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https://github.com/NousResearch/hermes-agent.git
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6030ca8cea
Port from anomalyco/opencode#35439/#35500: preserve full MCP catalogs across paginated tools/list responses. The MCP spec allows servers to paginate tools/list, resources/list, and prompts/list via an opaque nextCursor token. The Python SDK's ClientSession.list_* methods fetch exactly one page per call, and hermes never passed the cursor back — on a paginated server every tool, resource, and prompt past page 1 was silently invisible to the agent. Adds _paginate_full_list() (cursor-draining helper with a 50-page runaway cap and spec-correct opaque-string cursor validation) and applies it at all three discovery sites: _discover_tools(), the tools/list_changed refresh handler, and the list_resources/list_prompts utility handlers. The keepalive probe intentionally keeps its single-page call (liveness only). E2E: real stdio MCP server serving 3 pages (2/1/1 tools) — old code discovered 2 tools, new code discovers all 4.
103 lines
3.8 KiB
Python
103 lines
3.8 KiB
Python
"""Tests for MCP list_* pagination (nextCursor draining).
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The MCP spec allows servers to paginate ``tools/list``, ``resources/list``,
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and ``prompts/list`` via an opaque ``nextCursor`` token. The Python SDK
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fetches one page per call, so hermes must follow the cursor to see items
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past page 1. Port of the invariant behind anomalyco/opencode#35439/#35500.
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"""
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import asyncio
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from types import SimpleNamespace
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from unittest.mock import AsyncMock, MagicMock
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from tools.mcp_tool import _MCP_LIST_MAX_PAGES, _paginate_full_list
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def _tool(name):
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t = MagicMock()
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t.name = name
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return t
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class TestPaginateFullList:
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def test_single_page_no_cursor(self):
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"""A result without nextCursor returns just that page."""
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list_method = AsyncMock(
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return_value=SimpleNamespace(tools=[_tool("a"), _tool("b")])
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)
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items = asyncio.run(_paginate_full_list(list_method, "tools", "srv"))
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assert [t.name for t in items] == ["a", "b"]
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list_method.assert_called_once_with()
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def test_follows_next_cursor_across_pages(self):
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"""Pages are concatenated in order; cursor passed back verbatim."""
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pages = {
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None: SimpleNamespace(tools=[_tool("p1a"), _tool("p1b")], nextCursor="c2"),
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"c2": SimpleNamespace(tools=[_tool("p2a")], nextCursor="c3"),
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"c3": SimpleNamespace(tools=[_tool("p3a")], nextCursor=None),
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}
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async def fake_list(cursor=None):
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return pages[cursor]
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items = asyncio.run(_paginate_full_list(fake_list, "tools", "srv"))
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assert [t.name for t in items] == ["p1a", "p1b", "p2a", "p3a"]
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def test_empty_page_with_cursor_continues(self):
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"""An empty middle page doesn't abort the walk."""
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pages = {
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None: SimpleNamespace(resources=[_tool("r1")], nextCursor="c2"),
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"c2": SimpleNamespace(resources=[], nextCursor="c3"),
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"c3": SimpleNamespace(resources=[_tool("r2")]),
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}
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async def fake_list(cursor=None):
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return pages[cursor]
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items = asyncio.run(_paginate_full_list(fake_list, "resources", "srv"))
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assert [t.name for t in items] == ["r1", "r2"]
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def test_missing_items_attr_tolerated(self):
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"""A malformed result without the items attribute yields nothing."""
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list_method = AsyncMock(return_value=SimpleNamespace())
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items = asyncio.run(_paginate_full_list(list_method, "prompts", "srv"))
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assert items == []
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def test_runaway_cursor_capped(self):
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"""A server that returns a cursor forever is bounded by the page cap."""
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calls = {"n": 0}
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async def evil_list(cursor=None):
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calls["n"] += 1
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return SimpleNamespace(
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tools=[_tool(f"t{calls['n']}")], nextCursor=f"c{calls['n']}"
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)
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items = asyncio.run(_paginate_full_list(evil_list, "tools", "srv"))
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assert calls["n"] == _MCP_LIST_MAX_PAGES
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assert len(items) == _MCP_LIST_MAX_PAGES
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class TestDiscoveryUsesPagination:
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def test_discover_tools_drains_all_pages(self):
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"""MCPServerTask._discover_tools registers tools from every page."""
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from tools.mcp_tool import MCPServerTask
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server = MCPServerTask("pag_srv")
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server._config = {"command": "test"}
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pages = {
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None: SimpleNamespace(tools=[_tool("first")], nextCursor="page-2"),
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"page-2": SimpleNamespace(tools=[_tool("second")]),
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}
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async def fake_list(cursor=None):
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return pages[cursor]
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server.session = MagicMock()
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server.session.list_tools = fake_list
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# capability gate: _advertises_tools() returns True when no
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# capability info was captured (legacy fallback), so no override
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# is needed here.
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asyncio.run(server._discover_tools())
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assert [t.name for t in server._tools] == ["first", "second"]
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