Merged PR 178588: Side channel JS SDK

From the end user's perspective, they will need to provide a third parameter to `powerbi.embed()` request.
The new input may be extended in the future to support other event hooks.

```javascript
powerbi.embed(..., config, { preQueryCallback: provideContext })
```
The code in `service.ts` is similar to the event listeners we set in the [constructor](https://powerbi.visualstudio.com/Embedded/_git/powerbi-javascript?path=%2Fsrc%2Fservice.ts&version=GBmaster&line=168&lineEnd=168&lineStartColumn=5&lineEndColumn=21&lineStyle=plain&_a=contents)

.gitignore

@@ -9,3 +9,4 @@ dist/powerbi.js.map
 *.js.map
 package-lock.json
 demo/package-lock.json
+.vscode

dist/powerbi-client.d.ts

@@ -1,4 +1,4 @@
-// powerbi-client v2.18.3
+// powerbi-client v2.18.4
 // Copyright (c) Microsoft Corporation.
 // Licensed under the MIT License.
 declare module "config" {
@@ -2127,6 +2127,10 @@ declare module "service" {
          * @hidden
          */
         private embedExisting;
+        /**
+         * @hidden
+         */
+        private registerApplicationContextHook;
         /**
          * Adds an event handler for DOMContentLoaded, which searches the DOM for elements that have the 'powerbi-embed-url' attribute,
          * and automatically attempts to embed a powerbi component based on information from other powerbi-* attributes.

package.json

@@ -1,6 +1,6 @@
 {
   "name": "powerbi-client",
-  "version": "2.18.3",
+  "version": "2.18.4",
   "description": "JavaScript library for embedding Power BI into your apps. Provides service which makes it easy to embed different types of components and an object model which allows easy interaction with these components such as changing pages, applying filters, and responding to data selection.",
   "main": "dist/powerbi.js",
   "types": "dist/powerbi-client.d.ts",
@@ -81,7 +81,7 @@
   },
   "dependencies": {
     "http-post-message": "^0.2",
-    "powerbi-models": "^1.9.2",
+    "powerbi-models": "^1.9.3",
     "powerbi-router": "^0.1",
     "window-post-message-proxy": "^0.2"
   },

src/config.ts

@@ -3,7 +3,7 @@
 
 /** @ignore *//** */
 const config = {
-  version: '2.18.3',
+  version: '2.18.4',
   type: 'js'
 };
 

src/embed.ts

@@ -227,12 +227,15 @@ export abstract class Embed {
     this.commands = [];
     this.groups = [];
 
+    const registerQueryCallback = !!(<IEmbedConfiguration>config).eventHooks?.applicationContextProvider;
+    delete (<IEmbedConfiguration>config).eventHooks;
+
     this.populateConfig(config, isBootstrap);
 
     if (this.embedtype === 'create') {
-      this.setIframe(false /* set EventListener to call create() on 'load' event*/, phasedRender, isBootstrap);
+      this.setIframe(false /* set EventListener to call create() on 'load' event*/, phasedRender, isBootstrap, registerQueryCallback);
     } else {
-      this.setIframe(true /* set EventListener to call load() on 'load' event*/, phasedRender, isBootstrap);
+      this.setIframe(true /* set EventListener to call load() on 'load' event*/, phasedRender, isBootstrap, registerQueryCallback);
     }
   }
 
@@ -702,10 +705,14 @@ export abstract class Embed {
    *
    * @hidden
    */
-  private setIframe(isLoad: boolean, phasedRender?: boolean, isBootstrap?: boolean): void {
+  private setIframe(isLoad: boolean, phasedRender?: boolean, isBootstrap?: boolean, registerQueryCallback?: boolean): void {
     if (!this.iframe) {
       const iframeContent = document.createElement("iframe");
-      const embedUrl = this.config.uniqueId ? addParamToUrl(this.config.embedUrl, 'uid', this.config.uniqueId) : this.config.embedUrl;
+      let embedUrl = this.config.uniqueId ? addParamToUrl(this.config.embedUrl, 'uid', this.config.uniqueId) : this.config.embedUrl;
+
+      if (!isBootstrap && registerQueryCallback)
+        embedUrl = addParamToUrl(embedUrl, "registerQueryCallback", "true");
+
       iframeContent.style.width = '100%';
       iframeContent.style.height = '100%';
       iframeContent.setAttribute("src", embedUrl);

src/service.ts

@@ -300,6 +300,7 @@ export class Service implements IService {
    * @returns {Embed}
    */
   embed(element: HTMLElement, config: IComponentEmbedConfiguration | IEmbedConfigurationBase = {}): Embed {
+    this.registerApplicationContextHook(config as IEmbedConfiguration);
     return this.embedInternal(element, config);
   }
 
@@ -314,6 +315,7 @@ export class Service implements IService {
    * @returns {Embed}
    */
   load(element: HTMLElement, config: IComponentEmbedConfiguration | IEmbedConfigurationBase = {}): Embed {
+    this.registerApplicationContextHook(config as IEmbedConfiguration);
     return this.embedInternal(element, config, /* phasedRender */ true, /* isBootstrap */ false);
   }
 
@@ -440,6 +442,30 @@ export class Service implements IService {
     return component;
   }
 
+  /**
+   * @hidden
+   */
+  private registerApplicationContextHook(config: IEmbedConfiguration): void {
+    const applicationContextProvider = config?.eventHooks?.applicationContextProvider;
+    if (!applicationContextProvider) {
+      return;
+    }
+
+    if (typeof applicationContextProvider !== 'function') {
+      throw new Error("applicationContextProvider must be a function");
+    }
+
+    this.router.post(`preQuery`, async (req, _res) => {
+      try {
+        let result = await applicationContextProvider(req.body);
+        _res.send(200, result);
+      } catch (error) {
+        _res.send(400, null);
+        console.error(error);
+      }
+    });
+  }
+
   /**
    * Adds an event handler for DOMContentLoaded, which searches the DOM for elements that have the 'powerbi-embed-url' attribute,
    * and automatically attempts to embed a powerbi component based on information from other powerbi-* attributes.