Add more type related helpers

[lread]

Originally raised by me as lread/rewrite-cljc-playground#5

Related to #113 - capturing valuable feedback from @sogaiu so I don't lose it. Need to review and evaluate more type related helpers.

Snippit from @sogaiu

(defn string-value
  "Return the string value for a node."
  [node]
  (when-let [lines (:lines node)]
    (cs/join "\n" lines)))
(defn string-node?
  "Returns true if node represents a string, else false."
  [node]
  (string-value node))
(defn string?
  "Returns true if zipper represents a string, else false."
  [zloc]
  (some-> zloc rz/node string-node?))
(defn symbol-value
  "Return the symbol value for a node."
  [node]
  (:value node))
(defn symbol-node?
  "Returns true if node represents a symbol, else false."
  [node]
  (clojure.core/symbol? (symbol-value node)))
(defn symbol?
  "Returns true if zipper represents a symbol, else false."
  [zloc]
  (some-> zloc rz/node symbol-node?))

Also: pointer to similar can be found within clj-kondo fork of rewrite-clj.

[lread]

Issue comments from rewrite-cljc-playground:

@lread:
Was chatting with @borkdude on Slack and type came up again. Perhaps a (type node) might a good addition. @borkdude said that such a feature would allow him to avoid code like this.

@lread:
More chats on Slack, @SevereOverfl0w was wondering about querying node types.

We agreed the existing granularity provided by (rewrite-cljc.node/tag n) is coarser than we'd like.

@borkdude chimed in with examples of what he uses for his custom version of rewrite-clj in clj-kondo:

(defn boolean-token? [node]
  (boolean? (:value node)))

(defn char-token? [node]
  (char? (:value node)))

(defn string-from-token [node]
  (when-let [lines (:lines node)]
    (str/join "\n" lines)))

(defn number-token? [node]
  (number? (:value node)))

(defn symbol-token? [node]
  (symbol? (:value node)))

(defn symbol-from-token [node]
  (when-let [?sym (:value node)]
    (when (symbol? ?sym)
      ?sym)))

And then @borkdude also shared another idea:

a function that returned some keyword could also be handy if you want to dispatch on something:

(defn tag+ [node] (if (symbol? (:value node)) :symbol) ...)
(case (tag+ node) :symbol ...)

I think I have something like that too in clj-kondo
this could also go into some extra utils lib
or utils ns

[lread]

I think I like the idea of a tag+ (or maybe node-type) to avoid littering our already wide node and zip APIs with a bunch of new little functions.

[borkdude]

One idea is to also use (isa? :rewrite-clj/symbol :rewrite-clj/token), possibly.

[lread]

One idea is to also use (isa? :rewrite-clj/symbol :rewrite-clj/token), possibly.

Directly related: #131 (comment)

[borkdude]

I already wondered where I left that comment, thanks.

[lread]

Ha! Yeah, I was searching for it yesterday, oddly enough!