Ensure paths constructed by tox stay meaningful (#2587)

Resolves #2562

Author: gaborbernat

docs/changelog/2562.bugfix.rst

@@ -0,0 +1,2 @@
+Ensure paths constructed by tox are stable by resolving relative paths to fully qualified one, this insures that running
+tox from a different folder than project root still generates meaningful paths - by :user:`gaborbernat`.

src/tox/config/main.py

@@ -29,7 +29,6 @@ def __init__(
         pos_args: Sequence[str] | None,
         work_dir: Path,
     ) -> None:
-
         self._pos_args = None if pos_args is None else tuple(pos_args)
         self._work_dir = work_dir
         self._root = root
@@ -93,6 +92,9 @@ def make(cls, parsed: Parsed, pos_args: Sequence[str] | None, source: Source) ->
         # work dir is where we put our own files
         root: Path = source.path.parent if parsed.root_dir is None else parsed.root_dir
         work_dir: Path = source.path.parent if parsed.work_dir is None else parsed.work_dir
+        # if these are relative we need to expand them them to ensure paths built on this can resolve independent on cwd
+        root = root.resolve()
+        work_dir = work_dir.resolve()
         return cls(
             config_source=source,
             options=parsed,

tests/config/test_main.py

@@ -1,6 +1,7 @@
 from __future__ import annotations
 
 import os
+from pathlib import Path
 
 from tests.conftest import ToxIniCreator
 from tox.config.loader.api import Override
@@ -83,3 +84,19 @@ def test_args_are_paths_when_with_change_dir(tox_project: ToxProjectCreator) ->
     result = project.run("c", "-e", "py", "-k", "commands", "--", *args)
     result.assert_success()
     assert result.out == f"[testenv:py]\ncommands = magic.py {project.path} ..{os.sep}tox.ini a.txt . ..\n"
+
+
+def test_relative_config_paths_resolve(tox_project: ToxProjectCreator) -> None:
+    project = tox_project({"tox.ini": "[tox]"})
+    result = project.run(
+        "c",
+        "-c",
+        str(Path(project.path.name) / "tox.ini"),
+        "-k",
+        "change_dir",
+        "env_dir",
+        from_cwd=project.path.parent,
+    )
+    result.assert_success()
+    expected = f"[testenv:py]\nchange_dir = {project.path}\nenv_dir = {project.path / '.tox' / 'py'}\n\n[tox]\n"
+    assert result.out == expected