Add new FastMCP Plugin support (#3970)

tests/cli/test_plugin_cli.py

@@ -0,0 +1,95 @@
+"""Tests for the `fastmcp plugin` CLI."""
+
+from __future__ import annotations
+
+import json
+import os
+import subprocess
+import sys
+import textwrap
+from pathlib import Path
+
+
+def _run_fastmcp(
+    *args: str, cwd: Path, env_extra: dict[str, str] | None = None
+) -> subprocess.CompletedProcess[str]:
+    """Invoke the `fastmcp` CLI as a subprocess."""
+    env = os.environ.copy()
+    env["PYTHONPATH"] = str(cwd)
+    if env_extra:
+        env.update(env_extra)
+    return subprocess.run(
+        [sys.executable, "-m", "fastmcp.cli", *args],
+        cwd=cwd,
+        capture_output=True,
+        text=True,
+        env=env,
+    )
+
+
+class TestManifestCLI:
+    def test_manifest_for_top_level_class(self, tmp_path: Path):
+        (tmp_path / "demo.py").write_text(
+            textwrap.dedent(
+                """
+                from fastmcp.server.plugins import Plugin, PluginMeta
+
+                class Demo(Plugin):
+                    meta = PluginMeta(name="demo", version="0.1.0")
+                """
+            )
+        )
+        result = _run_fastmcp("plugin", "manifest", "demo:Demo", cwd=tmp_path)
+        assert result.returncode == 0, result.stderr
+        manifest = json.loads(result.stdout)
+        assert manifest["name"] == "demo"
+        assert manifest["entry_point"] == "demo:Demo"
+
+    def test_manifest_for_nested_class(self, tmp_path: Path):
+        """`__qualname__` produces dotted paths for nested classes; the CLI
+        must traverse the dots to resolve the inner class."""
+        (tmp_path / "demo.py").write_text(
+            textwrap.dedent(
+                """
+                from fastmcp.server.plugins import Plugin, PluginMeta
+
+                class Outer:
+                    class Inner(Plugin):
+                        meta = PluginMeta(name="inner", version="0.1.0")
+                """
+            )
+        )
+        result = _run_fastmcp("plugin", "manifest", "demo:Outer.Inner", cwd=tmp_path)
+        assert result.returncode == 0, result.stderr
+        manifest = json.loads(result.stdout)
+        assert manifest["name"] == "inner"
+        assert manifest["entry_point"] == "demo:Outer.Inner"
+
+    def test_manifest_emits_clean_error_for_invalid_meta(self, tmp_path: Path):
+        """A plugin with invalid meta must produce a clean error, not a traceback."""
+        (tmp_path / "bad.py").write_text(
+            textwrap.dedent(
+                """
+                from fastmcp.server.plugins import Plugin, PluginMeta
+
+                class Bad(Plugin):
+                    meta = PluginMeta(
+                        name="bad",
+                        version="0.1.0",
+                        dependencies=["not a valid pep508 spec!!"],
+                    )
+                """
+            )
+        )
+        result = _run_fastmcp("plugin", "manifest", "bad:Bad", cwd=tmp_path)
+        assert result.returncode == 1
+        # Error goes through logger.error, not as a Python traceback.
+        assert "Traceback" not in result.stderr
+        assert "PEP 508" in result.stderr
+
+    def test_manifest_emits_clean_error_for_missing_module(self, tmp_path: Path):
+        result = _run_fastmcp(
+            "plugin", "manifest", "nonexistent_module:Thing", cwd=tmp_path
+        )
+        assert result.returncode == 1
+        assert "Traceback" not in result.stderr