Bug 1656220 - Implement recording attributions for search engines. r=dao

Differential Revision: https://phabricator.services.mozilla.com/D87501

browser/actors/ContentSearchParent.jsm

@@ -253,6 +253,7 @@ let ContentSearch = {
     }
     win.BrowserSearch.recordSearchInTelemetry(engine, data.healthReportKey, {
       selection: data.selection,
+      url: submission.uri,
     });
   },
 

browser/app/profile/firefox.js

@@ -1313,7 +1313,8 @@ pref("prompts.tab_modal.enabled", true);
 pref("prompts.defaultModalType", 3);
 
 pref("browser.topsites.useRemoteSetting", false);
-pref("browser.topsites.attributionURL", "");
+
+pref("browser.partnerlink.attributionURL", "https://topsites.mozilla.io/cid/amzn_2020_a1");
 
 // Whether to show tab level system prompts opened via nsIPrompt(Service) as
 // SubDialogs in the TabDialogBox (true) or as TabModalPrompt in the

browser/base/content/browser.js

@@ -4346,7 +4346,7 @@ const BrowserSearch = {
       csp,
     });
 
-    return engine;
+    return { engine, url: submission.uri };
   },
 
   /**
@@ -4356,7 +4356,7 @@ const BrowserSearch = {
    * BrowserSearch.loadSearch for the preferred API.
    */
   async loadSearchFromContext(terms, usePrivate, triggeringPrincipal, csp) {
-    let engine = await BrowserSearch._loadSearch(
+    let { engine, url } = await BrowserSearch._loadSearch(
       terms,
       usePrivate && !PrivateBrowsingUtils.isWindowPrivate(window)
         ? "window"
@@ -4369,7 +4369,7 @@ const BrowserSearch = {
       csp
     );
     if (engine) {
-      BrowserSearch.recordSearchInTelemetry(engine, "contextmenu");
+      BrowserSearch.recordSearchInTelemetry(engine, "contextmenu", { url });
     }
   },
 
@@ -4377,7 +4377,7 @@ const BrowserSearch = {
    * Perform a search initiated from the command line.
    */
   async loadSearchFromCommandLine(terms, usePrivate, triggeringPrincipal, csp) {
-    let engine = await BrowserSearch._loadSearch(
+    let { engine, url } = await BrowserSearch._loadSearch(
       terms,
       "current",
       usePrivate,
@@ -4386,7 +4386,7 @@ const BrowserSearch = {
       csp
     );
     if (engine) {
-      BrowserSearch.recordSearchInTelemetry(engine, "system");
+      BrowserSearch.recordSearchInTelemetry(engine, "system", { url });
     }
   },
 

browser/components/extensions/parent/ext-search.js

@@ -117,7 +117,8 @@ this.search = class extends ExtensionAPI {
           BrowserUsageTelemetry.recordSearch(
             tabbrowser,
             engine,
-            "webextension"
+            "webextension",
+            { url: submission.uri }
           );
         },
       },

browser/components/search/content/searchbar.js

@@ -421,6 +421,7 @@
         isOneOff: aOneOff,
         isSuggestion: !aOneOff && telemetrySearchDetails,
         selection: telemetrySearchDetails,
+        url: submission.uri,
       };
       BrowserSearch.recordSearchInTelemetry(engine, "searchbar", details);
       // null parameter below specifies HTML response for search

browser/components/urlbar/UrlbarInput.jsm

@@ -474,7 +474,7 @@ class UrlbarInput {
         selectedOneOff.engine,
         searchString
       );
-      this._recordSearch(selectedOneOff.engine, event);
+      this._recordSearch(selectedOneOff.engine, event, { url });
 
