Revised the ModelTransformer so that it can support more complicated transformations.

tests/e2e/api/package.json

@@ -21,7 +21,8 @@
     "!*.tsbuildinfo",
     "!/dist/**/__tests__/",
     "!/dist/**/__mocks__/",
-    "!/dist/**/__snapshops__/"
+    "!/dist/**/__snapshops__/",
+    "!/dist/**/__test_data__/"
   ],
   "sideEffects": false,
   "scripts": {

tests/e2e/api/src/__test_data__/dummy-model.ts

@@ -0,0 +1,13 @@
+import { Model } from '../models/model';
+
+/**
+ * A dummy model that can be used in test files.
+ */
+export class DummyModel extends Model {
+	public name: string = '';
+
+	public constructor( partial?: Partial< DummyModel > ) {
+		super();
+		Object.assign( this, partial );
+	}
+}

tests/e2e/api/src/framework/__tests__/model-repository.spec.ts

@@ -12,15 +12,8 @@ import {
 	UpdatesChildModels,
 	UpdatesModels,
 } from '../model-repository';
+import { DummyModel } from '../../__test_data__/dummy-model';
 
-class DummyModel extends Model {
-	public name: string = '';
-
-	public constructor( partial?: Partial< DummyModel > ) {
-		super();
-		Object.assign( this, partial );
-	}
-}
 type DummyModelParams = ModelRepositoryParams< DummyModel, never, { search: string }, 'name' >
 
 class DummyChildModel extends Model {

tests/e2e/api/src/framework/__tests__/model-transformer.spec.ts

@@ -1,90 +1,90 @@
-import { Model } from '../../models/model';
-import { ModelTransformer } from '../model-transformer';
+import { ModelTransformation, ModelTransformer } from '../model-transformer';
+import { DummyModel } from '../../__test_data__/dummy-model';
 
-class DummyModel extends Model {
-	public name: string = '';
+class DummyTransformation implements ModelTransformation {
+	public readonly priority: number;
 
-	public constructor( partial?: Partial< DummyModel > ) {
-		super();
-		Object.assign( this, partial );
+	private readonly fn: ( ( p: any ) => any ) | null;
+
+	public constructor( priority: number, fn: ( ( p: any ) => any ) | null ) {
+		this.priority = priority;
+		this.fn = fn;
+	}
+
+	public fromModel( properties: any ): any {
+		if ( ! this.fn ) {
+			return properties;
+		}
+
+		return this.fn( properties );
+	}
+
+	public toModel( properties: any ): any {
+		if ( ! this.fn ) {
+			return properties;
+		}
+
+		return this.fn( properties );
 	}
 }
 
 describe( 'ModelTransformer', () => {
-	describe( 'fromModel', () => {
-		it( 'should convert models plainly', () => {
-			const model = new DummyModel( { name: 'Test' } );
+	it( 'should prioritize transformers correctly', () => {
+		const fn1 = jest.fn();
+		fn1.mockReturnValue( { name: 'fn1' } );
+		const fn2 = jest.fn();
+		fn2.mockReturnValue( { name: 'fn2' } );
 
-			const transformed = ModelTransformer.fromModel( model );
+		const transformer = new ModelTransformer< DummyModel >(
+			[
+				// Ensure the priorities are backwards so sorting is tested.
+				new DummyTransformation( 1, fn2 ),
+				new DummyTransformation( 0, fn1 ),
+			],
+		);
 
-			expect( transformed ).toMatchObject(
-				{
-					name: 'Test',
-				},
-			);
-		} );
+		const transformed = transformer.toModel( DummyModel, { name: 'fn0' } );
 
-		it( 'should convert models with key changes', () => {
-			const model = new DummyModel( { name: 'Test' } );
-
-			const transformed = ModelTransformer.fromModel(
-				model,
-				{ name: 'new-test' },
-			);
-
-			expect( transformed ).toMatchObject(
-				{
-					'new-test': 'Test',
-				},
-			);
-		} );
-
-		it( 'should convert models with transformations', () => {
-			const model = new DummyModel( { name: 'Test' } );
-
-			const transformed = ModelTransformer.fromModel(
-				model,
-				undefined,
-				{ name: ( val ) => 'Transform-' + val },
-			);
-
-			expect( transformed ).toMatchObject(
-				{
-					name: 'Transform-Test',
-				},
-			);
-		} );
+		expect( fn1 ).toHaveBeenCalledWith( { name: 'fn0' } );
+		expect( fn2 ).toHaveBeenCalledWith( { name: 'fn1' } );
+		expect( transformed ).toMatchObject( { name: 'fn2' } );
 	} );
 
