2018-02-23 18:58:03 +00:00
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---
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created_at: '2013-11-15T10:54:50.000Z'
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title: We have an employee whose last name is Null (2010)
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url: http://stackoverflow.com/questions/4456438/how-can-i-pass-the-string-null-through-wsdl-soap-from-actionscript-3-to-a-co?rq=1
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author: gojko
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points: 67
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story_text: ''
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comment_text:
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num_comments: 35
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story_id:
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story_title:
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story_url:
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parent_id:
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created_at_i: 1384512890
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_tags:
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- story
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- author_gojko
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- story_6738743
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objectID: '6738743'
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2018-06-08 12:05:27 +00:00
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year: 2010
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2018-02-23 18:58:03 +00:00
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---
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2018-03-03 09:35:28 +00:00
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# Tracking it down
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2018-02-23 18:19:40 +00:00
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2018-03-03 09:35:28 +00:00
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At first I thought this was a coercion bug where `null` was getting
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coerced to `"null"` and a test of `"null" == null` was passing. It's
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not. **I was close, but so very, very wrong. Sorry about that\!**
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2018-02-23 18:19:40 +00:00
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2018-03-03 09:35:28 +00:00
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I've since done lots of [fiddling on
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wonderfl.net](http://wonderfl.net/c/dd23/read) and tracing through the
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code in `mx.rpc.xml.*`. At line 1795 of `XMLEncoder` (in the 3.5
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source), in `setValue`, all of the XMLEncoding boils down to
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2018-02-23 18:19:40 +00:00
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2018-03-03 09:35:28 +00:00
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currentChild.appendChild(xmlSpecialCharsFilter(Object(value)));
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which is essentially the same as:
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currentChild.appendChild("null");
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This code, according to my original fiddle, returns an empty XML
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element. But why?
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# Cause
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According to commenter Justin Mclean on bug report
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[FLEX-33664](https://issues.apache.org/jira/browse/FLEX-33644), the
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following is the culprit (see last two tests in my
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[fiddle](http://wonderfl.net/c/dd23/read) which verify this):
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var thisIsNotNull:XML = <root>null</root>;
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if(thisIsNotNull == null){
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// always branches here, as (thisIsNotNull == null) strangely returns true
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// despite the fact that thisIsNotNull is a valid instance of type XML
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}
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When `currentChild.appendChild` is passed the string `"null"`, it first
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converts it to a root XML element with text `null`, and then tests that
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element against the null literal. This is a weak equality test, so
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either the XML containing null is coerced to the null type, or the null
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type is coerced to a root xml element containing the string "null", and
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the test passes where it arguably should fail. One fix might be to
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always use [strict
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equality](http://help.adobe.com/en_US/FlashPlatform/reference/actionscript/3/operators.html#strict_equality)
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tests when checking XML (or anything, really) for "nullness."
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# Solution
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The only reasonable workaround I can think of, short of fixing this bug
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in every damn version of ActionScript, is to test fields for "null" and
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**escape them as [CDATA
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values](https://stackoverflow.com/q/1239466/203705).**
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The only reasonable workaround I can think of, short of fixing this bug
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in every damn version of ActionScript, is to test fields for "null" and
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**CDATA values are the most appropriate way to mutate an entire text
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value that would otherwise cause encoding/decoding problems.** Hex
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encoding, for instance, is meant for individual characters. CDATA values
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are preferred when you're escaping the entire text of an element. The
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biggest reason for this is that it maintains human readability.
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