Refactor Section config to use NamedTuple

Users configure the sections as a List[List[str]]. That continues
to be the case.

But now we parse that raw list into a list of a NamedTuple
called Section. This makes our consuming code, `formatter.py`
and `linter.py` more clear because we can access the values
by name, rather than index.

But more importantly, this is a "prefactor" to add support
for nested headers. In a followup, we will add the field
'top_level: bool' so that `formatter.py` can know how to
render the section. This factoring simplifies that
change.

Change-Id: Ie80a525af61e879dd872079b2b9d0513db40e82d

reno/config.py

@@ -10,10 +10,12 @@
 # License for the specific language governing permissions and limitations
 # under the License.
 
-import collections
 import logging
 import os.path
 import textwrap
+from typing import Any
+from typing import List
+from typing import NamedTuple
 
 import yaml
 
@@ -22,7 +24,20 @@ from reno import defaults
 LOG = logging.getLogger(__name__)
 
 
-Opt = collections.namedtuple('Opt', 'name default help')
+class Opt(NamedTuple):
+    name: str
+    default: Any
+    help: str
+
+
+class Section(NamedTuple):
+    name: str
+    title: str
+
+    @classmethod
+    def from_raw_yaml(cls, val: List[List[str]]) -> List["Section"]:
+        return [Section(*entry) for entry in val]
+
 
 _OPTIONS = [
     Opt('notesdir', defaults.NOTES_SUBDIR,
@@ -219,13 +234,13 @@ _OPTIONS = [
 ]
 
 
-class Config(object):
+class Config:
 
     _OPTS = {o.name: o for o in _OPTIONS}
 
     @classmethod
     def get_default(cls, opt):
-        "Return the default for an option."
+        """Return the default for an option."""
         try:
             return cls._OPTS[opt].default
         except KeyError:
@@ -301,12 +316,14 @@ class Config(object):
         # Replace prelude section name if it has been changed.
         self._rename_prelude_section(**kwds)
 
-        for n, v in kwds.items():
+        for name, val in kwds.items():
-            if n not in self._OPTS:
+            if name not in self._OPTS:
                 LOG.warning('ignoring unknown configuration value %r = %r',
-                            n, v)
+                            name, val)
             else:
-                setattr(self, n, v)
+                if name == "sections":
+                    val = Section.from_raw_yaml(val)
+                setattr(self, name, val)
 
     def override_from_parsed_args(self, parsed_args):
         """Set the values of the configuration options from parsed CLI args.

reno/formatter.py

@@ -94,19 +94,19 @@ def format_report(loader, config, versions_to_include, title=None,
             report.append('')
 
         # Add other sections.
-        for section_name, section_title in config.sections:
+        for section in config.sections:
             notes = [
                 (n, fn, sha)
                 for fn, sha in notefiles
-                if file_contents[fn].get(section_name)
+                if file_contents[fn].get(section.name)
-                for n in file_contents[fn].get(section_name, [])
+                for n in file_contents[fn].get(section.name, [])
             ]
             if notes:
                 report.append(_section_anchor(
-                    section_title, version_title, title, branch))
+                    section.title, version_title, title, branch))
                 report.append('')
-                report.append(section_title)
+                report.append(section.title)
-                report.append('-' * len(section_title))
+                report.append('-' * len(section.title))
                 report.append('')
                 for n, fn, sha in notes:
                     if show_source:

reno/linter.py

@@ -21,14 +21,14 @@ LOG = logging.getLogger(__name__)
 
 
 def lint_cmd(args, conf):
-    "Check some common mistakes"
+    """Check some common mistakes"""
     LOG.debug('starting lint')
     notesdir = os.path.join(conf.reporoot, conf.notespath)
     notes = glob.glob(os.path.join(notesdir, '*.yaml'))
 
     error = 0
     allowed_section_names = [conf.prelude_section_name] + \
-                            [s[0] for s in conf.sections]
+                            [s.name for s in conf.sections]
 
     uids = {}
     with loader.Loader(conf, ignore_cache=True) as ldr:

reno/loader.py

@@ -143,6 +143,9 @@ class Loader(object):
                 f'mapping. Did you forget a top-level key?'
             )
 
