Add option to add default value to optional properties

[Deraen]

I have a case where I need default values to be added to the maps, even though the properties are optional.

Should be simple to add new condition to optional check to look at a new property, like :default/force or such, and then include default value if that is set, even if the property is optional.

https://github.com/metosin/malli/blob/master/src/malli/transform.cljc#L394

#351 #397

Some ideas for the option name

• :default/always
• :default/missing-key
• :default/force

[dharrigan]

This would be great,

i.e., this presently doesn't work (whether optional or not)

(def locale-check [:map [:locale {:default "en_GB"} [:enum {:swagger/type "string"} "en_GB" "es_ES"]]])

(-> (c/explain locale-check {})
    (me/humanize)) ;; {:locale ["missing required key"]}

Funnily enough, decode does the right thing:

(c/decode locale-check {} mt/default-value-transformer) ;; {:locale "en_GB"}

[ikitommi]

Are there really a use cases that the schema itself should control how to add the defaults? should it be recursive?

Simple solution would be add this option to mt/default-value-transformer to add the defaults.

[ikitommi]

see #668

[Deraen]

@dharrigan That is working as intended.

:default option doesn't do anything without default-value-transformer, so the explain wont see the default value if you didn't call decode to apply default-value-transformer first.
If you add :optional true to the property, you can see the decode doesn't add the default value.

[Deraen]

@ikitommi Transformer level option probably makes sense. I think on the project where I had use for this, I used :default/force for every property which had :default value.

On Reitit I could also set :coercion route-data for specific route trees if I need to enable this only for certain routes.