Parse args from file (#12085)

Co-authored-by: Ran Benita <ran@unusedvar.com>
Co-authored-by: Bruno Oliveira <bruno@soliv.dev>

.gitignore

@@ -51,6 +51,7 @@ coverage.xml
 .settings
 .vscode
 __pycache__/
+.python-version
 
 # generated by pip
 pip-wheel-metadata/

AUTHORS

@@ -235,6 +235,7 @@ Kyle Altendorf
 Lawrence Mitchell
 Lee Kamentsky
 Lev Maximov
+Levon Saldamli
 Lewis Cowles
 Llandy Riveron Del Risco
 Loic Esteve

changelog/11871.feature.rst

@@ -0,0 +1 @@
+Added support for reading command line arguments from a file using the prefix character ``@``, like e.g.: ``pytest @tests.txt``. The file must have one argument per line.

doc/en/how-to/usage.rst

@@ -17,7 +17,8 @@ in the current directory and its subdirectories. More generally, pytest follows
 Specifying which tests to run
 ------------------------------
 
-Pytest supports several ways to run and select tests from the command-line.
+Pytest supports several ways to run and select tests from the command-line or from a file
+(see below for :ref:`reading arguments from file <args-from-file>`).
 
 **Run tests in a module**
 
@@ -91,6 +92,28 @@ For more information see :ref:`marks <mark>`.
 
 This will import ``pkg.testing`` and use its filesystem location to find and run tests from.
 
+.. _args-from-file:
+
+**Read arguments from file**
+
+.. versionadded:: 8.2
+
+All of the above can be read from a file using the ``@`` prefix:
+
+.. code-block:: bash
+
+    pytest @tests_to_run.txt
+
+where ``tests_to_run.txt`` contains an entry per line, e.g.:
+
+.. code-block:: text
+
+    tests/test_file.py
+    tests/test_mod.py::test_func[x1,y2]
+    tests/test_mod.py::TestClass
+    -m slow
+
+This file can also be generated using ``pytest --collect-only -q`` and modified as needed.
 
 Getting help on version, option names, environment variables
 --------------------------------------------------------------

src/_pytest/config/argparsing.py

@@ -415,6 +415,7 @@ class MyOptionParser(argparse.ArgumentParser):
             add_help=False,
             formatter_class=DropShorterLongHelpFormatter,
             allow_abbrev=False,
+            fromfile_prefix_chars="@",
         )
         # extra_info is a dict of (param -> value) to display if there's
         # an usage error to provide more contextual information to the user.

testing/acceptance_test.py

@@ -2,6 +2,7 @@
 import dataclasses
 import importlib.metadata
 import os
+from pathlib import Path
 import subprocess
 import sys
 import types
@@ -541,6 +542,32 @@ class TestGeneralUsage:
         res = pytester.runpytest(p)
         res.assert_outcomes(passed=3)
 
+    # Warning ignore because of:
+    # https://github.com/python/cpython/issues/85308
+    # Can be removed once Python<3.12 support is dropped.
+    @pytest.mark.filterwarnings("ignore:'encoding' argument not specified")
+    def test_command_line_args_from_file(
+        self, pytester: Pytester, tmp_path: Path
+    ) -> None:
+        pytester.makepyfile(
+            test_file="""
+            import pytest
+
+            class TestClass:
+                @pytest.mark.parametrize("a", ["x","y"])
+                def test_func(self, a):
+                    pass
+            """
+        )
+        tests = [
+            "test_file.py::TestClass::test_func[x]",
+            "test_file.py::TestClass::test_func[y]",
+            "-q",
+        ]
+        args_file = pytester.maketxtfile(tests="\n".join(tests))
+        result = pytester.runpytest(f"@{args_file}")
+        result.assert_outcomes(failed=0, passed=2)
+
 
 class TestInvocationVariants:
     def test_earlyinit(self, pytester: Pytester) -> None:

testing/test_parseopt.py

@@ -125,6 +125,17 @@ class TestParser:
         args = parser.parse([Path(".")])
         assert getattr(args, parseopt.FILE_OR_DIR)[0] == "."
 
+    # Warning ignore because of:
+    # https://github.com/python/cpython/issues/85308
+    # Can be removed once Python<3.12 support is dropped.
+    @pytest.mark.filterwarnings("ignore:'encoding' argument not specified")
+    def test_parse_from_file(self, parser: parseopt.Parser, tmp_path: Path) -> None:
+        tests = [".", "some.py::Test::test_method[param0]", "other/test_file.py"]
+        args_file = tmp_path / "tests.txt"
+        args_file.write_text("\n".join(tests), encoding="utf-8")
+        args = parser.parse([f"@{args_file.absolute()}"])
+        assert getattr(args, parseopt.FILE_OR_DIR) == tests
+
     def test_parse_known_args(self, parser: parseopt.Parser) -> None:
         parser.parse_known_args([Path(".")])
         parser.addoption("--hello", action="store_true")