test(mcp_server): cover _get_prompt nameless-arg crash + required-arg enforcement

Three direct unit tests using a mocked _fetch_manifest (no subprocess/hub needed):
- nameless required arg no longer raises KeyError (regression)
- named required arg blocks the call when absent from arguments
- named required arg passes through when provided + substitution verified

Mutation-verified: restoring arg["name"] causes the regression test to crash.

Author: Zawwarsami16

tests/test_mcp_server_prompt_args.py

@@ -0,0 +1,83 @@
+"""Unit coverage for ZhubMCPServer._get_prompt edge cases.
+
+Tests the required-arg check path with a mocked _fetch_manifest so there is
+no need for a running hub or subprocess.  The specific regression tested here:
+_get_prompt previously accessed arg["name"] with bracket notation after safely
+calling arg.get("required").  A publisher that sent a prompt argument object
+missing the "name" field (malformed manifest) caused an uncaught KeyError
+instead of returning a clean error tuple.
+"""
+
+import asyncio
+from unittest.mock import AsyncMock, patch
+
+import pytest
+
+from zhub.mcp_server import ZhubMCPServer
+
+
+def _make_server() -> ZhubMCPServer:
+    s = ZhubMCPServer(hub="http://fake", ai="fake", key="zk_fake")
+    s._http = object()  # prevent start() needing a real httpx client
+    return s
+
+
+def _manifest_with_prompts(prompts: list) -> dict:
+    return {"name": "fake", "prompts": prompts}
+
+
+@pytest.mark.asyncio
+async def test_get_prompt_nameless_required_arg_does_not_crash():
+    """A required arg with no 'name' field must not raise KeyError."""
+    server = _make_server()
+    manifest = _manifest_with_prompts([
+        {
+            "name": "greet",
+            "arguments": [{"required": True}],  # <-- no "name" key
+            "messages": [{"role": "user", "content": "Hello!"}],
+        },
+    ])
+    with patch.object(server, "_fetch_manifest", new=AsyncMock(return_value=manifest)):
+        result, err = await server._get_prompt("greet", {})
+    # nameless required arg is unenforced (can't be checked) — returns the rendered prompt
+    assert err is None
+    assert result is not None
+    assert result["messages"][0]["role"] == "user"
+
+
+@pytest.mark.asyncio
+async def test_get_prompt_named_required_arg_blocks_when_absent():
+    """A required arg with a name still blocks if missing from the call."""
+    server = _make_server()
+    manifest = _manifest_with_prompts([
+        {
+            "name": "summarize",
+            "arguments": [{"name": "text", "required": True}],
+            "messages": [{"role": "user", "content": "Summarize: {text}"}],
+        },
+    ])
+    with patch.object(server, "_fetch_manifest", new=AsyncMock(return_value=manifest)):
+        result, err = await server._get_prompt("summarize", {})
+    assert result is None
+    assert err is not None
+    assert "text" in err
+
+
+@pytest.mark.asyncio
+async def test_get_prompt_named_required_arg_passes_when_provided():
+    """A required arg with a name passes when the arg is provided."""
+    server = _make_server()
+    manifest = _manifest_with_prompts([
+        {
+            "name": "summarize",
+            "arguments": [{"name": "text", "required": True}],
+            "messages": [{"role": "user", "content": "Summarize: {text}"}],
+        },
+    ])
+    with patch.object(server, "_fetch_manifest", new=AsyncMock(return_value=manifest)):
+        result, err = await server._get_prompt("summarize", {"text": "hello world"})
+    assert err is None
+    assert result is not None
+    content = result["messages"][0]["content"]
+    text = content if isinstance(content, str) else content.get("text", "")
+    assert "hello world" in text