Allow setting default value via minibuffer-default (#324)

CHANGELOG.md

@@ -20,6 +20,8 @@ The format is based on [Keep a Changelog].
   default is t) ([#261]).
 
 ### Enhancements
+* The prompt gets selected when using `next-history-element` and the
+  prompt equals the default ([#323], [#324]).
 * Computation of candidates is faster for `describe-variable` ([#312],
   [#316], [#320], [#321]).
 * Candidates of `completing-read-multiple` which are submitted by
@@ -66,6 +68,9 @@ The format is based on [Keep a Changelog].
   they contain ([#266], [#302], [#318]).
 
 ### Bugs fixed
+* `minibuffer-default` is now treated as the default when set, before
+  it would have no effect. When a list the car is used as default as
+  of now ([#324]).
 * `selectrum-extend-current-candidate-highlight`,
   `selectrum-show-indices`, `selectrum-right-margin-padding` and
   `selectrum-multiline-display-settings` wouldn't use the local
@@ -155,6 +160,8 @@ The format is based on [Keep a Changelog].
 [#318]: https://github.com/raxod502/selectrum/pull/318
 [#320]: https://github.com/raxod502/selectrum/issues/320
 [#321]: https://github.com/raxod502/selectrum/pull/321
+[#323]: https://github.com/raxod502/selectrum/issues/323
+[#324]: https://github.com/raxod502/selectrum/pull/324
 
 ## 3.0 (released 2020-10-20)
 ### Breaking changes

selectrum.el

@@ -807,7 +807,8 @@ the update."
                        (not (member selectrum--default-candidate
                                     selectrum--refined-candidates)))
                   -1)
-                 ((and selectrum--init-p
+                 ((and (or selectrum--init-p
+                           (eq this-command 'next-history-element))
                        (equal selectrum--default-candidate
                               (minibuffer-contents)))
                   -1)
@@ -1273,7 +1274,8 @@ TABLE defaults to `minibuffer-completion-table'. PRED defaults to
   "Set up minibuffer for interactive candidate selection.
 CANDIDATES is the list of strings that was passed to
 `selectrum-read'. DEFAULT-CANDIDATE, if provided, is added to the
-list and sorted first."
+list and sorted first. If `minibuffer-default' is set it will
+have precedence over DEFAULT-CANDIDATE."
   (setq-local selectrum-active-p t)
   (add-hook
    'minibuffer-exit-hook #'selectrum--minibuffer-exit-hook nil 'local)
@@ -1297,10 +1299,15 @@ list and sorted first."
                (funcall selectrum-preprocess-candidates-function
                         candidates))
          (setq selectrum--total-num-candidates (length candidates))))
-  (setq selectrum--default-candidate
-        (if (and default-candidate (symbolp default-candidate))
-            (symbol-name default-candidate)
-          default-candidate))
+  ;; If the default is added by setup hook it should have
+  ;; precedence like with default completion.
+  (let ((default (or (car-safe minibuffer-default)
+                     minibuffer-default
+                     default-candidate)))
+    (setq selectrum--default-candidate
+          (if (and default (symbolp default))
+              (symbol-name default)
+            default)))
   ;; Make sure to trigger an "user input changed" event, so that
   ;; candidate refinement happens in `post-command-hook' and an index
   ;; is assigned.