For loop bugfix - explore enabling break and continue within for loops

[lohvht-zz]

Attempt to fix the loss of continue and break for for-loops in TagUI scripts due to the IIFE pattern.

Proposed fix

upon translating from TagUI script to javascript, replace continues and breaks into returning corresponding flags.

then check the flag and carry out break/continue accordingly

[kensoh]

Made a commit in for_loop_break_continue branch - 8700c0c

samples/loop_demo can't work. in generated loop_demo.js, when for_loop_signal is set, the moment after // end of JS code line if put casper.echo(for_loop_signal); it shows blank.

casper.then(function() { // start of JS code
for_loop_signal = '[BREAK_SIGNAL]'; return;
}); // end of JS code

problem is variables set with casper.then() blocks remains in casper context. ie the moment exit IIFE pattern, for_loop_signal variable remains blanks and the code to break or continue does not trigger.

})(n); // end of IIFE pattern
if (for_loop_signal == '[BREAK_SIGNAL]') {for_loop_signal = ''; break;}
else if (for_loop_signal == '[CONTINUE_SIGNAL]') {for_loop_signal = ''; continue;}}
});

We can look into this together next week...

[kensoh]

Experimental implementation using file IO doesn't work as well - 6cbf1f5

[Aussiroth]

http://docs.casperjs.org/en/latest/modules/casper.html#thenbypassif

[Aussiroth]

TagUI script to test this issue here:

for n from 1 to 10
{
	echo n
	if n equals to 6
	{
		for k from 80 to 85
		{
			echo k
			if k equals to 83
			{
				break;
			}
		}
	}
}

for cde from 1 to 5
{
	echo "cde " + cde
}

for abc from 1 to 5
{
	echo "abc " + abc
}

Expected output:

1
2
3
4
5
6
81
82
83
7
8
9
10
cde 1
cde 2
cde 3
cde 4
cde 5
abc 1
abc 2
abc 3
abc 4
abc 5

Actual output:

1
2
3
4
5
6
7
81
82
83
abc 1
abc 2
abc 3
abc 4
abc 5

Issue with nested loop is likely due to finding the outermost for loop break signal and jumping to it, instead of the one for the inner for loop.
Unsure as to the weird behaviour for why the cde loop does not work, whereas the abc loop works whether cde loop is there or not.

[kensoh]

above commit gives following output. uses a teleport marker (variable of the loop) to track which loop to break. however, still not showing 7 8 9 10.

1
2
3
4
5
6
80
81
82
83
cde 1
cde 2
cde 3
cde 4
cde 5
abc 1
abc 2
abc 3
abc 4
abc 5

[kensoh]

above commit adds stricter conditions to give correct output. turns out the stack also contains the terminating marker, thus the outer loop for the n for loop will have the market for k for loop and results in false-positive match. below stricter condition to check for real match -

if (casper.steps[s].toString() == ("function () {for_loop_signal = '[BREAK_SIGNAL]["+teleport_marker+"]';}"))

1
2
3
4
5
6
80
81
82
83
7
8
9
10
cde 1
cde 2
cde 3
cde 4
cde 5
abc 1
abc 2
abc 3
abc 4
abc 5

[kensoh]

looks ok for repeated use of for loop variables. would have thought will have issues as the markers are similar, but below works, haven't figure out why.

for n from 1 to 10
{       
        echo n
        if n equals to 6
        {       
                for k from 80 to 85
                {       
                        echo k
                        if k equals to 83
                        {       
                                break;
                        }
                }
        }
}

for cde from 1 to 5
{
        echo "cde " + cde
}

for abc from 1 to 5
{
        echo "abc " + abc
}

for n from 30 to 35
{
        echo n
}

for k from 20 to 25
{
        echo k
}

1
2
3
4
5
6
80
81
82
83
7
8
9
10
cde 1
cde 2
cde 3
cde 4
cde 5
abc 1
abc 2
abc 3
abc 4
abc 5
30
31
32
33
34
35
20
21
22
23
24
25

[kensoh]

Adding on, it works because the later steps in stack are not created yet, so later blocks of for loops with similar variable names wont trigger false-positive if a search is done from the back.

[kensoh]

I'll clean up the code and add continue so that you guys can stress test... continue's implementation is probably adding a marker near the start of the loop and searching from forward direction instead of from the back.

reference debugging code that can be used in the last casper.then block in generated js

for (s = casper.steps.length-1; s >= 0; s--) {
casper.echo('\n\n\n\n\n' + s + ' ------------------------------------------------------------\n' + casper.steps[s].toString());}

[kensoh]

Getting very close to final working version that works for continue or break step. for your stress / edge-cases testing..

to use, use continue or continue; or break or break; in a for loop

[kensoh]

merged to cutting edge release, now prepping to release v4.0