build(check): run tests in installcheck rather than check

With `VPATH` builds, `completions/` symlinks are not created in the
source tree, but in the build one. This causes issues because the "main"
completion files the symlinks point to are not actually in the build
dir, and arranging them seems to be quite a chore with autotools it
seems. So the symlinks are dangling, and tests that depend on their
presence will fail.

Run tests against the installed tree instead; there we must have
everything in place, and testing the installed setup is a good thing
anyway.

Refs #968

Author: scop

README.md

@@ -34,11 +34,12 @@ you simply don't want to use one, you can install bash completion using the
 standard commands for GNU autotools packages:
 
 ```shell
-autoreconf -i  # if not installing from prepared release tarball
+autoreconf -i      # if not installing from prepared release tarball
 ./configure
-make           # GNU make required
-make check     # optional, requires python3 with pytest >= 3.6, pexpect
-make install   # as root
+make               # GNU make required
+make check         # optional
+make install       # as root
+make installcheck  # optional, requires python3 with pytest >= 3.6, pexpect
 ```
 
 These commands install the completions and helpers, as well as a

test/t/Makefile.am

@@ -707,8 +707,13 @@ all:
 
 PYTEST = @PYTEST@
 
-check-local:
+# Some tests require completions/ symlinks to be in place, which would be a
+# chore to achieve in the build dir with VPATH builds (well not the symlinks,
+# but the "main" files they target), e.g. "make distcheck". Therefore we test
+# the installed tree instead, which isn't a bad idea in the first place.
+installcheck-local:
 	ABS_TOP_BUILDDIR="$(abs_top_builddir)" \
+	BASH_COMPLETION_TEST_BASH_COMPLETION="$(DESTDIR)/$(pkgdatadir)/bash_completion" \
 		$(PYTEST) $(PYTESTFLAGS) $(srcdir)
 
 clean-local:

test/t/conftest.py

@@ -273,8 +273,12 @@ def bash(request) -> pexpect.spawn:
         bash.expect_exact(PS1)
 
         # Load bashrc and bash_completion
+        bash_completion = os.environ.get(
+            "BASH_COMPLETION_TEST_BASH_COMPLETION",
+            "%s/../bash_completion" % testdir,
+        )
         assert_bash_exec(bash, "source '%s/config/bashrc'" % testdir)
-        assert_bash_exec(bash, "source '%s/../bash_completion'" % testdir)
+        assert_bash_exec(bash, "source '%s'" % bash_completion)
 
         # Use command name from marker if set, or grab from test filename
         cmd = None  # type: Optional[str]