async-to-gen - npm Package Compare versions

Comparing version 1.0.6 to 1.1.0

index.js

@@ -9,5 +9,8 @@ var babylon = require('babylon');
  * MagicString has two important functions that can be called: .toString() and
- * .generateMap() which returns a source map, as well as a property .isEdited
- * which is true when any async functions were transformed.
+ * .generateMap() which returns a source map, as well as these properties:
  *
+ *   - .isEdited: true when any functions were transformed.
+ *   - .containsAsync: true when any async functions were transformed.
+ *   - .containsAsyncGen: true when any async generator functions were transformed.
+ *
  * Options:
@@ -24,2 +27,4 @@ *
   editor.isEdited = false;
+  editor.containsAsync = false;
+  editor.containsAsyncGen = false;
 
@@ -47,5 +52,5 @@ // Cheap trick for files that don't actually contain async functions
 
-  if (ast.isEdited) {
-    editor.isEdited = true;
-  }
+  editor.isEdited = Boolean(ast.containsAsync || ast.containsAsyncGen);
+  editor.containsAsync = Boolean(ast.containsAsync);
+  editor.containsAsyncGen = Boolean(ast.containsAsyncGen);
 
@@ -85,2 +90,54 @@ return editor;
 
+/**
+ * A helper function which accepts a generator function and returns an
+ * Async Iterable based on invoking the generating and resolving an iteration
+ * of Promises.
+ *
+ * Automatically included at the end of files containing async generator
+ * functions, but also exported from this module for other uses.
+ * See ./async-node for an example of another usage.
+ */
+var asyncGenHelper =
+  'function __asyncGen(g){' +
+    'var q=[],' +
+        'T=["next","throw","return"],' +
+        'I={};' +
+    'for(var i=0;i<3;i++){' +
+      'I[T[i]]=a.bind(0,i)' +
+    '}' +
+    'Symbol&&(' +
+      'Symbol.iterator&&(I[Symbol.iterator]=t),' +
+      'Symbol.asyncIterator&&(I[Symbol.asyncIterator]=t));' +
+    'function t(){' +
+      'return this' +
+    '}' +
+    'function a(t,v){' +
+      'return new Promise(function(s,j){' +
+        'q.push([s,j,v,t]);' +
+        'q.length===1&&c(v,t)' +
+      '})' +
+    '}' +
+    'function c(v,t){' +
+      'try{' +
+        'var r=g[T[t|0]](v),' +
+            'w=r.value&&r.value.__await;' +
+        'w?' +
+          'Promise.resolve(w).then(c,d):' +
+          'n(r,0)' +
+      '}catch(e){' +
+        'n(e,1)' +
+      '}' +
+    '}' +
+    'function d(e){' +
+      'c(e,1)' +
+    '}' +
+    'function n(r,s){' +
+      'q.shift()[s](r);' +
+      'q.length&&c(q[0][2],q[0][3])' +
+    '}' +
+    'return I' +
+  '}';
+
+module.exports.asyncGenHelper = asyncGenHelper;
+
 // A collection of methods for each AST type names which contain async functions to
@@ -117,4 +174,9 @@ // be transformed.
     leave: function (editor, node, ast) {
-      if (ast.isEdited && ast.shouldIncludeHelper) {
-        editor.append('\n' + asyncHelper + '\n');
+      if (ast.shouldIncludeHelper) {
+        if (ast.containsAsync) {
+          editor.append('\n' + asyncHelper + '\n');
+        }
+        if (ast.containsAsyncGen) {
+          editor.append('\n' + asyncGenHelper + '\n');
+        }
       }
@@ -125,3 +187,3 @@ }
     enter: function (editor, node, ast) {
-      var envRecord = ast.scope[ast.scope.length - 1];
+      var envRecord = currentScope(ast);
       if (envRecord.async) {
@@ -132,4 +194,17 @@ envRecord.referencesThis = true;
   },
+  Identifier: {
+    enter: function (editor, node, ast) {
+      if (node.name === 'arguments') {
+        var envRecord = currentScope(ast);
+        if (envRecord.async) {
+          envRecord.referencesArgs = true;
+        }
+      }
+    }
+  },
   MemberExpression: {
     leave: leaveMemberExpression
+  },
+  ForAwaitStatement: {
+    leave: leaveForAwait
   }
@@ -157,4 +232,8 @@ };
 
-  // unlike await, yield must not be followed by a new line
-  if (node.loc.start.line !== node.argument.loc.start.line) {
+  var envRecord = currentScope(ast);
+  if (envRecord.generator) {
+    start += '{__await:';
+    end += '}';
+  } else if (node.loc.start.line !== node.argument.loc.start.line) {
+    // unlike await, yield must not be followed by a new line
     start += '(';
@@ -177,3 +256,8 @@ end += ')';
   if (node.async) {
-    ast.isEdited = true;
+    if (node.generator) {
+      ast.containsAsyncGen = true;
+    } else {
+      ast.containsAsync = true;
+    }
+
     var idx = findTokenIndex(ast.tokens, node.start);
@@ -185,24 +269,12 @@ while (ast.tokens[idx].value !== 'async') {
 
