Fix Test to correctly handle test outputs which do not end with a newline when using rewriteToFile

[ChrisJefferson]

Given a statement in a .tst file which does not end in a newline, rewriteToFile gets very confused, and in particular can "lose" lines of output if run over and over again. This just prints a warning, and inserts a newline.

As an example of the problem, consider this test file:

gap> Print(x -> x);
gap> 1;
gap> 2;
gap> 3;

Running test with rewriteToFile gives:

gap> Print(x->x);
function ( x )
    return x;
endgap> 1;
1
gap> 2;
2
gap> 3;
3

Running again on this gives the following, where the 1 has been lost

gap> Print(x->x);
function ( x )
    return x;
endgap> 2;
2
gap> 3;
3

[coveralls]

Coverage decreased (-0.001%) to 84.476% when pulling 1774013 on ChrisJefferson:fix-rewriteBug into 7a7f72b on gap-system:master.

[fingolfin]

I have not actually tested this PR, but the description seems useful, and the code looks plausible to me. Thanks!

[fingolfin]

Or you could do this, and then we could backport this to stable-4.11 (however, I am perfectly fine with merging this as-is):

Suggested change

	if pf.cmp[i] <> "" and Last(pf.cmp[i]) <> '\n' then
	if pf.cmp[i] <> "" and not EndsWith(pf.cmp[i], "\n") then

[fingolfin]

Question (just to check my understanding of the code, which is limited): When is pf.cmp[i] an empty string? If a command is expected to not output anything, maybe?

[ChrisJefferson]

Yeps, tests with no output will have pf.cmp[i] empty. This won't cause a problem as we will just start outputting the next input on the line after the previous input. It's just when the line is non-empty but not \n terminated.

[fingolfin]

@ChrisJefferson feel free to merge this at any time, though it'd be nice if you could set at least the appropriate "release notes" label (and if you deem this should be added to release notes, also make sure the PR title can be copied verbatim to release notes for users). Thanks!

[ChrisJefferson]

Added labels, tweaked titles. I don't think this really needs backporting, as it is a very long-standing issue, and (hopefully) 4.11 should only get required fixes now really?