build: switch to tomli for TOML v1 compliant parser

Fixes #308

Signed-off-by: Filipe Laíns <lains@riseup.net>

CHANGELOG.rst

@@ -9,6 +9,7 @@ Unreleased
 - Improved output (`PR #333`_, Fixes `#142`_)
 - The CLI now honnors `NO_COLOR`_ (`PR #333`_)
 - Added logging to ``build`` and ``build.env`` (`PR #333`_)
+- Switch to a TOML v1 compliant parser (`PR #336`_, Fixes `#308`_)
 
 
 Breaking Changes
@@ -17,7 +18,9 @@ Breaking Changes
 - Dropped support for Python 2 and 3.5.
 
 .. _PR #333: https://github.com/pypa/build/pull/333
+.. _PR #336: https://github.com/pypa/build/pull/336
 .. _#142: https://github.com/pypa/build/issues/142
+.. _#308: https://github.com/pypa/build/issues/308
 .. _NO_COLOR: https://no-color.org
 
 

docs/installation.rst

@@ -37,6 +37,9 @@ This package can build itself with only the ``toml`` and ``pep517``
 dependencies. The ``--skip-dependency-check`` flag should be used in this
 case.
 
+We have a dependency on tomli_, but toml_ can be used instead, which may make
+bootstraping easier.
+
 
 Compatibility
 =============
@@ -66,6 +69,9 @@ versions:
 .. _git tag: https://github.com/pypa/build/tags
 .. _project page: https://pypi.org/project/build/
 
+.. _tomli: https://github.com/hukkin/tomli
+.. _toml: https://github.com/uiri/toml
+
 
 .. |3DCE51D60930EBA47858BA4146F633CBB0EB4BF2| replace:: ``3DCE51D60930EBA47858BA4146F633CBB0EB4BF2``
 .. _3DCE51D60930EBA47858BA4146F633CBB0EB4BF2: https://keyserver.ubuntu.com/pks/lookup?op=get&search=0x3dce51d60930eba47858ba4146f633cbb0eb4bf2

setup.cfg

@@ -27,7 +27,7 @@ packages = find:
 install_requires =
     packaging>=19.0
     pep517>=0.9.1
-    toml>=0.10.0
+    tomli>=1.0.0 # toml can be used instead
     colorama;os_name == "nt" # not actually a runtime dependency, only supplied as there is not "recomended dependency" support
     importlib-metadata>=0.22;python_version < "3.8"
 python_requires = >=3.6

src/build/__init__.py

@@ -20,7 +20,17 @@
 from typing import AbstractSet, Any, Callable, Dict, Iterator, Mapping, Optional, Sequence, Set, Tuple, Type, Union
 
 import pep517.wrappers
-import toml
+
+
+try:
+    import tomli as toml
+
+    TOMLDecodeError: Type[Exception] = toml.TOMLDecodeError
+except ModuleNotFoundError:  # pragma: no cover
+    import toml as _toml
+
+    toml = _toml  # type: ignore
+    TOMLDecodeError = _toml.TomlDecodeError
 
 
 RunnerType = Callable[[Sequence[str], Optional[str], Optional[Mapping[str, str]]], None]
@@ -191,7 +201,7 @@ def __init__(
             spec = {}
         except PermissionError as e:
             raise BuildException(f"{e.strerror}: '{e.filename}' ")
-        except toml.TomlDecodeError as e:
+        except TOMLDecodeError as e:
             raise BuildException(f'Failed to parse {spec_file}: {e} ')
 
         build_system = spec.get('build-system')