Add JSON types

CHANGELOG.md

@@ -8,10 +8,13 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ## [Unreleased]
 
 ### Changed
+The input to fromJson() is now a JsonValue, enforcing basic JSON requirements:
+property values must be legal JSON values. This is meant to allow the
+compiler to flag accidental deserializations of already-deserialized objects.
 
 ### Added
 
-## [v0.3.0] - 2020-11-6
+## [v0.3.0] - 2020-11-06
 
 ### Changed
 - updated node example to be a properly formatted node module

from_json/as.ts

@@ -6,7 +6,7 @@ import { FromJsonStrategy, Serializable } from "../serializable.ts";
 export function fromJsonAs<T>(
   type: T & { new (): Serializable },
 ): FromJsonStrategy {
-  return (value: T) => {
+  return (value) => {
     if (Array.isArray(value)) {
       return value.map((item) => new type().fromJson(item));
     }

from_json/as_test.ts

@@ -13,8 +13,8 @@ test({
       test = true;
     }
     const testObj = new Test();
-    assertEquals(fromJsonAs(Test)(testObj).test, testObj.test);
-    assert(fromJsonAs(Test)(testObj) instanceof Test);
+    assertEquals(fromJsonAs(Test)({ test: true }).test, testObj.test);
+    assert(fromJsonAs(Test)({ test: true }) instanceof Test);
   },
 });
 

from_json/date.ts

@@ -1,10 +1,10 @@
 // Copyright 2018-2020 Gamebridge.ai authors. All rights reserved. MIT license.
 
-import { FromJsonStrategy } from "../serializable.ts";
+import { FromJsonStrategy, JsonValue } from "../serializable.ts";
 
 /** allows authors to pass a regex to parse as a date */
 export function createDateStrategy(regex: RegExp): FromJsonStrategy {
-  return (value: any): any | Date => {
+  return (value: JsonValue): any | Date => {
     return typeof value === "string" && regex.exec(value)
       ? new Date(value)
       : value;

serializable.ts

@@ -4,6 +4,18 @@ import { SerializePropertyOptionsMap } from "./serialize_property_options_map.ts
 import { defaultToJson } from "./to_json/default.ts";
 import { recursiveToJson } from "./to_json/recursive.ts";
 
+/** A JSON object where each property value is a simple JSON value. */
+export type JsonObject = { [key: string]: JsonValue };
+
+/** A property value in a JSON object. */
+export type JsonValue =
+  | null
+  | boolean
+  | number
+  | string
+  | JsonValue[]
+  | JsonObject;
+
 /** to be implemented by external authors on their models  */
 export declare interface TransformKey {
   /** a function that will be called against
@@ -22,19 +34,18 @@ export abstract class Serializable {
   public toJson(): string {
     return toJson(this);
   }
-  public fromJson(): this;
   public fromJson(json: string): this;
-  public fromJson(json: Record<string, any>): this;
-  public fromJson(json: string | Record<string, any> = {}): this {
+  public fromJson(json: JsonValue): this;
+  public fromJson(json: string | JsonValue): this {
     return fromJson(this, json);
   }
 }
 
 /** Functions used when hydrating data */
-export type FromJsonStrategy = (value: any) => any;
+export type FromJsonStrategy = (value: JsonValue) => any;
 
 /** Functions used when dehydrating data */
-export type ToJsonStrategy = (value: any) => any;
+export type ToJsonStrategy = (value: any) => JsonValue;
 
 /** options to use when (de)serializing values */
 export class SerializePropertyOptions {
@@ -69,13 +80,15 @@ export class SerializePropertyOptions {
  * Converts value from functions provided as parameters
  */
 export function composeStrategy(
-  ...fns:
-    | (FromJsonStrategy | FromJsonStrategy[])[]
-    | (ToJsonStrategy | ToJsonStrategy[])[]
-): FromJsonStrategy | ToJsonStrategy {
-  return (val: unknown): unknown =>
+  ...fns: (FromJsonStrategy | FromJsonStrategy[])[]
+): FromJsonStrategy;
+export function composeStrategy(
+  ...fns: (ToJsonStrategy | ToJsonStrategy[])[]
+): ToJsonStrategy;
+export function composeStrategy(...fns: any): any {
+  return (val: any): any =>
     fns.flat().reduce(
-      (acc: unknown, f: FromJsonStrategy | ToJsonStrategy) => f(acc),
+      (acc: any, f: FromJsonStrategy | ToJsonStrategy) => f(acc),
       val,
     );
 }
@@ -95,7 +108,7 @@ const ERROR_MESSAGE_MISSING_PROPERTIES_MAP =
 /** Converts to object using mapped keys */
 export function toPojo(
   context: any,
-): Record<string, unknown> {
+): JsonObject {
   const serializablePropertyMap = SERIALIZABLE_CLASS_MAP.get(
     context?.constructor?.prototype,
   );
@@ -106,7 +119,7 @@ export function toPojo(
         ?.prototype}`,
     );
   }
-  const record: Record<string, unknown> = {};
+  const record: JsonObject = {};
   for (
     let {
       propertyKey,
@@ -148,16 +161,16 @@ function toJson<T>(context: T): string {
 /** Convert from object/string to mapped object on the context */
 function fromJson<T>(context: Serializable, json: string): T;
 
-function fromJson<T>(context: Serializable, json: Record<string, any>): T;
+function fromJson<T>(context: Serializable, json: JsonValue): T;
 
 function fromJson<T>(
   context: Serializable,
-  json: string | Record<string, any>,
+  json: string | JsonValue,
 ): T;
 
 function fromJson<T>(
   context: Serializable,
-  json: string | Record<string, any>,
+  json: string | JsonValue,
 ): T {
   const serializablePropertyMap = SERIALIZABLE_CLASS_MAP.get(
     context?.constructor?.prototype,
@@ -176,7 +189,7 @@ function fromJson<T>(
     JSON.parse(
       _json,
       /** Processes the value through the provided or default `fromJsonStrategy` */
-      function revive(key: string, value: unknown): unknown {
+      function revive(key: string, value: JsonValue): unknown {
         // After the last iteration of the fromJsonStrategy a function
         // will be called one more time with a empty string key
         if (key === "") {

serialize_property_test.ts

@@ -216,7 +216,7 @@ test({
     }
     class Test extends Serializable {
       @SerializeProperty({
-        fromJsonStrategy: (v: OtherClass) => new OtherClass().fromJson(v),
+        fromJsonStrategy: (v) => new OtherClass().fromJson(v),
       })
       array!: OtherClass[];
     }

to_json/recursive.ts

@@ -1,8 +1,8 @@
 // Copyright 2018-2020 Gamebridge.ai authors. All rights reserved. MIT license.
 
-import { Serializable, toPojo } from "../serializable.ts";
+import { JsonObject, Serializable, toPojo } from "../serializable.ts";
 
 /** Recursively serialize a serializable class */
-export function recursiveToJson(value: Serializable): any {
+export function recursiveToJson(value: Serializable): JsonObject {
   return toPojo(value);
 }