SPEL: Error message is useless at helping developer resolve problem actual problem, EL1027E:(pos 4): Indexing into type ... [SPR-8876]

[spring-projects-issues]

Darryl L. Miles opened SPR-8876 and commented

After having used Spring Roo to produce a skeleton application to modify (therefore using the best coding conventions and project design).
When modifiying such a project I came into a situation that was difficult to solve from readying the Exception message.

org.springframework.expression.spel.SpelEvaluationException: EL1027E:(pos 4): Indexing into type 'com.example.MyParentClass' is not supported

org.springframework.expression.spel.ast.Indexer:174
in method => public TypedValue getValueInternal(ExpressionState state) throws EvaluationException
at line => throw new SpelEvaluationException(getStartPosition(),SpelMessage.INDEXING_NOT_SUPPORTED_FOR_TYPE, targetObjectTypeDescriptor.asString());

There is not enough information presented to the developer to have any idea about which thing is the problem.
The index/indexValue local variables look very useful at providing the developer anough information to be able to fix the problem.
So this bug request that such messages provide information to allow diagnosis of the problem from the message.

The only way to develop is to set a breakpoint and manually inspect the state of Spring internals before allowing it to throw the exception.

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No further details from SPR-8876

[spring-projects-issues]

Chris Beams commented

Hi Darryl,

Thanks for the report. Could you provide a bit more information about the expression that led to this error? And perhaps you could provide a suggestion as to what error message would have helped you more?

[spring-projects-issues]

Phil Webb commented

Without further information I am not sure how we could improve the error message so I am going to mark this as "won't fix" for now.