[FIX]: Avoid eager PyRIT imports during pytest startup

rampart/__init__.py

@@ -6,7 +6,9 @@
 Public API re-exports for convenient top-level access.
 """
 
-from rampart.attacks import Attacks
+from importlib import import_module
+from typing import TYPE_CHECKING
+
 from rampart.core.adapter import AgentAdapter, Session
 from rampart.core.errors import DriverError, EvaluatorError, InfrastructureError
 from rampart.core.evaluator import BaseEvaluator, Evaluator
@@ -41,11 +43,22 @@
     ToolCall,
     Turn,
 )
-from rampart.drivers.llm import LLMDriver
-from rampart.evaluators import LLMJudge, TranscriptScope
-from rampart.probes import Probes
 from rampart.pytest_plugin._collection import record_result
 
+if TYPE_CHECKING:
+    from rampart.attacks import Attacks
+    from rampart.drivers.llm import LLMDriver
+    from rampart.evaluators import LLMJudge, TranscriptScope
+    from rampart.probes import Probes
+
+__lazy_imports__: dict[str, tuple[str, str]] = {
+    "Attacks": ("rampart.attacks", "Attacks"),
+    "LLMDriver": ("rampart.drivers.llm", "LLMDriver"),
+    "LLMJudge": ("rampart.evaluators", "LLMJudge"),
+    "Probes": ("rampart.probes", "Probes"),
+    "TranscriptScope": ("rampart.evaluators", "TranscriptScope"),
+}
+
 __all__ = [
     "AgentAdapter",
     "AppManifest",
@@ -90,3 +103,31 @@
     "resolve_as_attack",
     "resolve_as_probe",
 ]
+
+
+def __getattr__(name: str) -> object:
+    """Load a PyRIT-backed public export only when requested.
+
+    Args:
+        name: Name of the requested module attribute.
+
+    Returns:
+        The requested public API object.
+
+    Raises:
+        AttributeError: If ``name`` is not a lazy public export.
+    """
+    try:
+        module_name, attribute_name = __lazy_imports__[name]
+    except KeyError:
+        message = f"module {__name__!r} has no attribute {name!r}"
+        raise AttributeError(message) from None
+
+    value = getattr(import_module(module_name), attribute_name)
+    globals()[name] = value
+    return value
+
+
+def __dir__() -> list[str]:
+    """Return eager and lazy public module attributes."""
+    return sorted({*globals(), *__all__})

tests/unit/test_public_api.py

@@ -0,0 +1,78 @@
+# Copyright (c) Microsoft Corporation.
+# Licensed under the MIT license.
+
+"""Tests for the top-level RAMPART public API."""
+
+from __future__ import annotations
+
+import subprocess  # ruff: ignore[suspicious-subprocess-import]
+import sys
+from types import SimpleNamespace
+from typing import Any
+
+import pytest
+
+import rampart
+
+
+def test_pytest_plugin_import_does_not_load_heavy_dependencies() -> None:
+    """Plugin startup should not import heavy execution dependencies."""
+    script = """
+import sys
+
+import rampart.pytest_plugin.plugin
+
+heavy_modules = sorted(
+    name
+    for name in sys.modules
+    if name == "pyrit"
+    or name.startswith("pyrit.")
+    or name == "transformers"
+    or name.startswith("transformers.")
+)
+if heavy_modules:
+    raise SystemExit(f"unexpected heavy imports: {heavy_modules}")
+"""
+
+    result = subprocess.run(  # ruff: ignore[subprocess-without-shell-equals-true]
+        [sys.executable, "-c", script],
+        capture_output=True,
+        text=True,
+        check=False,
+    )
+
+    assert result.returncode == 0, result.stderr
+
+
+@pytest.mark.parametrize(
+    ("name", "module_name", "attribute_name"),
+    [
+        ("Attacks", "rampart.attacks", "Attacks"),
+        ("LLMDriver", "rampart.drivers.llm", "LLMDriver"),
+        ("LLMJudge", "rampart.evaluators", "LLMJudge"),
+        ("Probes", "rampart.probes", "Probes"),
+        ("TranscriptScope", "rampart.evaluators", "TranscriptScope"),
+    ],
+)
+def test_heavy_public_export_is_loaded_on_demand(
+    monkeypatch: pytest.MonkeyPatch,
+    name: str,
+    module_name: str,
+    attribute_name: str,
+) -> None:
+    """A deferred top-level export should resolve once and then be cached."""
+    sentinel = object()
+    previous: Any = rampart.__dict__.pop(name, None)
+
+    def fake_import_module(requested_module: str) -> SimpleNamespace:
+        assert requested_module == module_name
+        return SimpleNamespace(**{attribute_name: sentinel})
+
+    monkeypatch.setattr(rampart, "import_module", fake_import_module)
+    try:
+        assert getattr(rampart, name) is sentinel
+        assert rampart.__dict__[name] is sentinel
+    finally:
+        rampart.__dict__.pop(name, None)
+        if previous is not None:
+            rampart.__dict__[name] = previous