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https://github.com/PrefectHQ/fastmcp.git
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Add fastmcp generate-cli command
Connects to any MCP server, reads its tool/resource/prompt schemas, and writes a standalone Python CLI script with typed subcommands.
This commit is contained in:
Jeremiah Lowin
parent
fe432de156
commit
2c705faa87
3 changed files with 902 additions and 0 deletions
403
tests/cli/test_generate_cli.py
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403
tests/cli/test_generate_cli.py
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"""Tests for fastmcp generate-cli command."""
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from pathlib import Path
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from typing import Any
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from unittest.mock import patch
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import mcp.types
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import pytest
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from fastmcp import FastMCP
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from fastmcp.cli import generate as generate_module
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from fastmcp.cli.client import Client
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from fastmcp.cli.generate import (
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_derive_server_name,
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_schema_type_to_python,
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_tool_function_source,
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generate_cli_command,
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generate_cli_script,
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serialize_transport,
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)
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from fastmcp.client.transports.stdio import StdioTransport
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# ---------------------------------------------------------------------------
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# _schema_type_to_python
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# ---------------------------------------------------------------------------
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class TestSchemaTypeToPython:
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def test_string(self):
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assert _schema_type_to_python({"type": "string"}) == "str"
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def test_integer(self):
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assert _schema_type_to_python({"type": "integer"}) == "int"
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def test_number(self):
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assert _schema_type_to_python({"type": "number"}) == "float"
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def test_boolean(self):
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assert _schema_type_to_python({"type": "boolean"}) == "bool"
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def test_array(self):
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assert _schema_type_to_python({"type": "array"}) == "list"
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def test_object(self):
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assert _schema_type_to_python({"type": "object"}) == "dict"
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def test_null(self):
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assert _schema_type_to_python({"type": "null"}) == "None"
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def test_unknown_defaults_to_str(self):
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assert _schema_type_to_python({"type": "foobar"}) == "str"
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def test_missing_type_defaults_to_str(self):
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assert _schema_type_to_python({}) == "str"
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def test_any_of(self):
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result = _schema_type_to_python(
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{"anyOf": [{"type": "string"}, {"type": "integer"}]}
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)
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assert result == "str | int"
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def test_type_list(self):
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result = _schema_type_to_python({"type": ["string", "null"]})
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assert result == "str | None"
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# ---------------------------------------------------------------------------
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# serialize_transport
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# ---------------------------------------------------------------------------
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class TestSerializeTransport:
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def test_url_string(self):
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code, imports = serialize_transport("http://localhost:8000/mcp")
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assert code == "'http://localhost:8000/mcp'"
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assert imports == set()
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def test_stdio_transport_basic(self):
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transport = StdioTransport(command="fastmcp", args=["run", "server.py"])
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code, imports = serialize_transport(transport)
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assert "StdioTransport" in code
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assert "command='fastmcp'" in code
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assert "args=['run', 'server.py']" in code
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assert "from fastmcp.client.transports import StdioTransport" in imports
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def test_stdio_transport_with_env(self):
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transport = StdioTransport(
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command="python", args=["-m", "myserver"], env={"KEY": "val"}
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)
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code, imports = serialize_transport(transport)
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assert "env={'KEY': 'val'}" in code
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def test_dict_passthrough(self):
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d: dict[str, Any] = {"mcpServers": {"test": {"url": "http://localhost"}}}
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code, imports = serialize_transport(d)
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assert "mcpServers" in code
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assert imports == set()
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# ---------------------------------------------------------------------------
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# _tool_function_source
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# ---------------------------------------------------------------------------
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class TestToolFunctionSource:
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def test_required_param(self):
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tool = mcp.types.Tool(
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name="greet",
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inputSchema={
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"properties": {"name": {"type": "string", "description": "Who"}},
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"required": ["name"],
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},
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)
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source = _tool_function_source(tool)
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assert "async def greet(" in source
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assert "name: Annotated[str" in source
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assert "= None" not in source
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assert "_call_tool('greet', {'name': name})" in source
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def test_optional_param(self):
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tool = mcp.types.Tool(
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name="search",
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inputSchema={
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"properties": {
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"query": {"type": "string", "description": "Search query"},
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"limit": {"type": "integer", "description": "Max results"},
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},
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"required": ["query"],
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},
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)
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source = _tool_function_source(tool)
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assert "query: Annotated[str" in source
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assert "limit: Annotated[int | None" in source
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assert "= None" in source
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def test_param_with_default(self):
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tool = mcp.types.Tool(
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name="fetch",
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inputSchema={
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"properties": {
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"url": {"type": "string", "description": "URL"},
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"timeout": {
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"type": "integer",
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"description": "Timeout",
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"default": 30,
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},
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},
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"required": ["url"],
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},
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)
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source = _tool_function_source(tool)
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assert "timeout: Annotated[int" in source
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assert "= 30" in source
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def test_no_params(self):
