Settle an empty version like a missing one

A dependency pinned to an empty string carries no version either, so it
takes the deferred path and a registry miss is reported for its
requester instead of being skipped quietly. A leftover docstring line
in normalize_dependencies is removed.

esphome/platformio/library.py

@@ -802,7 +802,6 @@ def normalize_dependencies(
     warning for entries that cannot be normalized.
 
     Bare-name spellings carry no version; the walk settles them once the graph is known.
-    framework libraries (Wire, SPI) that need no registry install.
     """
     if dependencies is None:
         return []
@@ -1426,7 +1425,8 @@ def convert_libraries(
             for dependency in normalize_dependencies(
                 component.data.get("dependencies"), component.name
             ):
-                if "version" not in dependency:
+                if not dependency.get("version"):
+                    # An empty version is as good as none; it settles the same way
                     if not is_lib_ignored(
                         dependency.get("name"), lib_ignore
                     ) and dependency_is_usable(

tests/unit_tests/test_platformio_library.py

@@ -1565,6 +1565,26 @@ def test_registry_miss_resolves_again_as_a_git_source(tmp_path, monkeypatch) ->
     assert [d.name for d in emitted["C"].dependencies] == ["o/B"]
 
 
+def test_empty_version_is_settled_like_a_missing_one(
+    tmp_path, monkeypatch, caplog: pytest.LogCaptureFixture
+) -> None:
+    """``{"Foo": ""}`` carries no version either, so it is matched, fetched by
+    name or reported like a version-less entry rather than failing or vanishing."""
+    asked = _patch_download_with_manifests(
+        monkeypatch,
+        tmp_path,
+        {
+            "esphome/A": {"name": "A", "dependencies": {"Foo": "", "Bar": ""}},
+            "Bar": {"name": "Bar"},
+        },
+        unknown={"Foo"},
+    )
+    top = convert_libraries([Library("esphome/A", None, None)], _backend())
+    assert [d.name for d in top[0].dependencies] == ["Bar"]
+    assert (None, "Foo") in asked
+    assert "Dependency Foo of esphome/A was not resolved; skipping" in caplog.text
+
+
 def test_bundled_name_is_satisfied_by_a_replacement_pulled_in_later(
     tmp_path, monkeypatch
 ) -> None: