The Tor Browser: comparison toolkit/mozapps/extensions/test/xpcshell/test_DeferredSave.js

comparison: toolkit/mozapps/extensions/test/xpcshell/test_DeferredSave.js

toolkit/mozapps/extensions/test/xpcshell/test_DeferredSave.js

changeset 0: 6474c204b198

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+:0d053e4cdaec
+/* Any copyright is dedicated to the Public Domain.
+* http://creativecommons.org/publicdomain/zero/1.0/
+*/
+// Test behaviour of module to perform deferred save of data
+// files to disk
+"use strict";
+const testFile = gProfD.clone();
+testFile.append("DeferredSaveTest");
+Components.utils.import("resource://gre/modules/Promise.jsm");
+let DSContext = Components.utils.import("resource://gre/modules/DeferredSave.jsm", {});
+let DeferredSave = DSContext.DeferredSave;
+// Test wrapper to let us do promise/task based testing of DeferredSave
+function DeferredSaveTester(aDataProvider) {
+let tester = {
+// Deferred for the promise returned by the mock writeAtomic
+waDeferred: null,
+// The most recent data "written" by the mock OS.File.writeAtomic
+writtenData: undefined,
+dataToSave: "Data to save",
+save: (aData, aWriteHandler) => {
+tester.writeHandler = aWriteHandler || writer;
+tester.dataToSave = aData;
+return tester.saver.saveChanges();
+},
+flush: (aWriteHandler) => {
+tester.writeHandler = aWriteHandler || writer;
+return tester.saver.flush();
+},
+get lastError() {
+return tester.saver.lastError;
+}
+};
+// Default write handler for most cases where the test case doesn't need
+// to do anything while the write is in progress; just completes the write
+// on the next event loop
+function writer(aTester) {
+do_print("default write callback");
+let length = aTester.writtenData.length;
+do_execute_soon(() => aTester.waDeferred.resolve(length));
+}
+if (!aDataProvider)
+aDataProvider = () => tester.dataToSave;
+tester.saver = new DeferredSave(testFile.path, aDataProvider);
+// Install a mock for OS.File.writeAtomic to let us control the async
+// behaviour of the promise
+DSContext.OS.File.writeAtomic = function mock_writeAtomic(aFile, aData, aOptions) {
+do_print("writeAtomic: " + aFile + " data: '" + aData + "', " + aOptions.toSource());
+tester.writtenData = aData;
+tester.waDeferred = Promise.defer();
+tester.writeHandler(tester);
+return tester.waDeferred.promise;
+};
+return tester;
+};
+/**
+* Install a mock nsITimer factory that triggers on the next spin of
+* the event loop after it is scheduled
+*/
+function setQuickMockTimer() {
+let quickTimer = {
+initWithCallback: function(aFunction, aDelay, aType) {
+do_print("Starting quick timer, delay = " + aDelay);
+do_execute_soon(aFunction);
+},
+cancel: function() {
+do_throw("Attempted to cancel a quickMockTimer");
+}
+};
+DSContext.MakeTimer = () => {
+do_print("Creating quick timer");
+return quickTimer;
+};
+}
+/**
+* Install a mock nsITimer factory in DeferredSave.jsm, returning a promise that resolves
+* when the client code sets the timer. Test cases can use this to wait for client code to
+* be ready for a timer event, and then signal the event by calling mockTimer.callback().
+* This could use some enhancement; clients can re-use the returned timer,
+* but with this implementation it's not possible for the test to wait for
+* a second call to initWithCallback() on the re-used timer.
+* @return Promise{mockTimer} that resolves when initWithCallback()
+*         is called
+*/
+function setPromiseMockTimer() {
+let waiter = Promise.defer();
+let mockTimer = {
+callback: null,
+delay: null,
+type: null,
+isCancelled: false,
+initWithCallback: function(aFunction, aDelay, aType) {
+do_print("Starting timer, delay = " + aDelay);
+this.callback = aFunction;
+this.delay = aDelay;
+this.type = aType;
+// cancelled timers can be re-used
+this.isCancelled = false;
+waiter.resolve(this);
+},
+cancel: function() {
+do_print("Cancelled mock timer");
+this.callback = null;
+this.delay = null;
+this.type = null;
+this.isCancelled = true;
+// If initWithCallback was never called, resolve to let tests check for cancel
+waiter.resolve(this);
+}
+};
+DSContext.MakeTimer = () => {
+do_print("Creating mock timer");
+return mockTimer;
+};
+return waiter.promise;
+}
+/**
+* Return a Promise<null> that resolves after the specified number of milliseconds
+*/
+function delay(aDelayMS) {
+let deferred = Promise.defer();
+do_timeout(aDelayMS, () => deferred.resolve(null));
+return deferred.promise;
+}
+function run_test() {
+run_next_test();
+}
+// Modify set data once, ask for save, make sure it saves cleanly
+add_task(function test_basic_save_succeeds() {
+setQuickMockTimer();
+let tester = DeferredSaveTester();
+let data = "Test 1 Data";
+yield tester.save(data);
+do_check_eq(tester.writtenData, data);
+do_check_eq(1, tester.saver.totalSaves);
+});
+// Two saves called during the same event loop, both with callbacks
+// Make sure we save only the second version of the data
+add_task(function test_two_saves() {
+setQuickMockTimer();
