chore(iast): restore, update and improve the native import smoke_test (…

…#11278)

## Description

The previous smoke test for importing ddtrace IAST native module (both
positive and negative routes) was removed on a previous PR.

This restores it, adapting it to the new version (now the `_native`
module doesn't produce an `ImportError` if `DD_IAST_ENABLED=0` but a
warning log message). It will also run both positive and negative tests
in a subprocess so the `.so` module doesn't have to be restarted or
reloaded, which is not trivial for native modules.

## Checklist
- [X] PR author has checked that all the criteria below are met
- The PR description includes an overview of the change
- The PR description articulates the motivation for the change
- The change includes tests OR the PR description describes a testing
strategy
- The PR description notes risks associated with the change, if any
- Newly-added code is easy to change
- The change follows the [library release note
guidelines](https://ddtrace.readthedocs.io/en/stable/releasenotes.html)
- The change includes or references documentation updates if necessary
- Backport labels are set (if
[applicable](https://ddtrace.readthedocs.io/en/latest/contributing.html#backporting))

## Reviewer Checklist
- [x] Reviewer has checked that all the criteria below are met 
- Title is accurate
- All changes are related to the pull request's stated goal
- Avoids breaking
[API](https://ddtrace.readthedocs.io/en/stable/versioning.html#interfaces)
changes
- Testing strategy adequately addresses listed risks
- Newly-added code is easy to change
- Release note makes sense to a user of the library
- If necessary, author has acknowledged and discussed the performance
implications of this PR as reported in the benchmarks PR comment
- Backport labels are set in a manner that is consistent with the
[release branch maintenance
policy](https://ddtrace.readthedocs.io/en/latest/contributing.html#backporting)

---------

Signed-off-by: Juanjo Alvarez <[email protected]>

tests/smoke_test.py

@@ -1,8 +1,9 @@
+import copy
+import os
 from platform import system
+import subprocess
 import sys
-
-import ddtrace.appsec._ddwaf
-import ddtrace.bootstrap.sitecustomize as module
+import textwrap
 
 
 def mac_supported_iast_version():
@@ -14,13 +15,74 @@ def mac_supported_iast_version():
     return True
 
 
+# Code need to be run in a separate subprocess to reload since reloading .so files doesn't
+# work like normal Python ones
+test_native_load_code = """
+import os
+import sys
+import logging
+
+log_messages = []
+
+class ListHandler(logging.Handler):
+    def emit(self, record):
+        log_messages.append(record.getMessage())
+
+# the _native module will produce the "IAST not enabled..." message using the root logger (logger.warning)
+# so we have to configure the capture handler on the root logger
+root_logger = logging.getLogger()
+root_logger.addHandler(ListHandler())
+root_logger.setLevel(logging.WARNING)
+
+try:
+    from ddtrace.appsec._iast._taint_tracking._native import ops
+
+    if os.environ.get("DD_IAST_ENABLED") == "False":
+        assert any(
+            "IAST not enabled but native module is being loaded" in message
+            for message in log_messages
+        )
+    else:
+        assert ops
+        assert len(log_messages) == 0
+except ImportError as e:
+    assert False, "Importing the native module failed, _native probably not compiled correctly: %s" % str(e)
+"""
+
 if __name__ == "__main__":
+    # ASM IAST smoke test
+    if sys.version_info >= (3, 6, 0) and system() != "Windows" and mac_supported_iast_version():
+        print("Running native IAST module load test...")
+        test_code = textwrap.dedent(test_native_load_code)
+        cmd = [sys.executable, "-c", test_code]
+        orig_env = os.environ.copy()
+        copied_env = copy.deepcopy(orig_env)
+
+        try:
+            print("Running native module load test with DD_IAST_ENABLED=False...")
+            copied_env["DD_IAST_ENABLED"] = "False"
+            result = subprocess.run(cmd, env=copied_env, capture_output=True, text=True)
+            assert result.returncode == 0, "Failed with DD_IAST_ENABLED=0: %s, %s" % (result.stdout, result.stderr)
+
+            print("Running native module load test with DD_IAST_ENABLED=True...")
+            copied_env["DD_IAST_ENABLED"] = "True"
+            result = subprocess.run(cmd, env=copied_env, capture_output=True, text=True)
+            assert result.returncode == 0, "Failed with DD_IAST_ENABLED=1: %s, %s" % (result.stdout, result.stderr)
+            print("IAST module load tests completed successfully")
+        finally:
+            os.environ = orig_env
+
     # ASM WAF smoke test
-    if system() == "Linux":
-        if not sys.maxsize > 2**32:
-            # 32-bit linux DDWAF not ready yet.
-            sys.exit(0)
-
-    ddtrace.appsec._ddwaf.version()
-    assert ddtrace.appsec._ddwaf._DDWAF_LOADED
-    assert module.loaded
+    if system() != "Linux" or sys.maxsize > 2**32:
+        import ddtrace.appsec._ddwaf
+        import ddtrace.bootstrap.sitecustomize as module
+
+        print("Running WAF module load test...")
+        # Proceed with the WAF module load test
+        ddtrace.appsec._ddwaf.version()
+        assert ddtrace.appsec._ddwaf._DDWAF_LOADED
+        assert module.loaded
+        print("WAF module load test completed successfully")
+    else:
+        # Skip the test for 32-bit Linux systems
+        print("Skipping test, 32-bit DDWAF not ready yet")