build: drop toml fallback

CHANGELOG.rst

@@ -6,6 +6,9 @@ Changelog
 Unreleased
 ==========
 
+- Removed the ``toml`` library fallback; ``toml`` can no longer be used
+  as a substitute for ``tomli``.
+  (`PR #567`_)
 - Added ``runner`` parameter to ``util.project_wheel_metadata``
   (`PR #566`_, Fixes `#553`_)
 - Modified ``ProjectBuilder`` constructor signature,
@@ -20,6 +23,7 @@ Unreleased
 .. _#553: https://github.com/pypa/build/issues/553
 .. _PR #537: https://github.com/pypa/build/pull/537
 .. _PR #566: https://github.com/pypa/build/pull/566
+.. _PR #567: https://github.com/pypa/build/pull/567
 
 
 0.10.0 (2023-01-11)

pyproject.toml

@@ -36,7 +36,6 @@ dependencies = [
   # not actually a runtime dependency, only supplied as there is not "recommended dependency" support
   'colorama; os_name == "nt"',
   'importlib-metadata >= 0.22; python_version < "3.8"',
-  # toml can be used instead -- in case it makes bootstrapping easier
   'tomli >= 1.1.0; python_version < "3.11"',
 ]
 
@@ -54,7 +53,6 @@ test = [
   "pytest-mock >= 2",
   "pytest-rerunfailures >= 9.1",
   "pytest-xdist >= 1.34",
-  "toml >= 0.10.0",
   "wheel >= 0.36.0",
   'setuptools >= 42.0.0; python_version < "3.10"',
   'setuptools >= 56.0.0; python_version >= "3.10"',

src/build/__init__.py

@@ -34,19 +34,10 @@
 from ._util import check_dependency, parse_wheel_filename
 
 
-TOMLDecodeError: type[Exception]
-toml_loads: Callable[[str], Mapping[str, Any]]
-
 if sys.version_info >= (3, 11):
-    from tomllib import TOMLDecodeError
-    from tomllib import loads as toml_loads
+    import tomllib
 else:
-    try:
-        from tomli import TOMLDecodeError
-        from tomli import loads as toml_loads
-    except ModuleNotFoundError:  # pragma: no cover
-        from toml import TomlDecodeError as TOMLDecodeError  # type: ignore[import,no-redef]
-        from toml import loads as toml_loads  # type: ignore[no-redef]
+    import tomli as tomllib
 
 
 RunnerType = Callable[[Sequence[str], Optional[str], Optional[Mapping[str, str]]], None]
@@ -86,12 +77,12 @@ def _validate_source_directory(source_dir: PathType) -> None:
 def _read_pyproject_toml(path: PathType) -> Mapping[str, Any]:
     try:
         with open(path, 'rb') as f:
-            return toml_loads(f.read().decode())
+            return tomllib.loads(f.read().decode())
     except FileNotFoundError:
         return {}
     except PermissionError as e:
         raise BuildException(f"{e.strerror}: '{e.filename}' ")  # noqa: B904 # use raise from
-    except TOMLDecodeError as e:
+    except tomllib.TOMLDecodeError as e:
         raise BuildException(f'Failed to parse {path}: {e} ')  # noqa: B904 # use raise from
 
 

tests/constraints.txt

@@ -3,7 +3,6 @@ packaging==19.0
 pyproject_hooks==1.0
 setuptools==42.0.0; python_version < "3.10"
 setuptools==56.0.0; python_version >= "3.10"
-toml==0.10.0
 tomli==1.1.0
 virtualenv==20.0.35
 wheel==0.36.0

tests/test_projectbuilder.py

@@ -2,7 +2,6 @@
 
 
 import copy
-import importlib
 import logging
 import os
 import sys
@@ -540,31 +539,6 @@ def test_metadata_invalid_wheel(tmp_dir, package_test_bad_wheel):
         builder.metadata_path(tmp_dir)
 
 
-@pytest.fixture
-def mock_tomli_not_available(mocker):
-    loads = mocker.patch('tomli.loads')
-    mocker.patch.dict(sys.modules, {'tomli': None})
-    importlib.reload(build)
-    try:
-        yield
-    finally:
-        loads.assert_not_called()
-        mocker.stopall()
-        importlib.reload(build)
-
-
-@pytest.mark.skipif(sys.version_info >= (3, 11), reason='No need to test old toml support on 3.11+')
-def test_toml_instead_of_tomli(mocker, mock_tomli_not_available, tmp_dir, package_test_flit):
-    mocker.patch('pyproject_hooks.BuildBackendHookCaller', autospec=True)
-
-    builder = build.ProjectBuilder(package_test_flit)
-    builder._hook.build_sdist.return_value = 'dist.tar.gz'
-
-    builder.build('sdist', '.')
-
-    builder._hook.build_sdist.assert_called_with(os.path.abspath('.'), None)
-
-
 def test_log(mocker, caplog, package_test_flit):
     mocker.patch('pyproject_hooks.BuildBackendHookCaller', autospec=True)
     mocker.patch('build.ProjectBuilder._call_backend', return_value='some_path')