Bug 1875071 - Simplify OpenSearchEngine loading and install process in the search service. r=search-reviewers,mcheang

The current process creates the OpenSearchEngine and gets it to load its data. Once the data is loaded,
it notifies the SearchService that is ready to be added.

This changes the structure so that the SearchService loads the data, creates the engine and then adds it
straight away.

This also means that the contextual search provider can be simplified and doesn't need to tell the engine
not to add itself to the SearchService.

Differential Revision: https://phabricator.services.mozilla.com/D198814

browser/modules/test/browser/browser_ContentSearch.js

@@ -207,9 +207,10 @@ add_task(async function badImage() {
   // If the bad image URI caused an exception to be thrown within ContentSearch,
   // then we'll hang waiting for the CurrentState responses triggered by the new
   // engine.  That's what we're testing, and obviously it shouldn't happen.
-  let vals = await waitForNewEngine(browser, "contentSearchBadImage.xml");
-  let engine = vals[0];
-  let finalCurrentStateMsg = vals[vals.length - 1];
+  let [engine, currentStateMsg] = await waitForNewEngine(
+    browser,
+    "contentSearchBadImage.xml"
+  );
   let expectedCurrentState = await currentStateObj();
   let expectedEngine = expectedCurrentState.engines.find(
     e => e.name == engine.name
@@ -221,7 +222,7 @@ add_task(async function badImage() {
     "Sanity check: icon of engine in expected state should be the placeholder: " +
       expectedEngine.iconData
   );
-  checkMsg(finalCurrentStateMsg, {
+  checkMsg(currentStateMsg, {
     type: "CurrentState",
     data: expectedCurrentState,
   });
@@ -237,8 +238,10 @@ add_task(
     let { browser } = await addTab();
 
     // Add the test engine that provides suggestions.
-    let vals = await waitForNewEngine(browser, "contentSearchSuggestions.xml");
-    let engine = vals[0];
+    let [engine] = await waitForNewEngine(
+      browser,
+      "contentSearchSuggestions.xml"
+    );
 
     let searchStr = "browser_ContentSearch.js-suggestions-";
 
@@ -391,40 +394,36 @@ function checkMsg(actualMsg, expectedMsgData) {
   checkArrayBuffers(actualMsg, expectedMsgData);
 }
 
-async function waitForTestMsg(browser, type, count = 1) {
+async function waitForTestMsg(browser, type) {
+  // We call SpecialPowers.spawn twice because we must let the first one
+  // complete so that the listener is added before we return from this function.
+  // In the second one, we wait for the signal that the expected message has
+  // been received.
   await SpecialPowers.spawn(
     browser,
-    [SERVICE_EVENT_TYPE, type, count],
-    (childEvent, childType, childCount) => {
-      content.eventDetails = [];
+    [SERVICE_EVENT_TYPE, type],
+    async (childEvent, childType) => {
       function listener(event) {
         if (event.detail.type != childType) {
           return;
         }
 
-        content.eventDetails.push(event.detail);
-
-        if (--childCount > 0) {
-          return;
-        }
-
+        content.eventDetails = event.detail;
         content.removeEventListener(childEvent, listener, true);
       }
+      // Ensure any previous details are cleared, so that we don't
+      // get the wrong ones by mistake.
+      content.eventDetails = undefined;
       content.addEventListener(childEvent, listener, true);
     }
   );
 
-  let donePromise = SpecialPowers.spawn(
-    browser,
-    [type, count],
-    async (childType, childCount) => {
-      await ContentTaskUtils.waitForCondition(() => {
-        return content.eventDetails.length == childCount;
-      }, "Expected " + childType + " event");
-
-      return childCount > 1 ? content.eventDetails : content.eventDetails[0];
-    }
-  );
+  let donePromise = SpecialPowers.spawn(browser, [type], async childType => {
+    await ContentTaskUtils.waitForCondition(() => {
+      return !!content.eventDetails;
+    }, "Expected " + childType + " event");
+    return content.eventDetails;
+  });
 
   return { donePromise };
 }
@@ -434,13 +433,12 @@ async function waitForNewEngine(browser, basename) {
 
   // Wait for the search events triggered by adding the new engine.
   // There are two events triggerd by engine-added and engine-loaded
-  let statePromise = await waitForTestMsg(browser, "CurrentState", 2);
+  let statePromise = await waitForTestMsg(browser, "CurrentState");
 
   let engine = await SearchTestUtils.promiseNewSearchEngine({
     url: getRootDirectory(gTestPath) + basename,
   });
-  let results = await statePromise.donePromise;
-  return [engine, ...results];
+  return [engine, await statePromise.donePromise];
 }
 
 async function addTab() {