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[CLJ-1016] Global scope overrides lexical scope for classes (Clojure assumes no classes in default package / Clojure cannot handle yFiles JARs in classpath) Created: 21/Jun/12  Updated: 24/May/13

Status: Open
Project: Clojure
Component/s: None
Affects Version/s: Release 1.5
Fix Version/s: None

Type: Defect Priority: Major
Reporter: Edward Z. Yang Assignee: Unassigned
Resolution: Unresolved Votes: 0
Labels: None

Attachments: Text File collision-workaround.patch    

 Description   

The most visible symptom of this bug is having a class named 'w' (default package) in your classpath (such classes are produced by Java obfuscation tools such as yFiles) and then attempting to load Clojure's core class. For example:

java -cp hotspotapi.jar:clojure-1.4.0-slim.jar clojure.main

(where hotspotapi.jar is a stereotypical example of an obfuscated JAR) results in:

Exception in thread "main" java.lang.ExceptionInInitializerError
at clojure.main.<clinit>(main.java:20)
Caused by: java.lang.NoSuchFieldException: close, compiling:(clojure/core.clj:6139)
at clojure.lang.Compiler.analyzeSeq(Compiler.java:6462)
at clojure.lang.Compiler.analyze(Compiler.java:6262)
at clojure.lang.Compiler.analyze(Compiler.java:6223)
at clojure.lang.Compiler$BodyExpr$Parser.parse(Compiler.java:5618)
at clojure.lang.Compiler$TryExpr$Parser.parse(Compiler.java:2178)
at clojure.lang.Compiler.analyzeSeq(Compiler.java:6455)
at clojure.lang.Compiler.analyze(Compiler.java:6262)
at clojure.lang.Compiler.analyze(Compiler.java:6223)
at clojure.lang.Compiler$BodyExpr$Parser.parse(Compiler.java:5618)
at clojure.lang.Compiler$LetExpr$Parser.parse(Compiler.java:5919)
at clojure.lang.Compiler.analyzeSeq(Compiler.java:6455)
at clojure.lang.Compiler.analyze(Compiler.java:6262)
at clojure.lang.Compiler.analyzeSeq(Compiler.java:6443)
at clojure.lang.Compiler.analyze(Compiler.java:6262)
at clojure.lang.Compiler.analyzeSeq(Compiler.java:6443)
at clojure.lang.Compiler.analyze(Compiler.java:6262)
at clojure.lang.Compiler.analyze(Compiler.java:6223)
at clojure.lang.Compiler$BodyExpr$Parser.parse(Compiler.java:5618)
at clojure.lang.Compiler$FnMethod.parse(Compiler.java:5054)
at clojure.lang.Compiler$FnExpr.parse(Compiler.java:3674)
at clojure.lang.Compiler.analyzeSeq(Compiler.java:6453)
at clojure.lang.Compiler.analyze(Compiler.java:6262)
at clojure.lang.Compiler.analyzeSeq(Compiler.java:6443)
at clojure.lang.Compiler.analyze(Compiler.java:6262)
at clojure.lang.Compiler.access$100(Compiler.java:37)
at clojure.lang.Compiler$DefExpr$Parser.parse(Compiler.java:518)
at clojure.lang.Compiler.analyzeSeq(Compiler.java:6455)
at clojure.lang.Compiler.analyze(Compiler.java:6262)
at clojure.lang.Compiler.analyze(Compiler.java:6223)
at clojure.lang.Compiler.eval(Compiler.java:6515)
at clojure.lang.Compiler.load(Compiler.java:6952)
at clojure.lang.RT.loadResourceScript(RT.java:359)
at clojure.lang.RT.loadResourceScript(RT.java:350)
at clojure.lang.RT.load(RT.java:429)
at clojure.lang.RT.load(RT.java:400)
at clojure.lang.RT.doInit(RT.java:436)
at clojure.lang.RT.<clinit>(RT.java:318)
... 1 more
Caused by: java.lang.NoSuchFieldException: close
at java.lang.Class.getField(Class.java:1537)
at clojure.lang.Compiler$StaticFieldExpr.<init>(Compiler.java:1180)
at clojure.lang.Compiler$HostExpr$Parser.parse(Compiler.java:923)
at clojure.lang.Compiler.analyzeSeq(Compiler.java:6455)
... 37 more
Could not find the main class: clojure.main. Program will exit.

To understand what is going on, consider this simple test:

import java.io.StringReader;

import clojure.lang.Compiler;
import clojure.lang.RT;

public class Test {
public static void main(String[] args) { RT.var("clojure.core", "require"); String s = "(let [mumble (new java.io.StringReader \"\")] (. mumble close))"; Compiler.load(new StringReader(s)); }
}

It should be clear that 'mumble' in the dot operator is referencing the locally defined mumble. However, if we define a class named 'mumble' in the default package, Clojure picks that one up instead.

To forestall any objections: yes, we know that placing classes in the default package is extremely poor form. Point of the matter is, the Java ecosystem is extremely diverse and there are a lot of JARs people may not have control over. While one might argue, "Don't put classes in the default namespace", point of the matter is, Clojure is wrong here, and these situations arise in practice, through no fault of the implementer.



 Comments   
Comment by Edward Z. Yang [ 21/Jun/12 11:01 AM ]

Here is a workaround patch which makes this error less likely to occur.

Comment by Andy Fingerhut [ 27/Aug/12 7:37 PM ]

Edward, it is Rich Hickey's policy only to consider for inclusion in Clojure patches written by people who have signed a Contributor Agreement: http://clojure.org/contributing

Were you interested in becoming a contributor?

Comment by Edward Z. Yang [ 27/Aug/12 9:24 PM ]

Sure, although the patch attached is emphatically not the one you want to actually applying, since it only band-aids the problem.

Comment by Andy Fingerhut [ 24/May/13 1:21 PM ]

I am not sure, but this ticket may be related to CLJ-1171. At least, there the issue was a global name not being shadowed by a local name bound with let. That seems similar to this issue.

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