automations: fix parse error on !lambda-tagged scalars

[marcelveldt]

What does this implement/fix?

Opening an existing automation in the editor failed with internal_error: Command failed: automations/parse for any device YAML that uses !lambda-tagged scalars (e.g. delay: !lambda return 0; or a lambda: !lambda | block). The automations/parse handler ran fine, but the response carried a ruamel TaggedScalar object straight into orjson.dumps, which raised TypeError: Type is not JSON serializable: TaggedScalar.

Root cause: _render_value in controllers/automations/parsing.py checked for a .yaml_tag attribute, but ruamel 0.18+ surfaces tagged scalars as TaggedScalar instances with the tag at .tag.value. The check never matched, so tagged scalars fell through unchanged.

• detect TaggedScalar in _render_value and route !lambda through the existing {"_lambda": ...} sentinel
• fall back to the plain string value for any other tag so the parse response stays JSON-serialisable
• add a fixture + regression test covering a !lambda plain scalar and a !lambda | block, asserting the full payload round-trips through orjson.dumps
• replace the synthetic-stand-in branch test with one driven by a real ruamel-produced TaggedScalar, plus a fallback-to-string case for an unknown tag

Related issue or feature (if applicable):

n/a

Types of changes

• Bugfix (non-breaking change which fixes an issue) — bugfix
• New feature (non-breaking change which adds functionality) — new-feature
• Enhancement to an existing feature — enhancement
• Breaking change (fix or feature that would cause existing functionality to not work as expected) — breaking-change
• Refactor (no behaviour change) — refactor
• Documentation only — docs
• Maintenance / chore — maintenance
• CI / workflow change — ci
• Dependencies bump — dependencies

Frontend coordination

• No frontend change needed
• Companion frontend PR: esphome/device-builder-dashboard-frontend#

Checklist

• The code change is tested and works locally.
• Pre-commit hooks pass (ruff, codespell, yaml/json/python checks).
• Tests have been added or updated under tests/ where applicable.
• components.json has not been hand-edited (regenerate via script/sync_components.py if a sync is needed).
• Architecture-level changes are reflected in docs/ARCHITECTURE.md and/or docs/API.md.

[codspeed-hq]

Merging this PR will not alter performance

✅ 25 untouched benchmarks

---

_{Comparing fix-automations-parse-tagged-lambda-scalar (21b3946) with main (8a340ad)}

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 99.24%. Comparing base (8a340ad) to head (21b3946).

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #930   +/-   ##
=======================================
  Coverage   99.24%   99.24%           
=======================================
  Files         191      191           
  Lines       14197    14200    +3     
=======================================
+ Hits        14090    14093    +3     
  Misses        107      107           

Flag	Coverage Δ
py3.12	99.19% <100.00%> (+<0.01%)	⬆️
py3.14	99.24% <100.00%> (+<0.01%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
..._device_builder/controllers/automations/parsing.py	100.00% <100.00%> (ø)

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

[Copilot]

Pull request overview

Fixes automations/parse failing on YAML values tagged with !lambda by ensuring ruamel’s tagged scalar values are rendered into JSON-serializable shapes (either the existing {"_lambda": ...} sentinel for !lambda, or a plain string fallback for unknown tags). This aligns the automations editor backend response with orjson’s serialization requirements while preserving the existing lambda sentinel contract.

Changes:

• Update _render_value to detect ruamel TaggedScalar values and render !lambda as the {"_lambda": ...} sentinel, falling back to str(value) for other tags.
• Add a regression fixture + parse-level test covering both !lambda plain scalars and !lambda | block scalars, including an orjson.dumps round-trip assertion.
• Replace the prior synthetic tagged-scalar branch test with one that uses a real ruamel-produced tagged scalar, plus an “unknown tag falls back to string” test.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated no comments.

File	Description
esphome_device_builder/controllers/automations/parsing.py	Render ruamel TaggedScalar values into JSON-safe representations; preserve !lambda via the existing sentinel.
tests/test_automations_parse.py	Add end-to-end regression coverage for !lambda-tagged scalars and assert payload is orjson-serializable.
tests/test_automations_branches.py	Update branch tests to use real ruamel tagged scalars and validate unknown-tag fallback behavior.
tests/fixtures/automation_yamls/lambda_tagged_scalars.yaml	New fixture exercising !lambda plain scalar and `!lambda