EE-22 New version of tracker that supports withComputation and async

packages/tracker/package.js

@@ -1,6 +1,6 @@
 Package.describe({
   summary: "Dependency tracker to allow reactive callbacks",
-  version: "1.2.1"
+  version: "1.3.4"
 });
 
 Package.onUse(function (api) {

packages/tracker/tracker.d.ts

@@ -16,6 +16,10 @@ export namespace Tracker {
      * True during the initial run of the computation at the time `Tracker.autorun` is called, and false on subsequent reruns and at other times.
      */
     firstRun: boolean;
+    /**
+     * Forces autorun blocks to be executed in synchronous-looking order by storing the value autorun promise thus making it awaitable.
+     */
+    firstRunPromise: Promise<unknown>
     /**
      * Invalidates this computation so that it will be rerun.
      */
@@ -48,7 +52,7 @@ export namespace Tracker {
    * The current computation, or `null` if there isn't one.  The current computation is the `Tracker.Computation` object created by the innermost active call to
    * `Tracker.autorun`, and it's the computation that gains dependencies when reactive data sources are accessed.
    */
-  var currentComputation: Computation;
+  var currentComputation: Computation | null;
 
   var Dependency: DependencyStatic;
   /**
@@ -109,6 +113,16 @@ export namespace Tracker {
     }
   ): Computation;
 
+  /**
+   * @summary Helper function to make the tracker work with promises.
+   * @param computation Computation that tracked
+   * @param func a function that needs to be called and be reactive. This may be async or not - but this function is typically called after an await
+   */
+  function withComputation<T>(
+    computation: Computation | null,
+    func: () => T
+  ): T;
+
   /**
    * Process all reactive updates immediately and ensure that all invalidated computations are rerun.
    */

packages/tracker/tracker.js

@@ -32,11 +32,6 @@ Tracker.active = false;
  */
 Tracker.currentComputation = null;
 
-function setCurrentComputation(c) {
-  Tracker.currentComputation = c;
-  Tracker.active = !! c;
-}
-
 function _debugFunc() {
   // We want this code to work without Meteor, and also without
   // "console" (which is technically non-standard and may be missing
@@ -201,6 +196,16 @@ Tracker.Computation = class Computation {
     this._onError = onError;
     this._recomputing = false;
 
+    /**
+     * @summary Forces autorun blocks to be executed in synchronous-looking order by storing the value autorun promise thus making it awaitable.
+     * @locus Client
+     * @memberOf Tracker.Computation
+     * @instance
+     * @name  firstRunPromise
+     * @returns {Promise<unknown>}
+     */
+    this.firstRunPromise = undefined;
+
     var errored = true;
     try {
       this._compute();
@@ -212,6 +217,22 @@ Tracker.Computation = class Computation {
     }
   }
 
+
+    /**
+   * Resolves the firstRunPromise with the result of the autorun function.
+   * @param {*} onResolved
+   * @param {*} onRejected
+   * @returns{Promise<unknown}
+   */
+    then(onResolved, onRejected) {
+      return this.firstRunPromise.then(onResolved, onRejected);
+    };
+
+
+    catch(onRejected) {
+      return this.firstRunPromise.catch(onRejected)
+    };
+
   // http://docs.meteor.com/#computation_oninvalidate
 
   /**
@@ -300,14 +321,21 @@ Tracker.Computation = class Computation {
   _compute() {
     this.invalidated = false;
 
-    var previous = Tracker.currentComputation;
-    setCurrentComputation(this);
     var previousInCompute = inCompute;
     inCompute = true;
+
     try {
-      withNoYieldsAllowed(this._func)(this);
+      // In case of async functions, the result of this function will contain the promise of the autorun function
+      // & make autoruns await-able.
+      const firstRunPromise = Tracker.withComputation(this, () => {
+        return withNoYieldsAllowed(this._func)(this);
+      });
+      // We'll store the firstRunPromise on the computation so it can be awaited by the callers, but only
+      // during the first run. We don't want things to get mixed up.
+      if (this.firstRun) {
+        this.firstRunPromise = Promise.resolve(firstRunPromise);
+      }
     } finally {
-      setCurrentComputation(previous);
       inCompute = previousInCompute;
     }
   }
@@ -566,15 +594,12 @@ Tracker._runFlush = function (options) {
  * thrown. Defaults to the error being logged to the console.
  * @returns {Tracker.Computation}
  */
-Tracker.autorun = function (f, options) {
+Tracker.autorun = function (f, options = {}) {
   if (typeof f !== 'function')
     throw new Error('Tracker.autorun requires a function argument');
 
-  options = options || {};
-
   constructingComputation = true;
-  var c = new Tracker.Computation(
-    f, Tracker.currentComputation, options.onError);
+  var c = new Tracker.Computation(f, Tracker.currentComputation, options.onError);
 
   if (Tracker.active)
     Tracker.onInvalidate(function () {
@@ -597,12 +622,25 @@ Tracker.autorun = function (f, options) {
  * @param {Function} func A function to call immediately.
  */
 Tracker.nonreactive = function (f) {
-  var previous = Tracker.currentComputation;
-  setCurrentComputation(null);
+  return Tracker.withComputation(null, f);
+};
+
+/**
+ * @summary Helper function to make the tracker work with promises.
+ * @param computation Computation that tracked
+ * @param func a function that needs to be called and be reactive. This may be async or not - but this function is typically called after an await
+ */
+Tracker.withComputation = function (computation, f) {
+  var previousComputation = Tracker.currentComputation;
+
+  Tracker.currentComputation = computation;
+  Tracker.active = !!computation;
+
   try {
     return f();
   } finally {
-    setCurrentComputation(previous);
+    Tracker.currentComputation = previousComputation;
+    Tracker.active = !!previousComputation;
   }
 };