-	describe( 'toModel', () => {
-		it( 'should create models plainly', () => {
-			const transformed = ModelTransformer.toModel(
-				DummyModel,
-				{ name: 'Test' },
-			);
+	it( 'should transform to model', () => {
+		const transformer = new ModelTransformer< DummyModel >(
+			[
+				new DummyTransformation(
+					0,
+					( p: any ) => {
+						p.name = 'Transformed-' + p.name;
+						return p;
+					},
+				),
+			],
+		);
 
-			expect( transformed ).toMatchObject( new DummyModel( { name: 'Test' } ) );
-		} );
+		const model = transformer.toModel( DummyModel, { name: 'Test' } );
 
-		it( 'should create models with key changes', () => {
-			const transformed = ModelTransformer.toModel(
-				DummyModel,
-				{ test: 'Test' },
-				{ test: 'name' },
-			);
+		expect( model ).toBeInstanceOf( DummyModel );
+		expect( model.name ).toEqual( 'Transformed-Test' );
+	} );
 
-			expect( transformed ).toMatchObject( new DummyModel( { name: 'Test' } ) );
-		} );
+	it( 'should transform from model', () => {
+		const transformer = new ModelTransformer< DummyModel >(
+			[
+				new DummyTransformation(
+					0,
+					( p: any ) => {
+						p.name = 'Transformed-' + p.name;
+						return p;
+					},
+				),
+			],
+		);
 
-		it( 'should create models with transformations', () => {
-			const transformed = ModelTransformer.toModel(
-				DummyModel,
-				{ name: 'Test' },
-				undefined,
-				{ name: ( val ) => 'Transform-' + val },
-			);
+		const transformed = transformer.fromModel( new DummyModel( { name: 'Test' } ) );
 
-			expect( transformed ).toMatchObject( new DummyModel( { name: 'Transform-Test' } ) );
-		} );
+		expect( transformed ).not.toBeInstanceOf( DummyModel );
+		expect( transformed.name ).toEqual( 'Transformed-Test' );
 	} );
 } );

tests/e2e/api/src/framework/model-transformer.ts

@@ -1,92 +1,76 @@
 import { Model } from '../models/model';
 
 /**
- * A map for converting between API/Model keys.
+ * An interface for an object that can perform transformations both to and from a representation
+ * and return the input data after performing the desired transformation.
  *
- * @typedef KeyChangeMap
- * @alias Object.<string,string>
+ * @interface ModelTransformation
  */
-type KeyChangeMap< F, T > = {
-	[ key in keyof F ]?: keyof T;
+export interface ModelTransformation {
+	readonly priority: number;
+	toModel( properties: any ): any;
+	fromModel( properties: any ): any;
 }
 
 /**
- * A map for transformations between API/Model data.
- *
- * @typedef TransformationMap
- * @alias Object.<string,Function>
+ * A class for transforming models to/from a generic representation.
  */
-type TransformationMap< T > = {
-	[ key in keyof T ]?: ( val: any ) => any;
-}
-
-export namespace ModelTransformer {
+export class ModelTransformer< T extends Model > {
 	/**
-	 * Given an object, this function will transform it using the described key changes and transformations.
+	 * An array of transformations to use when converting data to/from models.
 	 *
-	 * @param {*} data
-	 * @param {KeyChangeMap} keyChanges A map of keys to change into another key.
-	 * @param {TransformationMap} transformations A map of transformations to perform on values keyed by the key.
-	 * @return {*} The transformed data.
+	 * @type {Array.<ModelTransformation>}
 	 * @private
 	 */
-	function transform< F, T >(
-		data: F,
-		keyChanges?: KeyChangeMap< F, T >,
-		transformations?: TransformationMap< F >,
-	): any {
-		const transformed: any = {};
-
-		for ( const inputKey in data ) {
-			let key: string = inputKey;
-			if ( keyChanges && keyChanges.hasOwnProperty( inputKey ) ) {
-				key = keyChanges[ inputKey ] as string;
-			}
-
-			let value = data[ inputKey ];
-			if ( transformations && transformations.hasOwnProperty( inputKey ) ) {
-				value = ( transformations[ inputKey ] as ( val: any ) => any )( value );
-			}
-
-			transformed[ key ] = value;
-		}
-
-		return transformed;
-	}
+	private transformations: readonly ModelTransformation[];
 