       UrlbarUtils.addToFormHistory(
         this,
@@ -776,6 +776,7 @@ class UrlbarInput {
           isSuggestion: !!result.payload.suggestion,
           isFormHistory: result.source == UrlbarUtils.RESULT_SOURCE.HISTORY,
           alias: result.payload.keyword,
+          url,
         };
         const engine = Services.search.getEngineByName(result.payload.engine);
         this._recordSearch(engine, event, actionDetails);
@@ -1825,6 +1826,8 @@ class UrlbarInput {
    *   True if this query was initiated via a search alias.
    * @param {boolean} searchActionDetails.isFormHistory
    *   True if this query was initiated from a form history result.
+   * @param {string} searchActionDetails.url
+   *   The url this query was triggered with.
    */
   _recordSearch(engine, event, searchActionDetails = {}) {
     const isOneOff = this.view.oneOffSearchButtons.maybeRecordTelemetry(event);

browser/modules/BrowserUsageTelemetry.jsm

@@ -23,6 +23,7 @@ XPCOMUtils.defineLazyModuleGetters(this, {
   CustomizableUI: "resource:///modules/CustomizableUI.jsm",
   OS: "resource://gre/modules/osfile.jsm",
   PageActions: "resource:///modules/PageActions.jsm",
+  PartnerLinkAttribution: "resource:///modules/PartnerLinkAttribution.jsm",
   PrivateBrowsingUtils: "resource://gre/modules/PrivateBrowsingUtils.jsm",
   SearchTelemetry: "resource:///modules/SearchTelemetry.jsm",
   Services: "resource://gre/modules/Services.jsm",
@@ -604,7 +605,11 @@ let BrowserUsageTelemetry = {
     this._handleSearchAction(engine, source, details);
   },
 
-  _recordSearch(engine, source, action = null) {
+  _recordSearch(engine, url, source, action = null) {
+    PartnerLinkAttribution.makeSearchEngineRequest(engine, url).catch(
+      Cu.reportError
+    );
+
     let scalarKey = action ? "search_" + action : "search";
     Services.telemetry.keyedScalarAdd(
       "browser.engagement.navigation." + source,
@@ -626,15 +631,15 @@ let BrowserUsageTelemetry = {
         this._handleSearchAndUrlbar(engine, source, details);
         break;
       case "abouthome":
-        this._recordSearch(engine, "about_home", "enter");
+        this._recordSearch(engine, details.url, "about_home", "enter");
         break;
       case "newtab":
-        this._recordSearch(engine, "about_newtab", "enter");
+        this._recordSearch(engine, details.url, "about_newtab", "enter");
         break;
       case "contextmenu":
       case "system":
       case "webextension":
-        this._recordSearch(engine, source);
+        this._recordSearch(engine, details.url, source);
         break;
     }
   },
@@ -665,27 +670,27 @@ let BrowserUsageTelemetry = {
       }
 
       // If that's a legit one-off search signal, record it using the relative key.
-      this._recordSearch(engine, sourceName, "oneoff");
+      this._recordSearch(engine, details.url, sourceName, "oneoff");
       return;
     }
 
     // The search was not a one-off. It was a search with the default search engine.
     if (details.isFormHistory) {
       // It came from a form history result.
-      this._recordSearch(engine, sourceName, "formhistory");
+      this._recordSearch(engine, details.url, sourceName, "formhistory");
       return;
     } else if (details.isSuggestion) {
       // It came from a suggested search, so count it as such.
-      this._recordSearch(engine, sourceName, "suggestion");
+      this._recordSearch(engine, details.url, sourceName, "suggestion");
       return;
     } else if (details.alias) {
       // This one came from a search that used an alias.
-      this._recordSearch(engine, sourceName, "alias");
+      this._recordSearch(engine, details.url, sourceName, "alias");
       return;
     }
 
     // The search signal was generated by typing something and pressing enter.
-    this._recordSearch(engine, sourceName, "enter");
+    this._recordSearch(engine, details.url, sourceName, "enter");
   },
 
   /**

browser/modules/PartnerLinkAttribution.jsm

@@ -8,17 +8,14 @@ Cu.importGlobalProperties(["fetch"]);
 
 var EXPORTED_SYMBOLS = ["PartnerLinkAttribution"];
 
-ChromeUtils.defineModuleGetter(
-  this,
-  "Services",
-  "resource://gre/modules/Services.jsm"
+const { XPCOMUtils } = ChromeUtils.import(
+  "resource://gre/modules/XPCOMUtils.jsm"
 );
 
