Use macros with doseq to generate spec

Question

I find myself writing a lot of specs like this:

(s/def ::name string?) (s/def ::logUri string?) (s/def ::subnet (s/and string? #(> (count %) 5))) (s/def ::instanceType string?) ... (s/def ::key (s/and string? #(> (count %) 5))) (s/def ::instanceCount string?) (s/def ::bidPct string?)

I.e. Lots of s/and and s/def. This seems like a waste. So I decided to write a macro that did this for me. Something like:

(defmacro and-spec [validations] (doseq [[keyname & funcs] validations] `(s/def ~keyname (s/and ~@funcs))))

So I would be able to do something like:

(and-spec [[::name1 [string?]] [::name2 [string? #(> (count %) 5)]]])

And this would just do all my s/def stuff for me. Unfortunately, the above macro doesn't work, but I'm not sure why.

(s/valid? ::name1 "asdf") Execution error at emr-cli.utils/eval6038 (form-init17784784591561795514.clj:1). Unable to resolve spec: :emr-cli.utils/name1

Smaller versions of this work:

(defmacro small-and-spec-works [key-name validations] `(s/def ~key-name (s/and ~@validations))) => #'emr-cli.utils/tsmall (and-spec-small-works ::mykey [string?]) => :emr-cli.utils/mykey (s/valid? ::mykey "asdf") => true

But the second I introduce a let binding things start getting weird:

(defmacro small-and-spec [validation] (let [[key-name & valids] validation] `(s/def ~key-name (s/and ~@valids)))) => #'emr-cli.utils/small-and-spec (small-and-spec [::mykey2 [string?]]) => :emr-cli.utils/mykey2 (s/valid? ::mykey2 "asdf") Execution error (IllegalArgumentException) at emr-cli.utils/eval6012 (form-init17784784591561795514.clj:1). Key must be integer

How can I make the doseq macro work?
What is going wrong with the small-and-spec that creates the Key must be integer error?

akond · Accepted Answer · 2020-10-23 14:34:42Z

5

(defmacro and-spec [defs] `(do ~@(map (fn [[name rest]] `(s/def ~name (s/and ~@rest))) defs)))

doseq is for side effects. It always returns nil.

edited Oct 23, 2020 at 14:34

answered Oct 23, 2020 at 14:00

akond

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3 Comments

Logister Over a year ago

Yes, the "side effect" in question is the definition of multiple in-scope specs. I don't want the macro to return a list of defs.

Alex Miller Over a year ago

"I don't want the macro to return a list of defs." is actually what you want though, in a do

amalloy Over a year ago

Specifically because just creating a source code list does not cause it to be evaluated. The "contract" of a macro is that any code it returns will be evaluated. Code it produces as a side effect and then throws away is, naturally, thrown away.

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