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tool = mcp.types.Tool(
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name="ping",
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inputSchema={"properties": {}},
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)
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source = _tool_function_source(tool)
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assert "async def ping(" in source
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assert "_call_tool('ping', {})" in source
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def test_preserves_underscores(self):
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tool = mcp.types.Tool(
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name="get_forecast",
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inputSchema={
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"properties": {"city": {"type": "string"}},
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"required": ["city"],
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},
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)
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source = _tool_function_source(tool)
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assert "async def get_forecast(" in source
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def test_description_in_docstring(self):
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tool = mcp.types.Tool(
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name="greet",
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description="Say hello to someone.",
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inputSchema={
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"properties": {"name": {"type": "string"}},
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"required": ["name"],
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},
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)
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source = _tool_function_source(tool)
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assert '"""Say hello to someone."""' in source
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# ---------------------------------------------------------------------------
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# _derive_server_name
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# ---------------------------------------------------------------------------
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class TestDeriveServerName:
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def test_bare_name(self):
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assert _derive_server_name("weather") == "weather"
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def test_qualified_name(self):
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assert _derive_server_name("cursor:weather") == "weather"
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def test_python_file(self):
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assert _derive_server_name("server.py") == "server"
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def test_url(self):
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assert _derive_server_name("http://localhost:8000/mcp") == "localhost"
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# ---------------------------------------------------------------------------
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# generate_cli_script — produces compilable Python
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# ---------------------------------------------------------------------------
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class TestGenerateCliScript:
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def _make_tools(self) -> list[mcp.types.Tool]:
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return [
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mcp.types.Tool(
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name="greet",
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description="Say hello",
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inputSchema={
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"properties": {
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"name": {"type": "string", "description": "Who to greet"},
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},
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"required": ["name"],
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},
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),
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mcp.types.Tool(
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name="add_numbers",
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description="Add two numbers",
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inputSchema={
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"properties": {
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"a": {"type": "integer", "description": "First number"},
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"b": {"type": "integer", "description": "Second number"},
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},
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"required": ["a", "b"],
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},
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),
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]
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def test_compiles(self):
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script = generate_cli_script(
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server_name="test",
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server_spec="test",
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transport_code='"http://localhost:8000/mcp"',
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extra_imports=set(),
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tools=self._make_tools(),
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)
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compile(script, "<generated>", "exec")
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def test_contains_tool_functions(self):
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script = generate_cli_script(
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server_name="test",
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server_spec="test",
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transport_code='"http://localhost:8000/mcp"',
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extra_imports=set(),
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tools=self._make_tools(),
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)
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assert "async def greet(" in script
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assert "async def add_numbers(" in script
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def test_contains_generic_commands(self):
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script = generate_cli_script(
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server_name="test",
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server_spec="test",
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transport_code='"http://localhost:8000/mcp"',
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extra_imports=set(),
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tools=[],
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)
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assert "async def list_tools(" in script
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assert "async def list_resources(" in script
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assert "async def list_prompts(" in script
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assert "async def read_resource(" in script
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assert "async def get_prompt(" in script
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def test_embeds_transport(self):
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script = generate_cli_script(
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server_name="test",
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server_spec="test",
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transport_code="StdioTransport(command='fastmcp', args=['run', 'x.py'])",
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extra_imports={"from fastmcp.client.transports import StdioTransport"},
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tools=[],
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)
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assert "StdioTransport(command='fastmcp'" in script
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assert "from fastmcp.client.transports import StdioTransport" in script
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def test_no_tools_still_valid(self):
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script = generate_cli_script(
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server_name="empty",
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server_spec="empty",
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transport_code='"http://localhost"',
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extra_imports=set(),
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tools=[],
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)
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compile(script, "<generated>", "exec")
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assert "call_tool_app" in script
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def test_compiles_with_stdio_transport(self):
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transport = StdioTransport(command="fastmcp", args=["run", "server.py"])
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transport_code, extra_imports = serialize_transport(transport)
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script = generate_cli_script(
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server_name="test",
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server_spec="server.py",
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transport_code=transport_code,
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extra_imports=extra_imports,
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tools=self._make_tools(),
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)
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compile(script, "<generated>", "exec")
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# ---------------------------------------------------------------------------
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# generate_cli_command — integration tests
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# ---------------------------------------------------------------------------
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def _build_test_server() -> FastMCP:
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"""Create a minimal FastMCP server for integration tests."""
