fix(types): Accept readonly arrays as input for array type (#1936 by @adamkovalsky)

Author: adamkovalsky

packages/mobx-state-tree/__tests__/core/array.test.ts

@@ -560,3 +560,10 @@ test("assigning filtered instances works", () => {
     expect(done.every((t) => !isAlive(t))).toBe(true)
     expect(notDone.every((t) => isAlive(t))).toBe(true)
 })
+
+test("#1676 - should accept read-only arrays", () => {
+    const ArrayType = types.array(types.string)
+    const data = ["foo", "bar"] as const
+    const instance = ArrayType.create(data)
+    expect(getSnapshot(instance)).toEqual(["foo", "bar"])
+})

packages/mobx-state-tree/src/types/complex-types/array.ts

@@ -72,7 +72,7 @@ export interface IMSTArray<IT extends IAnyType> extends IObservableArray<IT["Typ
 
 /** @hidden */
 export interface IArrayType<IT extends IAnyType>
-    extends IType<IT["CreationType"][] | undefined, IT["SnapshotType"][], IMSTArray<IT>> {
+    extends IType<readonly IT["CreationType"][] | undefined, IT["SnapshotType"][], IMSTArray<IT>> {
     hooks(hooks: IHooksGetter<IMSTArray<IAnyType>>): IArrayType<IT>
 }
 
@@ -81,7 +81,7 @@ export interface IArrayType<IT extends IAnyType>
  * @hidden
  */
 export class ArrayType<IT extends IAnyType> extends ComplexType<
-    IT["CreationType"][] | undefined,
+    readonly IT["CreationType"][] | undefined,
     IT["SnapshotType"][],
     IMSTArray<IT>
 > {