helm actions when there is no match

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Sometimes you run out of matches in a helm selection buffer, and all that is left is the pattern you have typed in. It turns out you can perform some action on that pattern! Why would you do that? Suppose you are searching your bibliography, and you do not find what you are looking for. Then, you may want to send the pattern to Google, or some other search engine to see what comes up.

The key to handling this situation is to use two sources in your helm session. One that works on the candidates and deals with actions on them, and one that has no candidates, and works on the pattern. The variable helm-pattern contains what you typed in. We call the second source the Fallback option. The second source has no candidates, and we use (dummy) in place of the candidates.

It easy to add two sources. Here we define the sources as variables, and use the variables in the :sources list to the helm command.

(defun some-action (arg)
  (message-box "%s\n%s"
    (helm-get-selection)
    (helm-marked-candidates)))

(defun default-action (candidate)
  (browse-url
   (format
    "http://www.google.com/search?q=%s" (url-hexify-string helm-pattern))))

(defvar source1 '((name . "HELM")
                  (candidates . (1 2 3 4))
                  (action . (("open" . some-action)))))

(defvar fallback-source '((name . "fallback")
                          (dummy)
                          (action . (("Google" . default-action)))))

(helm :sources '(source1 fallback-source))
#<process open http://www.google.com/search?q=addtion%20pul>

When you run this, if you run out of search candidates, all that will be left is the fallback option, and when you press enter, it will launch a browser pointing to the google search for your pattern.

Copyright (C) 2015 by John Kitchin. See the License for information about copying.

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