fix: handle non-mapping YAML root in YamlConfigurationFileParser

[smuchow1962]

Summary

The host crashes at config-build time when an app-config folder contains a YAML file whose root is not a mapping.

I hit this running a real config: a Home Assistant !include target like automations.yaml whose content is a sequence root ([]) gets picked up by AddYamlAppConfig, and the parser casts the root unconditionally to a mapping. That throws InvalidCastException from inside HostBuilder.Build(), before the host (and any logging) is up, so the failure is opaque.

Repro

An app-config directory containing a YAML file with a sequence root:

# automations.yaml
[]

AddYamlAppConfig feeds it through YamlConfigurationFileParser, and (YamlMappingNode)RootNode throws during HostBuilder.Build().

Root cause

The parser guards only the zero-document case, then casts any root unconditionally to YamlMappingNode. A sequence root or a scalar root is a valid YAML document, so the cast throws instead of being handled.

Fix

A pattern-match guard. The configuration model is key/value pairs, so only a mapping root carries config data. A non-mapping root carries no key/value config, so it contributes nothing instead of throwing. This mirrors the existing empty-file guard right above it.

if (yaml.Documents[0].RootNode is not YamlMappingNode mapping) return _data;

Tests

Added regression cases to ConfigTests:

• sequence root ([]) — the automations.yaml case
• sequence root with items
• scalar root
• empty file

Each asserts the built configuration contributes no data instead of throwing.

Notes

Found by running a real config, not synthetically. Frank asked for the fix to be sent upstream.

I couldn't apply the pr: bugfix label from a fork — a maintainer may want to add it.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 82%. Comparing base (0116c98) to head (b17179a).

Additional details and impacted files

@@         Coverage Diff          @@
##           main   #1386   +/-   ##
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- Coverage    82%     82%   -1%     
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  Files       202     202           
  Lines      3941    3941           
  Branches    444     445    +1     
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- Hits       3240    3239    -1     
- Misses      531     532    +1     
  Partials    170     170           

Flag	Coverage Δ
unittests	82% <100%> (-1%)	⬇️

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