Extract type from Rails enums

playground/vanilla/Gemfile.lock

@@ -1,7 +1,7 @@
 PATH
   remote: ../..
   specs:
-    types_from_serializers (2.0.2)
+    types_from_serializers (2.1.0)
       listen (~> 3.2)
       oj_serializers (~> 2.0, >= 2.0.2)
       railties (>= 5.1)

playground/vanilla/app/models/song.rb

@@ -1,4 +1,7 @@
 class Song < ApplicationRecord
   belongs_to :composer
   has_many :video_clips
+
+  enum genre: { disco: "disco", rock: "rock", classical: "classical" }
+  enum tempo: %w[slow medium fast]
 end

playground/vanilla/app/serializers/song_serializer.rb

@@ -2,6 +2,8 @@ class SongSerializer < BaseSerializer
   attributes(
     :id,
     :title,
+    :genre,
+    :tempo,
   )
 
   has_one :composer, serializer: ComposerSerializer

playground/vanilla/db/migrate/20240227112250_add_enums_to_composers.rb

@@ -0,0 +1,6 @@
+class AddEnumsToComposers < ActiveRecord::Migration[6.0]
+  def change
+    add_column :composers, :genre, :string, null: false
+    add_column :composers, :tempo, :integer, null: true
+  end
+end

playground/vanilla/db/schema.rb

@@ -10,12 +10,15 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema.define(version: 2022_07_09_151259) do
+ActiveRecord::Schema.define(version: 2024_02_27_112250) do
+
   create_table "composers", force: :cascade do |t|
     t.text "first_name"
     t.text "last_name"
     t.datetime "created_at", precision: 6, null: false
     t.datetime "updated_at", precision: 6, null: false
+    t.string "genre", null: false
+    t.integer "tempo"
   end
 
   create_table "songs", force: :cascade do |t|

spec/types_from_serializers/__snapshots__/interfaces_SongSerializer.snap

@@ -1,10 +1,12 @@
-// TypesFromSerializers CacheKey c3af64a41d21e71dfae56644517994e1
+// TypesFromSerializers CacheKey 460b4a83a2e81c9d693ac5490f9e0b76
 //
 // DO NOT MODIFY: This file was automatically generated by TypesFromSerializers.
 import type Composer from './Composer'
 
 export default interface Song {
   id: number
   composer: Composer
+  genre: "disco" | "rock" | "classical"
+  tempo: "slow" | "medium" | "fast"
   title?: string
 }

spec/types_from_serializers/__snapshots__/interfaces_SongWithVideosSerializer.snap

@@ -1,4 +1,4 @@
-// TypesFromSerializers CacheKey 6774f7cbf07614cf9b4136fbd0c8b441
+// TypesFromSerializers CacheKey 3aa811bd4673913bbd09f2967979b304
 //
 // DO NOT MODIFY: This file was automatically generated by TypesFromSerializers.
 import type Composer from './Composer'
@@ -7,6 +7,8 @@ import type Video from './Video'
 export default interface SongWithVideos {
   id: number
   composer: Composer
+  genre: "disco" | "rock" | "classical"
+  tempo: "slow" | "medium" | "fast"
   title?: string
   videos: Video[]
 }

spec/types_from_serializers/__snapshots__/namespace_interfaces_SongSerializer.snap

@@ -1,4 +1,4 @@
-// TypesFromSerializers CacheKey c3af64a41d21e71dfae56644517994e1
+// TypesFromSerializers CacheKey 460b4a83a2e81c9d693ac5490f9e0b76
 //
 // DO NOT MODIFY: This file was automatically generated by TypesFromSerializers.
 import type Composer from './Composer'
@@ -8,6 +8,8 @@ declare global {
     interface Song {
       id: number
       composer: Composer
+      genre: "disco" | "rock" | "classical"
+      tempo: "slow" | "medium" | "fast"
       title?: string
     }
   }

spec/types_from_serializers/__snapshots__/namespace_interfaces_SongWithVideosSerializer.snap

@@ -1,4 +1,4 @@
-// TypesFromSerializers CacheKey 6774f7cbf07614cf9b4136fbd0c8b441
+// TypesFromSerializers CacheKey 3aa811bd4673913bbd09f2967979b304
 //
 // DO NOT MODIFY: This file was automatically generated by TypesFromSerializers.
 import type Composer from './Composer'
@@ -9,6 +9,8 @@ declare global {
     interface SongWithVideos {
       id: number
       composer: Composer
+      genre: "disco" | "rock" | "classical"
+      tempo: "slow" | "medium" | "fast"
       title?: string
       videos: Video[]
     }

types_from_serializers/lib/types_from_serializers/generator.rb

@@ -38,15 +38,12 @@ def ts_filename
         TypesFromSerializers.config.name_from_serializer.call(name).gsub("::", "/")
       end
 
-      # Internal: The columns corresponding to the serializer model, if it's a
-      # record.
-      def model_columns
-        @model_columns ||= _serializer_model_name&.to_model.try(:columns_hash) || {}
-      end
-
       # Internal: The TypeScript properties of the serialzeir interface.
       def ts_properties
         @ts_properties ||= begin
+          model_class = _serializer_model_name&.to_model
+          model_columns = model_class.try(:columns_hash) || {}
+          model_enums = model_class.try(:defined_enums) || {}
           types_from = try(:_serializer_types_from)
 
           prepare_attributes(
@@ -64,7 +61,7 @@ def ts_properties
                   multi: options[:association] == :many,
                   column_name: options.fetch(:value_from),
                 ).tap do |property|
-                  property.infer_type_from(model_columns, types_from)
+                  property.infer_type_from(model_columns, model_enums, types_from)
                 end
               end
             }
@@ -190,9 +187,11 @@ def inspect
 
     # Internal: Infers the property's type by checking a corresponding SQL
     # column, or falling back to a TypeScript interface if provided.
-    def infer_type_from(columns_hash, ts_interface)
+    def infer_type_from(columns_hash, defined_enums, ts_interface)
       if type
         type
+      elsif (enum = defined_enums[column_name.to_s])
+        self.type = enum.keys.map(&:inspect).join(" | ")
       elsif (column = columns_hash[column_name.to_s])
         self.multi = true if column.try(:array)
         self.optional = true if column.null && !column.default