feat: Support reading command line args from a file

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 +1,4 @@
+Added support for reading ``file_or_dir`` positional arguments from a file
+using the prefix character '@', like e.g.:
+
+``pytest @tests.txt``

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 +542,28 @@ class TestGeneralUsage:
         res = pytester.runpytest(p)
         res.assert_outcomes(passed=3)
 
+    @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]",
+        ]
+        args_file = pytester.maketxtfile(tests="\n".join(tests))
+        result = pytester.runpytest(f"@{args_file.absolute()}")
+        result.assert_outcomes(failed=0, passed=2)
+
 
 class TestInvocationVariants:
     def test_earlyinit(self, pytester: Pytester) -> None:

testing/test_parseopt.py

@@ -125,6 +125,14 @@ class TestParser:
         args = parser.parse([Path(".")])
         assert getattr(args, parseopt.FILE_OR_DIR)[0] == "."
 
+    @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")