Move stream, add error checks, add ESM goodness.

utils/Stream.js

@@ -1,17 +1,29 @@
 'use strict';
 
 const {Duplex} = require('stream');
-const defs = require('../defs');
+const defs = require('./defs');
 
-class Stream extends Duplex {
+class AsStream extends Duplex {
   static resolved = Promise.resolve();
 
   constructor(fn, options) {
     super(Object.assign({}, options, {writableObjectMode: true, readableObjectMode: true}));
-    if (typeof fn != 'function') throw Error('Only function is accepted as the first argument');
-    this._fn = fn;
+    if (typeof fn == 'function') {
+      this._fn = fn;
+    } else if (fn) {
+      if (typeof fn[Symbol.asyncIterator] == 'function') {
+        this._fn = fn[Symbol.asyncIterator].bind(fn);
+      } else if (typeof fn[Symbol.iterator] == 'function') {
+        this._fn = fn[Symbol.iterator].bind(fn);
+      }
+    }
+    if (!this._fn)
+      throw TypeError(
+        'Only a function or an object with an iterator is accepted as the first argument'
+      );
+
     // pump variables
-    this._paused = Stream.resolved;
+    this._paused = AsStream.resolved;
     this._resolvePaused = null;
     this._queue = [];
   }
@@ -42,7 +54,7 @@ class Stream extends Duplex {
     if (!this._resolvePaused) return;
     this._resolvePaused();
     this._resolvePaused = null;
-    this._paused = Stream.resolved;
+    this._paused = AsStream.resolved;
   }
   _pause() {
     if (this._resolvePaused) return;
@@ -125,11 +137,15 @@ class Stream extends Duplex {
   }
 
   static make(fn, options) {
-    return new Stream(fn, options);
+    return new AsStream(fn, options);
   }
 }
 
-Stream.stream = Stream.make;
-Stream.make.Constructor = Stream;
+AsStream.stream = AsStream.make;
+AsStream.make.Constructor = AsStream;
+
+module.exports = AsStream;
 
-module.exports = Stream;
+// to keep ESM happy:
+module.exports.asStream = AsStream.make;
+module.exports.make = AsStream.make;