JSCoverage
code coverage for JavaScript

Bug #39 - Instrumenting a site that uses Microsoft AJAX in proxy mode fails with ‘invalid character'

Trying to instrument a site that uses Microsoft AJAX using jscoverage in proxy 
mode fails with ‘invalid character’.

Repro:
-	download 0.5.1 from http://siliconforks.com/jscoverage/download.html
-	run “jscoverage-server.exe --verbose –proxy”
-	force browser to use 127.0.0.1:8080 as proxy
-	open http://www.asp.net/ajaxlibrary/act_AlwaysVisible.ashx
-	watch the server fail with SyntaxError: illegal character
o	URL in this case is the hash from ScriptManager, but a simpler page 
reveals this to happen with just MicrosoftAjax.js.

Same results if you run jscoverage.exe directly on MicrosoftAjax.js.

If you own the site then at least there's a workaround, which is to prettify the 
file beforehand. When the file is expanded with 'ajaxmin -pretty' then 
jscoverage is happy with it:

Repro, assuming retail MicrosoftAjax.js in d:\temp:

D:\temp\cover>copy ..\MicrosoftAjax.js
        1 file(s) copied.

D:\temp\cover>d:\jscoverage-0.5.1\jscoverage.exe d:\temp\cover d:\temp\cover2
jscoverage:MicrosoftAjax.js:1: SyntaxError: illegal character
jscoverage: parse error in file MicrosoftAjax.js

D:\temp\cover>ajaxmin -pretty MicrosoftAjax.js > MicrosoftAjax.pretty.js
Microsoft Ajax Minifier - JavaScript and CSS minification and verification 
utility
Copyright 2010 Microsoft Corporation


Minifying file 'MicrosoftAjax.js'...
Original Size: 101547 bytes; reduced size: 157173 bytes (-54.8% minification)
Gzip of output approximately 34280 bytes (78.2% compression)


D:\temp\cover>del MicrosoftAjax.js

D:\temp\cover>d:\jscoverage-0.5.1\jscoverage.exe d:\temp\cover d:\temp\cover2


D:\temp\cover>dir \temp\cover2
 Volume in drive D has no label.
 Volume Serial Number is D09F-409A

 Directory of D:\temp\cover2

08/22/2011  11:05 AM    <DIR>          .
08/22/2011  11:05 AM    <DIR>          ..
08/22/2011  11:05 AM             1,157 jscoverage-highlight.css
08/22/2011  11:05 AM             2,011 jscoverage-ie.css
08/22/2011  11:05 AM               425 jscoverage-throbber.gif
08/22/2011  11:05 AM             6,342 jscoverage.css
08/22/2011  11:05 AM             6,609 jscoverage.html
08/22/2011  11:05 AM            33,286 jscoverage.js
08/22/2011  11:04 AM                 0 MicrosoftAjax.js
08/22/2011  11:05 AM         1,128,521 MicrosoftAjax.pretty.js
               8 File(s)      1,178,351 bytes
               2 Dir(s)  189,092,405,248 bytes free

Hum...it seems that the problem is actually that the file uses UTF-8 encoding 
and jscoverage doesn't like the encoding characters at the beginning of the 
file.

Saving the files with ANSI encoding make jscoverage happy.

JSCoverage's character encoding detection is not very sophisticated: if a
JavaScript file is UTF-8, it will have to be served with the header
"Content-Type: text/javascript; charset=UTF-8" or the jscoverage-server might
get confused.

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