meson: Allow directory options outside of prefix

This bring us in line with Autotools and CMake and it is useful
for platforms like Nix, which install projects
into multiple independent prefixes.

As a consequence, `get_option` might return absolute paths for some
directory options, if a directory outside of prefix is passed.

This is technically a backwards incompatible change but its effect
should be minimal, thanks to widespread use of `join_paths`/`/` operator
and pkg-config generator module. It should only cause an issue when
a path were constructed by concatenating the value of directory path option.

Also remove a comment about commonpath since we do not use that since
<https://github.com/mesonbuild/meson/commit/00f5dadd5b7d71c30bd7393d165a87f554eb92e5>.

Fixes: https://github.com/mesonbuild/meson/issues/2561

1 files changed, 7 insertions, 7 deletions

diff --git a/unittests/allplatformstests.py b/unittests/allplatformstests.py
index 60ff123..3eea9a3 100644
--- a/unittests/allplatformstests.py
+++ b/unittests/allplatformstests.py
@@ -213,9 +213,9 @@ class AllPlatformTests(BasePlatformTests):
             elif opt['name'] == 'libdir':
                 self.assertEqual(libdir, opt['value'])
 
-    def test_libdir_must_be_inside_prefix(self):
+    def test_libdir_can_be_outside_prefix(self):
         '''
-        Tests that libdir is forced to be inside prefix no matter how it is set.
+        Tests that libdir is allowed to be outside prefix.
         Must be a unit test for obvious reasons.
         '''
         testdir = os.path.join(self.common_test_dir, '1 trivial')
@@ -226,19 +226,19 @@ class AllPlatformTests(BasePlatformTests):
             args = ['--prefix', '/opt', '--libdir', '/opt/lib32']
         self.init(testdir, extra_args=args)
         self.wipe()
-        # libdir not being inside prefix is not ok
+        # libdir not being inside prefix is ok too
         if is_windows():
             args = ['--prefix', 'x:/usr', '--libdir', 'x:/opt/lib32']
         else:
             args = ['--prefix', '/usr', '--libdir', '/opt/lib32']
-        self.assertRaises(subprocess.CalledProcessError, self.init, testdir, extra_args=args)
+        self.init(testdir, extra_args=args)
         self.wipe()
-        # libdir must be inside prefix even when set via mesonconf
+        # libdir can be outside prefix even when set via mesonconf
         self.init(testdir)
         if is_windows():
-            self.assertRaises(subprocess.CalledProcessError, self.setconf, '-Dlibdir=x:/opt', False)
+            self.setconf('-Dlibdir=x:/opt', will_build=False)
         else:
-            self.assertRaises(subprocess.CalledProcessError, self.setconf, '-Dlibdir=/opt', False)
+            self.setconf('-Dlibdir=/opt', will_build=False)
 
     def test_prefix_dependent_defaults(self):
         '''