[jira] [Updated] (JEXL-330) JexlException.Parsing.getMessage() throws StringIndexOutOfBoundsException when parse error is in long expression

["Henri Biestro (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/JEXL-330?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Henri Biestro updated JEXL-330:
-------------------------------
    Fix Version/s: 3.2

> JexlException.Parsing.getMessage() throws StringIndexOutOfBoundsException when parse error is in long expression
> ----------------------------------------------------------------------------------------------------------------
>
>                 Key: JEXL-330
>                 URL: https://issues.apache.org/jira/browse/JEXL-330
>             Project: Commons JEXL
>          Issue Type: Bug
>    Affects Versions: 3.1
>            Reporter: David Costanzo
>            Assignee: Henri Biestro
>            Priority: Major
>             Fix For: 3.2
>
>
> JEXL makes some nice diagnostic messages available from {{Exception.getMessage()}}. However, in the case where a {{JexlException.Parsing}} is thrown in the middle of a long expression,  {{getMessage()}} throws a {{StringIndexOutOfBoundsException}} instead of returning a nice diagnostic message.
> I encountered this in JEXL 3.1, but have confirmed that it is reproducible using a recent clone of the GitHub repository.
> *Impact:*
> In the case where the JEXL programmer includes the badly-formed expression, my program, which uses JEXL, throws an unhanded exception, instead of printing out a clear message to the JEXL programmer.
> *Steps to Reproduce:* 
> {code:java}
> @Test
> public void testLongParseError() throws IOException {
>     JexlEngine jexl = new JexlBuilder().create();
>     // Extended form of: 'literal' + VARIABLE   'literal'
>     // missing + operator here ---------------^
>     String longExpression = "" + //
>         "'THIS IS A VERY VERY VERY VERY VERY VERY VERY " + //
>         "VERY VERY LONG STRING CONCATENATION ' + VARIABLE ' <--- " + //
>         "error: missing + between VARIABLE and literal'";
>     try {
>         jexl.createExpression(longExpression);
>         Assert.fail("parsing malformed expression did not throw exception");
>     } catch (JexlException.Parsing exception) {
>         Assert.assertEquals("???", exception.getMessage());
>     }
> }
> {code}
>  
> *What Happens:*
> {{createExpression()}} throws a {{JexlException.Parsing}}, as expected.
> Calling {{getMessage()}} on the resulting {{JexlException.Parsing}}, in turn, throws {{StringIndexOutOfBoundsException}}.
>  
> *Expected Result:*
> {{getMessage()}} returns a brief description of the syntax error.
>  
> *Technical Details:*
> The problem might be in {{JexlException.parseError}}. In the case where the expression is long (in this case, the part after the VARIABLE), it tries to extract a snippet of the error.
> {code:java}
> protected String parserError(String prefix, String expr) {
>     int length = expr.length();
>     if (length < MAX_EXCHARLOC) {
>         return prefix + " error in '" + expr + "'";
>     } else {
>         int begin = info.getColumn(); // <---- column in original expression, not within expr
>                                       //        In this case, begin > length
>         int end = begin + (MAX_EXCHARLOC / 2);
>         begin -= (MAX_EXCHARLOC / 2);
>         if (begin < 0) {
>             end -= begin;
>             begin = 0;
>         }
>         return prefix + " error near '... "
>                 + expr.substring(begin, end > length ? length : end) + " ...'";
>     }
> }
> {code}
> However, the expression that it's given is already an extract, not the entire line:
> {code:java}
> ' <--- error: missing + between VARIABLE and literal'{code}
> {{info.getColumn()}} returns an index in the _original_ expression, which is already already past the end of the {{expr}}.  So when {{JexlException.parseError}} invokes {{expr.substring()}}, it throws {{StringIndexOutOfBoundsException}}.



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