Make -D- option for compiled datalog behave same as if interpreted

[Gueckmooh]

Makes compiled datalog handle -D- option as interpreted datalog. Fixes #2348
It is a second and less inclusive attempt after #2400.

Change slightly the generated code so that, if the output directory is - the io config is stdout.

As I said in #2400:
I don't know what is the best solution, to change slightly the generated code so that it puts "IO" to "stdout" when the output file is - or to change method IOSystem::getWriter to do the change before getting the appropriate factory.

In my opinion IOSystem should not have this intelligence and it should just expect the caller to know where it wants to put the output.. I'll try to do the change in the generated code, doing it in the getWriter method would be a piece of cake if we want to go for this solution afterwards.

.decl foo(a:number)
.output foo
foo(1).

$souffle test.dl -D-
---------------
foo
a
===============
1
===============

Before:

$ souffle test.dl -o test && ./test -D-
Output directory - does not exists!

After:

$souffle test.dl -o test && ./test -D-
---------------
foo
a
===============
1
===============

I still don't know how to test that, if you have any pointer to do that I would add a test to the PR.

[codecov]

Codecov Report

Merging #2401 (519c438) into master (0334b07) will increase coverage by 0.09%.
The diff coverage is 85.75%.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2401      +/-   ##
==========================================
+ Coverage   77.56%   77.65%   +0.09%     
==========================================
  Files         467      472       +5     
  Lines       30785    31045     +260     
==========================================
+ Hits        23877    24107     +230     
- Misses       6908     6938      +30     

Impacted Files	Coverage Δ
src/parser/ParserDriver.h	100.00% <ø> (ø)
src/synthesiser/Synthesiser.h	100.00% <ø> (ø)
.../ast/transform/SimplifyConstantBinaryConstraints.h	50.00% <50.00%> (ø)
src/MainDriver.cpp	70.39% <70.27%> (+0.15%)	⬆️
src/parser/scanner.ll	78.01% <76.92%> (+5.49%)	⬆️
tests/libsouffle_interface/vfs_overlay_test.cpp	85.93% <85.93%> (ø)
src/parser/SrcLocation.cpp	91.86% <87.50%> (+7.24%)	⬆️
src/parser/ParserDriver.cpp	89.44% <88.33%> (-0.39%)	⬇️
src/parser/VirtualFileSystem.cpp	88.37% <88.37%> (ø)
...st/transform/SimplifyConstantBinaryConstraints.cpp	100.00% <100.00%> (ø)
... and 12 more

[quentin]

That's a nice solution!

About testing it, you probably want to pass -D-, for that you need to modify the test harness here and look how it's done to customize the facts directory:

souffle/cmake/SouffleTests.cmake

Line 229 in 8aae521

set(SOUFFLE_PARAMS "-D" "." "-F" "${FACTS_DIR}")

In the CMakeLists.txt you would pass the new option as in:

souffle/tests/semantic/CMakeLists.txt

Line 238 in 8aae521

souffle_run_test_helper(TEST_NAME pragma2 FUNCTORS CATEGORY semantic)

Then just put the expected output in your test's .out file.

[Gueckmooh]

I've added a test in a new directory "behavior", because I did not find appropriate directory to put my test. Let me know if there is another better place for it.

[quentin]

Great, could you just move the test to the existing semantic directory? Most tests about I/Os are located there.
Thanks.