Re-write flag values to place generated files in undeclared outputs d…

…ir (#7)

Some common pytest plugins, such as pytest-reportlog, pytest-json-report and pytest-html, allow the user to generate reports, accepting a file path as a flag. In Bazel, these generated files can only be accessed if placed inside the test undeclared outputs dir. However, bazel doesn't provide any way to expand environment variable values provided in args.

This commit rewrites flag values for the plugins mentioned above, prepend the test undeclared output dir folder to the value of the corresponding flags.

python_pytest/pytest_shim.py

@@ -16,6 +16,24 @@
     if os.environ.get("XML_OUTPUT_FILE"):
         pytest_args.append("--junitxml={xml_output_file}".format(xml_output_file=os.environ.get("XML_OUTPUT_FILE")))
 
+    # Handle plugins that generate reports - if they are provided with relative paths (via args),
+    # re-write it under bazel's test undeclared outputs dir.
+    if os.environ.get("TEST_UNDECLARED_OUTPUTS_DIR"):
+        undeclared_output_dir = os.environ.get("TEST_UNDECLARED_OUTPUTS_DIR")
+
+        # Flags that take file paths as value.
+        path_flags = [
+            "--report-log",  # pytest-reportlog
+            "--json-report-file",  # pytest-json-report
+            "--html",  # pytest-html
+        ]
+        for i, arg in enumerate(args):
+            for flag in path_flags:
+                if arg.startswith(f"{flag}="):
+                    arg_split = arg.split("=", 1)
+                    if len(arg_split) == 2 and not os.path.isabs(arg_split[1]):
+                        args[i] = f"{flag}={undeclared_output_dir}/{arg_split[1]}"
+
     if os.environ.get("TESTBRIDGE_TEST_ONLY"):
         # TestClass.test_fn -> TestClass::test_fn
         module_name = os.environ.get("TESTBRIDGE_TEST_ONLY").replace(".", "::")