Handle sdists that do not have any requirements

grpc-tools (which fails to build a wheel with a message saying to install grpcio-tools) is such a project

Author: thatch

metadata_please/sdist.py

@@ -12,6 +12,9 @@ def from_zip_sdist(zf: ZipFile) -> bytes:
     """
     requires = [f for f in zf.namelist() if f.endswith("/requires.txt")]
     requires.sort(key=len)
+    if not requires:
+        return b""
+
     data = zf.read(requires[0])
     assert data is not None
     requires_lines, extras = convert_sdist_requires(data.decode("utf-8"))
@@ -27,6 +30,9 @@ def from_zip_sdist(zf: ZipFile) -> bytes:
 def basic_metadata_from_zip_sdist(zf: ZipFile) -> BasicMetadata:
     requires = [f for f in zf.namelist() if f.endswith("/requires.txt")]
     requires.sort(key=len)
+    if not requires:
+        return BasicMetadata((), frozenset())
+
     data = zf.read(requires[0])
     assert data is not None
     return BasicMetadata.from_sdist_pkg_info_and_requires(b"", data)
@@ -39,6 +45,8 @@ def from_tar_sdist(tf: TarFile) -> bytes:
     # XXX Why do ZipFile and TarFile not have a common interface ?!
     requires = [f for f in tf.getnames() if f.endswith("/requires.txt")]
     requires.sort(key=len)
+    if not requires:
+        return b""
 
     fo = tf.extractfile(requires[0])
     assert fo is not None
@@ -57,6 +65,8 @@ def basic_metadata_from_tar_sdist(tf: TarFile) -> BasicMetadata:
     # XXX Why do ZipFile and TarFile not have a common interface ?!
     requires = [f for f in tf.getnames() if f.endswith("/requires.txt")]
     requires.sort(key=len)
+    if not requires:
+        return BasicMetadata((), frozenset())
 
     fo = tf.extractfile(requires[0])
     assert fo is not None

metadata_please/tests/sdist.py

@@ -46,6 +46,18 @@ def test_basic_metadata(self) -> None:
         )
         self.assertEqual({"e"}, bm.provides_extra)
 
+    def test_basic_metadata_no_requires_file(self) -> None:
+        z = MemoryZipFile(
+            ["foo.egg-info/PKG-INFO", "foo/__init__.py"],
+            read_value=b"\n",
+        )
+        bm = basic_metadata_from_zip_sdist(z)  # type: ignore
+        self.assertEqual(
+            (),
+            bm.reqs,
+        )
+        self.assertEqual(set(), bm.provides_extra)
+
     def test_basic_metadata_absl_py_09(self) -> None:
         z = MemoryZipFile(
             ["foo.egg-info/requires.txt", "foo/__init__.py"],