feat: add "recover" method

closes #12

Author: raveclassic

src/__tests__/remote-data.spec.ts

@@ -719,5 +719,20 @@ describe('RemoteData', () => {
 				expect(success(1).exists(p)).toBe(true);
 			});
 		});
+		describe('recover', () => {
+			const f = (error: string) => (error === 'foo' ? some(1) : none);
+			it('initial', () => {
+				expect(initialRD.recover(f)).toBe(initialRD);
+			});
+			it('pending', () => {
+				expect(pendingRD.recover(f)).toBe(pendingRD);
+			});
+			it('failure', () => {
+				expect(failure<string, number>('foo').recover(f)).toEqual(success(1));
+			});
+			it('success', () => {
+				expect(successRD.recover(f)).toBe(successRD);
+			});
+		});
 	});
 });

src/remote-data.ts

@@ -347,6 +347,13 @@ export class RemoteInitial<L, A> {
 	exists(p: Predicate<A>): boolean {
 		return false;
 	}
+
+	/**
+	 * Processes failure error into new RemoteData if function f return some value
+	 */
+	recover(f: (error: L) => Option<A>): RemoteData<L, A> {
+		return this;
+	}
 }
 
 export class RemoteFailure<L, A> {
@@ -633,6 +640,13 @@ export class RemoteFailure<L, A> {
 	exists(p: Predicate<A>): boolean {
 		return false;
 	}
+
+	/**
+	 * Processes failure error into new RemoteData if function f return some value
+	 */
+	recover(f: (error: L) => Option<A>): RemoteData<L, A> {
+		return f(this.error).fold<RemoteData<L, A>>(this, success); //tslint:disable-line no-use-before-declare
+	}
 }
 
 export class RemoteSuccess<L, A> {
@@ -919,6 +933,13 @@ export class RemoteSuccess<L, A> {
 	exists(p: Predicate<A>): boolean {
 		return p(this.value);
 	}
+
+	/**
+	 * Processes failure error into new RemoteData if function f return some value
+	 */
+	recover(f: (error: L) => Option<A>): RemoteData<L, A> {
+		return this;
+	}
 }
 
 export class RemotePending<L, A> {
@@ -1210,6 +1231,13 @@ export class RemotePending<L, A> {
 	exists(p: Predicate<A>): boolean {
 		return false;
 	}
+
+	/**
+	 * Processes failure error into new RemoteData if function f return some value
+	 */
+	recover(f: (error: L) => Option<A>): RemoteData<L, A> {
+		return this;
+	}
 }
 
 /**