 	/**
-	 * Given a model this will transform it into a standard object.
+	 * Creates a new model transformer instance.
 	 *
-	 * @param {F} data The model data to transform.
-	 * @param {KeyChangeMap} keyChanges A map of keys to change into another key.
-	 * @param {TransformationMap} transformations A map of transformations to perform on values keyed by the key.
-	 * @return {*} The transformed data.
-	 * @template F
+	 * @param {Array.<ModelTransformation>} transformations The transformations to use.
 	 */
-	export function fromModel< F extends Partial< Model > >(
-		data: F,
-		keyChanges?: KeyChangeMap< F, any >,
-		transformations?: TransformationMap< F >,
-	): any {
-		return transform( data, keyChanges, transformations );
+	public constructor( transformations: ModelTransformation[] ) {
+		// Ensure that the transformations are sorted by priority.
+		transformations.sort( ( a, b ) => ( a.priority > b.priority ) ? 1 : -1 );
+
+		this.transformations = transformations;
 	}
 
 	/**
-	 * Given an object this will transform it into a model object.
+	 * Takes the input data and runs all of the transformations on it before returning the created model.
 	 *
-	 * @param {Function} modelClass The model class we want to instantiate.
-	 * @param {*} data The raw data to transform.
-	 * @param {KeyChangeMap} keyChanges A map of keys to change into another key.
-	 * @param {TransformationMap} transformations A map of transformations to perform on values keyed by the key.
-	 * @return {T} The created model.
+	 * @param {Function.<T>} modelClass The model class we're trying to create.
+	 * @param {*} data The data we're transforming.
+	 * @return {T} The transformed model.
 	 * @template T
 	 */
-	export function toModel< T extends Model, F >(
-		modelClass: new ( properties: Partial< T > ) => T,
-		data: F,
-		keyChanges?: KeyChangeMap< F, T >,
-		transformations?: TransformationMap< F >,
-	): T {
-		return new modelClass( transform( data, keyChanges, transformations ) );
+	public toModel( modelClass: new( properties: Partial< T > ) => T, data: any ): T {
+		const transformed: any = this.transformations.reduce(
+			( properties: any, transformer: ModelTransformation ) => {
+				return transformer.toModel( properties );
+			},
+			data,
+		);
+
+		return new modelClass( transformed );
+	}
+
+	/**
+	 * Takes the input model and runs all of the transformations on it before returning the data.
+	 *
+	 * @param {Partial.<T>} model The model to transform.
+	 * @return {*} The transformed data.
+	 * @template T
+	 */
+	public fromModel( model: Partial< T > ): any {
+		// Convert the model class to raw properties so that the transformations can be simple.
+		const raw = JSON.parse( JSON.stringify( model ) );
+
+		return this.transformations.reduce(
+			( properties: any, transformer: ModelTransformation ) => {
+				return transformer.fromModel( properties );
+			},
+			raw,
+		);
 	}
 }

tests/e2e/api/src/framework/transformations/__tests__/key-change-transformation.spec.ts

@@ -0,0 +1,28 @@
+import { KeyChangeTransformation } from '../key-change-transformation';
+import { DummyModel } from '../../../__test_data__/dummy-model';
+
+describe( 'KeyChangeTransformation', () => {
+	let transformation: KeyChangeTransformation< DummyModel >;
+
+	beforeEach( () => {
+		transformation = new KeyChangeTransformation<DummyModel>(
+			{
+				name: 'new-name',
+			},
+		);
+	} );
+
+	it( 'should transform to model', () => {
+		const transformed = transformation.toModel( { 'new-name': 'Test Name' } );
+
+		expect( transformed ).toHaveProperty( 'name', 'Test Name' );
+		expect( transformed ).not.toHaveProperty( 'new-name' );
+	} );
+
+	it( 'should transform from model', () => {
+		const transformed = transformation.fromModel( { name: 'Test Name' } );
+
+		expect( transformed ).toHaveProperty( 'new-name', 'Test Name' );
+		expect( transformed ).not.toHaveProperty( 'name' );
+	} );
+} );

