Returns a validation error message, or undefined if the contribution is valid. Mirrors VS Code validateGrammarExtensionPoint manifest checks (without language registry lookup), plus a path-containment guard against escaping the plugin directory.
undefined
validateGrammarExtensionPoint
Returns a validation error message, or
undefinedif the contribution is valid. Mirrors VS CodevalidateGrammarExtensionPointmanifest checks (without language registry lookup), plus a path-containment guard against escaping the plugin directory.