Support window.onload (#2643)

14 files changed, 162 insertions, 88 deletions

diff --git a/.eslintrc.json b/.eslintrc.json
index 43405e21e..c6b145d78 100644
--- a/.eslintrc.json
+++ b/.eslintrc.json
@@ -14,6 +14,7 @@
     "@typescript-eslint/array-type": ["error", "array-simple"],
     "@typescript-eslint/explicit-member-accessibility": ["off"],
     "@typescript-eslint/no-non-null-assertion": ["off"],
+    "@typescript-eslint/no-use-before-define": ["off"],
     "@typescript-eslint/no-parameter-properties": ["off"],
     "@typescript-eslint/no-unused-vars": [
       "error",
diff --git a/cli/main.rs b/cli/main.rs
index 50d65c06d..ec6c46616 100644
--- a/cli/main.rs
+++ b/cli/main.rs
@@ -314,6 +314,7 @@ fn run_script(flags: DenoFlags, argv: Vec<String>) {
     worker
       .execute_mod_async(&main_module, false)
       .and_then(move |()| {
+        js_check(worker.execute("window.dispatchEvent(new Event('load'))"));
         worker.then(|result| {
           js_check(result);
           Ok(())
diff --git a/js/dom_types.ts b/js/dom_types.ts
index 07f7d7898..a7c36df32 100644
--- a/js/dom_types.ts
+++ b/js/dom_types.ts
@@ -71,11 +71,16 @@ export enum NodeType {
   DOCUMENT_FRAGMENT_NODE = 11
 }
 
+export const eventTargetHost: unique symbol = Symbol();
+export const eventTargetListeners: unique symbol = Symbol();
+export const eventTargetMode: unique symbol = Symbol();
+export const eventTargetNodeType: unique symbol = Symbol();
+
 export interface EventTarget {
-  host: EventTarget | null;
-  listeners: { [type in string]: EventListener[] };
-  mode: string;
-  nodeType: NodeType;
+  [eventTargetHost]: EventTarget | null;
+  [eventTargetListeners]: { [type in string]: EventListener[] };
+  [eventTargetMode]: string;
+  [eventTargetNodeType]: NodeType;
   addEventListener(
     type: string,
     callback: (event: Event) => void | null,
diff --git a/js/dom_util.ts b/js/dom_util.ts
index 2f22a4b51..7a5dc80b9 100644
--- a/js/dom_util.ts
+++ b/js/dom_util.ts
@@ -9,16 +9,18 @@ export function isNode(nodeImpl: domTypes.EventTarget | null): boolean {
 export function isShadowRoot(nodeImpl: domTypes.EventTarget | null): boolean {
   return Boolean(
     nodeImpl &&
-      nodeImpl.nodeType === domTypes.NodeType.DOCUMENT_FRAGMENT_NODE &&
-      "host" in nodeImpl
+      nodeImpl[domTypes.eventTargetNodeType] ===
+        domTypes.NodeType.DOCUMENT_FRAGMENT_NODE &&
+      nodeImpl[domTypes.eventTargetHost] != null
   );
 }
 
 export function isSlotable(nodeImpl: domTypes.EventTarget | null): boolean {
   return Boolean(
     nodeImpl &&
-      (nodeImpl.nodeType === domTypes.NodeType.ELEMENT_NODE ||
-        nodeImpl.nodeType === domTypes.NodeType.TEXT_NODE)
+      (nodeImpl[domTypes.eventTargetNodeType] ===
+        domTypes.NodeType.ELEMENT_NODE ||
+        nodeImpl[domTypes.eventTargetNodeType] === domTypes.NodeType.TEXT_NODE)
   );
 }
 
@@ -36,7 +38,7 @@ export function isShadowInclusiveAncestor(
     }
 
     if (isShadowRoot(node)) {
-      node = node && node.host;
+      node = node && node[domTypes.eventTargetHost];
     } else {
       node = null; // domSymbolTree.parent(node);
     }
@@ -77,7 +79,7 @@ export function retarget(
         return a;
       }
 