+let tester = DeferredSaveTester();
+let firstCallback_happened = false;
+let firstData = "Test first save";
+let secondData = "Test second save";
+// first save should not resolve until after the second one is called,
+// so we can't just yield this promise
+tester.save(firstData).then(count => {
+do_check_eq(secondData, tester.writtenData);
+do_check_false(firstCallback_happened);
+firstCallback_happened = true;
+}, do_report_unexpected_exception);
+yield tester.save(secondData);
+do_check_true(firstCallback_happened);
+do_check_eq(secondData, tester.writtenData);
+do_check_eq(1, tester.saver.totalSaves);
+});
+// Two saves called with a delay in between, both with callbacks
+// Make sure we save the second version of the data
+add_task(function test_two_saves_delay() {
+let timerPromise = setPromiseMockTimer();
+let tester = DeferredSaveTester();
+let firstCallback_happened = false;
+let delayDone = false;
+let firstData = "First data to save with delay";
+let secondData = "Modified data to save with delay";
+tester.save(firstData).then(count => {
+do_check_false(firstCallback_happened);
+do_check_true(delayDone);
+do_check_eq(secondData, tester.writtenData);
+firstCallback_happened = true;
+}, do_report_unexpected_exception);
+// Wait a short time to let async events possibly spawned by the
+// first tester.save() to run
+yield delay(2);
+delayDone = true;
+// request to save modified data
+let saving = tester.save(secondData);
+// Yield to wait for client code to set the timer
+let activeTimer = yield timerPromise;
+// and then trigger it
+activeTimer.callback();
+// now wait for the DeferredSave to finish saving
+yield saving;
+do_check_true(firstCallback_happened);
+do_check_eq(secondData, tester.writtenData);
+do_check_eq(1, tester.saver.totalSaves);
+do_check_eq(0, tester.saver.overlappedSaves);
+});
+// Test case where OS.File immediately reports an error when the write begins
+// Also check that the "error" getter correctly returns the error
+// Then do a write that succeeds, and make sure the error is cleared
+add_task(function test_error_immediate() {
+let tester = DeferredSaveTester();
+let testError = new Error("Forced failure");
+function writeFail(aTester) {
+aTester.waDeferred.reject(testError);
+}
+setQuickMockTimer();
+yield tester.save("test_error_immediate", writeFail).then(
+count => do_throw("Did not get expected error"),
+error => do_check_eq(testError.message, error.message)
+);
+do_check_eq(testError, tester.lastError);
+// This write should succeed and clear the error
+yield tester.save("test_error_immediate succeeds");
+do_check_eq(null, tester.lastError);
+// The failed save attempt counts in our total
+do_check_eq(2, tester.saver.totalSaves);
+});
+// Save one set of changes, then while the write is in progress, modify the
+// data two more times. Test that we re-write the dirty data exactly once
+// after the first write succeeds
+add_task(function dirty_while_writing() {
+let tester = DeferredSaveTester();
+let firstData = "First data";
+let secondData = "Second data";
+let thirdData = "Third data";
+let firstCallback_happened = false;
+let secondCallback_happened = false;
+let writeStarted = Promise.defer();
+function writeCallback(aTester) {
+writeStarted.resolve(aTester.waDeferred);
+}
+setQuickMockTimer();
+do_print("First save");
+tester.save(firstData, writeCallback).then(
+count => {
+do_check_false(firstCallback_happened);
+do_check_false(secondCallback_happened);
+do_check_eq(tester.writtenData, firstData);
+firstCallback_happened = true;
+}, do_report_unexpected_exception);
+do_print("waiting for writer");
+let writer = yield writeStarted.promise;
+do_print("Write started");
+// Delay a bit, modify the data and call saveChanges, delay a bit more,
+// modify the data and call saveChanges again, another delay,
+// then complete the in-progress write
+yield delay(1);
+tester.save(secondData).then(
+count => {
+do_check_true(firstCallback_happened);
+do_check_false(secondCallback_happened);
+do_check_eq(tester.writtenData, thirdData);
+secondCallback_happened = true;
+}, do_report_unexpected_exception);
+// wait and then do the third change
+yield delay(1);
+let thirdWrite = tester.save(thirdData);
+// wait a bit more and then finally finish the first write
+yield delay(1);
+writer.resolve(firstData.length);
+// Now let everything else finish
+yield thirdWrite;
+do_check_true(firstCallback_happened);
+do_check_true(secondCallback_happened);
+do_check_eq(tester.writtenData, thirdData);
+do_check_eq(2, tester.saver.totalSaves);
+do_check_eq(1, tester.saver.overlappedSaves);
+});
+// A write callback for the OS.File.writeAtomic mock that rejects write attempts
+function disabled_write_callback(aTester) {
+do_throw("Should not have written during clean flush");
+deferred.reject(new Error("Write during supposedly clean flush"));
+}
+// special write callback that disables itself to make sure
+// we don't try to write twice
+function write_then_disable(aTester) {
+do_print("write_then_disable");
