Add support for doc_id in properties (#755)

Author: delvedor

compiler/model/metamodel.ts

@@ -125,6 +125,7 @@ export class Property {
   required: boolean
   description?: string
   docUrl?: string
+  docId?: string
   since?: string
   serverDefault?: boolean | string | number
   deprecation?: Deprecation

compiler/model/utils.ts

@@ -661,7 +661,7 @@ function hoistPropertyAnnotations (property: model.Property, jsDocs: JSDoc[]): v
   // We want to enforce a single jsDoc block.
   assert(jsDocs, jsDocs.length < 2, 'Use a single multiline jsDoc block instead of multiple single line blocks')
 
-  const validTags = ['stability', 'prop_serializer', 'doc_url', 'aliases', 'identifier', 'since', 'server_default', 'variant']
+  const validTags = ['stability', 'prop_serializer', 'doc_url', 'aliases', 'identifier', 'since', 'server_default', 'variant', 'doc_id']
   const tags = parseJsDocTags(jsDocs)
   if (jsDocs.length === 1) {
     const description = jsDocs[0].getDescription()
@@ -680,6 +680,9 @@ function hoistPropertyAnnotations (property: model.Property, jsDocs: JSDoc[]): v
     } else if (tag === 'since') {
       assert(jsDocs, semver.valid(value), `${property.name}'s @since is not valid semver: ${value}`)
       property.since = value
+    } else if (tag === 'doc_id') {
+      assert(jsDocs, value.trim() !== '', `Property ${property.name}'s @doc_id is cannot be empty`)
+      property.docId = value
     } else if (tag === 'server_default') {
       assert(jsDocs, property.type.kind === 'instance_of' || property.type.kind === 'union_of', `Default values can only be configured for instance_of or union_of types, you are using ${property.type.kind}`)
       assert(jsDocs, !property.required, 'Default values can only be specified on optional properties')