fix: Respect cc_model_filenames in Python backend auto-fill

[nightflight-dk]

fix: Respect cc_model_filenames in Python backend auto-fill

Problem

When backend is set to "python" and default_model_filename is left empty, AutoCompleteBackendFields unconditionally sets default_model_filename to "model.py". This ignores any cc_model_filenames mappings the user may have configured to use a custom model filename (e.g., custom_model.py per device).

This causes the Python backend stub to always look for model.py, even when cc_model_filenames explicitly maps to a different file.

Fix

In model_config_utils.cc, the auto-fill of default_model_filename now checks that cc_model_filenames is also empty before defaulting to "model.py":

if (config->default_model_filename().empty() &&
    config->cc_model_filenames().empty()) {
  config->set_default_model_filename(kPythonFilename);
}

[nightflight-dk]

@whoisj this helps provide cc dependent implementation part of the same repo

[whoisj]

LGTM. I'll run it through our internal CI lab.

@nightflight-dk, could you please address the pre-commit issues? Thanks.

CI Pipeline ID: 49121709

you can always run pre-commit locally via

pre-commit run --files <file you've changed>

[whoisj]

LGTM. @yinggeh are you satisfied with the requested test case?

[Copilot]

Pull request overview

Fixes Python backend auto-fill so default_model_filename is only defaulted to model.py when both default_model_filename and cc_model_filenames are empty, preserving user-provided compute-capability filename mappings.

Changes:

• Update AutoCompleteBackendFields to skip defaulting default_model_filename when cc_model_filenames is populated.
• Add a dedicated unit test binary covering Python backend defaulting / non-defaulting behavior.
• Ignore /build_test output directory.

Reviewed changes

Copilot reviewed 3 out of 4 changed files in this pull request and generated 2 comments.

File	Description
src/model_config_utils.cc	Adjusts Python backend auto-fill condition to respect cc_model_filenames.
src/test/model_config_utils_test.cc	Adds unit tests validating the new auto-fill behavior and preservation rules.
src/test/CMakeLists.txt	Adds model_config_utils_test target and links required dependencies.
.gitignore	Ignores build_test directory.

---

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[Copilot]

TempModelDir::~TempModelDir uses system("rm -rf ...") for cleanup. This is non-portable (breaks on Windows), can behave incorrectly if the path contains spaces/shell metacharacters, and system may not be declared here (no include), causing a compile failure in C++ builds. Prefer using the existing filesystem helper (e.g., triton::core::DeletePath(root_path_)), and optionally assert/expect the returned Status in teardown/cleanup.

Suggested change

	std::string cmd = "rm -rf " + root_path_;
	(void)system(cmd.c_str());
	auto status = tc::DeletePath(root_path_);
	EXPECT_TRUE(status.IsOk()) << status.AsString();

[Copilot]

Test setup ignores failures from mkdir(...) and from writing the placeholder file (stream open/write errors). If either step fails, the test may pass/fail for the wrong reason. Please check the return value of mkdir (and consider handling EEXIST), and validate the std::ofstream state (or use triton::core::MakeDirectory / WriteTextFile which return a Status).

[yinggeh]

In this case, which python file backend should load if not "gpu"?