Make the project compatible with Towncrier >= 24.7

Towncrier 24.7 changed the way that its `find_fragments()` function
works to accept a `Config` dataclass instead of specific components of
the config. This commit adds a new version of the
`lookup_towncrier_fragments()` helper function to use the new API, and
chooses which one to use based on the version of Towncrier obtained from
`importlib.metadata`. It also slightly changes the way that Towncrier
config can be obtained: the previous `get_towncrier_config()` function
(which returned a `dict`) is now renamed as
`get_towncrier_config_as_dict()`, and `get_towncrier_config()` returns
the new `Config` dataclass object. This API change should be ok as
`get_towncrier_config()` was only called in one place before.

setup.cfg

@@ -52,6 +52,7 @@ classifiers =
 [options]
 include_package_data = True
 install_requires =
+  packaging
   sphinx
   towncrier >= 23
 package_dir =

src/sphinxcontrib/towncrier/_fragment_discovery.py

@@ -2,11 +2,14 @@
 
 
 from functools import lru_cache
+from importlib.metadata import version
 from pathlib import Path
 from typing import Optional, Set
 
 from sphinx.util import logging
 
+from packaging.version import Version
+
 
 try:
     # pylint: disable=no-name-in-module
@@ -17,7 +20,9 @@
         find_fragments,
     )
 
-from ._towncrier import get_towncrier_config  # noqa: WPS436
+from ._towncrier import (  # noqa: WPS436
+    get_towncrier_config, get_towncrier_config_as_dict,
+)
 
 
 logger = logging.getLogger(__name__)
@@ -42,11 +47,21 @@ def _find_config_file(base: Path) -> Path:
 # pylint: disable=fixme
 # FIXME: refactor `lookup_towncrier_fragments` to drop noqas
 @lru_cache(maxsize=1, typed=True)  # noqa: WPS210
-def lookup_towncrier_fragments(  # noqa: WPS210
+def lookup_towncrier_fragments(
         working_dir: Optional[str] = None,
         config_path: Optional[str] = None,
 ) -> Set[Path]:
     """Emit RST-formatted Towncrier changelog fragment paths."""
+    tc_version = Version(version('towncrier'))
+    if tc_version >= Version('24.7.0'):
+        return _lookup_towncrier_fragments_post24_7(working_dir, config_path)
+    return _lookup_towncrier_fragments_pre24_7(working_dir, config_path)
+
+
+# used for towncrier version 24.7 and above
+def _lookup_towncrier_fragments_post24_7(  # noqa: WPS210
+    working_dir: Optional[str] = None, config_path: Optional[str] = None,
+) -> Set[Path]:
     project_path = Path.cwd() if working_dir is None else Path(working_dir)
 
     final_config_path = (
@@ -66,6 +81,39 @@ def lookup_towncrier_fragments(  # noqa: WPS210
         )
         return set()
 
+    fragment_dir = (towncrier_config.directory or 'newsfragments')
+    fragment_base_directory = project_path / fragment_dir
+
+    _fragments, fragment_filenames = find_fragments(
+        str(fragment_base_directory), towncrier_config, strict=False,
+    )
+
+    return {Path(fname[0]) for fname in fragment_filenames}
+
+
+# used for versions of towncrier before 24.7
+def _lookup_towncrier_fragments_pre24_7(  # noqa: WPS210
+    working_dir: Optional[str] = None, config_path: Optional[str] = None,
+) -> Set[Path]:
+    project_path = Path.cwd() if working_dir is None else Path(working_dir)
+
+    final_config_path = (
+        _resolve_spec_config(project_path, config_path)
+        or _find_config_file(project_path)
+    )
+
+    try:
+        towncrier_config = get_towncrier_config_as_dict(
+            project_path,
+            final_config_path,
+        )
+    except KeyError as key_err:
+        # NOTE: The error is missing key 'towncrier' or similar
+        logger.warning(
+            f'Missing key {key_err!s} in file {final_config_path!s}',
+        )
+        return set()
+
     fragment_directory: Optional[str] = 'newsfragments'
     try:
         fragment_base_directory = project_path / towncrier_config['directory']

src/sphinxcontrib/towncrier/_towncrier.py

@@ -8,10 +8,18 @@
 
 
 def get_towncrier_config(
+    project_path: Path,
+    final_config_path: Union[Path, None],
+) -> Any:
+    """Return the towncrier config in native format."""
+    return load_config_from_file(str(project_path), str(final_config_path))
+
+
+def get_towncrier_config_as_dict(
         project_path: Path,
         final_config_path: Union[Path, None],
 ) -> Dict[str, Any]:  # FIXME: add a better type  # pylint: disable=fixme
     """Return the towncrier config dictionary."""
-    config = load_config_from_file(str(project_path), str(final_config_path))
+    native_config = get_towncrier_config(project_path, final_config_path)
 
-    return _dataclass_to_dict(config)
+    return _dataclass_to_dict(native_config)