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server = FastMCP("TestServer")
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@server.tool
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def greet(name: str) -> str:
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"""Say hello to someone."""
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return f"Hello, {name}!"
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@server.tool
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def add(a: int, b: int) -> int:
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"""Add two numbers."""
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return a + b
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@server.resource("test://greeting")
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def greeting_resource() -> str:
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"""A static greeting resource."""
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return "Hello from resource!"
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@server.prompt
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def ask(topic: str) -> str:
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"""Ask about a topic."""
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return f"Tell me about {topic}"
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return server
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@pytest.fixture()
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def _patch_client():
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"""Patch resolve_server_spec and _build_client to use an in-process server."""
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server = _build_test_server()
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def fake_resolve(server_spec: Any, **kwargs: Any) -> str:
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return "fake://server"
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def fake_build_client(resolved: Any, **kwargs: Any) -> Client:
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return Client(server)
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with (
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patch.object(generate_module, "resolve_server_spec", side_effect=fake_resolve),
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patch.object(generate_module, "_build_client", side_effect=fake_build_client),
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):
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yield
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class TestGenerateCliCommand:
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@pytest.mark.usefixtures("_patch_client")
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async def test_writes_file(self, tmp_path: Path):
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output = tmp_path / "cli.py"
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await generate_cli_command("test-server", str(output))
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assert output.exists()
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content = output.read_text()
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compile(content, str(output), "exec")
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@pytest.mark.usefixtures("_patch_client")
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async def test_contains_tools(self, tmp_path: Path):
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output = tmp_path / "cli.py"
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await generate_cli_command("test-server", str(output))
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content = output.read_text()
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assert "async def greet(" in content
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assert "async def add(" in content
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@pytest.mark.usefixtures("_patch_client")
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async def test_default_output_path(
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self, tmp_path: Path, monkeypatch: pytest.MonkeyPatch
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):
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monkeypatch.chdir(tmp_path)
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await generate_cli_command("test-server")
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assert (tmp_path / "cli.py").exists()
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@pytest.mark.usefixtures("_patch_client")
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async def test_error_if_exists(self, tmp_path: Path):
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output = tmp_path / "cli.py"
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output.write_text("existing")
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with pytest.raises(SystemExit):
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await generate_cli_command("test-server", str(output))
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@pytest.mark.usefixtures("_patch_client")
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async def test_force_overwrites(self, tmp_path: Path):
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output = tmp_path / "cli.py"
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output.write_text("existing")
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await generate_cli_command("test-server", str(output), force=True)
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content = output.read_text()
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assert content != "existing"
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assert "async def greet(" in content
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@pytest.mark.usefixtures("_patch_client")
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async def test_file_is_executable(self, tmp_path: Path):
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output = tmp_path / "cli.py"
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await generate_cli_command("test-server", str(output))
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assert output.stat().st_mode & 0o111
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