feat: strict string typings (#227)

src/schema/fields.ts

@@ -363,13 +363,13 @@ interface SpanField extends BaseField {
   validation?: Validator
 }
 
-interface StringField extends BaseField {
+interface StringField<S extends string = string> extends BaseField {
   type: 'string'
   options?: {
     /**
      * A list of predefined values that the user can choose from. The array can either include string values ['sci-fi', 'western'] or objects [{title: 'Sci-Fi', value: 'sci-fi'}, ...]
      */
-    list?: Array<string | { title: string; value: string }>
+    list?: Array<S | { title: string; value: S }>
     /**
      * Controls how the items defined in the list option are presented. If set to 'radio' the list will render radio buttons. If set to 'dropdown' you'll get a dropdown menu instead. Default is dropdown.
      */
@@ -458,10 +458,15 @@ export type FieldType<
     : T extends
         | PureType<'date'>
         | PureType<'datetime'>
-        | PureType<'string'>
         | PureType<'text'>
         | PureType<'url'>
     ? string
+    : T extends PureType<'string'>
+    ? T extends {
+        options: { list: Array<infer S | { title: string; value: infer S }> }
+      }
+      ? S
+      : string
     : T extends PureType<'file'>
     ? File
     : T extends PureType<'geopoint'>

test/types/fields.ts

@@ -117,6 +117,24 @@ describe('field types', () => {
       .use()[1]
     expectTypeOf(string).toEqualTypeOf<string>()
 
+    /**
+     * enum like string example
+     */
+    enum AllowedStringValues {
+      FOO = 'foo',
+      BAR = 'bar',
+    }
+    const enumString = defineDocument('enumStringExample', {
+      test: {
+        type: 'string',
+        options: { list: [AllowedStringValues.FOO, AllowedStringValues.BAR] },
+      },
+    })
+      .builder.pick('test')
+      .first()
+      .use()[1]
+    expectTypeOf(enumString).toEqualTypeOf<AllowedStringValues>()
+
     /**
      * 'text'
      */