Improve BasicMetadata to be more immutable

Author: thatch

metadata_please/sdist.py

@@ -14,10 +14,10 @@ def from_zip_sdist(zf: ZipFile) -> bytes:
     requires.sort(key=len)
     data = zf.read(requires[0])
     assert data is not None
-    requires, extras = convert_sdist_requires(data.decode("utf-8"))
+    requires_lines, extras = convert_sdist_requires(data.decode("utf-8"))
 
     buf: list[str] = []
-    for req in requires:
+    for req in requires_lines:
         buf.append(f"Requires-Dist: {req}\n")
     for extra in sorted(extras):
         buf.append(f"Provides-Extra: {extra}\n")
@@ -43,10 +43,10 @@ def from_tar_sdist(tf: TarFile) -> bytes:
     fo = tf.extractfile(requires[0])
     assert fo is not None
 
-    requires, extras = convert_sdist_requires(fo.read().decode("utf-8"))
+    requires_lines, extras = convert_sdist_requires(fo.read().decode("utf-8"))
 
     buf: list[str] = []
-    for req in requires:
+    for req in requires_lines:
         buf.append(f"Requires-Dist: {req}\n")
     for extra in sorted(extras):
         buf.append(f"Provides-Extra: {extra}\n")

metadata_please/tests/sdist.py

@@ -41,7 +41,7 @@ def test_basic_metadata(self) -> None:
         )
         bm = basic_metadata_from_zip_sdist(z)  # type: ignore
         self.assertEqual(
-            ["a", "b; extra == 'e'"],
+            ("a", "b; extra == 'e'"),
             bm.reqs,
         )
         self.assertEqual({"e"}, bm.provides_extra)
@@ -60,12 +60,12 @@ def test_basic_metadata_absl_py_09(self) -> None:
         )
         bm = basic_metadata_from_zip_sdist(z)  # type: ignore
         self.assertEqual(
-            [
+            (
                 "six",
                 'enum34; python_version < "3.4"',
                 # Quoting on the following line is an implementation detail
                 "pytest; (python_version < \"3.4\") and extra == 'test'",
-            ],
+            ),
             bm.reqs,
         )
         self.assertEqual({"test"}, bm.provides_extra)
@@ -102,7 +102,7 @@ def test_basic_metadata(self) -> None:
         )
         bm = basic_metadata_from_tar_sdist(t)  # type: ignore
         self.assertEqual(
-            ["a", "b; extra == 'e'"],
+            ("a", "b; extra == 'e'"),
             bm.reqs,
         )
         self.assertEqual({"e"}, bm.provides_extra)

metadata_please/types.py

@@ -11,14 +11,14 @@ class BasicMetadata:
     # Popualted from Requires-Dist or requires.txt
     reqs: Sequence[str]
     # Populated from Provides-Extra
-    provides_extra: set[str]
+    provides_extra: frozenset[str]
 
     @classmethod
     def from_metadata(cls, metadata: bytes) -> BasicMetadata:
         msg = message_from_string(metadata.decode("utf-8"))
         return BasicMetadata(
             msg.get_all("Requires-Dist") or (),
-            set(msg.get_all("Provides-Extra") or ()),
+            frozenset(msg.get_all("Provides-Extra") or ()),
         )
 
     @classmethod
@@ -33,7 +33,7 @@ def from_sdist_pkg_info_and_requires(
         )
 
 
-def convert_sdist_requires(data: str) -> tuple[list[str], set[str]]:
+def convert_sdist_requires(data: str) -> tuple[tuple[str, ...], frozenset[str]]:
     # This is reverse engineered from looking at a couple examples, but there
     # does not appear to be a formal spec.  Mentioned at
     # https://setuptools.readthedocs.io/en/latest/formats.html#requires-txt
@@ -64,4 +64,4 @@ def convert_sdist_requires(data: str) -> tuple[list[str], set[str]]:
                 lst.append(f"{line}; {current_markers}")
             else:
                 lst.append(line)
-    return lst, extras
+    return tuple(lst), frozenset(extras)