[Feature] Warn about unrecognized environment variables (#33581)

Signed-off-by: Gregory Shtrasberg <Gregory.Shtrasberg@amd.com>

tests/config/test_config_generation.py

@@ -78,3 +78,27 @@ def test_ray_runtime_env(monkeypatch: pytest.MonkeyPatch):
     )
 
     ray.shutdown()
+
+
+def test_unrecognized_env():
+    import os
+
+    # Test that if fail_on_environ_validation is True, then an error
+    # is raised when an unrecognized vLLM environment variable is set
+    os.environ["VLLM_UNRECOGNIZED_ENV_VAR"] = "some_value"
+    engine_args = EngineArgs(
+        fail_on_environ_validation=True,
+    )
+    with pytest.raises(ValueError, match="Unknown vLLM environment variable detected"):
+        engine_args.create_engine_config()
+
+    # Test that if fail_on_environ_validation is False, then no error is raised
+    engine_args = EngineArgs()
+    engine_args.create_engine_config()
+
+    # Test that when the unrecognized env var is removed, no error is raised
+    os.environ.pop("VLLM_UNRECOGNIZED_ENV_VAR", None)
+    engine_args = EngineArgs(
+        fail_on_environ_validation=True,
+    )
+    engine_args.create_engine_config()