interpreter: Warn when environment() ops are overriden

Warn when someone tries to use append() or prepend() on an env var
which already has an operation set on it. People seem to think that
multiple append/prepend operations stack, but they don't.

Closes https://github.com/mesonbuild/meson/issues/5087

1 files changed, 11 insertions, 0 deletions

diff --git a/run_unittests.py b/run_unittests.py
index 99e3c49..156e4b8 100755
--- a/run_unittests.py
+++ b/run_unittests.py
@@ -1672,6 +1672,17 @@ class AllPlatformTests(BasePlatformTests):
         self.build()
         self.run_tests()
 
+    def test_env_ops_dont_stack(self):
+        '''
+        Test that env ops prepend/append do not stack, and that this usage issues a warning
+        '''
+        testdir = os.path.join(self.unit_test_dir, '59 test env doesn\'t stack')
+        out = self.init(testdir)
+        self.assertRegex(out, r'WARNING: Overriding.*TEST_VAR_APPEND')
+        self.assertRegex(out, r'WARNING: Overriding.*TEST_VAR_PREPEND')
+        self.assertNotRegex(out, r'WARNING: Overriding.*TEST_VAR_SET')
+        self.run_tests()
+
     def test_testsetups(self):
         if not shutil.which('valgrind'):
             raise unittest.SkipTest('Valgrind not installed.')