topic Re: Error message - which line? in Discussions

Error message - which line?

hogi — Wed, 11 Feb 2026 15:08:41 GMT

JMP helps the user to find errors in the code. If an unresolved name is used in the code, JMP stops the evaluation and shows an error message - pointing to the erronous line of code

print(1);
result = x + zzz_missing;

Let's make a slight change to the code. When JMP runs this code

myFunc = Function( {x},
	{},
	result = x + zzz_missing;
	Return( result );
);
myFunc( 3 );

it returns again an error message:

But it points to line 3 of the code where x is defined. This is very surprising: the error "happens" in line 4 : the user missed a Name expr() to protect result - and JMP accidentally evaluates the expression!

As we have already discussed this behavior in another post ( ), we will directly move on to the next surprise.

Indeed, even more surprising is the error message for this code:

myFunc = Function( {x},
	{Default Local},
	result = x + zzz_missing;
	Return( result );
);
myFunc( 3 );

-> no info about the line !?! - not even a wrong one.

why?

Re: Error message - which line?

hogi — Wed, 11 Feb 2026 07:12:51 GMT

Log Capture

according to scripting index, it captures the output to the log and returns it as a string.

but it does more than this!

It acts like try() - and allows the execution of the code to continue after a fatal error inside the evaluated expression.

log=Log capture(
   result = zzz_missing;
   print(1)
);
Print(2);
Show(log)

print(1) is skipped - print(2) is executed.

almost perfect. Unfortunately (!) it forgets to write the line of code where the error occurs!

Re: Error message - which line?

hogi — Tue, 10 Feb 2026 18:01:11 GMT

Same restriction with Try(): no info about the line of code

Try(
	result = zzz_missing;
	Print( 1 );
,
	Print( exception_msg )
	
);

Re: Error message - which line?

hogi — Tue, 10 Feb 2026 18:03:27 GMT

Is there a command
- like log Capture() or Try() - which doesn't stop when there is an error in the enclosed expression

- which returns the line of code that produces the error?

Re: Error message - which line?

hogi — Tue, 10 Feb 2026 18:09:39 GMT

Ah: by

@Ryan_Gilmore , could you please re-activate the wish for voting.

@Ben_BarrIngh , @russ_wolfinger , fyi.

Re: Error message - which line?

hogi — Tue, 10 Feb 2026 18:13:38 GMT

maybe combine the request with this one:

Re: Error message - which line?

hogi — Tue, 10 Feb 2026 18:18:05 GMT

By the way - does anybody know what is returned in the exception message ?

Re: Error message - which line?

hogi — Tue, 10 Feb 2026 18:22:48 GMT

Can a JSL code trigger a "child" execution - which might die with an error message about the line of error?
And the main code still survives and is executed further, either when the child execution is finished - or when the child execution is terminated?

Re: Error message - which line?

hogi — Tue, 10 Feb 2026 21:11:56 GMT

// demo command 
MyExpr = Expr(
	Print( 1 );
	z = 5;
	x = xyz;
	Print( 2 );
);




stopnow = 0; // if there is an error, don't execute subsequent blocks of code
summary = "";

// execute blocks of code and collect replies and error messages
For Each( {part, line}, Name Expr( myExpr ), 
	Try(
		Eval( Name Expr( part ) );
		new = "";
	,
		new = "part " || Char( line ) || ":   " || Char( Name Expr( part ) ) || "\!n" || Char( exception_msg );
		stopNow = 1;
	);
	Wait( 0 );
	summary = summary || new || (tmp = Char( Get Log( -1 )[1] ) ; If( tmp == "/*:", "", "\!N" || tmp || "\!N" ));
	Clear Log();
	If( stopnow, break() );
);
Show(summary);

Assumes trivial code with <=1 reply per code block.
Can be easily extended to work with more complicated code.