-ChromeUtils.defineModuleGetter(
-  this,
-  "Region",
-  "resource://gre/modules/Region.jsm"
-);
+XPCOMUtils.defineLazyModuleGetters(this, {
+  Services: "resource://gre/modules/Services.jsm",
+  Region: "resource://gre/modules/Region.jsm",
+});
 
 var PartnerLinkAttribution = {
   async makeRequest({ targetURL, source }) {
@@ -34,7 +31,7 @@ var PartnerLinkAttribution = {
 
     const attributionUrl = Services.prefs.getStringPref(
       Services.prefs.getBoolPref("browser.topsites.useRemoteSetting")
-        ? "browser.topsites.attributionURL"
+        ? "browser.partnerlink.attributionURL"
         : `browser.newtabpage.searchTileOverride.${partner}.attributionURL`,
       ""
     );
@@ -42,15 +39,67 @@ var PartnerLinkAttribution = {
       record("attribution", "abort");
       return;
     }
-    const request = new Request(attributionUrl);
-    request.headers.set("X-Region", Region.home);
-    request.headers.set("X-Source", source);
-    request.headers.set("X-Target-URL", targetURL);
-    const response = await fetch(request);
-    record("attribution", response.ok ? "success" : "failure");
+    let result = await sendRequest(attributionUrl, source, targetURL);
+    record("attribution", result ? "success" : "failure");
+  },
+
+  /**
+   * Makes a request to the attribution URL for a search engine search.
+   *
+   * @param {nsISearchEngine} engine
+   *   The search engine to save the attribution for.
+   * @param {nsIURI} targetUrl
+   *   The target URL to filter and include in the attribution.
+   */
+  async makeSearchEngineRequest(engine, targetUrl) {
+    if (!engine.sendAttributionRequest) {
+      return;
+    }
+
+    let searchUrlQueryParamName = engine.searchUrlQueryParamName;
+    if (!searchUrlQueryParamName) {
+      Cu.reportError("makeSearchEngineRequest can't find search terms key");
+      return;
+    }
+
+    let url = targetUrl;
+    if (typeof url == "string") {
+      url = Services.io.newURI(url);
+    }
+
+    let targetParams = new URLSearchParams(url.query);
+    if (!targetParams.has(searchUrlQueryParamName)) {
+      Cu.reportError(
+        "makeSearchEngineRequest can't remove target search terms"
+      );
+      return;
+    }
+
+    const attributionUrl = Services.prefs.getStringPref(
+      "browser.partnerlink.attributionURL",
+      ""
+    );
+
+    targetParams.delete(searchUrlQueryParamName);
+    let strippedTargetUrl = `${url.prePath}${url.filePath}`;
+    let newParams = targetParams.toString();
+    if (newParams) {
+      strippedTargetUrl += "?" + newParams;
+    }
+
+    await sendRequest(attributionUrl, "searchurl", strippedTargetUrl);
   },
 };
 
+async function sendRequest(attributionUrl, source, targetURL) {
+  const request = new Request(attributionUrl);
+  request.headers.set("X-Region", Region.home);
+  request.headers.set("X-Source", source);
+  request.headers.set("X-Target-URL", targetURL);
+  const response = await fetch(request);
+  return response.ok;
+}
+
 function recordTelemetryEvent(method, objectString, value, extra) {
   Services.telemetry.setEventRecordingEnabled("partner_link", true);
   Services.telemetry.recordEvent(

browser/modules/test/browser/browser.ini

@@ -15,10 +15,15 @@ support-files =
   !/browser/components/search/test/browser/testEngine.xml
   !/browser/components/search/test/browser/testEngine_diacritics.xml
   testEngine_chromeicon.xml
-skip-if = (debug && os == "linux" && bits == 64 && os_version == "18.04") # Bug 1649755 
+skip-if = (debug && os == "linux" && bits == 64 && os_version == "18.04") # Bug 1649755
 [browser_EveryWindow.js]
 [browser_LiveBookmarkMigrator.js]
 [browser_PageActions.js]
+[browser_PartnerLinkAttribution.js]
+support-files =
+  search-engines/basic/manifest.json
+  search-engines/simple/manifest.json
+  search-engines/engines.json
 [browser_PermissionUI.js]
 [browser_PermissionUI_prompts.js]
 [browser_preloading_tab_moving.js]

