Add a single tmpdir fixture for all Python versions

See comments in `conftest.py`, but in general:

* because of our code, we would like to use `tmp_path` and `Path`
  it returns,
* but we have also our custom `tmt.utils.Path` we should be using
  instead of the original `pathlib.Path`,
* because of RHEL8, we also get pytest without `tmp_path` fixture,
* and `tmpdir` fixture returns `py.path.local`.

The patch adds our custom fixture which returns `tmt.utils.Path`
no matter what pytest we get. It's achieved by a test import,
trivial wrapper class, and two fixtures hiding the actual pytest
fixture involved.

tests/unit/conftest.py

@@ -1,20 +1,88 @@
-from pathlib import Path
+import pathlib
+from typing import Any
 
 import _pytest.logging
+import _pytest.tmpdir
+import py.path
 import pytest
 
 from tmt.log import Logger
+from tmt.utils import Path
 
 
 @pytest.fixture(name='root_logger')
 def fixture_root_logger(caplog: _pytest.logging.LogCaptureFixture) -> Logger:
     return Logger.create(verbose=0, debug=0, quiet=False)
 
 
+# Temporary directories and paths
+#
+# * the recommended way is to use `tmp_path` and `tmp_path_factory` fixtures
+# * `tmp_path*` fixtures are not available in RHEL-8, `tmpdir` (and `tmpdir_factory`)
+#   fixtures are - but these return `py.path.local` instead of a lovely `pathlib.Path`
+# * `pathlib.Path` is also not good enough, as it may lack some methods in older
+#   Python versions, that's why we have our own `tmt.utils.Path`.
+#
+# So, what we need:
+#
+# * a single name, we can't switch between `tmp_path` and `tmpdir` in every test
+# * `tmt.utils.Path`, no strings, no `py.path.local`
+# * works across all supported Python versions, from 3.6 in RHEL8 till 3.11 or so
+#
+# To solve this, we add here:
+#
+# * a wrapper class, representing the "tmp path factory". It's initialized with an
+#   actual factory, has the same public API, but returns our `tmt.utils.Path`
+# * two new fixtures, `tmppath` and `tmppath_factory` that consume available fixtures
+#   and return corresponding `tmt.utils.Path`.
+# * tests using `tmppath*` instead of pytest's own `tmp_path*` and `tmpdir*` fixtures
+#
+class TempPathFactory:
+    def __init__(self, actual_factory: Any) -> None:
+        self._actual_factory = actual_factory
+
+    def getbasetemp(self) -> Path:
+        return Path(str(self._actual_factory.getbasetemp()))
+
+    def mktemp(self, basename: str, numbered: bool = True) -> Path:
+        return Path(str(self._actual_factory.mktemp(basename, numbered=numbered)))
+
+
+try:
+    # If the import succeeds, we're about to wrap `Path` by `tmp_path`...
+    from _pytest.tmpdir import tmp_path_factory  # noqa: F401
+
+    @pytest.fixture(scope='session')
+    def tmppath_factory(
+        tmp_path_factory: '_pytest.tmpdir.TempPathFactory') -> TempPathFactory:  # noqa: F811
+        return TempPathFactory(tmp_path_factory)
+
+    @pytest.fixture()
+    def tmppath(tmp_path: pathlib.Path) -> Path:
+        return Path(str(tmp_path))
+
+except ImportError:
+    # ... and if the import fails, we're wrapping `py.path.local` from `tmpdir` family.
+
+    # ignore[name-defined]: when inspected with our daily Python 3.9 or something,
+    # the pytest is probably way newer than the one in RHEL8, and therefore the
+    # name indeed would not exist. But this whole branch applies only with the old
+    # pytest, therefore things are safe.
+    @pytest.fixture(scope='session')
+    def tmppath_factory(
+            tmpdir_factory: '_pytest.tmpdir.TempdirFactory'  # type: ignore[name-defined]
+            ) -> TempPathFactory:
+        return TempPathFactory(tmpdir_factory)
+
+    @pytest.fixture()
+    def tmppath(tmpdir: py.path.local) -> Path:
+        return Path(str(tmpdir))
+
+
 @pytest.fixture(scope='module')
-def source_dir(tmpdir_factory):
+def source_dir(tmppath_factory: TempPathFactory) -> Path:
     """ Create dummy directory structure and remove it after tests """
-    source_location = Path(tmpdir_factory.mktemp('source'))
+    source_location = tmppath_factory.mktemp('source')
     (source_location / 'library').mkdir(parents=True)
     (source_location / 'lib_folder').mkdir()
     (source_location / 'tests').mkdir()
@@ -26,6 +94,6 @@ def source_dir(tmpdir_factory):
 
