fix parsing of metadata attribute, add test

src/poetry/repositories/link_sources/html.py

@@ -42,7 +42,18 @@ def _link_cache(self) -> LinkCache:
                     yanked = unescape(yanked_value)
                 else:
                     yanked = "data-yanked" in anchor
-                metadata = anchor.get("data-dist-info-metadata")
+
+                # see https://peps.python.org/pep-0714/#clients
+                # and https://peps.python.org/pep-0658/#specification
+                metadata: str | bool
+                for metadata_key in ("data-core-metadata", "data-dist-info-metadata"):
+                    metadata_value = anchor.get(metadata_key)
+                    if metadata_value:
+                        metadata = unescape(metadata_value)
+                    else:
+                        metadata = metadata_key in anchor
+                    if metadata:
+                        break
                 link = Link(
                     url, requires_python=pyrequire, yanked=yanked, metadata=metadata
                 )

tests/repositories/link_sources/test_html.py

@@ -91,6 +91,66 @@ def test_yanked(
     assert page.yanked(canonicalize_name("demo"), Version.parse("0.1")) == expected
 
 
+@pytest.mark.parametrize(
+    "metadata, expected_has_metadata, expected_hash_name, expected_hash",
+    [
+        ("", False, None, None),
+        # new
+        ("data-core-metadata", True, None, None),
+        ("data-core-metadata=''", True, None, None),
+        ("data-core-metadata='foo'", True, None, None),
+        ("data-core-metadata='sha256=abcd'", True, "sha256", "abcd"),
+        # old
+        ("data-dist-info-metadata", True, None, None),
+        ("data-dist-info-metadata=''", True, None, None),
+        ("data-dist-info-metadata='foo'", True, None, None),
+        ("data-dist-info-metadata='sha256=abcd'", True, "sha256", "abcd"),
+        # conflicting (new wins)
+        ("data-core-metadata data-dist-info-metadata='sha256=abcd'", True, None, None),
+        ("data-dist-info-metadata='sha256=abcd' data-core-metadata", True, None, None),
+        (
+            "data-core-metadata='sha256=abcd' data-dist-info-metadata",
+            True,
+            "sha256",
+            "abcd",
+        ),
+        (
+            "data-dist-info-metadata data-core-metadata='sha256=abcd'",
+            True,
+            "sha256",
+            "abcd",
+        ),
+        (
+            "data-core-metadata='sha256=abcd' data-dist-info-metadata='sha256=1234'",
+            True,
+            "sha256",
+            "abcd",
+        ),
+        (
+            "data-dist-info-metadata='sha256=1234' data-core-metadata='sha256=abcd'",
+            True,
+            "sha256",
+            "abcd",
+        ),
+    ],
+)
+def test_metadata(
+    html_page_content: HTMLPageGetter,
+    metadata: str,
+    expected_has_metadata: bool,
+    expected_hash_name: str | None,
+    expected_hash: str | None,
+) -> None:
+    anchors = f'<a href="https://example.org/demo-0.1.whl" {metadata}>demo-0.1.whl</a>'
+    content = html_page_content(anchors)
+    page = HTMLPage("https://example.org", content)
+
+    link = next(page.links)
+    assert link.has_metadata is expected_has_metadata
+    assert link.metadata_hash_name == expected_hash_name
+    assert link.metadata_hash == expected_hash
+
+
 @pytest.mark.parametrize(
     "anchor, base_url, expected",
     (