DSC Resource declared in `yaml` not discovered if `schema:` is present and not working if `schema:` is absent. about dsc

[michaeltlombardi]

@joshcorr, the implication in the example document that the schema keyword isn't required is a mistake on my part. I originally created that example to show how users and authors could edit the data files with IntelliSense and validation provided by the JSON Schemas. I'll update that example shortly to be more correct, I can see how the missing key implies that it's not required.

I did some testing, and the following definition is discoverable and functional, but fails our schema validation:

$schema:     https://raw.githubusercontent.com/PowerShell/DSC/main/schemas/2023/10/bundled/resource/manifest.vscode.json
type:        Example/Foo
version:     0.1.0
description: An example resource to manage the foo application.
tags:
  - foo
get:
  executable:  foo
  args:       [get]
  input:      stdin
set:
  executable: foo
  input:      stdin
  preTest:    false
  return:     state
schema:
  !command
  executable:  foo
  args:       [schema]

Note that for DSC to correctly parse the data from YAML, you have to use the !<tag> syntax, whereas in JSON you embed the data by the <tag> keyword - in this case, command:

{
  // ... rest of the manifest
  "schema": {
    "command": { "executable": "foo", "args": ["schema"] }
  }
}

# ... rest of the manifest
schema:
  !command
  executable:  foo
  args:       [schema]

This is non-intuitive, and difficult to represent with a shared schema (and VS Code will complain that !command, !url, and !embedded are unknown tags).

I believe the fix is to use the serde_yaml::with::singleton_map customization - the example seem to show the behavior we want.