t:dataTable style attributes don't work with Facelets
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                 Key: TOMAHAWK-914
                 URL: https://issues.apache.org/jira/browse/TOMAHAWK-914
             Project: MyFaces Tomahawk
          Issue Type: Bug
          Components: Extended Datatable
    Affects Versions: 1.1.4-SNAPSHOT, 1.1.5-SNAPSHOT
         Environment: MyFaces Core 1.1.5, Facelets 1.1.11
            Reporter: Jeff Bischoff
         Attachments: HtmlDataTable.java.diff, JSFAttr.java.diff

Problem: style and styleClass attributes on t:dataTable do not work in Facelets 
due to use of fully-qualified names in the map.

Fix: Patch attached to resolve this by changing the names as stored in the map. 
Includes code to accept hacks based on the old behaviour, but warns that it is 
now deprecated.

Bonus: Also includes fix for problem in Facelets where the EL can not return a 
null style. This is due to changes in the EL spec, and prevents the former 
(very useful) style rollover behaviour. Fix works by converting any empty 
String returned by the EL in these Style attributes into null. (Reverse 
Coercion)

Background:

After converting my application from JSP to Facelets, I set out to make my 
"rowStyleClass" attribute on t:dataTable work like it used to.

First, I had to get the attribute working in Facelets. With considerable 
discussion on the user list (see [1] and [2]) and a lot of help from Mike, I 
think we've identified some pretty simple code changes to enable this and other 
similar attributes. I plan to introduce a patch for this, probably tomorrow.

What happened next was that during testing of this change, I could confirm that 
the attribute did indeed now work, but I was baffled by unexpected behaviour. 
My EL expression which had previously returned null in certain situations was 
now returning the empty String. I went to Facelets list for some clarification 
on this (see [3]) and it turned out to be a requirement of the new EL spec to 
coerce the nulls into empty string.

Getting an empty String instead of null for this ValueBinding lookup creates a 
problem because the extended dataTable treats a null value differently and goes 
looking at the more standard style attributes like rowClasses. With an empty 
string returned, it assumes it needs to look no further. As a user, there is no 
way for me to specify that under certain conditions, it should fallback to the 
other style attributes, e.g. rowClasses.

The best fix we have collectively come up with so far is to coerce the empty 
string back into a null in the dataTable, so that the renderer does the right 
thing. I don't see too much downside to this approach, as an empty style string 
has no relevance in CSS. However, I feel a proposed change like this requires 
extra discussion before making a decision on it. It's another one of those 
situation where we have to decide how we want to handle unexpected results due 
to changes in the newer specs. 

[1] https://facelets.dev.java.net/servlets/ReadMsg?list=users&msgNo=6875
[2] 
http://www.nabble.com/Re%3A-Facelets-support-for-a-Tomahawk-dataTable-trick--tf3236491.html
[3] https://facelets.dev.java.net/servlets/ReadMsg?list=users&msgNo=6941 

Regards,

Jeff Bischoff
Kenneth L Kurz & Associates, Inc. 

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