@if block parsing problem when located within lambda return value

[0xxon]

I tried making some script-code backwards compatible and notices that this code...

function test()
	{
	local make_epoch_result = function(pass_name: string): function(ts: time)
		{
@if ( Version::at_least("4.1") )
		return function [pass_name] (ts: time)
@else
		return function (ts: time)
@endif
			{
			print pass_name;
			};
		};

	}

Throws the following error when run with a current master version of Zeek:

error in ./test2.zeek, line 7: syntax error, at or near "@else"

I think that this is supposed to work fine - but someone please correct me if I am incorrect. One can work around this problem by changing the placement of the { after the return statement.

[awelzel]

This appears to be fixable via the following hunk, but not sure #2289 is that easy, too.

 anonymous_function:
-               TOK_FUNCTION begin_lambda lambda_body
-                       { $$ = $3; }
+               TOK_FUNCTION begin_lambda conditional_list lambda_body
+                       { $$ = $4; }
        ;

[vpax]

@awelzel will that change really work? The { for the body that precedes the @if in the example is part of the lambda_body, so that conditional will be prior to any elements of the body.

[awelzel]

@awelzel will that change really work? The { for the body that precedes the @if in the example is part of the lambda_body, so that conditional will be prior to any elements of the body.

I will take a closer look tomorrow. I added a btest with above example and it seemed to work. Will double check and get back to you. Thanks for looking.

[awelzel]

@vpax - the example of this ticket involves a lamda returning a lambda. It's the @else following function [pass_name] (ts: time) (begin_lambda) what upsets the parsing. The first @if within the lambda_body seems to work out as it's part of the first lambda_body's stmt_list.

The proposed fix is similar to what we do for func_hdr / func_body:

zeek/src/parse.y

Lines 1401 to 1406 in fad18cb

	| func_hdr
	{
	func_hdr_location = @1;
	func_hdr_cond_epoch = conditional_epoch;
	}
	conditional_list func_body

I've opened a PR, please chime in if I misunderstood or you have further concerns/thoughts. Thanks!

[vpax]

@awelzel I see. Given that change, does the snippet at the top now work correctly?

[awelzel]

@awelzel I see. Given that change, does the snippet at the top now work correctly?

Yep. I've added it here as a test-case:

https://github.com/zeek/zeek/pull/2346/files#diff-c7537e2ab0b02836a74f51fd55edd9a3fee02a971df499131030bd24b12f7dc1R8

[vpax]

Yep. I've added it here as a test-case:

Great!