browser/modules/test/browser/browser_PartnerLinkAttribution.js

@@ -0,0 +1,286 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/
+ */
+
+/**
+ * This file tests urlbar telemetry with search related actions.
+ */
+
+"use strict";
+
+const SCALAR_URLBAR = "browser.engagement.navigation.urlbar";
+
+// The preference to enable suggestions in the urlbar.
+const SUGGEST_URLBAR_PREF = "browser.urlbar.suggest.searches";
+// The name of the search engine used to generate suggestions.
+const SUGGESTION_ENGINE_NAME =
+  "browser_UsageTelemetry usageTelemetrySearchSuggestions.xml";
+
+XPCOMUtils.defineLazyModuleGetters(this, {
+  CustomizableUITestUtils:
+    "resource://testing-common/CustomizableUITestUtils.jsm",
+  Region: "resource://gre/modules/Region.jsm",
+  SearchTelemetry: "resource:///modules/SearchTelemetry.jsm",
+  SearchTestUtils: "resource://testing-common/SearchTestUtils.jsm",
+  UrlbarTestUtils: "resource://testing-common/UrlbarTestUtils.jsm",
+  HttpServer: "resource://testing-common/httpd.js",
+});
+
+let gCUITestUtils = new CustomizableUITestUtils(window);
+SearchTestUtils.init(Assert, registerCleanupFunction);
+
+var gHttpServer = null;
+var gRequests = [];
+
+function submitHandler(request, response) {
+  gRequests.push(request);
+  response.setStatusLine(request.httpVersion, 200, "Ok");
+}
+
+add_task(async function setup() {
+  // Ensure the initial init is complete.
+  await Services.search.init();
+
+  // Clear history so that history added by previous tests doesn't mess up this
+  // test when it selects results in the urlbar.
+  await PlacesUtils.history.clear();
+
+  let searchExtensions = getChromeDir(getResolvedURI(gTestPath));
+  searchExtensions.append("search-engines");
+
+  await SearchTestUtils.useMochitestEngines(searchExtensions);
+
+  SearchTestUtils.useMockIdleService();
+  let response = await fetch(`resource://search-extensions/engines.json`);
+  let json = await response.json();
+  await SearchTestUtils.updateRemoteSettingsConfig(json.data);
+
+  gHttpServer = new HttpServer();
+  gHttpServer.registerPathHandler("/", submitHandler);
+  gHttpServer.start(-1);
+
+  await SpecialPowers.pushPrefEnv({
+    set: [
+      // Enable search suggestions in the urlbar.
+      [SUGGEST_URLBAR_PREF, true],
+      // Clear historical search suggestions to avoid interference from previous
+      // tests.
+      ["browser.urlbar.maxHistoricalSearchSuggestions", 0],
+      // Use the default matching bucket configuration.
+      ["browser.urlbar.matchBuckets", "general:5,suggestion:4"],
+      //
+      [
+        "browser.partnerlink.attributionURL",
+        `http://localhost:${gHttpServer.identity.primaryPort}/`,
+      ],
+    ],
+  });
+
+  await gCUITestUtils.addSearchBar();
+
+  // Make sure to restore the engine once we're done.
+  registerCleanupFunction(async function() {
+    await SearchTestUtils.updateRemoteSettingsConfig();
+    await gHttpServer.stop();
+    gHttpServer = null;
+    await PlacesUtils.history.clear();
+    gCUITestUtils.removeSearchBar();
+  });
+});
+
+function searchInAwesomebar(value, win = window) {
+  return UrlbarTestUtils.promiseAutocompleteResultPopup({
+    window: win,
+    waitForFocus,
+    value,
+    fireInputEvent: true,
+  });
+}
+
+add_task(async function test_simpleQuery_no_attribution() {
+  await Services.search.setDefault(
+    Services.search.getEngineByName("Simple Engine")
+  );
+
+  let tab = await BrowserTestUtils.openNewForegroundTab(
+    gBrowser,
+    "about:blank"
+  );
+
+  info("Simulate entering a simple search.");
+  let promiseLoad = BrowserTestUtils.waitForDocLoadAndStopIt(
+    "https://example.com/?sourceId=Mozilla-search&search=simple+query",
+    tab
+  );
+  await searchInAwesomebar("simple query");
+  EventUtils.synthesizeKey("KEY_Enter");
+  await promiseLoad;
+
+  await new Promise(resolve => Services.tm.dispatchToMainThread(resolve));
+
+  Assert.equal(gRequests.length, 0, "Should not have submitted an attribution");
+
+  BrowserTestUtils.removeTab(tab);
+
+  await Services.search.setDefault(Services.search.getEngineByName("basic"));
+});
+
+async function checkAttributionRecorded(actionFn, cleanupFn) {
+  let tab = await BrowserTestUtils.openNewForegroundTab(
+    gBrowser,
+    "data:text/plain;charset=utf8,simple%20query"
+  );
+
+  let promiseLoad = BrowserTestUtils.waitForDocLoadAndStopIt(
+    "https://mochi.test:8888/browser/browser/components/search/test/browser/?search=simple+query&foo=1",
+    tab