 
 @pytest.fixture()
-def target_dir(tmpdir_factory):
+def target_dir(tmppath_factory: TempPathFactory) -> Path:
     """ Return target directory path and clean up after tests """
-    return Path(tmpdir_factory.mktemp('target'))
+    return tmppath_factory.mktemp('target')

tests/unit/test_report_junit.py

@@ -11,16 +11,16 @@
 
 
 @pytest.fixture()
-def report_fix(tmpdir, root_logger):
+def report_fix(tmppath: Path, root_logger):
     # need to provide genuine workdir paths - mock would break os.path.* calls
-    step_mock = MagicMock(workdir=str(tmpdir))
+    step_mock = MagicMock(workdir=tmppath)
     plan_mock = MagicMock()
     name_property = PropertyMock(return_value='name')
 
     type(plan_mock).name = name_property
     type(step_mock).plan = plan_mock
 
-    out_file_path = str(tmpdir.join("out.xml"))
+    out_file_path = str(tmppath / "out.xml")
 
     def get(key, default=None):
         if key == "file":
@@ -31,7 +31,7 @@ def get(key, default=None):
         logger=root_logger,
         step=step_mock,
         data=ReportJUnitData(name='x', how='junit'),
-        workdir=Path(str(tmpdir.join('junit'))))
+        workdir=tmppath / 'junit')
     report.get = get
     report.info = MagicMock()
 

tests/unit/test_utils.py

@@ -9,7 +9,6 @@
 from datetime import timedelta
 from typing import Any, List, Tuple
 
-import py
 import pytest
 
 import tmt
@@ -40,8 +39,8 @@
 
 
 @pytest.fixture()
-def local_git_repo(tmpdir: py.path.local) -> Path:
-    origin = Path(str(tmpdir)) / 'origin'
+def local_git_repo(tmppath: Path) -> Path:
+    origin = tmppath / 'origin'
     origin.mkdir()
 
     run(Command('git', 'init'), cwd=origin)
@@ -136,9 +135,11 @@ def test_config():
     assert config2.last_run.resolve() == run.resolve()
 
 
-def test_last_run_race(tmpdir, monkeypatch):
+def test_last_run_race(tmppath: Path, monkeypatch):
     """ Race in last run symlink should't be fatal """
-    monkeypatch.setattr(tmt.utils, 'CONFIG_PATH', Path(str(tmpdir.mkdir('config'))))
+    config_path = tmppath / 'config'
+    config_path.mkdir()
+    monkeypatch.setattr(tmt.utils, 'CONFIG_PATH', config_path)
     mock_logger = unittest.mock.MagicMock()
     monkeypatch.setattr(tmt.utils.log, 'warning', mock_logger)
     config = tmt.utils.Config()
@@ -147,7 +148,9 @@ def test_last_run_race(tmpdir, monkeypatch):
 
     def create_last_run(config, counter):
         try:
-            val = config.last_run = Path(str(tmpdir.mkdir(f"run-{counter}")))
+            last_run_path = tmppath / f"run-{counter}"
+            last_run_path.mkdir()
+            val = config.last_run = last_run_path
             results.put(val)
         except Exception as err:
             results.put(err)
@@ -173,21 +176,21 @@ def create_last_run(config, counter):
     assert config.last_run, "Some run was stored as last run"
 
 
-def test_workdir_env_var(tmpdir, monkeypatch, root_logger):
+def test_workdir_env_var(tmppath: Path, monkeypatch, root_logger):
     """ Test TMT_WORKDIR_ROOT environment variable """
     # Cannot use monkeypatch.context() as it is not present for CentOS Stream 8
-    monkeypatch.setenv('TMT_WORKDIR_ROOT', str(tmpdir))
+    monkeypatch.setenv('TMT_WORKDIR_ROOT', str(tmppath))
     common = Common(logger=root_logger)
     common._workdir_init()
     monkeypatch.delenv('TMT_WORKDIR_ROOT')
-    assert common.workdir == Path(f'{tmpdir}/run-001')
+    assert common.workdir == tmppath / 'run-001'
 
