fix(packaging): Format METADATA correctly if given empty requires_file

examples/wheel/BUILD.bazel

@@ -294,6 +294,12 @@ starlark  # Example comment
 """.splitlines(),
 )
 
+write_file(
+    name = "empty_requires_file",
+    out = "empty_requires.txt",
+    content = [""],
+)
+
 write_file(
     name = "extra_requires_file",
     out = "extra_requires.txt",
@@ -324,6 +330,15 @@ py_wheel(
     deps = [":example_pkg"],
 )
 
+py_wheel(
+    name = "empty_requires_files",
+    distribution = "empty_requires_files",
+    python_tag = "py3",
+    requires_file = ":empty_requires.txt",
+    version = "0.0.1",
+    deps = [":example_pkg"],
+)
+
 # Package just a specific py_libraries, without their dependencies
 py_wheel(
     name = "minimal_data_files",
@@ -367,6 +382,7 @@ py_test(
         ":custom_package_root_multi_prefix",
         ":custom_package_root_multi_prefix_reverse_order",
         ":customized",
+        ":empty_requires_files",
         ":extra_requires",
         ":filename_escaping",
         ":minimal_data_files",

examples/wheel/wheel_test.py

@@ -495,6 +495,30 @@ def test_requires_file_and_extra_requires_files(self):
                 requires,
             )
 
+    def test_empty_requires_file(self):
+        filename = self._get_path("empty_requires_files-0.0.1-py3-none-any.whl")
+
+        with zipfile.ZipFile(filename) as zf:
+            self.assertAllEntriesHasReproducibleMetadata(zf)
+            metadata_file = None
+            for f in zf.namelist():
+                if os.path.basename(f) == "METADATA":
+                    metadata_file = f
+            self.assertIsNotNone(metadata_file)
+
+            metadata = zf.read(metadata_file).decode("utf-8")
+            metadata_lines = metadata.splitlines()
+
+            requires = []
+            for i, line in enumerate(metadata_lines):
+                if line.startswith("Name:"):
+                    self.assertTrue(metadata_lines[i + 1].startswith("Version:"))
+                if line.startswith("Requires-Dist:"):
+                    requires.append(line.strip())
+
+            print(requires)
+            self.assertEqual([], requires)
+
     def test_minimal_data_files(self):
         filename = self._get_path("minimal_data_files-0.0.1-py3-none-any.whl")
 

tools/wheelmaker.py

@@ -599,7 +599,12 @@ def get_new_requirement_line(reqs_text, extra):
 
                 reqs.append(get_new_requirement_line(reqs_text, extra))
 
-            metadata = metadata.replace(meta_line, "\n".join(reqs))
+            if reqs:
+                metadata = metadata.replace(meta_line, "\n".join(reqs))
+            # File is empty
+            # So replace the meta_line entirely, including removing newline chars
+            else:
+                metadata = re.sub(re.escape(meta_line) + r"(?:\r?\n)?", "", metadata, count=1)
 
         maker.add_metadata(
             metadata=metadata,