Bug 1862534: Groundwork for ATK accessibility API tests. r=eeejay,jmaher

This adds setup code and utility functions for ATK to the Python environment.
I also needed to prevent front-end accessibility checks (AccessibilityUtils) from force disabling accessibility for a11y engine tests.
Although the tests re-enabled it anyway, this seems to break AT-SPI's interaction with our ApplicationAccessible.
Disabling it really doesn't make sense in this case anyway.
This patch includes a simple role test to show all of this working.

Differential Revision: https://phabricator.services.mozilla.com/D192911

accessible/moz.build

@@ -32,6 +32,7 @@ DIRS += [
 TEST_DIRS += ["tests/mochitest"]
 
 BROWSER_CHROME_MANIFESTS += [
+    "tests/browser/atk/browser.toml",
     "tests/browser/bounds/browser.toml",
     "tests/browser/browser.toml",
     "tests/browser/e10s/browser.toml",

accessible/tests/browser/atk/a11y_setup.py

@@ -0,0 +1,64 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+"""Python environment for ATK a11y browser tests.
+"""
+
+import os
+import subprocess
+import sys
+
+import psutil
+
+# pyatspi can't be installed using pip. Rely on the system installation.
+# Get the path to the system installation of pyatspi.
+pyatspiFile = subprocess.check_output(
+    (
+        os.path.join(sys.base_prefix, "bin", "python3"),
+        "-c",
+        "import pyatspi; print(pyatspi.__file__)",
+    ),
+    encoding="utf-8",
+).rstrip()
+sys.path.append(os.path.dirname(os.path.dirname(pyatspiFile)))
+import pyatspi
+
+sys.path.pop()
+del pyatspiFile
+
+
+def getDoc():
+    """Get the Accessible for the document being tested."""
+    # We can compare the parent process ids to find the Firefox started by the
+    # test harness.
+    commonPid = psutil.Process().ppid()
+    for app in pyatspi.Registry.getDesktop(0):
+        if (
+            app.name == "Firefox"
+            and psutil.Process(app.get_process_id()).ppid() == commonPid
+        ):
+            break
+    else:
+        raise LookupError("Couldn't find Firefox application Accessible")
+    root = app[0]
+    for embeds in root.getRelationSet():
+        if embeds.getRelationType() == pyatspi.RELATION_EMBEDS:
+            break
+    else:
+        raise LookupError("Firefox root doesn't have RELATION_EMBEDS")
+    doc = embeds.getTarget(0)
+    child = doc[0]
+    if child.get_attributes().get("id") == "default-iframe-id":
+        # This is an iframe or remoteIframe test.
+        doc = child[0]
+    return doc
+
+
+def findByDomId(root, id):
+    for child in root:
+        if child.get_attributes().get("id") == id:
+            return child
+        descendant = findByDomId(child, id)
+        if descendant:
+            return descendant

accessible/tests/browser/atk/browser.toml

@@ -0,0 +1,15 @@
+[DEFAULT]
+subsuite = "a11y"
+skip-if = [
+  "os != 'linux'",
+  "headless",
+]
+support-files = ["head.js"]
+prefs = [
+  # Enabling the a11y service from XPCOM doesn't seem to be enough to get ATK
+  # working correctly. Force enable it before the test starts.
+  "accessibility.force_disabled=-1",
+  "javascript.options.asyncstack_capture_debuggee_only=false",
+]
+
+["browser_role.js"]

accessible/tests/browser/atk/browser_role.js

@@ -0,0 +1,33 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+const ATSPI_ROLE_DOCUMENT_WEB = 95;
+const ATSPI_ROLE_PARAGRAPH = 73;
+
+addAccessibleTask(
+  `
+<p id="p">p</p>
+  `,
+  async function (browser, docAcc) {
+    let role = await runPython(`
+      global doc
+      doc = getDoc()
+      return doc.getRole()
+    `);
+    is(role, ATSPI_ROLE_DOCUMENT_WEB, "doc has correct ATSPI role");
+    ok(
+      await runPython(`
+        global p
+        p = findByDomId(doc, "p")
+        return p == doc[0]
+      `),
+      "doc's first child is p"
+    );
+    role = await runPython(`p.getRole()`);
+    is(role, ATSPI_ROLE_PARAGRAPH, "p has correct ATSPI role");
+  },
+  { chrome: true, topLevel: true, iframe: true, remoteIframe: true }
+);

