msetup: Allow (re)configure of not empty builddir

Also prevent from using a parent directory as builddir by mistake.

Co-authored-by: Volker Weißmann <volker.weissmann@gmx.de>
Co-authored-by: Charles Brunet <charles.brunet@optelgroup.com>

mesonbuild/msetup.py

@@ -24,6 +24,7 @@ import argparse
 import tempfile
 import shutil
 import glob
+from pathlib import Path
 
 from . import environment, interpreter, mesonlib
 from . import build
@@ -157,6 +158,8 @@ class MesonApp:
 
     def validate_dirs(self, dir1: str, dir2: str, reconfigure: bool, wipe: bool) -> T.Tuple[str, str]:
         (src_dir, build_dir) = self.validate_core_dirs(dir1, dir2)
+        if Path(build_dir) in Path(src_dir).parents:
+            raise MesonException(f'Build directory {build_dir} cannot be a parent of source directory {src_dir}')
         if not os.listdir(build_dir):
             self.add_vcs_ignore_files(build_dir)
             return src_dir, build_dir
@@ -178,7 +181,7 @@ class MesonApp:
                 # Note that making this an error would not be backward compatible (and also isn't
                 # universally agreed on): https://github.com/mesonbuild/meson/pull/4249.
                 raise SystemExit(0)
-        elif not has_partial_build and 'MESON_RUNNING_IN_PROJECT_TESTS' not in os.environ:
+        elif not has_partial_build and wipe:
             raise MesonException(f'Directory is not empty and does not contain a previous build:\n{build_dir}')
         return src_dir, build_dir
 

unittests/allplatformstests.py

@@ -2046,6 +2046,7 @@ class AllPlatformTests(BasePlatformTests):
         self.assertFalse(os.path.isfile(promoted_wrap))
         subprocess.check_call(self.wrap_command + ['promote', 'athing'], cwd=workdir)
         self.assertTrue(os.path.isfile(promoted_wrap))
+        self.new_builddir()  # Ensure builddir is not parent or workdir
         self.init(workdir)
         self.build()
 

unittests/platformagnostictests.py

@@ -163,3 +163,38 @@ class PlatformAgnosticTests(BasePlatformTests):
 
         # Wipe with a different backend is allowed
         self.init(testdir, extra_args=['--wipe', '--backend=none'])
+
+    def test_validate_dirs(self):
+        testdir = os.path.join(self.common_test_dir, '1 trivial')
+
+        # Using parent as builddir should fail
+        self.builddir = os.path.dirname(self.builddir)
+        with self.assertRaises(subprocess.CalledProcessError) as cm:
+            self.init(testdir)
+        self.assertIn('cannot be a parent of source directory', cm.exception.stdout)
+
+        # Reconfigure of empty builddir should work
+        self.new_builddir()
+        self.init(testdir, extra_args=['--reconfigure'])
+
+        # Reconfigure of not empty builddir should work
+        self.new_builddir()
+        Path(self.builddir, 'dummy').touch()
+        self.init(testdir, extra_args=['--reconfigure'])
+
+        # Wipe of empty builddir should work
+        self.new_builddir()
+        self.init(testdir, extra_args=['--wipe'])
+
+        # Wipe of partial builddir should work
+        self.new_builddir()
+        Path(self.builddir, 'meson-private').mkdir()
+        Path(self.builddir, 'dummy').touch()
+        self.init(testdir, extra_args=['--wipe'])
+
+        # Wipe of not empty builddir should fail
+        self.new_builddir()
+        Path(self.builddir, 'dummy').touch()
+        with self.assertRaises(subprocess.CalledProcessError) as cm:
+            self.init(testdir, extra_args=['--wipe'])
+        self.assertIn('Directory is not empty', cm.exception.stdout)