-    var argNames = [];
-    var argValues = [];
-    if (node.referencesThis) {
-      argValues.push('this');
+    if (node.generator) {
+      while (ast.tokens[idx].value !== '*') {
+        idx++;
+      }
+      editor.overwrite(ast.tokens[idx].start, ast.tokens[idx + 1].start, ' ');
     }
-    if (node.referencesSuper) {
-      argNames.push('$uper');
-      argValues.push('p=>super[p]');
-    }
-    if (node.referencesSuperEq) {
-      argNames.push('$uperEq');
-      argValues.push('(p,v)=>(super[p]=v)');
-    }
 
-    editor.insertLeft(
-      node.body.start + 1,
-      'return __async(function*(' + argNames.join(',') + '){'
-    );
-    editor.insertRight(
-      node.body.end - 1,
-      (node.referencesThis ? '}.call(' : '}(') + argValues.join(',') + '))'
-    );
+    var wrapping = createAsyncWrapping(node);
+    editor.insertLeft(node.body.start + 1, 'return ' + wrapping[0]);
+    editor.insertRight(node.body.end - 1, wrapping[1]);
   }
@@ -219,17 +291,21 @@ }
   if (node.async) {
+    if (node.generator) {
+      ast.containsAsyncGen = true;
+    } else {
+      ast.containsAsync = true;
+    }
+
     ast.scope.pop();
-    if (node.referencesThis) {
-      ast.scope[ast.scope.length - 1].referencesThis = true;
-    }
-    if (node.referencesSuper) {
-      ast.scope[ast.scope.length - 1].referencesSuper = true;
-    }
-    if (node.referencesSuperEq) {
-      ast.scope[ast.scope.length - 1].referencesSuperEq = true;
-    }
-    ast.isEdited = true;
+    var envRecord = currentScope(ast);
+    envRecord.referencesThis |= node.referencesThis;
+    envRecord.referencesArgs |= node.referencesArgs;
+    envRecord.referencesSuper |= node.referencesSuper;
+    envRecord.referencesSuperEq |= node.referencesSuperEq;
+
+    var wrapping = createAsyncWrapping(node);
+
     editor.remove(node.start, node.start + 6);
     if (node.body.type === 'BlockStatement') {
-      editor.overwrite(node.body.start, node.body.start + 1, '__async(function*(){');
-      editor.overwrite(node.body.end - 1, node.body.end, node.referencesThis ? '}.call(this))' : '}())');
+      editor.overwrite(node.body.start, node.body.start + 1, wrapping[0]);
+      editor.overwrite(node.body.end - 1, node.body.end, wrapping[1]);
     } else {
@@ -240,5 +316,5 @@ var idx = findTokenIndex(ast.tokens, node.body.start) - 1;
       }
-      editor.insertRight(ast.tokens[idx].end, '__async(function*(){');
+      editor.insertRight(ast.tokens[idx].end, wrapping[0]);
       editor.insertLeft(node.body.start, 'return ');
-      editor.insertRight(node.body.end, node.referencesThis ? '}.call(this))' : '}())');
+      editor.insertRight(node.body.end, wrapping[1]);
     }
@@ -248,2 +324,35 @@ }
 
+function createAsyncWrapping(node) {
+  var argNames = [];
+  var argValues = [];
+
+  if (node.referencesThis) {
+    argValues.push('this');
+  }
+
+  if (node.referencesArgs) {
+    argNames.push('arguments');
+    argValues.push('arguments');
+  }
+
+  if (node.type !== 'ArrowFunctionExpression') {
+    if (node.referencesSuper) {
+      argNames.push('$uper');
+      argValues.push('p=>super[p]');
+    }
+
+    if (node.referencesSuperEq) {
+      argNames.push('$uperEq');
+      argValues.push('(p,v)=>(super[p]=v)');
+    }
+  }
+
+  var helperName = node.generator ? '__asyncGen' : '__async';
+
+  return [
+    helperName + '(function*(' + argNames.join(',') + '){',
+    (node.referencesThis ? '}.call(' : '}(') + argValues.join(',') + '))'
+  ];
+}
+
 function leaveMemberExpression(editor, node, ast, stack) {
@@ -254,3 +363,3 @@ // Only transform super member expressions.
   // Only within transformed async function scopes.
-  var envRecord = ast.scope[ast.scope.length - 1];
+  var envRecord = currentScope(ast);
   if (!envRecord.async) return;
@@ -304,2 +413,19 @@
 
