stream: extract Readable.from in its own file

See: nodejs/readable-stream#420
PR-URL: #30140
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Trivikram Kamat <trivikr.dev@gmail.com>
Reviewed-By: Gus Caplan <me@gus.host>
Reviewed-By: Beth Griggs <Bethany.Griggs@uk.ibm.com>

Author: mcollina

lib/_stream_readable.js

@@ -47,6 +47,7 @@ const {
 // Lazy loaded to improve the startup performance.
 letStringDecoder;
 letcreateReadableStreamAsyncIterator;
+letfrom;
 
 Object.setPrototypeOf(Readable.prototype,Stream.prototype);
 Object.setPrototypeOf(Readable,Stream);
@@ -1194,40 +1195,8 @@ function endReadableNT(state, stream) {
 }
 
 Readable.from=function(iterable,opts){
-letiterator;
-if(iterable&&iterable[Symbol.asyncIterator])
-iterator=iterable[Symbol.asyncIterator]();
-elseif(iterable&&iterable[Symbol.iterator])
-iterator=iterable[Symbol.iterator]();
-else
-thrownewERR_INVALID_ARG_TYPE('iterable',['Iterable'],iterable);
-
-constreadable=newReadable({
-objectMode: true,
- ...opts
-});
-// Reading boolean to protect against _read
-// being called before last iteration completion.
-letreading=false;
-readable._read=function(){
-if(!reading){
-reading=true;
-next();
-}
-};
-asyncfunctionnext(){
-try{
-const{ value, done }=awaititerator.next();
-if(done){
-readable.push(null);
-}elseif(readable.push(awaitvalue)){
-next();
-}else{
-reading=false;
-}
-}catch(err){
-readable.destroy(err);
-}
+if(from===undefined){
+from=require('internal/streams/from');
 }
-returnreadable;
+returnfrom(Readable,iterable,opts);
 };

lib/internal/streams/from.js

@@ -0,0 +1,46 @@
+'use strict';
+
+const{
+ERR_INVALID_ARG_TYPE
+}=require('internal/errors').codes;
+
+functionfrom(Readable,iterable,opts){
+letiterator;
+if(iterable&&iterable[Symbol.asyncIterator])
+iterator=iterable[Symbol.asyncIterator]();
+elseif(iterable&&iterable[Symbol.iterator])
+iterator=iterable[Symbol.iterator]();
+else
+thrownewERR_INVALID_ARG_TYPE('iterable',['Iterable'],iterable);
+
+constreadable=newReadable({
+objectMode: true,
+ ...opts
+});
+// Reading boolean to protect against _read
+// being called before last iteration completion.
+letreading=false;
+readable._read=function(){
+if(!reading){
+reading=true;
+next();
+}
+};
+asyncfunctionnext(){
+try{
+const{ value, done }=awaititerator.next();
+if(done){
+readable.push(null);
+}elseif(readable.push(awaitvalue)){
+next();
+}else{
+reading=false;
+}
+}catch(err){
+readable.destroy(err);
+}
+}
+returnreadable;
+}
+
+module.exports=from;

node.gyp

@@ -205,6 +205,7 @@
 'lib/internal/streams/async_iterator.js',
 'lib/internal/streams/buffer_list.js',
 'lib/internal/streams/duplexpair.js',
+'lib/internal/streams/from.js',
 'lib/internal/streams/legacy.js',
 'lib/internal/streams/destroy.js',
 'lib/internal/streams/state.js',