-      a = aRoot.host;
+      a = aRoot[domTypes.eventTargetHost];
     }
   }
 }
diff --git a/js/event_target.ts b/js/event_target.ts
index 0e06dc34f..e376e78a1 100644
--- a/js/event_target.ts
+++ b/js/event_target.ts
@@ -98,13 +98,19 @@ export class EventListener implements domTypes.EventListener {
   }
 }
 
+export const eventTargetAssignedSlot: unique symbol = Symbol();
+export const eventTargetHasActivationBehavior: unique symbol = Symbol();
+
 export class EventTarget implements domTypes.EventTarget {
-  public host: domTypes.EventTarget | null = null;
-  public listeners: { [type in string]: domTypes.EventListener[] } = {};
-  public mode = "";
-  public nodeType: domTypes.NodeType = domTypes.NodeType.DOCUMENT_FRAGMENT_NODE;
-  private _assignedSlot = false;
-  private _hasActivationBehavior = false;
+  public [domTypes.eventTargetHost]: domTypes.EventTarget | null = null;
+  public [domTypes.eventTargetListeners]: {
+    [type in string]: domTypes.EventListener[]
+  } = {};
+  public [domTypes.eventTargetMode] = "";
+  public [domTypes.eventTargetNodeType]: domTypes.NodeType =
+    domTypes.NodeType.DOCUMENT_FRAGMENT_NODE;
+  private [eventTargetAssignedSlot] = false;
+  private [eventTargetHasActivationBehavior] = false;
 
   public addEventListener(
     type: string,
@@ -112,7 +118,7 @@ export class EventTarget implements domTypes.EventTarget {
     options?: domTypes.AddEventListenerOptions | boolean
   ): void {
     requiredArguments("EventTarget.addEventListener", arguments.length, 2);
-    const normalizedOptions: domTypes.AddEventListenerOptions = this._normalizeAddEventHandlerOptions(
+    const normalizedOptions: domTypes.AddEventListenerOptions = eventTargetHelpers.normalizeAddEventHandlerOptions(
       options
     );
 
@@ -120,12 +126,14 @@ export class EventTarget implements domTypes.EventTarget {
       return;
     }
 
-    if (!hasOwnProperty(this.listeners, type)) {
-      this.listeners[type] = [];
+    const listeners = this[domTypes.eventTargetListeners];
+
+    if (!hasOwnProperty(listeners, type)) {
+      listeners[type] = [];
     }
 
-    for (let i = 0; i < this.listeners[type].length; ++i) {
-      const listener = this.listeners[type][i];
+    for (let i = 0; i < listeners[type].length; ++i) {
+      const listener = listeners[type][i];
       if (
         ((typeof listener.options === "boolean" &&
           listener.options === normalizedOptions.capture) ||
@@ -137,7 +145,7 @@ export class EventTarget implements domTypes.EventTarget {
       }
     }
 
-    this.listeners[type].push(new EventListener(callback, normalizedOptions));
+    listeners[type].push(new EventListener(callback, normalizedOptions));
   }
 
   public removeEventListener(
@@ -146,13 +154,14 @@ export class EventTarget implements domTypes.EventTarget {
     options?: domTypes.EventListenerOptions | boolean
   ): void {
     requiredArguments("EventTarget.removeEventListener", arguments.length, 2);
-    if (hasOwnProperty(this.listeners, type) && callback !== null) {
-      this.listeners[type] = this.listeners[type].filter(
+    const listeners = this[domTypes.eventTargetListeners];
+    if (hasOwnProperty(listeners, type) && callback !== null) {
+      listeners[type] = listeners[type].filter(
         (listener): boolean => listener.callback !== callback
       );
     }
 