+  );
+  await actionFn(tab);
+  await promiseLoad;
+
+  await BrowserTestUtils.waitForCondition(
+    () => gRequests.length == 1,
+    "Should have received an attribution submission"
+  );
+  Assert.equal(
+    gRequests[0].getHeader("x-region"),
+    Region.home,
+    "Should have set the region correctly"
+  );
+  Assert.equal(
+    gRequests[0].getHeader("X-Source"),
+    "searchurl",
+    "Should have set the source correctly"
+  );
+  Assert.equal(
+    gRequests[0].getHeader("X-Target-url"),
+    "https://mochi.test:8888/browser/browser/components/search/test/browser/?foo=1",
+    "Should have set the target url correctly and stripped the search terms"
+  );
+  if (cleanupFn) {
+    await cleanupFn();
+  }
+  BrowserTestUtils.removeTab(tab);
+  gRequests = [];
+}
+
+add_task(async function test_urlbar() {
+  await checkAttributionRecorded(async tab => {
+    await searchInAwesomebar("simple query");
+    EventUtils.synthesizeKey("KEY_Enter");
+  });
+});
+
+add_task(async function test_searchbar() {
+  await checkAttributionRecorded(async tab => {
+    let sb = BrowserSearch.searchBar;
+    // Write the search query in the searchbar.
+    sb.focus();
+    sb.value = "simple query";
+    sb.textbox.controller.startSearch("simple query");
+    // Wait for the popup to show.
+    await BrowserTestUtils.waitForEvent(sb.textbox.popup, "popupshown");
+    // And then for the search to complete.
+    await BrowserTestUtils.waitForCondition(
+      () =>
+        sb.textbox.controller.searchStatus >=
+        Ci.nsIAutoCompleteController.STATUS_COMPLETE_NO_MATCH,
+      "The search in the searchbar must complete."
+    );
+    EventUtils.synthesizeKey("KEY_Enter");
+  });
+});
+
+add_task(async function test_context_menu() {
+  let contextMenu;
+  await checkAttributionRecorded(
+    async tab => {
+      info("Select all the text in the page.");
+      await SpecialPowers.spawn(tab.linkedBrowser, [""], async function() {
+        return new Promise(resolve => {
+          content.document.addEventListener(
+            "selectionchange",
+            () => resolve(),
+            {
+              once: true,
+            }
+          );
+          content.document
+            .getSelection()
+            .selectAllChildren(content.document.body);
+        });
+      });
+
+      info("Open the context menu.");
+      contextMenu = document.getElementById("contentAreaContextMenu");
+      let popupPromise = BrowserTestUtils.waitForEvent(
+        contextMenu,
+        "popupshown"
+      );
+      BrowserTestUtils.synthesizeMouseAtCenter(
+        "body",
+        { type: "contextmenu", button: 2 },
+        gBrowser.selectedBrowser
+      );
+      await popupPromise;
+
+      info("Click on search.");
+      let searchItem = contextMenu.getElementsByAttribute(
+        "id",
+        "context-searchselect"
+      )[0];
+      searchItem.click();
+    },
+    () => {
+      contextMenu.hidePopup();
+      BrowserTestUtils.removeTab(gBrowser.selectedTab);
+    }
+  );
+});
+
+add_task(async function test_about_newtab() {
+  let tab = await BrowserTestUtils.openNewForegroundTab(
+    gBrowser,
+    "about:newtab",
+    false
+  );
+  await SpecialPowers.spawn(tab.linkedBrowser, [], async function() {
+    await ContentTaskUtils.waitForCondition(() => !content.document.hidden);
+  });
+
+  info("Trigger a simple serch, just text + enter.");
+  let promiseLoad = BrowserTestUtils.waitForDocLoadAndStopIt(
+    "https://mochi.test:8888/browser/browser/components/search/test/browser/?search=simple+query&foo=1",
+    tab
+  );
+  await typeInSearchField(
+    tab.linkedBrowser,
+    "simple query",
+    "newtab-search-text"
+  );
+  await BrowserTestUtils.synthesizeKey("VK_RETURN", {}, tab.linkedBrowser);
+  await promiseLoad;
+
+  await BrowserTestUtils.waitForCondition(
+    () => gRequests.length == 1,
+    "Should have received an attribution submission"
+  );
+  Assert.equal(
+    gRequests[0].getHeader("x-region"),
+    Region.home,
+    "Should have set the region correctly"
+  );
+  Assert.equal(
+    gRequests[0].getHeader("X-Source"),
+    "searchurl",
+    "Should have set the source correctly"
+  );
+  Assert.equal(
+    gRequests[0].getHeader("X-Target-url"),
+    "https://mochi.test:8888/browser/browser/components/search/test/browser/?foo=1",
+    "Should have set the target url correctly and stripped the search terms"
+  );
+
+  BrowserTestUtils.removeTab(tab);
+  gRequests = [];
+});

