Show keybindings for command aliases too

Fixes #143

3 files changed, 59 insertions, 2 deletions

diff --git a/CHANGELOG.md b/CHANGELOG.md
index f06934a..a82d54a 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,4 +1,4 @@
-# v0.13
+# v0.13 (unreleased)
 
 Buffer-local variables are now highlighted, and it's possible to see
 all the different values of a buffer-local variable.
@@ -8,6 +8,8 @@ Variable values are now shown before docstrings.
 Fixed an issue where special forms were incorrectly described as
 functions.
 
+Helpful now shows keybindings for aliases of the current command too.
+
 # v0.12
 
 Added a 'pretty view' for string values, keymap values, and hooks.
diff --git a/helpful.el b/helpful.el
index 7daa98f..0b67081 100644
--- a/helpful.el
+++ b/helpful.el
@@ -1315,11 +1315,37 @@ same bindings as `global-map'."
 
     matching-keymaps))
 
+(defun helpful--merge-alists (l1 l2)
+  "Given two alists mapping symbols to lists, return a single
+alist with the lists concatenated."
+  (let* ((l1-keys (-map #'-first-item l1))
+         (l2-keys (-map #'-first-item l2))
+         (l2-extra-keys (-difference l2-keys l1-keys))
+         (l2-extra-values
+          (--map (assoc it l2) l2-extra-keys))
+         (l1-with-values
+          (-map (-lambda ((key . values))
+                  (cons key (append values
+                                    (cdr (assoc key l2)))))
+                l1)))
+    (append l1-with-values l2-extra-values)))
+
+(defun helpful--keymaps-containing-aliases (command-sym)
+  "Return a list of pairs mapping keymap symbols to the
+keybindings for COMMAND-SYM in each keymap.
+
+Includes keybindings for aliases, unlike
+`helpful--keymaps-containing'."
+  (let* ((aliases (helpful--aliases 'helpful--dummy-command t))
+         (syms (cons command-sym aliases))
+         (syms-keymaps (-map #'helpful--keymaps-containing syms)))
+    (-reduce #'helpful--merge-alists syms-keymaps)))
+
 (defun helpful--format-keys (command-sym)
   "Describe all the keys that call COMMAND-SYM."
   (let (mode-lines
         global-lines)
-    (--each (helpful--keymaps-containing command-sym)
+    (--each (helpful--keymaps-containing-aliases command-sym)
       (-let [(map . keys) it]
         (dolist (key keys)
           (push
diff --git a/test/unit-test.el b/test/unit-test.el
index 85f275b..74ff231 100644
--- a/test/unit-test.el
+++ b/test/unit-test.el
@@ -553,6 +553,35 @@ associated a lambda with a keybinding."
     '(("minor-mode-map-alist (ido-mode)" "<open>" "C-x C-f"))))
   (ido-mode 0))
 
+(defalias 'helpful--dummy-command-alias #'helpful--dummy-command)
+
+(ert-deftest helpful--keymaps-containing-aliases ()
+  "Ensure that we find keymaps that we've bound command aliases
+in."
+  ;; Create keybindings that are very unlikely to clobber actually
+  ;; defined keybindings in the current emacs instance.
+  (global-set-key (kbd "C-c M-S-c") #'helpful--dummy-command)
+  (global-set-key (kbd "C-c M-S-d") #'helpful--dummy-command-alias)
+
+  (unwind-protect
+      (let* ((keymaps (helpful--keymaps-containing-aliases #'helpful--dummy-command))
+             (global-keybindings (cdr (assoc "global-map" keymaps))))
+        (should
+         (equal global-keybindings (list "C-c M-S-c" "C-c M-S-d"))))
+
+    ;; Undo keybindings.
+    (global-set-key (kbd "C-c M-S-c") nil)
+    (global-set-key (kbd "C-c M-S-d") nil)))
+
+(ert-deftest helpful--merge-alists ()
+  (should
+   (equal
+    (helpful--merge-alists '((a . (1 2 3)) (b . (4)))
+                           '((a . (10)) (c . (11))))
+    '((a . (1 2 3 10))
+      (b . (4))
+      (c . (11))))))
+
 (ert-deftest helpful--source ()
   (-let* (((buf pos opened) (helpful--definition #'helpful--source t))
           (source (helpful--source #'helpful--source t buf pos)))