Merge pull request #122 from nobrainr/fix/strict-schema-class-typing

Fix/strict schema class typing

Author: emyann

package-lock.json

@@ -68,7 +68,7 @@
     "typedoc": "^0.15.0",
     "typedoc-plugin-external-module-name": "^2.0.0",
     "typedoc-plugin-internal-external": "^2.0.1",
-    "typescript": "^3.4.2",
+    "typescript": "3.5.3",
     "webpack": "4.38.0",
     "webpack-cli": "^3.3.0"
   },

package.json

@@ -72,7 +72,7 @@ function transformItems<T, TSchema extends Schema<T | {}>>(schema: TSchema, type
     tree = new MorphismSchemaTree(schema);
   }
 
-  function mapper(source: any) {
+  const mapper: Mapper<TSchema> = (source: any) => {
     if (!source) {
       return source;
     }
@@ -96,7 +96,7 @@ function transformItems<T, TSchema extends Schema<T | {}>>(schema: TSchema, type
         return transformValuesFromObject(object, tree, [object], jsObject);
       }
     }
-  }
+  };
 
   return mapper;
 }
@@ -148,7 +148,17 @@ function morphism<TSchema extends Schema, TDestination>(
   type: Constructable<TDestination>
 ): Mapper<TSchema, TDestination>; // morphism({}, null, T) => mapper(S) => T
 
-function morphism<TSchema extends Schema, Target>(schema: TSchema, items: SourceFromSchema<TSchema>, type: Constructable<Target>): Target; // morphism({}, {}, T) => T
+function morphism<
+  TSchema = Schema<DestinationFromSchema<Schema>, SourceFromSchema<Schema>>,
+  Target = never,
+  Source extends SourceFromSchema<TSchema> = SourceFromSchema<TSchema>
+>(schema: TSchema, items: Source, type: Constructable<Target>): Target; // morphism({}, {}, T) => T
+
+function morphism<
+  TSchema = Schema<DestinationFromSchema<Schema>, SourceFromSchema<Schema>>,
+  Target = never,
+  Source extends SourceFromSchema<TSchema> = SourceFromSchema<TSchema>
+>(schema: TSchema, items: Source[], type: Constructable<Target>): Target[]; // morphism({}, [], T) => T[]
 
 function morphism<Target, Source, TSchema extends Schema<Target, Source>>(
   schema: TSchema,

src/morphism.ts

@@ -37,17 +37,17 @@ export type StrictSchema<Target = any, Source = any> = {
     | ActionString<Source>
     | ActionFunction<Target, Source, Target[destinationProperty]>
     | ActionAggregator<Source>
-    | ActionSelector<Source, Target[destinationProperty]>
-    | StrictSchema<Target[destinationProperty], Source>
+    | ActionSelector<Source, Target>
+    | StrictSchema<Target[destinationProperty], Source>;
 } & { [SCHEMA_OPTIONS_SYMBOL]?: SchemaOptions<Target> };
 export type Schema<Target = any, Source = any> = {
   /** `destinationProperty` is the name of the property of the target object you want to produce */
   [destinationProperty in keyof Target]?:
     | ActionString<Source>
     | ActionFunction<Target, Source, Target[destinationProperty]>
     | ActionAggregator<Source>
-    | ActionSelector<Source, Target[destinationProperty]>
-    | Schema<Target[destinationProperty], Source>
+    | ActionSelector<Source, Target>
+    | Schema<Target[destinationProperty], Source>;
 } & { [SCHEMA_OPTIONS_SYMBOL]?: SchemaOptions<Target | any> };
 
 export type Actions<Target, Source> = ActionFunction<Target, Source> | ActionAggregator | ActionString<Target> | ActionSelector<Source>;
@@ -172,6 +172,6 @@ export type DestinationFromSchema<T> = T extends StrictSchema<infer U> | Schema<
 export type ResultItem<TSchema extends Schema> = DestinationFromSchema<TSchema>;
 
 export interface Mapper<TSchema extends Schema | StrictSchema, TResult = ResultItem<TSchema>> {
-  (data: SourceFromSchema<TSchema>[]): TResult[];
-  (data: SourceFromSchema<TSchema>): TResult;
+  (data?: SourceFromSchema<TSchema>[] | null): TResult[];
+  (data?: SourceFromSchema<TSchema> | null): TResult;
 }

src/types.ts

@@ -161,6 +161,29 @@ describe('Typescript', () => {
       morphism<StrictSchema<D1, S1>>({ a: ({ _a }) => _a.toString() });
       morphism<StrictSchema<D1, S1>>({ a: ({ _a }) => _a.toString() });
     });
+
+    it('shoud infer result type from source when a class is provided', () => {
+      class Source {
+        constructor(public id: number, public ugly_field: string) {}
+      }
+
+      class Destination {
+        constructor(public id: number, public field: string) {}
+      }
+
+      const source = [new Source(1, 'abc'), new Source(1, 'def')];
+
+      const schema: StrictSchema<Destination, Source> = {
+        id: 'id',
+        field: 'ugly_field'
+      };
+      const expected = [new Destination(1, 'abc'), new Destination(1, 'def')];
+
+      const result = morphism(schema, source, Destination);
+      result.forEach((item, idx) => {
+        expect(item).toEqual(expected[idx]);
+      });
+    });
   });
 
   describe('Morphism Function Type Checking', () => {