Check if ag executable exists on remote system

[panaak]

If you have ag installed locally and want to do helm-ag in a remote directory, helm-ag.el just says:

failed: 'search term'

This PR tries to report missing remote executable.

[jcs090218]

This probably make sense to me.

@syohex What are your thoughts on this PR? 😄

[syohex]

https://github.com/emacsorphanage/helm-ag/blob/900f6a001f92215018292be4bee85a56aa8f3050/helm-ag.el#L284

I suppose this PR is not enough because (executable-find (car cmds)) of that line returns local command path. So if the executable path is different between local and remote(for example, local: /usr/bin/ag, remote: /usr/local/bin/ag), above condition expression returns unexpected result. I suppose you should write code which checks executable is installed on local and remote as below.

diff --git a/helm-ag.el b/helm-ag.el
index d21d1f3..07836e8 100644
--- a/helm-ag.el
+++ b/helm-ag.el
@@ -264,6 +264,13 @@ Default behaviour shows finish and result in mode-line."
       (while (re-search-forward "^\\([^:]+\\)" nil t)
         (replace-match (abbreviate-file-name (match-string-no-properties 1)))))))
 
+(defun helm-ag--executable-find (cmd)
+  (if (not (file-remote-p default-directory))
+      (executable-find cmd)
+    (let ((remote-paths (cl-loop for p in (exec-path)
+                                 collect (concat (file-remote-p default-directory) p))))
+      (locate-file cmd remote-paths exec-suffixes #'file-executable-p))))
+
 (defun helm-ag--init ()
   (let ((buf-coding buffer-file-coding-system))
     (helm-attrset 'recenter t)
@@ -279,10 +286,9 @@ Default behaviour shows finish and result in mode-line."
           (if (zerop (length (buffer-string)))
               (error "No ag output: '%s'" helm-ag--last-query)
             (unless (zerop ret)
-              (unless (executable-find (car cmds))
-                (error "'ag' is not installed."))
-              (unless (file-exists-p (concat (file-remote-p default-directory) (executable-find (car cmds))))
-                (error "'ag' is not installed on remote system."))
+              (unless (helm-ag--executable-find (car cmds))
+                (error "'%s' is not installed on %s system"
+                       (car cmds) (if (file-remote-p default-directory) "remote" "local")))
               (error "Failed: '%s'" helm-ag--last-query))))
         (when helm-ag--buffer-search
           (helm-ag--abbreviate-file-name))

[jcs090218]

@panaak Ping! :)