From 7bcb3bc6f72595047f5aeca7fe431b49af94fca0 Mon Sep 17 00:00:00 2001
From: Nahuel Espinosa <nahue.espinosa@gmail.com>
Date: Sat, 28 Jun 2025 16:22:12 -0300
Subject: [PATCH] fix(py_test): Support target names with a `test_` prefix

Signed-off-by: Nahuel Espinosa <nahue.espinosa@gmail.com>
---
 docs/py_test.md                |  3 ++-
 examples/pytest/BUILD.bazel    | 10 ++++++++++
 examples/pytest/prefix_test.py |  2 ++
 py/defs.bzl                    |  7 +++++--
 py/private/py_pytest_main.bzl  |  5 +++--
 5 files changed, 22 insertions(+), 5 deletions(-)
 create mode 100644 examples/pytest/prefix_test.py

diff --git a/docs/py_test.md b/docs/py_test.md
index ea1294df..ca5265a2 100644
--- a/docs/py_test.md
+++ b/docs/py_test.md
@@ -72,7 +72,7 @@ Run a Python program under Bazel. Most users should use the [py_test macro](#py_
 ## py_pytest_main
 
 <pre>
-py_pytest_main(<a href="#py_pytest_main-name">name</a>, <a href="#py_pytest_main-py_library">py_library</a>, <a href="#py_pytest_main-deps">deps</a>, <a href="#py_pytest_main-data">data</a>, <a href="#py_pytest_main-testonly">testonly</a>, <a href="#py_pytest_main-kwargs">kwargs</a>)
+py_pytest_main(<a href="#py_pytest_main-name">name</a>, <a href="#py_pytest_main-test_main">test_main</a>, <a href="#py_pytest_main-py_library">py_library</a>, <a href="#py_pytest_main-deps">deps</a>, <a href="#py_pytest_main-data">data</a>, <a href="#py_pytest_main-testonly">testonly</a>, <a href="#py_pytest_main-kwargs">kwargs</a>)
 </pre>
 
 py_pytest_main wraps the template rendering target and the final py_library.
@@ -83,6 +83,7 @@ py_pytest_main wraps the template rendering target and the final py_library.
 | Name  | Description | Default Value |
 | :------------- | :------------- | :------------- |
 | <a id="py_pytest_main-name"></a>name |  The name of the runable target that updates the test entry file.   |  none |
+| <a id="py_pytest_main-test_main"></a>test_main |  The name of the test entry file to be generated.   |  <code>None</code> |
 | <a id="py_pytest_main-py_library"></a>py_library |  Use this attribute to override the default py_library rule.   |  <code>&lt;unknown object com.google.devtools.build.skydoc.fakebuildapi.FakeStarlarkRuleFunctionsApi$RuleDefinitionIdentifier&gt;</code> |
 | <a id="py_pytest_main-deps"></a>deps |  A list containing the pytest library target, e.g., @pypi_pytest//:pkg.   |  <code>[]</code> |
 | <a id="py_pytest_main-data"></a>data |  A list of data dependencies to pass to the py_library target.   |  <code>[]</code> |
diff --git a/examples/pytest/BUILD.bazel b/examples/pytest/BUILD.bazel
index 9256da54..36425658 100644
--- a/examples/pytest/BUILD.bazel
+++ b/examples/pytest/BUILD.bazel
@@ -38,3 +38,13 @@ py_test(
     shard_count = 2,
     deps = ["@pypi_pytest//:pkg"],
 )
+
+py_test(
+    # NB: target name starts with a test_ prefix
+    name = "test_prefix",
+    srcs = ["prefix_test.py"],
+    pytest_main = True,
+    deps = [
+        "@pypi_pytest//:pkg",
+    ],
+)
diff --git a/examples/pytest/prefix_test.py b/examples/pytest/prefix_test.py
new file mode 100644
index 00000000..f186a7e6
--- /dev/null
+++ b/examples/pytest/prefix_test.py
@@ -0,0 +1,2 @@
+def test_always_passing():
+    assert True
diff --git a/py/defs.bzl b/py/defs.bzl
index b23ded39..79ca203f 100644
--- a/py/defs.bzl
+++ b/py/defs.bzl
@@ -163,8 +163,11 @@ def py_test(name, srcs = [], main = None, pytest_main = False, **kwargs):
         if main:
             fail("When pytest_main is set, the main attribute should not be set.")
         pytest_main_target = name + ".pytest_main"
-        main = pytest_main_target + ".py"
-        py_pytest_main(name = pytest_main_target)
+
+        # NB: The main name starts with a dot, so pytest does not mistakenly collect
+        # the file during test collection even if the target name starts with `test_`.
+        main = "." + pytest_main_target + ".py"
+        py_pytest_main(name = pytest_main_target, test_main = main)
         srcs.append(main)
         deps.append(pytest_main_target)
 
diff --git a/py/private/py_pytest_main.bzl b/py/private/py_pytest_main.bzl
index 4ce6292a..f311d3ed 100644
--- a/py/private/py_pytest_main.bzl
+++ b/py/private/py_pytest_main.bzl
@@ -58,11 +58,12 @@ _py_pytest_main = rule(
     },
 )
 
-def py_pytest_main(name, py_library = default_py_library, deps = [], data = [], testonly = True, **kwargs):
+def py_pytest_main(name, test_main = None, py_library = default_py_library, deps = [], data = [], testonly = True, **kwargs):
     """py_pytest_main wraps the template rendering target and the final py_library.
 
     Args:
         name: The name of the runable target that updates the test entry file.
+        test_main: The name of the test entry file to be generated.
         py_library: Use this attribute to override the default py_library rule.
         deps: A list containing the pytest library target, e.g., @pypi_pytest//:pkg.
         data: A list of data dependencies to pass to the py_library target.
@@ -70,7 +71,7 @@ def py_pytest_main(name, py_library = default_py_library, deps = [], data = [],
         **kwargs: The extra arguments passed to the template rendering target.
     """
 
-    test_main = name + ".py"
+    test_main = test_main or name + ".py"
     tags = kwargs.pop("tags", [])
     visibility = kwargs.pop("visibility", [])