epg: Add a way to detect gpg1 executable for tests

Fixes bug#23561.

* test/automated/epg-tests.el
(epg-tests-program-alist-for-passphrase-callback): New
constant.
(epg-tests-find-usable-gpg-configuration): New function,
renamed from `epg-tests-gpg-usable'.  All callers changed.
(epg-tests-gpg-usable): Remove.

* lisp/epg-config.el (epg-config--program-alist): Factor out
constructor element to...
(epg-config--configuration-constructor-alist): ...here.
(epg-find-configuration): Rename FORCE argument to NO-CACHE,
and add PROGRAM-ALIST argument.

1 files changed, 47 insertions, 35 deletions

diff --git a/lisp/epg-config.el b/lisp/epg-config.el
index 8a208044cba..9179e04dcc1 100644
--- a/lisp/epg-config.el
+++ b/lisp/epg-config.el
@@ -81,57 +81,69 @@ Note that the buffer name starts with a space."
 (defconst epg-config--program-alist
   '((OpenPGP
      epg-gpg-program
-     epg-config--make-gpg-configuration
      ("gpg2" . "2.1.6") ("gpg" . "1.4.3"))
     (CMS
      epg-gpgsm-program
-     epg-config--make-gpgsm-configuration
      ("gpgsm" . "2.0.4")))
   "Alist used to obtain the usable configuration of executables.
 The first element of each entry is protocol symbol, which is
 either `OpenPGP' or `CMS'.  The second element is a symbol where
-the executable name is remembered.  The third element is a
-function which constructs a configuration object (actually a
-plist).  The rest of the entry is an alist mapping executable
-names to the minimum required version suitable for the use with
-Emacs.")
+the executable name is remembered.  The rest of the entry is an
+alist mapping executable names to the minimum required version
+suitable for the use with Emacs.")
+
+(defconst epg-config--configuration-constructor-alist
+  '((OpenPGP . epg-config--make-gpg-configuration)
+    (CMS . epg-config--make-gpgsm-configuration))
+  "Alist used to obtain the usable configuration of executables.
+The first element of each entry is protocol symbol, which is
+either `OpenPGP' or `CMS'.  The second element is a function
+which constructs a configuration object (actually a plist).")
 
 (defvar epg--configurations nil)
 
 ;;;###autoload
-(defun epg-find-configuration (protocol &optional force)
+(defun epg-find-configuration (protocol &optional no-cache program-alist)
   "Find or create a usable configuration to handle PROTOCOL.
 This function first looks at the existing configuration found by
-the previous invocation of this function, unless FORCE is non-nil.
-
-Then it walks through `epg-config--program-alist'.  If
-`epg-gpg-program' or `epg-gpgsm-program' is already set with
-custom, use it.  Otherwise, it tries the programs listed in the
-entry until the version requirement is met."
-  (let ((entry (assq protocol epg-config--program-alist)))
+the previous invocation of this function, unless NO-CACHE is non-nil.
+
+Then it walks through PROGRAM-ALIST or
+`epg-config--program-alist'.  If `epg-gpg-program' or
+`epg-gpgsm-program' is already set with custom, use it.
+Otherwise, it tries the programs listed in the entry until the
+version requirement is met."
+  (unless program-alist
+    (setq program-alist epg-config--program-alist))
+  (let ((entry (assq protocol program-alist)))
     (unless entry
       (error "Unknown protocol %S" protocol))
-    (cl-destructuring-bind (symbol constructor . alist)
+    (cl-destructuring-bind (symbol . alist)
         (cdr entry)
-      (or (and (not force) (alist-get protocol epg--configurations))
-          ;; If the executable value is already set with M-x
-          ;; customize, use it without checking.
-          (if (get symbol 'saved-value)
-              (let ((configuration (funcall constructor (symbol-value symbol))))
-                (push (cons protocol configuration) epg--configurations)
-                configuration)
-            (catch 'found
-              (dolist (program-version alist)
-                (let ((executable (executable-find (car program-version))))
-                  (when executable
-                    (let ((configuration
-                           (funcall constructor executable)))
-                      (when (ignore-errors
-                              (epg-check-configuration configuration
-                                                       (cdr program-version))
-                              t)
-                        (push (cons protocol configuration) epg--configurations)
-                        (throw 'found configuration))))))))))))
+      (let ((constructor
+             (alist-get protocol epg-config--configuration-constructor-alist)))
+        (or (and (not no-cache) (alist-get protocol epg--configurations))
+            ;; If the executable value is already set with M-x
+            ;; customize, use it without checking.
+            (if (and symbol (get symbol 'saved-value))
+                (let ((configuration
+                       (funcall constructor (symbol-value symbol))))
+                  (push (cons protocol configuration) epg--configurations)
+                  configuration)
+              (catch 'found
+                (dolist (program-version alist)
+                  (let ((executable (executable-find (car program-version))))
+                    (when executable
+                      (let ((configuration
+                             (funcall constructor executable)))
+                        (when (ignore-errors
+                                (epg-check-configuration configuration
+                                                         (cdr program-version))
+                                t)
+                          (unless no-cache
+                            (push (cons protocol configuration)
+                                  epg--configurations))
+                          (throw 'found configuration)))))))))))))
 
 ;; Create an `epg-configuration' object for `gpg', using PROGRAM.
 (defun epg-config--make-gpg-configuration (program)