+        valid_section_names = {
+            section.name for section in self._config.sections
+        }
         for section_name, section_content in content.items():
             if section_name == self._config.prelude_section_name:
                 if not isinstance(section_content, str):
@@ -152,14 +155,14 @@ class Loader(object):
                         section_name, filename,
                     )
             else:
-                if section_name not in dict(self._config.sections):
+                if section_name not in valid_section_names:
                     # TODO(stephenfin): Make this an error in a future release
                     LOG.warning(
                         'The %s section of %s is not a recognized section. '
                         'It should be one of: %s. '
                         'This will be an error in a future release.',
                         section_name, filename,
-                        ', '.join(dict(self._config.sections)),
+                        ', '.join(valid_section_names),
                     )
                 if isinstance(section_content, str):
                     # A single string is OK, but wrap it with a list

reno/tests/test_config.py

@@ -18,11 +18,26 @@ from unittest import mock
 import fixtures
 
 from reno import config
+from reno.config import Section
 from reno import defaults
 from reno import main
 from reno.tests import base
 
 
+def expected_options(**overrides):
+    """The default config options, along with any overrides set via kwargs."""
+    result = {
+        o.name: (
+            Section.from_raw_yaml(o.default)
+            if o.name == "sections"
+            else o.default
+        )
+        for o in config._OPTIONS
+    }
+    result.update(**overrides)
+    return result
+
+
 class TestConfig(base.TestCase):
     EXAMPLE_CONFIG = """
 collapse_pre_releases: false
@@ -36,11 +51,7 @@ collapse_pre_releases: false
     def test_defaults(self):
         c = config.Config(self.tempdir.path)
         actual = c.options
-        expected = {
+        self.assertEqual(expected_options(), actual)
-            o.name: o.default
-            for o in config._OPTIONS
-        }
-        self.assertEqual(expected, actual)
 
     def test_override(self):
         c = config.Config(self.tempdir.path)
@@ -48,11 +59,7 @@ collapse_pre_releases: false
             collapse_pre_releases=False,
         )
         actual = c.options
-        expected = {
+        expected = expected_options(collapse_pre_releases=False)
-            o.name: o.default
-            for o in config._OPTIONS
-        }
-        expected['collapse_pre_releases'] = False
         self.assertEqual(expected, actual)
 
     def test_override_multiple(self):
@@ -64,11 +71,7 @@ collapse_pre_releases: false
             notesdir='value2',
         )
         actual = c.options
-        expected = {
+        expected = expected_options(notesdir='value2')
-            o.name: o.default
-            for o in config._OPTIONS
-        }
-        expected['notesdir'] = 'value2'
         self.assertEqual(expected, actual)
 
     def test_load_file_not_present(self):
@@ -127,22 +130,14 @@ collapse_pre_releases: false
             o.name: getattr(c, o.name)
             for o in config._OPTIONS
         }
-        expected = {
+        self.assertEqual(expected_options(), actual)
-            o.name: o.default
-            for o in config._OPTIONS
-        }
-        self.assertEqual(expected, actual)
 
     def test_override_from_parsed_args_boolean_false(self):
         c = self._run_override_from_parsed_args([
             '--no-collapse-pre-releases',
         ])
         actual = c.options
-        expected = {
+        expected = expected_options(collapse_pre_releases=False)
-            o.name: o.default
-            for o in config._OPTIONS
-        }
-        expected['collapse_pre_releases'] = False
         self.assertEqual(expected, actual)
 
     def test_override_from_parsed_args_boolean_true(self):
@@ -150,11 +145,7 @@ collapse_pre_releases: false
             '--collapse-pre-releases',
         ])
         actual = c.options
-        expected = {
+        expected = expected_options(collapse_pre_releases=True)
-            o.name: o.default
-            for o in config._OPTIONS
-        }
-        expected['collapse_pre_releases'] = True
         self.assertEqual(expected, actual)
 
     def test_override_from_parsed_args_string(self):
@@ -162,11 +153,7 @@ collapse_pre_releases: false
             '--earliest-version', '1.2.3',
         ])
         actual = c.options
-        expected = {
+        expected = expected_options(earliest_version='1.2.3')
-            o.name: o.default
-            for o in config._OPTIONS
-        }
-        expected['earliest_version'] = '1.2.3'
         self.assertEqual(expected, actual)
 
     def test_override_from_parsed_args_ignore_non_options(self):