Gazelle not raising error when a target py_test exists in place of a py_binary

[engnatha]

🐞 bug report

Affected Rule

rules_python_gazelle_plugin functionality

Is this a regression?

Still needs assessment

Description

When gazelle runs over a BUILD file and finds a py_test target where it wants to make a py_binary target, the gazelle extension flags the conflict, but it does not elevate to an error. This is not the case for other target conflicts. For example, if a py_test exists where a py_library should, a full error is raised and the exit code respects this.

When this conflict happens, no other gazelle edits are recommended for the affected target. Recommendations to other targets proceed as normal.

🔬 Minimal Reproduction

Make a simple tree like

lib/demo/
  - example_lib.py
  - example_bin.py
  - example_test.py

The contents of each are
example_bin.py

from lib.demo import example_lib


def main() -> None:
    print("Lib call:", example_lib.some_helper())


if __name__ == "__main__":
    main()

example_lib.py

def some_helper() -> int:
    return 52

example_test.py

import unittest

from lib.demo import example_lib


def test_thing() -> None:
    assert example_lib.some_helper() == 52


if __name__ == "__main__":
    unittest.main()

Now make the BUILD file with the following contents

load("@rules_python//python:defs.bzl", "py_library", "py_test")

py_test(
    name = "example_bin",
    srcs = ["example_bin.py"],
)

py_library(
    name = "example_lib",
    srcs = ["example_lib.py"],
)

py_test(
    name = "example_test",
    srcs = ["example_test.py"],
)

Run bazel run //:gazelle -- -strict -mode diff and see the following output

$ bazel run //:gazelle -- -strict -mode fix
(21:34:13) INFO: Current date is 2026-02-16
(21:34:13) INFO: Analyzed target //:gazelle (0 packages loaded, 0 targets configured).
(21:34:13) INFO: Found 1 target...
Target //:gazelle up-to-date:
  bazel-bin/gazelle-runner.bash
  bazel-bin/gazelle
(21:34:13) INFO: Elapsed time: 0.129s, Critical Path: 0.05s
(21:34:13) INFO: 1 process: 4 action cache hit, 1 internal.
(21:34:13) INFO: Build completed successfully, 1 total action
gazelle: failed to generate target "//lib/demo:example_bin" of kind "py_binary": a target of kind "py_test" with the same name already exists

Now notice the difference in error when py_library is converted incorrectly to a py_test.

gazelle: failed to generate target "//lib/demo:example_bin" of kind "py_binary": a target of kind "py_test" with the same name already exists
gazelle: ERROR: failed to generate target "//lib/demo:example_lib" of kind "py_library": a target of kind "py_test" with the same name already exists. Use the '# gazelle:python_library_naming_convention' directive to change the naming convention.

The details are the same, but the latter scenario is reflected in the exit code with a value of 1.

🌍 Your Environment

Operating System:
debian linux

Output of bazel version:
8.4.2

Rules_python version:
1.8.3