-window (event-start event)))
     (let ((buffer completion-reference-buffer)
           (base-position completion-base-position)
+          (base-affixes completion-base-affixes)
           (insert-function completion-list-insert-choice-function)
           (completion-no-auto-exit (if no-exit t completion-no-auto-exit))
           (choice
@@ -9270,7 +9281,8 @@ minibuffer, but don't quit the completions window."
       (with-current-buffer buffer
         (choose-completion-string
          choice buffer
-         (or base-position
+         (or (and completion-use-base-affixes base-affixes)
+             base-position
              ;; If all else fails, just guess.
              (list (choose-completion-guess-base-position choice)))
          insert-function)))))
@@ -9424,9 +9436,11 @@ Called from `temp-buffer-show-hook'."
                 (buffer-substring (minibuffer-prompt-end) (point)))))))
     (with-current-buffer standard-output
       (let ((base-position completion-base-position)
+            (base-affixes completion-base-affixes)
             (insert-fun completion-list-insert-choice-function))
         (completion-list-mode)
         (setq-local completion-base-position base-position)
+        (setq-local completion-base-affixes base-affixes)
         (setq-local completion-list-insert-choice-function insert-fun))
       (setq-local completion-reference-buffer mainbuf)
       (if base-dir (setq default-directory base-dir))