add nested decoder

api/resource.rb

@@ -53,6 +53,11 @@ module Properties
       # list.  Otherwise, it's safe to leave empty.
       # If empty, we assume that `name` is the identifier.
       attr_reader :identity
+      # This is useful in case you need to change the query made for
+      # GET requests only. In particular, this is often used
+      # to extract an object from a parent object or a collection.
+      attr_reader :nested_decoder
+
       attr_reader :exclude
       attr_reader :async
       attr_reader :readonly
@@ -100,6 +105,18 @@ def validate
       end
     end
 
+    class NestedDecoder < Api::Object
+      attr_reader :keys
+      attr_reader :has_id_only_list
+
+      def validate
+        super
+
+        check :keys, type: Array, item_type: String, required: true
+        check :has_id_only_list, type: :boolean, default: false
+      end
+    end
+
     # Represents a response from the API that returns a list of objects.
     class ResponseList < Api::Object
       attr_reader :kind
@@ -190,6 +207,11 @@ def validate
       check :transport, type: Transport
       check :references, type: ReferenceLinks
 
+      check :nested_decoder, type: Api::Resource::NestedDecoder
+      if @nested_decoder&.has_id_only_list && @identity&.length != 1
+        raise 'Resource with :has_id_only_list in :nested_decoder must have exactly one :identity property"'
+      end
+
       check :collection_url_response, default: Api::Resource::ResponseList.new,
                                       type: Api::Resource::ResponseList
 

templates/terraform/nested_decoder.go.erb

@@ -0,0 +1,55 @@
+	config := meta.(*Config)
+
+	var v interface{}
+	var ok bool
+<% object.nested_decoder.keys[0...-1].each do |k| -%>
+	v, ok = res["<%=k-%>"]
+	if !ok || v == nil {
+		return nil, nil
+	}
+	res = v.(map[string]interface{})
+<% end -%>
+	v, ok = res["<%=object.nested_decoder.keys[-1]-%>"]
+	if !ok || v == nil {
+		return nil, nil
+	}
+	// Final nested resource is either a list of resources we need to filter
+	// or just the resource itself, which we return.
+	switch v.(type) {
+	case []interface{}:
+		break
+	case map[string]interface{}:
+		return v.(map[string]interface{}), nil
+	default:
+		return nil, fmt.Errorf("invalid value for <%= object.nested_decoder.keys.join(".") -%>: %v", v)
+	}
+
+	items := v.([]interface{})
+	for _, vRaw := range items {
+	<% if object.nested_decoder.has_id_only_list -%>
+		// If only an id is given in parent resource,
+		// construct a resource map for that id KV pair.
+		item := map[string]interface{}{"<%=object.identity.first.api_name%>": vRaw}
+	<% else %>
+		item := vRaw.(map[string]interface{})
+	<% end %>
+
+	<% object.identity.each do |prop| -%>
+	<% if settable_properties.include?(prop) -%>
+		id, err := expand<%= resource_name -%><%= titlelize_property(prop) -%>(d.Get("<%= prop.name.underscore -%>"), d, config)
+		if err != nil {
+			return nil, err
+		}
+	<% else -%>
+		id := d.Get("<%= prop.name.underscore -%>")
+	<% end # settable_properties.include?(prop)-%>
+
+		itemId := flatten<%= resource_name -%><%= titlelize_property(prop) -%>(item["<%= prop.api_name %>"], d)
+		log.Printf("[DEBUG] Checking equality of %#v, %#v", itemId, id)
+		if !reflect.DeepEqual(itemId, id) {
+			continue
+		}
+	<% end # object.identity.each -%>
+		return item, nil
+	}
+	return nil, nil

templates/terraform/resource.erb

@@ -217,15 +217,19 @@ func resource<%= resource_name -%>Read(d *schema.ResourceData, meta interface{})
         return handleNotFoundError(err, d, fmt.Sprintf("<%= resource_name -%> %q", d.Id()))
     }
 
-<%  unless object.self_link_query.nil? -%>
-<%#     This part of the template extracts the one resource we're interested in
-        from the list that gets returned.  self_link_query is a field which
-        describes a list result from a read. -%>
-<%=     compile_template('templates/terraform/self_link_query.erb',
-                         object: object,
-                         settable_properties: object.settable_properties,
-                         resource_name: resource_name) -%>
-<% end -%>
+<%  if object.nested_decoder -%>
+    res, err = resource<%= resource_name -%>Extractor(d, meta, res)
+    if err != nil {
+        return err
+    }
+
+    if res == nil {
+        // Object isn't there any more - remove it from the state.
+        log.Printf("[DEBUG] Removing <%= resource_name -%> because it couldn't be matched.")
+        d.SetId("")
+        return nil
+    }
+<%  end -%>
 
 <%  if object.custom_code.decoder -%>
     res, err = resource<%= resource_name -%>Decoder(d, meta, res)
@@ -606,6 +610,15 @@ func resource<%= resource_name -%>UpdateEncoder(d *schema.ResourceData, meta int
 }
 <% end -%>
 
+<%  if object.nested_decoder -%>
+func resource<%= resource_name -%>Extractor(d *schema.ResourceData, meta interface{}, res map[string]interface{}) (map[string]interface{}, error) {
+    <%=     compile_template('templates/terraform/nested_decoder.go.erb',
+                         object: object,
+                         settable_properties: object.settable_properties,
+                         resource_name: resource_name) -%>
+}
+<% end -%>
+
 <% if object.custom_code.decoder -%>
 func resource<%= resource_name -%>Decoder(d *schema.ResourceData, meta interface{}, res map[string]interface{}) (map[string]interface{}, error) {
 <%= lines(compile(object.custom_code.decoder)) -%>