508527 - missing array elements contribute to the length of the array

Status: RESOLVED FIXED

(Rhino Graveyard :: Core, defect)

Description

[rspeyer]

User-Agent:       Mozilla/5.0 (Macintosh; U; Intel Mac OS X 10_5_7; en-US) AppleWebKit/532.0 (KHTML, like Gecko) Chrome/3.0.196 Safari/532.0
Build Identifier: Rhino 1.7 release 2 2009 03 22

From 11.1.4 of the spec:

"Array elements may be elided at the beginning, middle or end of the element list. Whenever a comma in the element list is not preceded by an AssignmentExpression (i.e., a comma at the beginning or after another comma), the missing array element contributes to the length of the Array and increases the index of subsequent elements. Elided array elements are not defined. If an element is elided at the end of an array, that element does not contribute to the length of the Array."

Reproducible: Always

Actual Results:  
js> [,1,2].length
3
js> [1,,2].length
3
js> [1,2,].length
2
js> [,].length
0
js> [1,,].length
1


Expected Results:  
js> [,1,2].length
3
js> [1,,2].length
3
js> [1,2,].length
2
js> [,].length
1
js> [1,,].length
2

Comment 1

[rspeyer]

Attachment: made missing array literal elements still contribute to the length

As per 11.1.4 of the spec

Comment 2

[rspeyer]

Attachment: made missing array literal elements still contribute to the length (with tests)

Replacement for attachment 392691 [details] [diff] [review]. Added doctests.

Comment 3

[Norris Boyd]

You need to explicitly create a NativeArray rather than relying upon cx.newObject. The older code was written before it was explicitly standardized that array literals should call the standard built-in constructor. With your patch the following happens:

js> function Array() { print('hi'); }
js> var a = []
hi
Exception in thread "main" java.lang.ClassCastException: org.mozilla.javascript.NativeObject cannot be cast to org.mozilla.javascript.NativeArray
	at org.mozilla.javascript.ScriptRuntime.newArrayLiteral(ScriptRuntime.java:3469)
	at org.mozilla.javascript.Interpreter.interpretLoop(Interpreter.java:2059)
	at org.mozilla.javascript.Interpreter.interpret(Interpreter.java:845)
	at org.mozilla.javascript.InterpretedFunction.call(InterpretedFunction.java:164)
	at org.mozilla.javascript.ContextFactory.doTopCall(ContextFactory.java:426)
	at org.mozilla.javascript.ScriptRuntime.doTopCall(ScriptRuntime.java:3090)
	at org.mozilla.javascript.InterpretedFunction.exec(InterpretedFunction.java:175)
	at org.mozilla.javascript.tools.shell.Main.evaluateScript(Main.java:563)
	at org.mozilla.javascript.tools.shell.Main.processSource(Main.java:424)
	at org.mozilla.javascript.tools.shell.Main.processFiles(Main.java:196)
	at org.mozilla.javascript.tools.shell.Main$IProxy.run(Main.java:117)
	at org.mozilla.javascript.Context.call(Context.java:522)
	at org.mozilla.javascript.ContextFactory.call(ContextFactory.java:535)
	at org.mozilla.javascript.tools.shell.Main.exec(Main.java:179)
	at org.mozilla.javascript.tools.shell.Main.main(Main.java:157)

Comment 4

[rspeyer]

Attachment: missing array literal elements contribute to length (use default builtin constructor)

Comment 5

[Norris Boyd]

Checking in src/org/mozilla/javascript/ScriptRuntime.java;
/cvsroot/mozilla/js/rhino/src/org/mozilla/javascript/ScriptRuntime.java,v  <--  ScriptRuntime.java
new revision: 1.319; previous revision: 1.318
done
Checking in testsrc/doctests/array.length.doctest;
/cvsroot/mozilla/js/rhino/testsrc/doctests/array.length.doctest,v  <--  array.length.doctest
initial revision: 1.1
done