-    const normalizedOptions: domTypes.EventListenerOptions = this._normalizeEventHandlerOptions(
+    const normalizedOptions: domTypes.EventListenerOptions = eventTargetHelpers.normalizeEventHandlerOptions(
       options
     );
 
@@ -161,12 +170,12 @@ export class EventTarget implements domTypes.EventTarget {
       return;
     }
 
-    if (!this.listeners[type]) {
+    if (!listeners[type]) {
       return;
     }
 
-    for (let i = 0; i < this.listeners[type].length; ++i) {
-      const listener = this.listeners[type][i];
+    for (let i = 0; i < listeners[type].length; ++i) {
+      const listener = listeners[type][i];
 
       if (
         ((typeof listener.options === "boolean" &&
@@ -175,7 +184,7 @@ export class EventTarget implements domTypes.EventTarget {
             listener.options.capture === normalizedOptions.capture)) &&
         listener.callback === callback
       ) {
-        this.listeners[type].splice(i, 1);
+        listeners[type].splice(i, 1);
         break;
       }
     }
@@ -183,7 +192,8 @@ export class EventTarget implements domTypes.EventTarget {
 
   public dispatchEvent(event: domTypes.Event): boolean {
     requiredArguments("EventTarget.dispatchEvent", arguments.length, 1);
-    if (!hasOwnProperty(this.listeners, event.type)) {
+    const listeners = this[domTypes.eventTargetListeners];
+    if (!hasOwnProperty(listeners, event.type)) {
       return true;
     }
 
@@ -201,15 +211,21 @@ export class EventTarget implements domTypes.EventTarget {
       );
     }
 
-    return this._dispatch(event);
+    return eventTargetHelpers.dispatch(this, event);
   }
 
+  get [Symbol.toStringTag](): string {
+    return "EventTarget";
+  }
+}
+
+const eventTargetHelpers = {
   // https://dom.spec.whatwg.org/#concept-event-dispatch
-  _dispatch(
+  dispatch(
+    targetImpl: EventTarget,
     eventImpl: domTypes.Event,
     targetOverride?: domTypes.EventTarget
   ): boolean {
-    let targetImpl = this;
     let clearTargets = false;
     let activationTarget = null;
 
@@ -224,7 +240,7 @@ export class EventTarget implements domTypes.EventTarget {
     ) {
       const touchTargets: domTypes.EventTarget[] = [];
 
-      this._appendToEventPath(
+      eventTargetHelpers.appendToEventPath(
         eventImpl,
         targetImpl,
         targetOverride,
@@ -235,13 +251,15 @@ export class EventTarget implements domTypes.EventTarget {
 
       const isActivationEvent = eventImpl.type === "click";
 
-      if (isActivationEvent && targetImpl._hasActivationBehavior) {
+      if (isActivationEvent && targetImpl[eventTargetHasActivationBehavior]) {
         activationTarget = targetImpl;
       }
 
       let slotInClosedTree = false;
       let slotable =
-        isSlotable(targetImpl) && targetImpl._assignedSlot ? targetImpl : null;
+        isSlotable(targetImpl) && targetImpl[eventTargetAssignedSlot]
+          ? targetImpl
+          : null;
       let parent = getEventTargetParent(targetImpl, eventImpl);
 
       // Populate event path
@@ -254,7 +272,7 @@ export class EventTarget implements domTypes.EventTarget {
           if (
             isShadowRoot(parentRoot) &&
             parentRoot &&
-            parentRoot.mode === "closed"
+            parentRoot[domTypes.eventTargetMode] === "closed"
           ) {
             slotInClosedTree = true;
           }
@@ -266,7 +284,7 @@ export class EventTarget implements domTypes.EventTarget {
           isNode(parent) &&
           isShadowInclusiveAncestor(getRoot(targetImpl), parent)
         ) {
-          this._appendToEventPath(
+          eventTargetHelpers.appendToEventPath(
             eventImpl,
             parent,
             null,
@@ -282,12 +300,12 @@ export class EventTarget implements domTypes.EventTarget {
           if (
             isActivationEvent &&
             activationTarget === null &&
-            targetImpl._hasActivationBehavior
+            targetImpl[eventTargetHasActivationBehavior]
           ) {
             activationTarget = targetImpl;
           }
 
