Supplying custom data readers to defconfig

[lloydshark]

I'd like to optionally be able to supply custom data readers when specifying my config.

So the use of defconfig might look like the following.

(defn my-custom-reader [form]
  :some-other-value)

(defconfig my-configuration (io/resource "config.edn")
           :data-readers {'custom/my-reader my-custom-reader})

I originally thought I might have been able to achieve this by binding *data-readers*, but it turns out that the underlying edn reader doesn't allow for that (probably with good reason).

I would be happy to do the implementation for you to have a look at.

What do you think?

[jarohen]

I've solved this in Phoenix by making the edn/read-string call take *data-readers* (and, by extension, data_readers.clj) into account - more than happy to do the same here if need be. What do you think would be the best option?

Certainly happy to have a PR! Cheers

[lloydshark]

Hi James, thanks for the response.

My opinion (though not strong) I think it is more flexible if you allow them to be optionally passed in.

That way you know explicitly what is legal for your config file. If you really want data-readers to be consulted you can still pass it in.

[jarohen]

Yep, good point - so would you have them passed in as an optional extra argument to defconfig, say?

[lloydshark]

Yes, I was probably thinking an optional keyword argument... (just in case you ever want to add other optional parameters to defconfig) so the defconfig macro could be like the following.

(defmacro defconfig [name file-or-resource & {:keys [custom-data-readers]}]

When supplied they would be merged with the existing nomad data readers.

[jarohen]

I've just released 0.7.1-SNAPSHOT, which now takes *data-readers* into account. defconfig also takes an extra optional parameter:

(defconfig my-config (io/resource "...") {:data-readers {'my-reader/reader-type parse-reader-type}})

Let me know what you think :)

Cheers,

James

[lloydshark]

Thanks James - you beat me to it... I started on the code last night. I'll try it out (hopefully today).

[lloydshark]

OK, tried it out - I got the following error:

Caused by: java.lang.RuntimeException: No such var: nomad/data-readers

I think there's a missing ~ in front of data-readers in the defconfig macro.

[jarohen]

Thanks Lloyd, sorry for that :/
Have pushed another snapshot.

James

[lloydshark]

No trouble. I should have a chance today to try it out.

[lloydshark]

Thanks for that. Looks good to me, worked for my simple test cases.

I tried specifying the optional extra parameter, and then without it. I didn't try binding *data-readers* directly.

[lloydshark]

Hi James,

I'm wondering whether this change is likely to make it into the main release anytime soon. It certainly works for our needs.

Are you waiting for feedback on issue #19 before you would consider releasing it ?

• Boyd

[jarohen]

Sorry - had forgotten about this - I've just a 0.7.1 release. Let me know what you think :)

James

[lloydshark]

Hey no trouble. Will integrate into our main development line soon. Thanks again.

[jarohen]

No worries, thanks for your suggestion!