I've finally had time to the `:default-description' parameter in
`org-link-parameters'.

Ihor Radchenko <yantar92@gmail.com> writes:

> I recommend writing tests for org-insert-link in
> testing/lisp/test-ol.el and testing expected behaviour for various
> values of :default-description.

Good advice! I haven't written many tests before, so this was a
challenge. I've attached a patch with some tests for the expected
behaviour. These include a couple of macros and a function, to stop
the definitions being too huge and unwieldy.

All the tests pass on my machine.

They're very nearly just right, but for some reason
`test-ol-with-link-parameters-as' doesn't always reset the parameters
correctly for me. However I have them set to originally, it sets
`:default-description' to a lambda. This might be a quirk at my end
though -- if someone else could have a look I'd be very grateful.

The tests showed that my previous approach doesn't work generally
enough. I've moved where `type' is defined in the code, to cover all
cases.

> Firstly, def will be undefined inside the error clause.

I've defined def a bit further up in a `let', and run the error clause
inside this.

> Secondly, when :default-description is a lambda expression and that
> expression fails, your code will fail with "wrong-type-argument
> symbolp" when executing (symbol-name def). Please consider cases
> when `def' is not a string and not a function symbol.

Dealt with this by just using `message "<text> %S: "', since %S will
print a symbol, a string or a lambda correctly.

Hope this is a bit better!

Best,
Hugo