-          this._appendToEventPath(
+          eventTargetHelpers.appendToEventPath(
             eventImpl,
             parent,
             targetImpl,
@@ -328,7 +346,7 @@ export class EventTarget implements domTypes.EventTarget {
         const tuple = eventImpl.path[i];
 
         if (tuple.target === null) {
-          this._invokeEventListeners(tuple, eventImpl);
+          eventTargetHelpers.invokeEventListeners(targetImpl, tuple, eventImpl);
         }
       }
 
@@ -346,7 +364,7 @@ export class EventTarget implements domTypes.EventTarget {
             eventImpl.bubbles) ||
           eventImpl.eventPhase === domTypes.EventPhase.AT_TARGET
         ) {
-          this._invokeEventListeners(tuple, eventImpl);
+          eventTargetHelpers.invokeEventListeners(targetImpl, tuple, eventImpl);
         }
       }
     }
@@ -372,10 +390,11 @@ export class EventTarget implements domTypes.EventTarget {
     // }
 
     return !eventImpl.defaultPrevented;
-  }
+  },
 
   // https://dom.spec.whatwg.org/#concept-event-listener-invoke
-  _invokeEventListeners(
+  invokeEventListeners(
+    targetImpl: EventTarget,
     tuple: domTypes.EventPath,
     eventImpl: domTypes.Event
   ): void {
@@ -396,11 +415,16 @@ export class EventTarget implements domTypes.EventTarget {
 
     eventImpl.currentTarget = tuple.item;
 
-    this._innerInvokeEventListeners(eventImpl, tuple.item.listeners);
-  }
+    eventTargetHelpers.innerInvokeEventListeners(
+      targetImpl,
+      eventImpl,
+      tuple.item[domTypes.eventTargetListeners]
+    );
+  },
 
   // https://dom.spec.whatwg.org/#concept-event-listener-inner-invoke
-  _innerInvokeEventListeners(
+  innerInvokeEventListeners(
+    targetImpl: EventTarget,
     eventImpl: domTypes.Event,
     targetListeners: { [type in string]: domTypes.EventListener[] }
   ): boolean {
@@ -471,9 +495,9 @@ export class EventTarget implements domTypes.EventTarget {
     }
 
     return found;
-  }
+  },
 
-  _normalizeAddEventHandlerOptions(
+  normalizeAddEventHandlerOptions(
     options: boolean | domTypes.AddEventListenerOptions | undefined
   ): domTypes.AddEventListenerOptions {
     if (typeof options === "boolean" || typeof options === "undefined") {
@@ -487,9 +511,9 @@ export class EventTarget implements domTypes.EventTarget {
     } else {
       return options;
     }
-  }
+  },
 
-  _normalizeEventHandlerOptions(
+  normalizeEventHandlerOptions(
     options: boolean | domTypes.EventListenerOptions | undefined
   ): domTypes.EventListenerOptions {
     if (typeof options === "boolean" || typeof options === "undefined") {
@@ -501,10 +525,10 @@ export class EventTarget implements domTypes.EventTarget {
     } else {
       return options;
     }
-  }
+  },
 
