interpreter: Revert old path joining behavior (fixes #9450)

mesonbuild/interpreter/primitives/string.py

@@ -2,6 +2,7 @@
 # SPDX-license-identifier: Apache-2.0
 
 import re
+import os
 from pathlib import PurePath
 
 import typing as T
@@ -159,7 +160,7 @@ class StringHolder(ObjectHolder[str]):
     @FeatureNew('/ with string arguments', '0.49.0')
     @typed_operator(MesonOperator.DIV, str)
     def op_div(self, other: str) -> str:
-        return (PurePath(self.held_object) / other).as_posix()
+        return os.path.join(self.held_object, other).replace('\\', '/')
 
     @typed_operator(MesonOperator.INDEX, int)
     def op_index(self, other: int) -> str:

test cases/common/111 pathjoin/meson.build

@@ -7,6 +7,7 @@ assert(join_paths('foo', 'bar', 'baz') == 'foo/bar/baz', 'Path joining is broken
 assert(join_paths('/foo', 'bar')       == '/foo/bar', 'Path joining is broken')
 assert(join_paths('foo', '/bar')       == '/bar', 'Absolute path joining is broken')
 assert(join_paths('/foo', '/bar')      == '/bar', 'Absolute path joining is broken')
+assert(join_paths('/foo', '')          == '/foo/', 'Trailing / on path')
 
 # Test array form since people are using that too
 assert(join_paths(['foo'])               == 'foo', 'Single argument join is broken')
@@ -15,6 +16,7 @@ assert(join_paths(['foo', 'bar', 'baz']) == 'foo/bar/baz', 'Path joining is brok
 assert(join_paths(['/foo', 'bar'])       == '/foo/bar', 'Path joining is broken')
 assert(join_paths(['foo', '/bar'])       == '/bar', 'Absolute path joining is broken')
 assert(join_paths(['/foo', '/bar'])      == '/bar', 'Absolute path joining is broken')
+assert(join_paths(['/foo', ''])          == '/foo/', 'Trailing / on path')
 
 # Division operator should do the same as join_paths
 assert('foo' / 'bar'       == 'foo/bar',     'Path division is broken')
@@ -22,3 +24,4 @@ assert('foo' /'bar' /'baz' == 'foo/bar/baz', 'Path division is broken')
 assert('/foo' / 'bar'      == '/foo/bar',    'Path division is broken')
 assert('foo' / '/bar'      == '/bar',        'Absolute path division is broken')
 assert('/foo' / '/bar'     == '/bar',        'Absolute path division is broken')
+assert('/foo' / ''         == '/foo/',       'Trailing / on path')