Sync from v0.13

tests/standalone_tests/lazy_imports.py

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+# SPDX-License-Identifier: Apache-2.0
+# SPDX-FileCopyrightText: Copyright contributors to the vLLM project
+
+# Description: Test the lazy import module
+# The utility function cannot be placed in `vllm.utils`
+# this needs to be a standalone script
+import sys
+from contextlib import nullcontext
+
+from vllm_test_utils import BlameResult, blame
+
+# List of modules that should not be imported too early.
+# Lazy import `torch._inductor.async_compile` to avoid creating
+# too many processes before we set the number of compiler threads.
+# Lazy import `cv2` to avoid bothering users who only use text models.
+# `cv2` can easily mess up the environment.
+module_names = ["torch._inductor.async_compile", "cv2"]
+
+
+def any_module_imported():
+    return any(module_name in sys.modules for module_name in module_names)
+
+
+# In CI, we only check finally if the module is imported.
+# If it is indeed imported, we can rerun the test with `use_blame=True`,
+# which will trace every function call to find the first import location,
+# and help find the root cause.
+# We don't run it in CI by default because it is slow.
+use_blame = False
+context = blame(any_module_imported) if use_blame else nullcontext()
+with context as result:
+    import vllm  # noqa
+
+if use_blame:
+    assert isinstance(result, BlameResult)
+    print(f"the first import location is:\n{result.trace_stack}")
+
+assert not any_module_imported(), (
+    f"Some the modules in {module_names} are imported. To see the first"
+    f" import location, run the test with `use_blame=True`."
+)