@50Wliu could you review this pull request? Thanks!

@MoritzKn May I ask for your input here? Do you need to double-escape backslashes in EL?

@50Wliu I haven't used it for quite some time and don't have a setup at hand to test it right now. The specification says:

1.3 Literals
There are literals for boolean, integer, floating point, string, and null in an evalexpression.

• Boolean - true and false
• Integer - As defined by the IntegerLiteral construct in Section 1.19
• Floating point - As defined by the FloatingPointLiteral construct in
  Section 1.19
• String - With single and double quotes - " is escaped as \", ' is escaped as \',
  and \ is escaped as \\. Quotes only need to be escaped in a string value enclosed
  in the same type of quote
• Null - null

-- http://download.oracle.com/otn-pub/jcp/jsp-2.1-fr-spec-oth-JSpec/jsp-2_1-fr-spec-el.pdf

However this may not apply for this case since it's embedded in the JSP code.

My hunch is that since this is embedded in JSP, we should be adding escape character support to JSP instead of EL.

The reason I fixed in EL was due to broken punctuation.definition.string.end.java.el being defined in unified expression language, so I thought that it must be the place to fix it, rather than JSP, which does not define it. Another argument to support this was that bug originates from a function being part of the attribute value.

My understanding is that JSP file is for tags and attributes (key = value), and values are parsed as EL (scope source.java.el) - though I might be wrong here, and would appreciate any corrections. Thanks!

From the "Quoting and Escape Conventions" section of http://download.oracle.com/otn-pub/jcp/jsp-2_3-mrel2-eval-spec/JSP2.3MR.pdf?AuthParam=1517623843_d412f1e03b76e1d552dbf301b0948086 (not sure how up-to-date that is), backslash escaping is done in attribute values (in this case EL). So I think what's happening here is the same thing as what's happening when writing grammar files - the backslash needs to be double-escaped once for EL and then the second time for JSP.

@50Wliu I think this is what we do - escape only \\', right? Should we proceed with this fix or do you have any concerns? Thanks.

@sadikovi No, I believe that we should add proper escape tokenization to the JSP language.

@50Wliu thanks for the review and comment! I used previous escape scope as a guidance and thought that this fox should be there as well. I am going to close this PR - currently there are other more critical issues to fix:)