[ci][build] add tests for python only compilation (#10915)

Signed-off-by: youkaichao <youkaichao@gmail.com>

tests/standalone_tests/lazy_torch_compile.py

@@ -0,0 +1,28 @@
+# 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
+
+module_name = "torch._inductor.async_compile"
+
+# 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(
+    lambda: module_name in sys.modules) 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 module_name not in sys.modules, (
+    f"Module {module_name} is imported. To see the first"
+    f" import location, run the test with `use_blame=True`.")

tests/standalone_tests/python_only_compile.sh

@@ -0,0 +1,30 @@
+#!/bin/bash
+# This script tests if the python only compilation works correctly
+# for users who do not have any compilers installed on their system
+
+set -e
+set -x
+
+cd /vllm-workspace/
+
+# uninstall vllm
+pip3 uninstall -y vllm
+# restore the original files
+mv test_docs/vllm ./vllm
+
+# remove all compilers
+apt remove --purge build-essential -y
+apt autoremove -y
+
+echo 'import os; os.system("touch /tmp/changed.file")' >> vllm/__init__.py
+
+VLLM_USE_PRECOMPILED=1 pip3 install -vvv -e .
+
+# Run the script
+python3 -c 'import vllm'
+
+# Check if the clangd log file was created
+if [ ! -f /tmp/changed.file ]; then
+    echo "changed.file was not created, python only compilation failed"
+    exit 1
+fi