TOX-3117 bugfix -c pyproject with non legacy (#3471)

Running tox -c pyproject.toml with content not ini legacy end up with a failure:
could not recognize config file pyproject.toml

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Author: AdrianCert

docs/changelog/3117.bugfix.rst

@@ -0,0 +1 @@
+multiple source_type supports for the same filename. Like pyproject.toml can be load by both TomlPyProject & LegacyToml

src/tox/config/source/discover.py

@@ -68,8 +68,8 @@ def _locate_source() -> Source | None:
 
 def _load_exact_source(config_file: Path) -> Source:
     # if the filename matches to the letter some config file name do not fallback to other source types
-    exact_match = next((s for s in SOURCE_TYPES if config_file.name == s.FILENAME), None)  # pragma: no cover
-    for src_type in (exact_match,) if exact_match is not None else SOURCE_TYPES:  # pragma: no branch
+    exact_match = [s for s in SOURCE_TYPES if config_file.name == s.FILENAME]  # pragma: no cover
+    for src_type in exact_match or SOURCE_TYPES:  # pragma: no branch
         try:
             return src_type(config_file)
         except ValueError:  # noqa: PERF203

tests/config/source/test_toml_pyproject.py

@@ -64,6 +64,22 @@ def test_config_in_toml_extra(tox_project: ToxProjectCreator) -> None:
     assert "# !!! unused: " not in outcome.out, outcome.out
 
 
+def test_config_in_toml_explicit_mentioned(tox_project: ToxProjectCreator) -> None:
+    project = tox_project({
+        "pyproject.toml": """
+    [tool.tox.env_run_base]
+    description = "Do magical things"
+    commands = [
+        ["python", "--version"]
+    ]
+    """
+    })
+
+    outcome = project.run("l", "-c", "pyproject.toml")
+    outcome.assert_success()
+    assert "could not recognize config file pyproject.toml" not in outcome.out, outcome.out
+
+
 def test_config_in_toml_replace_default(tox_project: ToxProjectCreator) -> None:
     project = tox_project({"pyproject.toml": '[tool.tox.env_run_base]\ndescription = "{missing:miss}"'})
     outcome = project.run("c", "-k", "description")