 
-def test_workdir_root_full(tmpdir, monkeypatch, root_logger):
+def test_workdir_root_full(tmppath, monkeypatch, root_logger):
     """ Raise if all ids lower than WORKDIR_MAX are exceeded """
-    monkeypatch.setenv('TMT_WORKDIR_ROOT', str(tmpdir))
+    monkeypatch.setenv('TMT_WORKDIR_ROOT', str(tmppath))
     monkeypatch.setattr(tmt.utils, 'WORKDIR_MAX', 1)
-    possible_workdir = Path(str(tmpdir)) / 'run-001'
+    possible_workdir = tmppath / 'run-001'
     # First call success
     common1 = Common(logger=root_logger)
     common1._workdir_init()
@@ -203,9 +206,9 @@ def test_workdir_root_full(tmpdir, monkeypatch, root_logger):
     assert common2.workdir.resolve() == possible_workdir.resolve()
 
 
-def test_workdir_root_race(tmpdir, monkeypatch, root_logger):
+def test_workdir_root_race(tmppath, monkeypatch, root_logger):
     """ Avoid race in workdir creation """
-    monkeypatch.setattr(tmt.utils, 'WORKDIR_ROOT', Path(str(tmpdir)))
+    monkeypatch.setattr(tmt.utils, 'WORKDIR_ROOT', tmppath)
     results = queue.Queue()
     threads = []
 
@@ -546,23 +549,23 @@ def test_multiple_values(self):
             StructuredFieldError, field.get, "section", "key")
 
 
-def test_run_interactive_not_joined(tmpdir, root_logger):
+def test_run_interactive_not_joined(tmppath, root_logger):
     output = ShellScript("echo abc; echo def >2").to_shell_command().run(
         shell=True,
         interactive=True,
-        cwd=Path(str(tmpdir)),
+        cwd=tmppath,
         env={},
         log=None,
         logger=root_logger)
     assert output.stdout is None
     assert output.stderr is None
 
 
-def test_run_interactive_joined(tmpdir, root_logger):
+def test_run_interactive_joined(tmppath, root_logger):
     output = ShellScript("echo abc; echo def >2").to_shell_command().run(
         shell=True,
         interactive=True,
-        cwd=Path(str(tmpdir)),
+        cwd=tmppath,
         env={},
         join=True,
         log=None,
@@ -650,14 +653,13 @@ def test_get_distgit_handler_explicit():
     assert instance.__class__.__name__ == 'RedHatGitlab'
 
 
-def test_fedora_dist_git(tmpdir):
+def test_fedora_dist_git(tmppath):
     # Fake values, production hash is too long
-    path = Path(str(tmpdir))
-    path.joinpath('sources').write_text('SHA512 (fn-1.tar.gz) = 09af\n')
-    path.joinpath('tmt.spec').write_text('')
+    (tmppath / 'sources').write_text('SHA512 (fn-1.tar.gz) = 09af\n')
+    (tmppath / 'tmt.spec').write_text('')
     fedora_sources_obj = tmt.utils.FedoraDistGit()
     assert [("https://src.fedoraproject.org/repo/pkgs/rpms/tmt/fn-1.tar.gz/sha512/09af/fn-1.tar.gz",  # noqa: E501
-            "fn-1.tar.gz")] == fedora_sources_obj.url_and_name(cwd=path)
+            "fn-1.tar.gz")] == fedora_sources_obj.url_and_name(cwd=tmppath)
 
 
 class TestValidateGitStatus:
@@ -689,15 +691,15 @@ def test_all_good(
 
     @classmethod
     def test_no_remote(cls, local_git_repo: Path, root_logger):
-        tmpdir = local_git_repo
-        tmt.Tree.init(logger=root_logger, path=tmpdir, template=None, force=None)
-        tmpdir.joinpath('main.fmf').write_text('test: echo')
+        tmt.Tree.init(logger=root_logger, path=local_git_repo, template=None, force=None)
+        with open(local_git_repo / 'main.fmf', 'w') as f:
+            f.write('test: echo')
         run(ShellScript('git add main.fmf .fmf/version').to_shell_command(),
-            cwd=tmpdir)
+            cwd=local_git_repo)
         run(ShellScript('git commit -m initial_commit').to_shell_command(),
-            cwd=tmpdir)
+            cwd=local_git_repo)
 
-        test = tmt.Tree(logger=root_logger, path=tmpdir).tests()[0]
+        test = tmt.Tree(logger=root_logger, path=local_git_repo).tests()[0]
         val, msg = validate_git_status(test)
         assert not val
         assert "Failed to get remote branch" in msg