Implement declarative config for compatibility with setuptools declarative config

setup.py

@@ -68,6 +68,9 @@ def parse(root):
         [setuptools.file_finders]
         setuptools_scm = setuptools_scm.integration:find_files
 
+        [setuptools.finalize_distribution_options]
+        setuptools_scm = setuptools_scm.integration:infer_version
+
         [setuptools_scm.parse_scm]
         .hg = setuptools_scm.hg:parse
         .git = setuptools_scm.git:parse
@@ -111,6 +114,7 @@ def parse(root):
         "Topic :: Utilities",
     ],
     python_requires=">=2.7, !=3.0.*, !=3.1.*, !=3.2.*, !=3.3.*",
+    extras_require=dict(toml=["toml"]),
 )
 
 if __name__ == "__main__":

src/setuptools_scm/__init__.py

@@ -146,18 +146,23 @@ def get_version(
     config.fallback_version = fallback_version
     config.parse = parse
     config.git_describe_command = git_describe_command
+    return _get_version(config)
 
+
+def _get_version(config):
     parsed_version = _do_parse(config)
 
     if parsed_version:
         version_string = format_version(
-            parsed_version, version_scheme=version_scheme, local_scheme=local_scheme
+            parsed_version,
+            version_scheme=config.version_scheme,
+            local_scheme=config.local_scheme,
         )
         dump_version(
-            root=root,
+            root=config.root,
             version=version_string,
-            write_to=write_to,
-            template=write_to_template,
+            write_to=config.write_to,
+            template=config.write_to_template,
         )
 
         return version_string

src/setuptools_scm/config.py

@@ -105,3 +105,19 @@ def tag_regex(self):
     @tag_regex.setter
     def tag_regex(self, value):
         self._tag_regex = _check_tag_regex(value)
+
+    def _load(self, values):
+        vars(self).update(values)
+        return self
+
+    @classmethod
+    def from_file(cls, name="pyproject.toml"):
+        """
+        Read Configuration from pyproject.toml (or similar).
+        Raises exceptions when file is not found or toml is
+        not installed or the file has invalid format or does
+        not contain the [tool.setuptools_scm] section.
+        """
+        with open(name) as strm:
+            defn = __import__("toml").load(strm)
+        return cls()._load(defn.get("tool", {})["setuptools_scm"])

src/setuptools_scm/integration.py

@@ -1,8 +1,9 @@
 from pkg_resources import iter_entry_points
 
 from .version import _warn_if_setuptools_outdated
-from .utils import do
-from . import get_version
+from .config import Configuration
+from .utils import do, trace_exception
+from . import get_version, _get_version
 
 
 def version_keyword(dist, keyword, value):
@@ -28,3 +29,11 @@ def find_files(path=""):
         if res:
             return res
     return []
+
+
+def infer_version(dist):
+    try:
+        config = Configuration.from_file()
+    except Exception:
+        return trace_exception()
+    dist.metadata.version = _get_version(config)

src/setuptools_scm/utils.py

@@ -10,6 +10,7 @@
 import os
 import io
 import platform
+import traceback
 
 
 DEBUG = bool(os.environ.get("SETUPTOOLS_SCM_DEBUG"))
@@ -25,6 +26,10 @@ def trace(*k):
         sys.stdout.flush()
 
 
+def trace_exception():
+    DEBUG and traceback.print_exc()
+
+
 def ensure_stripped_str(str_or_bytes):
     if isinstance(str_or_bytes, str):
         return str_or_bytes.strip()

testing/test_config.py

@@ -1,3 +1,5 @@
+from __future__ import unicode_literals
+
 from setuptools_scm.config import Configuration
 
 import pytest
@@ -18,3 +20,9 @@ def test_tag_regex(tag, expected_version):
     match = config.tag_regex.match(tag)
     version = match.group("version")
     assert version == expected_version
+
+
+def test_config_from_pyproject(tmpdir):
+    fn = tmpdir / "pyproject.toml"
+    fn.write_text("[tool.setuptools_scm]\n", encoding="utf-8")
+    assert Configuration.from_file(str(fn))

testing/test_integration.py

@@ -0,0 +1,16 @@
+import sys
+
+from setuptools_scm.utils import do
+
+
+def test_pyproject_support(tmpdir, monkeypatch):
+    monkeypatch.delenv("SETUPTOOLS_SCM_DEBUG")
+    pkg = tmpdir.ensure("package", dir=42)
+    pkg.join("pyproject.toml").write(
+        """[tool.setuptools_scm]
+fallback_version = "12.34"
+"""
+    )
+    pkg.join("setup.py").write("__import__('setuptools').setup()")
+    res = do((sys.executable, "setup.py", "--version"), pkg)
+    assert res == "12.34"

tox.ini

@@ -25,9 +25,12 @@ skip_install=
     test: False
 deps=
     pytest
+    setuptools >= 42
 commands=
     test: py.test []
     selfcheck: python setup.py --version
+extras =
+    toml
 
 [testenv:flake8]
 skip_install=True