+function leaveForAwait(editor, node, ast) {
+  var idx = findTokenIndex(ast.tokens, node.start) + 1;
+  while (ast.tokens[idx].value !== 'await') {
+    idx++;
+  }
+  editor.remove(ast.tokens[idx].start, ast.tokens[idx + 1].start);
+
+  var tmpName = '$await' + (ast.scope.length - 1);
+  editor.move(node.left.start, node.left.end, node.body.start + 1);
+  editor.insertLeft(node.left.end, '=yield{__await:' + tmpName + '};');
+  editor.insertLeft(node.left.start, 'let ' + tmpName);
+}
+
+function currentScope(ast) {
+  return ast.scope[ast.scope.length - 1];
+}
+
 // Given the AST output of babylon parse, walk through in a depth-first order,
@@ -306,0 +432,0 @@ // calling methods on the given visitor, providing editor as the first argument.

package.json

 {
   "name": "async-to-gen",
-  "version": "1.0.6",
+  "version": "1.1.0",
   "description": "Transform async functions to generator functions with speed and simplicity.",
@@ -21,3 +21,3 @@ "author": "Lee Byron <[e-mail]> (http://leebyron.com/)",
   "scripts": {
-    "test": "DIFF=$(./async-to-gen test/source.js | diff test/expected.js -); if [ -n \"$DIFF\" ]; then echo \"$DIFF\"; exit 1; fi; RES=$(node -e 'require(\"./register\");require(\"./test/test-node-module.js\")'); if [ \"$RES\" != 42 ]; then echo 'Node register hook failed'; exit 1; fi; ASYNC_NODE=$(./async-node ./test/test-node-module.js); if [ \"$ASYNC_NODE\" != 42 ]; then echo 'async-node failed'; exit 1; fi;",
+    "test": "DIFF=$(./async-to-gen test/source.js | diff test/expected.js -); if [ -n \"$DIFF\" ]; then echo \"$DIFF\"; exit 1; fi; RES=$(node -e 'require(\"./register\");require(\"./test/test-node-module.js\")'); if [ \"$RES\" != 42 ]; then echo 'Node register hook failed'; exit 1; fi; ASYNC_NODE=$(./async-node ./test/test-node-module.js); if [ \"$ASYNC_NODE\" != 42 ]; then echo 'async-node failed'; exit 1; fi; ASYNC_GEN_NODE=$(./async-node ./test/test-async-generator.js); if [ \"$ASYNC_GEN_NODE\" != 42 ]; then echo 'async-node failed for async generators'; exit 1; fi;",
     "test-update": "./async-to-gen test/source.js > test/expected.js"
@@ -24,0 +24,0 @@ },

README.md

@@ -19,3 +19,7 @@ async-to-gen
 
+Also, `async-to-gen` provides support for [async generators](https://github.com/tc39/proposal-async-iteration)
+which return Async Iterators, a great syntax and primitive for producing and
+operating on streams of data.
 
+
 ## Get Started!
@@ -183,3 +187,46 @@
 
+#### Streams
 
+Streaming data can be a challenging thing to get right. While [Observables](http://reactivex.io/documentation/observable.html) have provided a great library for
+streamed data, Async Generators provides language-level support for this concept!
+
+Consider subscribing to a web socket within an program using async functions:
+
+```js
+async function* stockTickerInEuro(symbol) {
+  var socket = await openWebSocket('ws://stocks.com/' + symbol)
+  try {
+    for await (var usd of socket) {
+      var euro = usd * await loadExchangeRateUSD2EUR()
+      yield euro
+    }
+  } finally {
+    closeWebSocket(socket)
+  }
+}
+```
+
+Then calling this function produces an Async Iterator (an Iterator of Promises)
+of stock ticker values.
+
+```js
+var ticker = stockTickerInEuro('AAPL')
+ticker.next().then(step => console.log(step.value))
+```
+
+Or use `for-await` loops within another async function:
+
+```js
+async function bloombergTerminal() {
+  for await (var price of stockTickerInEuro('AAPL')) {
+    console.log(price)
+  }
+}
+```
+
+NOTE: The behavior of `for-await` loops using this tool is not identical to the
+proposed spec addition. Where the proposed spec's `for-await` expects a
+`Symbol.asyncIterator` method for the iterated source, this tool expects
+`Symbol.iterator` instead since it transforms it to a `for-of` loop.
+
 ## Dead-Simple Transforms
@@ -191,4 +238,4 @@
 
-It also includes a very small (217 character) conversion function at the bottom
-of the file.
+It also includes a very small conversion function at the bottom of the file.
+How small? 217 chars for async functions and 533 chars for async generators.
 
