CVT_WRITEQ doesn't quote at the outermost level

[kamahen]

PL_get_nchars() with CVT_WRITEQ does the right thing with f('a b') or f("a b") but not for a b or "a b" -- the latter result in strings without surrounding quotes. (I have test cases in an upcoming PR)

Is this expected behaviour?

[kamahen]

Test cases for these are in test_cpp.cpp (predicate get_nchars_string/4) and test_cpp.pl (tests nchars). (Requires SWI-Prolog/packages-cpp#68)
You can replicate this by the following (the test code outputs its interpretation of the flags - I do this to make sure that my flags handling is correct):

~/src/swipl-devel/build.debug/src/swipl -l ~/src/swipl-devel/packages/cpp/test_cpp.pl 
Welcome to SWI-Prolog (threaded, 64 bits, version 9.3.1-3-gac96195a7-DIRTY)

?- get_nchars_string("a b", [all,writeq,variable], S, F).
S = "a b",
F = "all,variable,writeq".

?- get_nchars_string(f("a b"), [all,writeq,variable], S, F).
S = "f(\"a b\")",
F = "all,variable,writeq".