Details
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Type:
Defect
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Status:
Open
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Priority:
Major
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Resolution: Unresolved
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Affects Version/s: Release 1.6
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Fix Version/s: None
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Component/s: None
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Labels:
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Patch:Code
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Approval:Triaged
Description
Most implementations of Iterators for Clojure's collections do not implement the next method correctly. In case the iterator is exhausted the methods fail with some case dependent error, but not with the NoSuchElementException as required by the official Java contract for that method. This causes problems when working with Java libraries relying on that behaviour.
Issue encountered in real world code using http://pipes.tinkerpop.com.
To reproduce:
(-> [] .iterator .next)
This throws a NPE instead of NSEE.
(doto (.iterator [1 2]) .next .next .next)
This throws an ArrayIndexOutOfBoundsException instead of NSEE.
The attached patch fixes the methods by adding a check for hasNext before actually trying to provide the next element. If there is no next element the correct exception is thrown.
Up-to-date patch file: 0001-Fix-iterator-implementations-to-throw-NSEE-when-exha.patch
To establish a baseline, this piece of code checks all the iterators I could find within Clojure 1.6.0 and makes sure they throw an appropriate exception:
(defn next-failure [] (let [ok (atom [])] (doseq [[tp v] (sorted-map :vec-0 [] :vec-n [1 2 3] :vec-start (subvec [1 2 3 4] 0 1) :vec-end (subvec [1 2 3 4] 3 4) :vec-ls-0 (.listIterator []) :vec-ls-n (.listIterator [1 2 3]) :vec-start-ls (.listIterator (subvec [1 2 3 4] 0 1)) :vec-end-ls (.listIterator (subvec [1 2 3 4] 3 4)) :seq () :list-n '(1 2 3) :set-hash-0 (hash-set) :set-hash-n (hash-set 1 2 3) :set-sor-0 (sorted-set) :set-sor-n (sorted-set 1 2 3) :map-arr-0 (array-map) :map-arr-n (array-map 1 2, 3 4) :map-hash-0 (hash-map) :map-hash-n (hash-map 1 2, 3 4) :map-sor-n (sorted-map) :map-sor-n (sorted-map 1 2, 3 4) :map-sor-ks-0 (.keys (sorted-map)) :map-sor-ks-n (.keys (sorted-map 1 2, 3 4)) :map-sor-vs-0 (.vals (sorted-map)) :map-sor-vs-n (.vals (sorted-map 1 2, 3 4)) :map-sor-rev-0 (.reverseIterator (sorted-map)) :map-sor-rev-n (.reverseIterator (sorted-map 1 2, 3 4)) :map-ks-0 (.keySet {}) :map-ks-n (.keySet {1 2, 3 4}) :map-vs-0 (.values {}) :map-vs-n (.values {1 2, 3 4}) :gvec-int-0 (vector-of :long) :gvec-int-n (vector-of :long 1 2 3))] (let [it (if (instance? java.util.Iterator v) v (.iterator v))] (when-not it (println "Null iterator:" tp)) (try (dotimes [_ 50] (.next it)) (catch java.util.NoSuchElementException nsee (swap! ok conj tp)) (catch Throwable t (println tp "threw" (class t)))))) (println "OK:" @ok)))The output as of current Clojure master (201a0dd970) is:
(defn next-failure [] (let [ok (atom [])] (doseq [[tp v] (sorted-map :vec-0 [] :vec-n [1 2 3] :vec-start (subvec [1 2 3 4] 0 1) :vec-end (subvec [1 2 3 4] 3 4) :vec-ls-0 (.listIterator []) :vec-ls-n (.listIterator [1 2 3]) :vec-start-ls (.listIterator (subvec [1 2 3 4] 0 1)) :vec-end-ls (.listIterator (subvec [1 2 3 4] 3 4)) :seq () :list-n '(1 2 3) :set-hash-0 (hash-set) :set-hash-n (hash-set 1 2 3) :set-sor-0 (sorted-set) :set-sor-n (sorted-set 1 2 3) :map-arr-0 (array-map) :map-arr-n (array-map 1 2, 3 4) :map-hash-0 (hash-map) :map-hash-n (hash-map 1 2, 3 4) :map-sor-n (sorted-map) :map-sor-n (sorted-map 1 2, 3 4) :map-sor-ks-0 (.keys (sorted-map)) :map-sor-ks-n (.keys (sorted-map 1 2, 3 4)) :map-sor-vs-0 (.vals (sorted-map)) :map-sor-vs-n (.vals (sorted-map 1 2, 3 4)) :map-sor-rev-0 (.reverseIterator (sorted-map)) :map-sor-rev-n (.reverseIterator (sorted-map 1 2, 3 4)) :map-ks-0 (.keySet {}) :map-ks-n (.keySet {1 2, 3 4}) :map-vs-0 (.values {}) :map-vs-n (.values {1 2, 3 4}) :gvec-int-0 (vector-of :long) :gvec-int-n (vector-of :long 1 2 3))] (let [it (if (instance? java.util.Iterator v) v (.iterator v))] (when-not it (println "Null iterator:" tp)) (try (dotimes [_ 50] (.next it)) (catch java.util.NoSuchElementException nsee (swap! ok conj tp)) (catch Throwable t (println tp "threw" (class t)))))) (println "OK:" @ok)))