   // https://dom.spec.whatwg.org/#concept-event-path-append
-  _appendToEventPath(
+  appendToEventPath(
     eventImpl: domTypes.Event,
     target: domTypes.EventTarget,
     targetOverride: domTypes.EventTarget | null,
@@ -513,7 +537,8 @@ export class EventTarget implements domTypes.EventTarget {
     slotInClosedTree: boolean
   ): void {
     const itemInShadowTree = isNode(target) && isShadowRoot(getRoot(target));
-    const rootOfClosedTree = isShadowRoot(target) && target.mode === "closed";
+    const rootOfClosedTree =
+      isShadowRoot(target) && target[domTypes.eventTargetMode] === "closed";
 
     eventImpl.path.push({
       item: target,
@@ -525,31 +550,11 @@ export class EventTarget implements domTypes.EventTarget {
       slotInClosedTree
     });
   }
-
-  get [Symbol.toStringTag](): string {
-    return "EventTarget";
-  }
-}
+};
 
 /** Built-in objects providing `get` methods for our
  * interceptable JavaScript operations.
  */
-Reflect.defineProperty(EventTarget.prototype, "host", {
-  enumerable: true,
-  writable: true
-});
-Reflect.defineProperty(EventTarget.prototype, "listeners", {
-  enumerable: true,
-  writable: true
-});
-Reflect.defineProperty(EventTarget.prototype, "mode", {
-  enumerable: true,
-  writable: true
-});
-Reflect.defineProperty(EventTarget.prototype, "nodeType", {
-  enumerable: true,
-  writable: true
-});
 Reflect.defineProperty(EventTarget.prototype, "addEventListener", {
   enumerable: true
 });
diff --git a/js/globals.ts b/js/globals.ts
index 1d33f6523..3be55e979 100644
--- a/js/globals.ts
+++ b/js/globals.ts
@@ -69,6 +69,7 @@ window.console = console;
 window.setTimeout = timers.setTimeout;
 window.setInterval = timers.setInterval;
 window.location = (undefined as unknown) as domTypes.Location;
+window.onload = undefined as undefined | Function;
 // The following Crypto interface implementation is not up to par with the
 // standard https://www.w3.org/TR/WebCryptoAPI/#crypto-interface as it does not
 // yet incorporate the SubtleCrypto interface as its "subtle" property.
@@ -135,6 +136,28 @@ window.postMessage = workers.postMessage;
 window.Worker = workers.WorkerImpl;
 export type Worker = workers.Worker;
 
