Move the identifier grammar matrix to the shared test home

The accepted/rejected identifier parametrizations exercise the raw
validator, which lives in mcp.shared.extension; the server suite keeps
its class-level validation tests.

Author: maxisbey

tests/server/mcpserver/test_extension.py

@@ -27,7 +27,6 @@
     ResourceBinding,
     ToolBinding,
     compose_tool_call_interceptor,
-    validate_extension_identifier,
 )
 from mcp.server.mcpserver import Context, MCPServer, require_client_extension
 from mcp.server.mcpserver.resources import TextResource
@@ -363,50 +362,6 @@ async def test_version_pinned_method_is_method_not_found_at_a_disallowed_version
     assert exc_info.value.error.data == "com.example/pinned"
 
 
-@pytest.mark.parametrize(
-    "identifier",
-    [
-        "io.modelcontextprotocol/ui",
-        "com.example/my_ext",
-        "com.x-y.z2/n.a-b_c",
-        "example/x",
-        "a/b",
-        "com.example/9start",
-    ],
-)
-def test_grammar_conformant_extension_identifiers_are_accepted(identifier: str) -> None:
-    """Spec `_meta` key grammar: dot-separated labels (letter start, letter/digit end,
-    hyphens interior), a slash, then a name that starts and ends alphanumeric."""
-    validate_extension_identifier(identifier, owner="T")
-
-
-@pytest.mark.parametrize(
-    "identifier",
-    [
-        "noprefix",
-        "-foo/bar",
-        ".leading/x",
-        "a..b/x",
-        "foo-/x",
-        "9foo/x",
-        "foo/-bar",
-        "foo/bar-",
-        "foo/",
-        "/bar",
-        "foo/ba r",
-        "io.modelcontextprotocol/ui\n",
-        "",
-        None,
-        42,
-    ],
-)
-def test_malformed_extension_identifiers_are_rejected(identifier: Any) -> None:
-    """Spec `_meta` key grammar: malformed prefixes (bad label start/end, empty labels)
-    and malformed names are rejected, as are non-strings."""
-    with pytest.raises(TypeError):
-        validate_extension_identifier(identifier, owner="T")
-
-
 @pytest.mark.parametrize("method", ["tools/list", "completion/complete"])
 def test_method_binding_rejects_spec_methods(method: str) -> None:
     """SDK-defined: extension methods are additive — binding a spec-defined request method

tests/shared/test_extension.py

@@ -1,31 +1,60 @@
 """Tests for `mcp.shared.extension` — the extension-identifier grammar shared by
-the server and client extension surfaces.
+the server and client extension surfaces."""
 
-The grammar matrix (accepted and rejected identifiers) lives with the original
-server tests in `tests/server/mcpserver/test_extension.py`, which exercise the
-same function via the server module's re-export.
-"""
+from typing import Any
 
 import pytest
 
 import mcp.server.extension
 import mcp.shared.extension
-
-
-def test_validator_importable_from_shared_home() -> None:
-    """SDK-defined: the identifier grammar lives in `mcp.shared.extension` — one
-    source of truth for both the server and client extension surfaces."""
-    mcp.shared.extension.validate_extension_identifier("com.example/thing", owner="T")
-
-
-def test_validator_rejects_malformed_identifier_via_shared_path() -> None:
-    """SDK-defined: the shared-home function enforces the same `vendor-prefix/name`
-    grammar the server side always has."""
-    with pytest.raises(TypeError):
-        mcp.shared.extension.validate_extension_identifier("noprefix", owner="T")
+from mcp.shared.extension import validate_extension_identifier
 
 
 def test_server_extension_module_reexports_shared_validator() -> None:
     """SDK-defined: `mcp.server.extension.validate_extension_identifier` remains
     importable after the move and is the very same function object."""
     assert mcp.server.extension.validate_extension_identifier is mcp.shared.extension.validate_extension_identifier
+
+
+@pytest.mark.parametrize(
+    "identifier",
+    [
+        "io.modelcontextprotocol/ui",
+        "com.example/my_ext",
+        "com.x-y.z2/n.a-b_c",
+        "example/x",
+        "a/b",
+        "com.example/9start",
+    ],
+)
+def test_grammar_conformant_extension_identifiers_are_accepted(identifier: str) -> None:
+    """Spec `_meta` key grammar: dot-separated labels (letter start, letter/digit end,
+    hyphens interior), a slash, then a name that starts and ends alphanumeric."""
+    validate_extension_identifier(identifier, owner="T")
+
+
+@pytest.mark.parametrize(
+    "identifier",
+    [
+        "noprefix",
+        "-foo/bar",
+        ".leading/x",
+        "a..b/x",
+        "foo-/x",
+        "9foo/x",
+        "foo/-bar",
+        "foo/bar-",
+        "foo/",
+        "/bar",
+        "foo/ba r",
+        "io.modelcontextprotocol/ui\n",
+        "",
+        None,
+        42,
+    ],
+)
+def test_malformed_extension_identifiers_are_rejected(identifier: Any) -> None:
+    """Spec `_meta` key grammar: malformed prefixes (bad label start/end, empty labels)
+    and malformed names are rejected, as are non-strings."""
+    with pytest.raises(TypeError):
+        validate_extension_identifier(identifier, owner="T")