fix: Convert boolean value to lowercase in Root-Is-Purelib

Close #165

Signed-off-by: Frost Ming <me@frostming.com>

Author: frostming

news/165.bugfix.md

@@ -0,0 +1 @@
+Fix the Root-Is-Purelib to "true" instead of "True" to follow the spec of PEP 427.

pdm/pep517/wheel.py

@@ -347,7 +347,7 @@ def _write_metadata_file(self, fp: TextIO) -> None:
     def _write_wheel_file(self, fp: TextIO) -> None:
         fp.write(
             WHEEL_FILE_FORMAT.format(
-                is_purelib=self.meta.config.is_purelib, tag=self.tag
+                is_purelib=str(self.meta.config.is_purelib).lower(), tag=self.tag
             )
         )
 

tests/test_api.py

@@ -306,7 +306,7 @@ def test_build_purelib_project_with_build(tmp_path: Path) -> None:
             )
             version = zf.read("my_package/version.foo").decode("utf-8").strip()
             assert version == "0.1.0"
-            assert wheel_metadata["Root-Is-Purelib"] == "True"
+            assert wheel_metadata["Root-Is-Purelib"] == "true"
 
 
 @pytest.mark.skipif(