browser/modules/test/browser/search-engines/basic/manifest.json

@@ -0,0 +1,19 @@
+{
+  "name": "basic",
+  "manifest_version": 2,
+  "version": "1.0",
+  "description": "basic",
+  "applications": {
+    "gecko": {
+      "id": "basic@search.mozilla.org"
+    }
+  },
+  "hidden": true,
+  "chrome_settings_overrides": {
+    "search_provider": {
+      "name": "basic",
+      "search_url": "https://mochi.test:8888/browser/browser/components/search/test/browser/?search={searchTerms}&foo=1",
+      "suggest_url": "https://mochi.test:8888/browser/browser/modules/test/browser/usageTelemetrySearchSuggestions.sjs?{searchTerms}"
+    }
+  }
+}

browser/modules/test/browser/search-engines/engines.json

@@ -0,0 +1,24 @@
+{
+  "data": [
+    {
+      "webExtension": {
+        "id":"basic@search.mozilla.org"
+      },
+      "telemetryId": "telemetry",
+      "appliesTo": [{
+        "included": { "everywhere": true },
+        "default": "yes",
+        "sendAttributionRequest": true
+      }]
+    },
+    {
+      "webExtension": {
+        "id":"simple@search.mozilla.org"
+      },
+      "appliesTo": [{
+        "included": { "everywhere": true },
+        "default": "yes"
+      }]
+    }
+  ]
+}

