Consolidate sections.yaml + areas.yaml into single changelogs/changelogs.yaml

[Copilot]

Replaces the two separate changelogs/sections.yaml and changelogs/areas.yaml config files with a single changelogs/changelogs.yaml. Clean cutover — no fallback, no legacy file support, no deprecation path.

New file shape:

sections:
  bug_fixes:
    title: Bug Fixes
    description: |
      *Changes expected to improve the state of the world...*
areas:
  router:
    title: router
  tls:
    title: tls

envoy.base.utils

• typing.py: adds ChangelogConfigDict (total=False, keys sections: ChangelogSectionsDict, areas: ChangelogAreasDict)
• changelog.py:
  • CHANGELOG_SECTIONS_PATH + CHANGELOG_AREAS_PATH → CHANGELOG_CONFIG_PATH = "changelogs/changelogs.yaml"
  • New config cached property loads the combined file; raises ChangelogError on ReaderError, logs warning and returns partial value on TypeCastingError
  • sections / areas become thin views: config["sections"] and cast(..., config.get("areas", {})) — missing areas section is silently empty, missing sections surfaces naturally as KeyError
  • sections_path / areas_path → single config_path
  • validate_sections error message updated to reference changelogs/changelogs.yaml

envoy.code.check

• Import fallback updated: CHANGELOG_AREAS_PATH → CHANGELOG_CONFIG_PATH
• CHANGELOG_AREAS_FILE → CHANGELOG_CONFIG_FILE
• Error messages in check_entry_filename and check_areas_file now cite changelogs/changelogs.yaml

Tests

• Old sections / areas unit tests (which patched from_yaml directly) replaced with: one config property test covering all error paths + thin-view tests for sections and areas
• sections_path / areas_path tests replaced by config_path
• Integration fixture updated to write changelogs/changelogs.yaml with sections: top-level key
• check_areas_file expected strings updated from changelogs/areas.yaml → changelogs/changelogs.yaml

Original prompt

Background

Stacked on PR #4560 (branch copilot/add-areas-yaml-validation), which adds validation for changelogs/areas.yaml.

We want to consolidate changelogs/sections.yaml and changelogs/areas.yaml into a single config file: changelogs/changelogs.yaml.

This is an in-tree managed config consumed only by toolshed + envoy. No external consumers. The plan PR (envoy#45093) introducing areas.yaml hasn't merged yet, and sections.yaml only lives in envoy. So we do a clean cutover — no back-compat, no fallback to legacy paths, no deprecation warnings, no migration period. After this PR lands, sections.yaml and areas.yaml are simply no longer read by toolshed.

Scope (this PR — stacked on copilot/add-areas-yaml-validation)

File format

New file changelogs/changelogs.yaml with two top-level keys, each a mapping of registry-key → entry-with-title (and optional description for sections):

sections:
  bug_fixes:
    title: Bug Fixes
    description: |
      *Changes expected to improve the state of the world and are unlikely to have negative effects.*
  new_features:
    title: New Features
  # ...

areas:
  router:
    title: router
  tls:
    title: tls
  # ...

Toolshed changes — py/envoy.base.utils/envoy/base/utils/abstract/project/changelog.py

• Replace CHANGELOG_SECTIONS_PATH = "changelogs/sections.yaml" with CHANGELOG_CONFIG_PATH = "changelogs/changelogs.yaml".
• Delete the CHANGELOG_AREAS_PATH constant added in PR Add areas.yaml validation to changelog checker (file integrity + entry prefix mapping) #4560 (since the base branch this PR stacks on adds it).
• Add a config cached property on AChangelogs that reads changelogs/changelogs.yaml and returns a typed dict with sections and areas keys.
  • On ReaderError → raise ChangelogError (same as the existing sections property does).
  • On TypeCastingError → log a warning and return the partial value (same as existing sections behaviour).
• Rewrite sections and areas cached properties to be thin views: return self.config["sections"] and return self.config.get("areas", {}) respectively. (Areas-section absent in config → empty dict is fine; sections must be present, otherwise validation downstream will fail naturally.)
• Replace sections_path property with a config_path property pointing at the new file. Delete the areas_path property added in PR Add areas.yaml validation to changelog checker (file integrity + entry prefix mapping) #4560.
• Error messages that referenced changelogs/sections.yaml or changelogs/areas.yaml (in validate_sections, and in the new area checks from Add areas.yaml validation to changelog checker (file integrity + entry prefix mapping) #4560) should now reference changelogs/changelogs.yaml.

Toolshed changes — py/envoy.base.utils/envoy/base/utils/typing.py

• Add a ChangelogConfigDict typing entry (a TypedDict with sections: ChangelogSectionsDict and areas: ChangelogAreasDict keys; both can stay defined as they are).

Toolshed changes — py/envoy.code.check/envoy/code/check/abstract/changelog.py

• The check_areas_file / check_config_file method added in PR Add areas.yaml validation to changelog checker (file integrity + entry prefix mapping) #4560 keeps the same checks (duplicate titles, valid title chars, valid key chars) but now operates against the loaded config's areas section and reports changelogs/changelogs.yaml as the source path.
• The "always run" gating from Add areas.yaml validation to changelog checker (file integrity + entry prefix mapping) #4560 (currently gated on areas.yaml existing) should now gate on changelogs/changelogs.yaml existing AND containing an areas section. Without an areas section → skip area-prefix validation in check_entry_filename, skip check_config_file entirely (no errors).

Tests

• Update all tests in py/envoy.base.utils/tests/test_abstract_project_changelogs.py and py/envoy.code.check/tests/test_abstract_changelog.py that reference sections.yaml, areas.yaml, CHANGELOG_SECTIONS_PATH, CHANGELOG_AREAS_PATH, sections_path, areas_path to use the new changelogs.yaml / CHANGELOG_CONFIG_PATH / config_path.
• Update integration test fixtures (e.g. anything writing a sections.yaml to tmp_path like test_abstract_changelog_data_unknown_section) to write the consolidated changelogs.yaml instead.
• Add tests for the new config cached property: missing file → ChangelogError (NOT silent — it's a required config now); valid file → parsed dict; unparseable → ChangelogError; type-cast warning path → returns partial value.
• Test sections and areas are correctly extracted from config.

Out of scope (do NOT do in this PR)

• Do NOT add fallback to legacy sections.yaml or areas.yaml.
• Do NOT log deprecation warnings.
• Do NOT add area validation to the parse path (get_data_from_entries).
• Do NOT touch envoy repo. The envoy-side migration (creating changelogs/changelogs.yaml, deleting changelogs/sections.yaml, updating docs/BUILD genrule tools list, dropping areas.yaml from in-flight envoy#45093) is a coordinated follow-up that happens once this toolshed PR is published in a wheel.

Base branch

This PR is stacked on copilot/add-areas-yaml-validation (PR #4560). Base it on that branch. The diff this PR introduces sho...

This pull request was created from Copilot chat.