tests/e2e/api/src/framework/transformations/key-change-transformation.ts

@@ -0,0 +1,74 @@
+import { ModelTransformation } from '../model-transformer';
+import { Model } from '../../models/model';
+
+/**
+ * @typedef KeyChanges
+ * @alias Object.<string,string>
+ */
+type KeyChanges< T extends Model > = { readonly [ key in keyof Partial< T > ]: string };
+
+/**
+ * A model transformation that can be used to change property keys between two formats.
+ * This transformation has a very high priority so that it will be executed after all
+ * other transformations to prevent the changed key from causing problems.
+ */
+export class KeyChangeTransformation< T extends Model > implements ModelTransformation {
+	/**
+	 * Ensure that this transformation always happens at the very end since it changes the keys
+	 * in the transformed object.
+	 */
+	public readonly priority = 999999;
+
+	/**
+	 * The key change transformations that this object should perform.
+	 * This is structured with the model's property key as the key
+	 * of the object and the raw property key as the value.
+	 *
+	 * @type {KeyChanges}
+	 * @private
+	 */
+	private readonly changes: KeyChanges< T >;
+
+	/**
+	 * Creates a new transformation.
+	 *
+	 * @param {KeyChanges} changes The changes we want the transformation to make.
+	 */
+	public constructor( changes: KeyChanges< T > ) {
+		this.changes = changes;
+	}
+
+	/**
+	 * Performs a transformation from model properties to raw properties.
+	 *
+	 * @param {*} properties The properties to transform.
+	 * @return {*} The transformed properties.
+	 */
+	public fromModel( properties: any ): any {
+		for ( const key in this.changes ) {
+			const value = this.changes[ key ];
+
+			properties[ value ] = properties[ key ];
+			delete properties[ key ];
+		}
+
+		return properties;
+	}
+
+	/**
+	 * Performs a transformation from raw properties to model properties.
+	 *
+	 * @param {*} properties The properties to transform.
+	 * @return {*} The transformed properties.
+	 */
+	public toModel( properties: any ): any {
+		for ( const key in this.changes ) {
+			const value = this.changes[ key ];
+
+			properties[ key ] = properties[ value ];
+			delete properties[ value ];
+		}
+
+		return properties;
+	}
+}

tests/e2e/api/src/repositories/rest/products/simple-product.ts

@@ -3,30 +3,32 @@ import { CreateFn, ModelRepository } from '../../../framework/model-repository';
 import { SimpleProduct } from '../../../models';
 import { CreatesSimpleProducts, SimpleProductRepositoryParams } from '../../../models/products/simple-product';
 import { ModelTransformer } from '../../../framework/model-transformer';
+import { KeyChangeTransformation } from '../../../framework/transformations/key-change-transformation';
 
 function fromServer( data: any ): SimpleProduct {
 	if ( ! data.id ) {
 		throw new Error( 'An invalid response was received.' );
 	}
 
-	return ModelTransformer.toModel(
-		SimpleProduct,
-		data,
-		{
-			regular_price: 'regularPrice',
-		},
+	const t = new ModelTransformer< SimpleProduct >(
+		[
+			new KeyChangeTransformation< SimpleProduct >( { regularPrice: 'regular_price' } ),
+		],
 	);
+
+	return t.toModel( SimpleProduct, data );
 }
 
 function toServer( model: Partial< SimpleProduct > ): any {
+	const t = new ModelTransformer< SimpleProduct >(
+		[
+			new KeyChangeTransformation< SimpleProduct >( { regularPrice: 'regular_price' } ),
+		],
+	);
+
 	return Object.assign(
 		{ type: 'simple' },
-		ModelTransformer.fromModel(
-			model,
-			{
-				regularPrice: 'regular_price',
-			},
-		),
+		t.fromModel( model ),
 	);
 }
 

tests/e2e/api/src/repositories/rest/settings/setting-group.ts

@@ -3,19 +3,20 @@ import { ListFn, ModelRepository } from '../../../framework/model-repository';
 import { SettingGroup } from '../../../models';
 import { ListsSettingGroups, SettingGroupRepositoryParams } from '../../../models/settings/setting-group';
 import { ModelTransformer } from '../../../framework/model-transformer';
+import { KeyChangeTransformation } from '../../../framework/transformations/key-change-transformation';
 
 function fromServer( data: any ): SettingGroup {
 	if ( ! data.id ) {
 		throw new Error( 'An invalid response was received.' );
 	}
 
-	return ModelTransformer.toModel(
-		SettingGroup,
-		data,
-		{
-			parent_id: 'parentID',
-		},
+	const t = new ModelTransformer< SettingGroup >(
+		[
+			new KeyChangeTransformation< SettingGroup >( { parentID: 'parent_id' } ),
+		],
 	);
+
+	return t.toModel( SettingGroup, data );
 }
 
 function restList( httpClient: HTTPClient ): ListFn< SettingGroupRepositoryParams > {

tests/e2e/api/src/repositories/rest/settings/setting.ts

@@ -19,7 +19,8 @@ function fromServer( data: any ): Setting {
 		throw new Error( 'An invalid response was received.' );
 	}
 
-	return ModelTransformer.toModel( Setting, data );
+	const t = new ModelTransformer< Setting >( [] );
+	return t.toModel( Setting, data );
 }
 
 function restList( httpClient: HTTPClient ): ListChildFn< SettingRepositoryParams > {