browser/modules/test/browser/search-engines/simple/manifest.json

@@ -0,0 +1,29 @@
+{
+  "name": "Simple Engine",
+  "manifest_version": 2,
+  "version": "1.0",
+  "description": "Simple engine with a different name from the WebExtension id prefix",
+  "applications": {
+    "gecko": {
+      "id": "simple@search.mozilla.org"
+    }
+  },
+  "hidden": true,
+  "chrome_settings_overrides": {
+    "search_provider": {
+      "name": "Simple Engine",
+      "search_url": "https://example.com",
+      "params": [
+        {
+          "name": "sourceId",
+          "value": "Mozilla-search"
+        },
+        {
+          "name": "search",
+          "value": "{searchTerms}"
+        }
+      ],
+      "suggest_url": "https://example.com?search={searchTerms}"
+    }
+  }
+}

toolkit/components/search/SearchEngine.jsm

@@ -622,6 +622,9 @@ class SearchEngine {
   _definedAliases = [];
   // The urls associated with this engine.
   _urls = [];
+  // The query parameter name of the search url, cached in memory to avoid
+  // repeated look-ups.
+  _searchUrlQueryParamName = null;
 
   /**
    * Constructor.
@@ -1506,6 +1509,32 @@ class SearchEngine {
     return url.getSubmission(submissionData, this, purpose);
   }
 
+  get searchUrlQueryParamName() {
+    if (this._searchUrlQueryParamName != null) {
+      return this._searchUrlQueryParamName;
+    }
+
+    let submission = this.getSubmission(
+      "{searchTerms}",
+      SearchUtils.URL_TYPE.SEARCH
+    );
+
+    if (submission.postData) {
+      Cu.reportError("searchUrlQueryParamName can't handle POST urls.");
+      return (this._searchUrlQueryParamName = "");
+    }
+
+    let queryParams = new URLSearchParams(submission.uri.query);
+    let searchUrlQueryParamName = "";
+    for (let [key, value] of queryParams) {
+      if (value == "{searchTerms}") {
+        searchUrlQueryParamName = key;
+      }
+    }
+
+    return (this._searchUrlQueryParamName = searchUrlQueryParamName);
+  }
+
   // from nsISearchEngine
   supportsResponseType(type) {
     return this._getURLOfType(type) != null;

toolkit/components/search/nsISearchService.idl

@@ -50,6 +50,15 @@ interface nsISearchEngine : nsISupports
                                     [optional] in AString responseType,
                                     [optional] in AString purpose);
 
+  /**
+   * Returns the name of the parameter used for the search terms for a submission
+   * URL of type `SearchUtils.URL_TYPE.SEARCH`.
+   *
+   * @returns A string which is the name of the parameter, or empty string
+   *          if no parameter cannot be found or is not supported (e.g. POST).
+   */
+  readonly attribute AString searchUrlQueryParamName;
+
   /**
    * Determines whether the engine can return responses in the given
    * MIME type.  Returns true if the engine spec has a URL with the

toolkit/components/search/tests/SearchTestUtils.jsm

@@ -108,6 +108,22 @@ var SearchTestUtils = Object.freeze({
     }
   },
 
+  async useMochitestEngines(testDir) {
+    // Replace the path we load search engines from with
+    // the path to our test data.
+    let resProt = Services.io
+      .getProtocolHandler("resource")
+      .QueryInterface(Ci.nsIResProtocolHandler);
+    let originalSubstitution = resProt.getSubstitution("search-extensions");
+    resProt.setSubstitution(
+      "search-extensions",
+      Services.io.newURI("file://" + testDir.path)
+    );
+    gTestGlobals.registerCleanupFunction(() => {
+      resProt.setSubstitution("search-extensions", originalSubstitution);
+    });
+  },
+
   /**
    * Convert a list of engine configurations into engine objects.
    *
@@ -284,10 +300,14 @@ var SearchTestUtils = Object.freeze({
   /**
    * Simulates an update to the RemoteSettings configuration.
    *
-   * @param {object} config
+   * @param {object} [config]
    *  The new configuration.
    */
   async updateRemoteSettingsConfig(config) {
+    if (!config) {
+      let settings = RemoteSettings(SearchUtils.SETTINGS_KEY);
+      config = await settings.get();
+    }
     const reloadObserved = SearchTestUtils.promiseSearchNotification(
       "engines-reloaded"
     );