accessible/tests/browser/atk/head.js

@@ -0,0 +1,18 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+// Load the shared-head file first.
+Services.scriptloader.loadSubScript(
+  "chrome://mochitests/content/browser/accessible/tests/browser/shared-head.js",
+  this
+);
+
+// Loading and common.js from accessible/tests/mochitest/ for all tests, as
+// well as promisified-events.js.
+loadScripts(
+  { name: "common.js", dir: MOCHITESTS_DIR },
+  { name: "promisified-events.js", dir: MOCHITESTS_DIR }
+);

accessible/tests/browser/browser.toml

@@ -4,6 +4,7 @@ subsuite = "a11y"
 support-files = [
   "!/accessible/tests/mochitest/*.js",
   "*.sys.mjs",
+  "atk/a11y_setup.py",
   "head.js",
   "python_runner_wsh.py",
   "shared-head.js",

accessible/tests/browser/python_runner_wsh.py

@@ -30,8 +30,7 @@ def web_socket_transfer_data(request):
     if sys.platform == "win32":
         testDir = "windows"
     elif sys.platform == "linux":
-        # XXX ATK code goes here.
-        pass
+        testDir = "atk"
     if testDir:
         sys.path.append(
             os.path.join(

taskcluster/docker/recipes/ubuntu1804-test-system-setup-base.sh

@@ -74,6 +74,7 @@ apt_packages+=('pulseaudio-module-gconf')
 apt_packages+=('python-dev')
 apt_packages+=('python-pip')
 apt_packages+=('python3-pip')
+apt_packages+=('python3-pyatspi')
 apt_packages+=('qemu-kvm')
 apt_packages+=('rlwrap')
 apt_packages+=('screen')
@@ -158,4 +159,14 @@ rm -rf /usr/share/locale/   /usr/share/locale-langpack/     /usr/share/locales/
 # Further cleanup
 apt-get autoremove
 
+# We've changed python3 to use 3.7, but binary modules are only installed for
+# the distribution's default which is 3.6. Symlink a module we need for 3.7.
+ln -s /usr/lib/python3/dist-packages/gi/_gi.cpython-{36m,37m}-x86_64-linux-gnu.so
+
+# The packaged version of pyatspi is not compatible with Python 3.7. Hack it to
+# be compatible, since there's no package for 3.7 in this distribution.
+# Specifically, rename variables named "async" to "asynchronous", since "async"
+# is a reserved keyword in Python 3.7.
+sed -i 's/\basync\b/asynchronous/' /usr/lib/python3/dist-packages/pyatspi/registry.py
+
 rm -f "$0"

testing/mochitest/browser-test.js

@@ -1217,7 +1217,7 @@ Tester.prototype = {
 
     this.SimpleTest.reset();
     // Reset accessibility environment.
-    this.AccessibilityUtils.reset(this.a11y_checks);
+    this.AccessibilityUtils.reset(this.a11y_checks, this.currentTest.path);
 
     // Load the tests into a testscope
     let currentScope = (this.currentTest.scope = new testScope(

testing/mochitest/tests/SimpleTest/AccessibilityUtils.js

@@ -697,13 +697,17 @@ this.AccessibilityUtils = (function () {
       gEnv = { ...DEFAULT_ENV };
     },
 
-    reset(a11yChecks = false) {
+    reset(a11yChecks = false, testPath = "") {
       gA11YChecks = a11yChecks;
 
       const { Services } = SpecialPowers;
       // Disable accessibility service if it is running and if a11y checks are
-      // disabled.
-      if (!gA11YChecks && Services.appinfo.accessibilityEnabled) {
+      // disabled. However, don't do this for accessibility engine tests.
+      if (
+        !gA11YChecks &&
+        Services.appinfo.accessibilityEnabled &&
+        !testPath.startsWith("chrome://mochitests/content/browser/accessible/")
+      ) {
         Services.prefs.setIntPref(FORCE_DISABLE_ACCESSIBILITY_PREF, 1);
         Services.prefs.clearUserPref(FORCE_DISABLE_ACCESSIBILITY_PREF);
       }