Dynamic Var, Binding, Namespace visibility

Question

Getting unresolved on dynamic var when called from n-levels out from originating namespace

Setup:

File a.clj
-----------
(ns a)

(def ^:dynamic *poof* "poof")

(def x [1 '*poof* 3])

(defn- func-wbind [new-term]
  (binding [*poof* new-term]
    (println (eval x))))

(defn with-term [term]
  (println x)
  (println (eval x)) ; <== *** FAILS HERE ***
  (func-wbind term))

File b.clj
-----------
(ns b
 (:require [a :refer :all]))

(defn woof-it []
  (with-term "woof")) 

File c.clj
-----------
(ns c
(:require [b :refer :all]))

(defn try-it []
  (woof-it))

Loading REPL with 'c' and calling try-it fails on unresolved var for the dynamic.

Any help would be greatly appreciated.

Edit : Above modified and repeatable error.

Stack Trace:

ERROR in (endpoint-tests) (Compiler.java:6380)
Default
expected: (map? (endpoint-abstractions ep-any "www.yahoo.com"))
  actual: clojure.lang.Compiler$CompilerException: java.lang.RuntimeException: Unable to resolve symbol: *ph* in this context, compiling:(gl_ep/epref_tests.clj:17:1)
 at clojure.lang.Compiler.analyze (Compiler.java:6380)
    clojure.lang.Compiler.analyze (Compiler.java:6322)
    clojure.lang.Compiler$HostExpr$Parser.parse (Compiler.java:948)
    clojure.lang.Compiler.analyzeSeq (Compiler.java:6560)
    clojure.lang.Compiler.analyze (Compiler.java:6361)
    clojure.lang.Compiler.analyze (Compiler.java:6322)
    clojure.lang.Compiler.analyzeSeq (Compiler.java:6555)
    clojure.lang.Compiler.analyze (Compiler.java:6361)
    clojure.lang.Compiler.analyze (Compiler.java:6322)
    clojure.lang.Compiler$BodyExpr$Parser.parse (Compiler.java:5708)
    clojure.lang.Compiler$FnMethod.parse (Compiler.java:5139)
    clojure.lang.Compiler$FnExpr.parse (Compiler.java:3751)
    clojure.lang.Compiler.analyzeSeq (Compiler.java:6558)
    clojure.lang.Compiler.analyze (Compiler.java:6361)
    clojure.lang.Compiler.eval (Compiler.java:6616)

    clojure.lang.Compiler.eval (Compiler.java:6582)
    clojure.core$eval.invoke (core.clj:2852)
    gl_ep.html_extract$glg_hfm_transform$fn__5320$fn__5321.invoke (html_extract.clj:35)
    hickory.select$attr$fn__5193.invoke (select.clj:220)
    clojure.lang.AFn.applyToHelper (AFn.java:161)
    clojure.lang.AFn.applyTo (AFn.java:151)
    clojure.lang.AFunction$1.doInvoke (AFunction.java:29)
    clojure.lang.RestFn.invoke (RestFn.java:408)
    hickory.select$ordered_adjacent$fn__5271.invoke (select.clj:481)
    hickory.select$select_next_loc.invoke (select.clj:134)
    hickory.select$select_next_loc.invoke (select.clj:129)
    hickory.select$select_next_loc.invoke (select.clj:127)
    hickory.select$select_locs.invoke (select.clj:143)
    hickory.select$select.invoke (select.clj:154)
    gl_ep.html_extract$hickory_get.invoke (html_extract.clj:66)
    gl_ep.html_extract$mapglg$fn__5363.invoke (html_extract.clj:76)
    clojure.core$map$fn__4207.invoke (core.clj:2485)
    clojure.lang.LazySeq.sval (LazySeq.java:42)

    clojure.lang.LazySeq.seq (LazySeq.java:60)
    clojure.lang.RT.seq (RT.java:484)
    clojure.core$seq.invoke (core.clj:133)
    clojure.core$map$fn__4207.invoke (core.clj:2479)
    clojure.lang.LazySeq.sval (LazySeq.java:42)
    clojure.lang.LazySeq.seq (LazySeq.java:60)
    clojure.lang.RT.seq (RT.java:484)
    clojure.core$seq.invoke (core.clj:133)
    clojure.core$apply.invoke (core.clj:617)
    gl_ep.html_extract$mapglg.invoke (html_extract.clj:73)
    gl_ep.html_extract$extract.invoke (html_extract.clj:87)
    gl_ep.endpoint$abstractions.doInvoke (endpoint.clj:59)
    clojure.lang.RestFn.invoke (RestFn.java:423)
    gl_ep.endpoint$endpoint_abstractions.doInvoke (endpoint.clj:68)
    clojure.lang.RestFn.invoke (RestFn.java:423)
    gl_ep.epref_tests$fn__8816$fn__8817.invoke (epref_tests.clj:10)
    gl_ep.epref_tests/fn (epref_tests.clj:10)
    clojure.test$test_var$fn__7145.invoke (test.clj:701)
    clojure.test$test_var.invoke (test.clj:701)
    clojure.test$test_all_vars$fn__7149$fn__7156.invoke (test.clj:717)

    clojure.test$default_fixture.invoke (test.clj:671)
    clojure.test$test_all_vars$fn__7149.invoke (test.clj:717)
    clojure.test$default_fixture.invoke (test.clj:671)
    clojure.test$test_all_vars.invoke (test.clj:713)
    clojure.test$test_ns.invoke (test.clj:736)
    clojure.core$map$fn__4207.invoke (core.clj:2487)
    clojure.lang.LazySeq.sval (LazySeq.java:42)
    clojure.lang.LazySeq.seq (LazySeq.java:60)
    clojure.lang.Cons.next (Cons.java:39)
    clojure.lang.RT.boundedLength (RT.java:1654)
    clojure.lang.RestFn.applyTo (RestFn.java:130)
    clojure.core$apply.invoke (core.clj:619)
    clojure.test$run_tests.doInvoke (test.clj:751)
    clojure.lang.RestFn.invoke (RestFn.java:408)
    clojure.test$run_tests.invoke (test.clj:749)

Answer 1

When you eval a form, unqualified symbols in that form are resolved in the current namespace (as defined by clojure.core/*ns*) at runtime, not the namespace in which the call to eval was compiled. So the symbol *poof* is resolved in the REPL namespace. This works in namespace b because you did a :refer :all when requiring a, thereby creating a local alias to a/*poof* in b. There exists no such alias in c, and so resolving the symbol fails.

There are a couple of options to fix this. You could change the declaration of x to use a namespace-qualified symbol:

(def x [1 'a/*poof* 3])`

Or, you could make the call to eval in a binding of *ns* to namespace a.

(def x [1 '*poof* 3])

(defn- local-eval [x]
  (binding [*ns* (find-ns 'a)]
    (eval x)))

and then replace calls to eval with calls to local-eval.

See the Clojure documentation for a more detailed explanation of how symbols are resolved during evaluation.