feat(from): make from on non-iterables coerce to iterables

spec/asynciterable/from-spec.ts

@@ -126,6 +126,26 @@ test('AsyncIterable#from from promise with selector', async t => {
   t.end();
 });
 
+test('AsyncIterable#from from non-iterable', async t => {
+  const xs = {};
+  const res = from(xs);
+
+  const it = res[Symbol.asyncIterator]();
+  await hasNext(t, it, xs);
+  await noNext(t, it);
+  t.end();
+});
+
+test('AsyncIterable#from from array-like with selector', async t => {
+  const xs = {};
+  const res = from(xs, (x, i) => [x, i]);
+
+  const it = res[Symbol.asyncIterator]();
+  await hasNext(t, it, [xs, 0]);
+  await noNext(t, it);
+  t.end();
+});
+
 interface Observer<T> {
   next: (value: T) => void;
   error: (err: any) => void;

spec/iterable/from-spec.ts

@@ -59,3 +59,23 @@ test('Iterable#from from array-like with selector', t => {
   noNext(t, it);
   t.end();
 });
+
+test('Iterable#from from non-iterable', t => {
+  const xs = {};
+  const res = from(xs);
+
+  const it = res[Symbol.iterator]();
+  hasNext(t, it, xs);
+  noNext(t, it);
+  t.end();
+});
+
+test('Iterable#from from non-iterable with selector', t => {
+  const xs = {};
+  const res = from(xs, (x, i) => [x, i]);
+
+  const it = res[Symbol.iterator]();
+  hasNext(t, it, [xs, 0]);
+  noNext(t, it);
+  t.end();
+});

src/asynciterable.ts

@@ -2,9 +2,8 @@ import { OperatorAsyncFunction } from './interfaces';
 import { bindCallback } from './internal/bindcallback';
 import { identityAsync } from './internal/identity';
 import { toLength } from './internal/tolength';
-import { isIterable, isAsyncIterable } from './internal/isiterable';
+import { isArrayLike, isIterable, isAsyncIterable } from './internal/isiterable';
 import { Observable } from './observer';
-import { AsyncIterable } from './Ix';
 
 /**
  * This clas serves as the base for all operations which support [Symbol.asyncIterator].
@@ -89,14 +88,17 @@ export abstract class AsyncIterableX<T> implements AsyncIterable<T> {
     }
 
     const piped = (input: AsyncIterable<T>): AsyncIterableX<R> => {
-      return operations.reduce((prev: any, fn: OperatorAsyncFunction<T, R>) => fn(prev), input);
+      return operations.reduce(
+        (prev: any, fn: OperatorAsyncFunction<T, R>) => fn(prev),
+        input as any
+      );
     };
 
     return piped(this);
   }
 
   static from<TSource, TResult = TSource>(
-    source: AsyncIterableInput<TSource>,
+    source: AsyncIterableInput<TSource> | TSource,
     selector: (value: TSource, index: number) => TResult | Promise<TResult> = identityAsync,
     thisArg?: any
   ): AsyncIterableX<TResult> {
@@ -115,7 +117,10 @@ export abstract class AsyncIterableX<T> implements AsyncIterable<T> {
       return new FromArrayIterable<TSource, TResult>(source, fn);
     }
     /* tslint:enable */
-    throw new TypeError('Input type not supported');
+    return new FromAsyncIterable<TSource, TResult>(
+      new OfAsyncIterable<TSource>([source as TSource]),
+      fn
+    );
   }
 
   static of<TSource>(...args: TSource[]): AsyncIterableX<TSource> {
@@ -270,10 +275,6 @@ function isObservable(x: any): x is Observable<any> {
   return x != null && Object(x) === x && typeof x['subscribe'] === 'function';
 }
 
-function isArrayLike(x: any): x is ArrayLike<any> {
-  return x != null && Object(x) === x && typeof x['length'] === 'number';
-}
-
 class OfAsyncIterable<TSource> extends AsyncIterableX<TSource> {
   private _args: TSource[];
 

src/internal/isiterable.ts

@@ -1,3 +1,10 @@
+/**
+ * @ignore
+ */
+export function isArrayLike(x: any): x is ArrayLike<any> {
+  return x != null && Object(x) === x && typeof x['length'] === 'number';
+}
+
 /**
  * @ignore
  */

src/iterable.ts

@@ -2,7 +2,7 @@ import { OperatorFunction } from './interfaces';
 import { bindCallback } from './internal/bindcallback';
 import { identity } from './internal/identity';
 import { toLength } from './internal/tolength';
-import { isIterable } from './internal/isiterable';
+import { isArrayLike, isIterable } from './internal/isiterable';
 
 /**
  * This clas serves as the base for all operations which support [Symbol.iterator].
@@ -85,19 +85,26 @@ export abstract class IterableX<T> implements Iterable<T> {
     }
 
     const piped = (input: Iterable<T>): IterableX<R> => {
-      return operations.reduce((prev: any, fn: OperatorFunction<T, R>) => fn(prev), input);
+      return operations.reduce((prev: any, fn: OperatorFunction<T, R>) => fn(prev), input as any);
     };
 
     return piped(this);
   }
 
   static from<TSource, TResult = TSource>(
-    source: Iterable<TSource> | ArrayLike<TSource>,
-    fn: (value: TSource, index: number) => TResult = identity,
+    source: Iterable<TSource> | ArrayLike<TSource> | TSource,
+    selector: (value: TSource, index: number) => TResult = identity,
     thisArg?: any
   ): IterableX<TResult> {
+    const fn = bindCallback(selector, thisArg, 2);
+    if (isIterable(source)) {
+      return new FromIterable<TSource, TResult>(source, fn);
+    }
+    if (isArrayLike(source)) {
+      return new FromIterable<TSource, TResult>(source, fn);
+    }
     //tslint:disable-next-line
-    return new FromIterable<TSource, TResult>(source, bindCallback(fn, thisArg, 2));
+    return new FromIterable<TSource, TResult>(new OfIterable<TSource>([source as TSource]), fn);
   }
 
   static of<TSource>(...args: TSource[]): IterableX<TSource> {