Is it the YAML parser?

This extension heavily depends on an external package for parsing the YAML. Generic YAML errors/warnings originate from this package and the Home Assistant Extension propagates them to VS Code. Next to that, the Home Assistant extension validates your (valid) YAML against a schema which also can cause additional errors/warnings.

In some cases, errors/warnings are not correct because of an issue either in JPinkney/yaml-ast-parser or the Home Assistant Extension. To get a bug like this fixed, it has be be raised either in the YAML Parser or in the Home Assistant Extension (this repo). To see if the error/warning originates from the YAML Parser, update the language of the open file in VS Code from 'Home Assistant' to 'YAML'. Update the language of a file using ⌘K M or Ctrl+K M.

If VS Code still shows the error/warning when the language of the file is set to YAML, please raise an issue here: the YAML Parser.