Simulate input to interactive elisp functions

Note

It's time for another Emacs package showcase. This time it'll be simulating input to interactive Elisp functions.

Elisp has an interactive mode for functions that are meant to be invoked with M-x and expect input from the user. An interactive function is declared like this:

(defun interactive-func ()
  (interactive)
  ;; more statements
)

But what if we wanted to automate a workflow in Emacs that involves calling one of these functions from within another function and passing input to it?

Two examples from my workflow

Since the custom org agenda views just don't seem to want to work for me, I have created a couple of functions that will filter my agenda entries when I open it. This requires calling the interactive function org-agenda-filter and an input of filters to apply.
I want to have a function that starts a journal entry, clocks in, and takes me to the journal file in one click. This requires calling the interactive function org-roam-dailies-capture-today and an input of j to create a journal entry.

NB: This is what works for me, I'm aware these could be achieved in many other ways.

So, how do we do this? We can use the with-simulated-input package.

It does exactly what it says - it can simulate input to interactive functions. Let's see how we can use it in the two scenarios above:

We will simulate the filter "+foo+bar" which will filter by these categories (filter is a generic term, so let's assume foo and bar are categories in our agenda).
```
(defun org-home-agenda ()
  (interactive)
  (org-agenda nil "a")
  (org-agenda-day-view)
  (with-simulated-input "+foo+bar RET"
    (org-agenda-filter)))
```
We wrap the function in with-simulated-input and it does the magic for us.

We simulate pressing j in org-roam-dailies-capture-today (and do some other things afterwards such as clock in and decrypt the file):

(defun start-journal-entry ()
  "Starts a journal entry for today"
  (interactive)
  (with-simulated-input "j"
    (org-roam-dailies-capture-today))
  (org-capture-finalize)
  (org-roam-dailies-find-today)
  (org-mru-clock-in)
  (org-decrypt-entry))

Summary

with-simulated-input is a useful package to simulate input to interactive functions in automated workflows. It can open up a bunch of possibilities to programatically achieve a lot of manual stuff you do in Emacs. Try it out!

2021-04-19