@@ -195,0 +242,0 @@ **Before:**

test/expected.js

@@ -13,2 +13,12 @@ "use strict"
 
+// async gen function statement
+function foo() {return __asyncGen(function*(){
+  yield yield{__await: x}
+}())}
+
+// async gen function expression
+var bar = function () {return __asyncGen(function*(){
+  yield{__await: (yield x)}
+}())}
+
 // async arrow functions with body
@@ -27,2 +37,6 @@ var arrow1 = () => __async(function*(){
     yield this.x
+  }.call(this))},
+
+   bazGen() {return __asyncGen(function*(){
+    yield yield{__await: this.x}
   }.call(this))}
@@ -36,2 +50,6 @@ }
   }.call(this))}
+
+   woofGen() {return __asyncGen(function*(){
+    yield{__await: (yield this.x)};
+  }.call(this))}
 }
@@ -44,2 +62,6 @@
   }.call(this))}
+
+  static  woofGen() {return __asyncGen(function*(){
+    yield yield{__await: this.x};
+  }.call(this))}
 }
@@ -98,2 +120,18 @@
 
+// normal function referencing arguments
+function normalThis() {
+  return arguments;
+}
+
+// async function referencing arguments
+function asyncThis() {return __async(function*(arguments){
+  return arguments;
+}(arguments))}
+
+// async arrow function referencing arguments
+function within1() {return __async(function*(arguments){
+  () => () =>__async(function*(arguments){ return arguments}(arguments))
+}(arguments))}
+
+
 class SuperDuper extends BaseClass {
@@ -169,2 +207,17 @@ constructor(arg) {
 
+// await gen on its own line
+function ownLineGen() {return __asyncGen(function*(){
+  yield{__await:
+    someThing};
+}())}
+
+// for await
+function mapStream(stream, mapper) {return __asyncGen(function*(){
+  for (let $await1 of stream) {let item=yield{__await:$await1};
+    yield yield{__await: mapper(item)};
+  }
+}())}
+
 function __async(g){return new Promise(function(s,j){function c(a,x){try{var r=g[x?"throw":"next"](a)}catch(e){return j(e)}return r.done?s(r.value):Promise.resolve(r.value).then(c,d)}function d(e){return c(e,1)}c()})}
+
+function __asyncGen(g){var q=[],T=["next","throw","return"],I={};for(var i=0;i<3;i++){I[T[i]]=a.bind(0,i)}Symbol&&(Symbol.iterator&&(I[Symbol.iterator]=t),Symbol.asyncIterator&&(I[Symbol.asyncIterator]=t));function t(){return this}function a(t,v){return new Promise(function(s,j){q.push([s,j,v,t]);q.length===1&&c(v,t)})}function c(v,t){try{var r=g[T[t|0]](v),w=r.value&&r.value.__await;w?Promise.resolve(w).then(c,d):n(r,0)}catch(e){n(e,1)}}function d(e){c(e,1)}function n(r,s){q.shift()[s](r);q.length&&c(q[0][2],q[0][3])}return I}

test/source.js

@@ -13,2 +13,12 @@ "use strict"
 
+// async gen function statement
+async function* foo() {
+  yield await x
+}
+
+// async gen function expression
+var bar = async function* () {
+  await (yield x)
+}
+
 // async arrow functions with body
@@ -27,2 +37,6 @@ var arrow1 = async () => {
     await this.x
+  },
+
+  async* bazGen() {
+    yield await this.x
   }
@@ -36,2 +50,6 @@ }
   }
+
+  async* woofGen() {
+    await (yield this.x);
+  }
 }
@@ -44,2 +62,6 @@
   }
+
+  static async* woofGen() {
+    yield await this.x;
+  }
 }
@@ -98,2 +120,18 @@
 
+// normal function referencing arguments
+function normalThis() {
+  return arguments;
+}
+
+// async function referencing arguments
+async function asyncThis() {
+  return arguments;
+}
+
+// async arrow function referencing arguments
+async function within1() {
+  () => async () => arguments
+}
+
+
 class SuperDuper extends BaseClass {
@@ -168,1 +206,14 @@ constructor(arg) {
 }
+
+// await gen on its own line
+async function* ownLineGen() {
+  await
+    someThing;
+}
+
+// for await
+async function* mapStream(stream, mapper) {
+  for await (let item of stream) {
+    yield await mapper(item);
+  }
+}

test/test-node-module.js

@@ -8,3 +8,3 @@ // @flow
         await
-          42 :
+          arguments[0] :
         await
@@ -17,2 +17,2 @@ 99
 
-genAnswer().then(function (val) { console.log(val) });
+genAnswer(42).then(function (val) { console.log(val) });

New alerts

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License

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Found 1 instance in 1 package

Fixed alerts

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Found 1 instance in 1 package

Improved metrics

Total package byte prevSize

42954

increased by24.15%

Number of package files

12

increased by9.09%

Lines of code

830

increased by34.74%

Number of lines in readme file

274

increased by20.7%

No dependency changes