+window[domTypes.eventTargetHost] = null;
+window[domTypes.eventTargetListeners] = {};
+window[domTypes.eventTargetMode] = "";
+window[domTypes.eventTargetNodeType] = 0;
+window[eventTarget.eventTargetAssignedSlot] = false;
+window[eventTarget.eventTargetHasActivationBehavior] = false;
+window.addEventListener = eventTarget.EventTarget.prototype.addEventListener;
+window.dispatchEvent = eventTarget.EventTarget.prototype.dispatchEvent;
+window.removeEventListener =
+  eventTarget.EventTarget.prototype.removeEventListener;
+
+// Registers the handler for window.onload function.
+window.addEventListener(
+  "load",
+  (e: domTypes.Event): void => {
+    const onload = window.onload;
+    if (typeof onload === "function") {
+      onload(e);
+    }
+  }
+);
+
 // below are interfaces that are available in TypeScript but
 // have different signatures
 export interface ImportMeta {
diff --git a/js/window.ts b/js/window.ts
index 6773ea5b2..3d3d6601f 100644
--- a/js/window.ts
+++ b/js/window.ts
@@ -1,5 +1,4 @@
 // Copyright 2018-2019 the Deno authors. All rights reserved. MIT license.
-
 // (0, eval) is indirect eval.
 // See the links below for details:
 // - https://stackoverflow.com/a/14120023
diff --git a/tests/034_onload.out b/tests/034_onload.out
new file mode 100644
index 000000000..0939be8cd
--- /dev/null
+++ b/tests/034_onload.out
@@ -0,0 +1,7 @@
+log from nest_imported script
+log from imported script
+log from main
+got load event in onload function
+got load event in event handler (nest_imported)
+got load event in event handler (imported)
+got load event in event handler (main)
diff --git a/tests/034_onload.test b/tests/034_onload.test
new file mode 100644
index 000000000..d3105656f
--- /dev/null
+++ b/tests/034_onload.test
@@ -0,0 +1,2 @@
+args: run --reload tests/034_onload/main.ts
+output: tests/034_onload.out
diff --git a/tests/034_onload/imported.ts b/tests/034_onload/imported.ts
new file mode 100644
index 000000000..5cf2d7b4c
--- /dev/null
+++ b/tests/034_onload/imported.ts
@@ -0,0 +1,8 @@
+import "./nest_imported.ts";
+window.addEventListener(
+  "load",
+  (e: Event): void => {
+    console.log(`got ${e.type} event in event handler (imported)`);
+  }
+);
+console.log("log from imported script");
diff --git a/tests/034_onload/main.ts b/tests/034_onload/main.ts
new file mode 100644
index 000000000..68851950a
--- /dev/null
+++ b/tests/034_onload/main.ts
@@ -0,0 +1,14 @@
+import "./imported.ts";
+
+window.addEventListener(
+  "load",
+  (e: Event): void => {
+    console.log(`got ${e.type} event in event handler (main)`);
+  }
+);
+
+window.onload = (e: Event): void => {
+  console.log(`got ${e.type} event in onload function`);
+};
+
+console.log("log from main");
diff --git a/tests/034_onload/nest_imported.ts b/tests/034_onload/nest_imported.ts
new file mode 100644
index 000000000..2e2bee1d5
--- /dev/null
+++ b/tests/034_onload/nest_imported.ts
@@ -0,0 +1,7 @@
+window.addEventListener(
+  "load",
+  (e: Event): void => {
+    console.log(`got ${e.type} event in event handler (nest_imported)`);
+  }
+);
+console.log("log from nest_imported script");
diff --git a/tests/034_onload_imported.ts b/tests/034_onload_imported.ts
new file mode 100644
index 000000000..d97aabeca
--- /dev/null
+++ b/tests/034_onload_imported.ts
@@ -0,0 +1 @@
+console.log("from imported script");
diff --git a/website/manual.md b/website/manual.md
index 4025e5acc..0424a2d25 100644
--- a/website/manual.md
+++ b/website/manual.md
@@ -425,7 +425,7 @@ $ deno run --allow-net=deno.land allow-net-whitelist-example.ts
 Example:
 
 ```ts
-async function main() {
+window.onload = async function() {
   // create subprocess
   const p = Deno.run({
     args: ["echo", "hello"]
@@ -433,9 +433,7 @@ async function main() {
 
   // await its completion
   await p.status();
-}
-
-main();
+};
 ```
 
 Run it:
@@ -445,12 +443,17 @@ $ deno run --allow-run ./subprocess_simple.ts
 hello
 ```
 
+Here a function is assigned to `window.onload`. This function is called after
+the main script is loaded. This is the same as
+[onload](https://developer.mozilla.org/en-US/docs/Web/API/GlobalEventHandlers/onload)
+of the browsers, and it can be used as the main entrypoint.
+
 By default when you use `Deno.run()` subprocess inherits `stdin`, `stdout` and
 `stderr` of parent process. If you want to communicate with started subprocess
 you can use `"piped"` option.
 
 ```ts
-async function main() {
+window.onload = async function() {
   const decoder = new TextDecoder();
 
   const fileNames = Deno.args.slice(1);
@@ -479,9 +482,7 @@ async function main() {
   }
 
   Deno.exit(code);
-}
-
-main();
+};
 ```
 
 When you run it:
@@ -833,14 +834,12 @@ Example:
 
 import { serve } from "http/server.ts";
 
-async function main() {
+window.onload = async function() {
   const body = new TextEncoder().encode("Hello World\n");
   for await (const req of serve(":8000")) {
     req.respond({ body });
   }
-}
-
-main();
+};
 ```
 
 ```shell