Details
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Type:
Defect
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Status:
Closed
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Priority:
Minor
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Resolution: Completed
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Affects Version/s: None
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Fix Version/s: Release 1.3
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Component/s: None
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Labels:None
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Patch:Code and Test
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Approval:Ok
Description
This is really a request for improved error handling. If you use (alias) with a namespace that is not known it throws an NPE with imho a confusing error message.
Example:
user=> (alias 'R 'S)
java.lang.NullPointerException: Expecting Symbol + Namespace (NO_SOURCE_FILE:0)
user=> (.printStackTrace *e)
nil
user=> java.lang.NullPointerException: Expecting Symbol + Namespace (NO_SOURCE_FILE:0)
at clojure.lang.Compiler.eval(Compiler.java:5348)
at clojure.lang.Compiler.eval(Compiler.java:5300)
at clojure.core$eval__4281.invoke(core.clj:2135)
at clojure.main$repl__6358$read_eval_print__6366.invoke(main.clj:183)
at clojure.main$repl__6358.doInvoke(main.clj:200)
at clojure.lang.RestFn.invoke(RestFn.java:422)
at clojure.main$repl_opt__6392.invoke(main.clj:254)
at clojure.main$main__6418.doInvoke(main.clj:347)
at clojure.lang.RestFn.invoke(RestFn.java:398)
at clojure.lang.Var.invoke(Var.java:361)
at clojure.lang.AFn.applyToHelper(AFn.java:161)
at clojure.lang.Var.applyTo(Var.java:482)
at clojure.main.main(main.java:37)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at jline.ConsoleRunner.main(ConsoleRunner.java:69)
Caused by: java.lang.NullPointerException: Expecting Symbol + Namespace
at clojure.lang.Namespace.addAlias(Namespace.java:184)
at clojure.core$alias__4566.invoke(core.clj:2892)
at user$eval__11.invoke(NO_SOURCE_FILE:7)
at clojure.lang.Compiler.eval(Compiler.java:5332)
... 17 more
</code></pre>
And the clj:
<pre><code>(defn alias
"Add an alias in the current namespace to another
namespace. Arguments are two symbols: the alias to be used, and
the symbolic name of the target namespace. Use :as in the ns macro in preference
to calling this directly."
[alias namespace-sym]
(.addAlias *ns* alias (find-ns namespace-sym)))
Clearly, the clojure is doing find-ns and the namespace is not known so it passes a null down. Seems like the code in either the clj or java level could say "Hey dummy, you used an unknown namespace" instead of "Expecting Symbol + Namespace". Maybe this would be useful as an additional sentence in the alias doc string too.
Attachments
Activity
aaron said: Tried to submit a patch but keep getting 500 errors on assembla. I'll try again later, but i'll paste the patch in here so it is somewhere else.
From 32c32d65ec43598f36872a742bdebec5907d17d7 Mon Sep 17 00:00:00 2001
From: Aaron Bedra <aaron@aaronbedra.com>
Date: Tue, 26 Oct 2010 23:34:55 -0400
Subject: [PATCH] clarifying error message on alias
—
src/jvm/clojure/lang/Namespace.java | 9 +++++++--
1 files changed, 7 insertions
, 2 deletions
diff --git a/src/jvm/clojure/lang/Namespace.java b/src/jvm/clojure/lang/Namespace.java
index 1936973..87a9082 100644
— a/src/jvm/clojure/lang/Namespace.java
+++ b/src/jvm/clojure/lang/Namespace.java
@@ -210,8 +210,13 @@ public Namespace lookupAlias(Symbol alias){
}
public void addAlias(Symbol alias, Namespace ns){
- if (alias == null || ns == null)
- throw new NullPointerException("Expecting Symbol + Namespace");
+ if (alias == null && ns == null)
+ throw new NullPointerException("Received unknown alias and namespace");
+ else if (ns == null)
+ throw new NullPointerException("Received unknown namespace");
+ else if (alias == null)
+ throw new NullPointerException("Received unknown alias");
+
IPersistentMap map = getAliases();
while(!map.containsKey(alias))
{
1.7.3.2
, 2 deletions
diff --git a/src/jvm/clojure/lang/Namespace.java b/src/jvm/clojure/lang/Namespace.java
index 1936973..87a9082 100644
— a/src/jvm/clojure/lang/Namespace.java
+++ b/src/jvm/clojure/lang/Namespace.java
@@ -210,8 +210,13 @@ public Namespace lookupAlias(Symbol alias){
}
public void addAlias(Symbol alias, Namespace ns){
- if (alias == null || ns == null)
- throw new NullPointerException("Expecting Symbol + Namespace");
+ if (alias == null && ns == null)
+ throw new NullPointerException("Received unknown alias and namespace");
+ else if (ns == null)
+ throw new NullPointerException("Received unknown namespace");
+ else if (alias == null)
+ throw new NullPointerException("Received unknown alias");
+
IPersistentMap map = getAliases();
while(!map.containsKey(alias))
{
- 1.7.3.2
Converted from http://www.assembla.com/spaces/clojure/tickets/320