I was wondering how to construct a multi-key map conditionally while I was coding in Clojure. Ideally, I would like to build it "in one pass" like {:bar 2 (when true :baz 3)}, but from what I had collected from Blue Sky, it seemed that's impossible, or it's just not an idiomatic way to program like that in Clojure. (Or, is this just a side effect of writing too much imperative code?)
Basically there are two ways, assoc / into / conj for collection manipulation, and cond-> (conditional thread-first) for general conditional operations.
;;; Using into
(into {:clojure 1} (when true {:elisp 2}))
;; => {:clojure 1, :elisp 2}
(into {:clojure 1} (when false {:elisp 2}))
;; => {:clojure 1}
;;; Using conj
(conj {:clojure 1} {:elisp 2} {:babashka 3})
;; => {:clojure 1, :elisp 2, :babashka 3}
(conj {:clojure 1} (when false {:elisp 2}))
;; => {:clojure 1}
;;; Using cond-> + assoc
(assoc {:clojure 1} :elisp 2 :babashka 3)
;; => {:clojure 1, :elisp 2, :babashka 3}
(cond->
{:clojure 1}
(= 1 1) (assoc :elisp 2)
(= 2 1) (assoc :common-lisp 3))
;; => {:clojure 1, :elisp 2}