+let length = aTester.writtenData.length;
+aTester.writeHandler = disabled_write_callback;
+do_execute_soon(() => aTester.waDeferred.resolve(length));
+}
+// Flush tests. First, do an ordinary clean save and then call flush;
+// there should not be another save
+add_task(function flush_after_save() {
+setQuickMockTimer();
+let tester = DeferredSaveTester();
+let dataToSave = "Flush after save";
+yield tester.save(dataToSave);
+yield tester.flush(disabled_write_callback);
+do_check_eq(1, tester.saver.totalSaves);
+});
+// Flush while a write is in progress, but the in-memory data is clean
+add_task(function flush_during_write() {
+let tester = DeferredSaveTester();
+let dataToSave = "Flush during write";
+let firstCallback_happened = false;
+let writeStarted = Promise.defer();
+function writeCallback(aTester) {
+writeStarted.resolve(aTester.waDeferred);
+}
+setQuickMockTimer();
+tester.save(dataToSave, writeCallback).then(
+count => {
+do_check_false(firstCallback_happened);
+firstCallback_happened = true;
+}, do_report_unexpected_exception);
+let writer = yield writeStarted.promise;
+// call flush with the write callback disabled, delay a bit more, complete in-progress write
+let flushing = tester.flush(disabled_write_callback);
+yield delay(2);
+writer.resolve(dataToSave.length);
+// now wait for the flush to finish
+yield flushing;
+do_check_true(firstCallback_happened);
+do_check_eq(1, tester.saver.totalSaves);
+});
+// Flush while dirty but write not in progress
+// The data written should be the value at the time
+// flush() is called, even if it is changed later
+add_task(function flush_while_dirty() {
+let timerPromise = setPromiseMockTimer();
+let tester = DeferredSaveTester();
+let firstData = "Flush while dirty, valid data";
+let firstCallback_happened = false;
+tester.save(firstData, write_then_disable).then(
+count => {
+do_check_false(firstCallback_happened);
+firstCallback_happened = true;
+do_check_eq(tester.writtenData, firstData);
+}, do_report_unexpected_exception);
+// Wait for the timer to be set, but don't trigger it so the write won't start
+let activeTimer = yield timerPromise;
+let flushing = tester.flush();
+// Make sure the timer was cancelled
+do_check_true(activeTimer.isCancelled);
+// Also make sure that data changed after the flush call
+// (even without a saveChanges() call) doesn't get written
+tester.dataToSave = "Flush while dirty, invalid data";
+yield flushing;
+do_check_true(firstCallback_happened);
+do_check_eq(tester.writtenData, firstData);
+do_check_eq(1, tester.saver.totalSaves);
+});
+// And the grand finale - modify the data, start writing,
+// modify the data again so we're in progress and dirty,
+// then flush, then modify the data again
+// Data for the second write should be taken at the time
+// flush() is called, even if it is modified later
+add_task(function flush_writing_dirty() {
+let timerPromise = setPromiseMockTimer();
+let tester = DeferredSaveTester();
+let firstData = "Flush first pass data";
+let secondData = "Flush second pass data";
+let firstCallback_happened = false;
+let secondCallback_happened = false;
+let writeStarted = Promise.defer();
+function writeCallback(aTester) {
+writeStarted.resolve(aTester.waDeferred);
+}
+tester.save(firstData, writeCallback).then(
+count => {
+do_check_false(firstCallback_happened);
+do_check_eq(tester.writtenData, firstData);
+firstCallback_happened = true;
+}, do_report_unexpected_exception);
+// Trigger the timer callback as soon as the DeferredSave sets it
+let activeTimer = yield timerPromise;
+activeTimer.callback();
+let writer = yield writeStarted.promise;
+// the first write has started
+// dirty the data and request another save
+// after the second save completes, there should not be another write
+tester.save(secondData, write_then_disable).then(
+count => {
+do_check_true(firstCallback_happened);
+do_check_false(secondCallback_happened);
+do_check_eq(tester.writtenData, secondData);
+secondCallback_happened = true;
+}, do_report_unexpected_exception);
+let flushing = tester.flush(write_then_disable);
+// Flush should have cancelled our timer
+do_check_true(activeTimer.isCancelled);
+tester.dataToSave = "Flush, invalid data: changed late";
+// complete the first write
+writer.resolve(firstData.length);
+// now wait for the second write / flush to complete
+yield flushing;
+do_check_true(firstCallback_happened);
+do_check_true(secondCallback_happened);
+do_check_eq(tester.writtenData, secondData);
+do_check_eq(2, tester.saver.totalSaves);
+do_check_eq(1, tester.saver.overlappedSaves);
+});
+// A data provider callback that throws an error the first
+// time it is called, and a different error the second time
+// so that tests can (a) make sure the promise is rejected
+// with the error and (b) make sure the provider is only
+// called once in case of error
+const expectedDataError = "Failed to serialize data";
+let badDataError = null;
+function badDataProvider() {
+let err = new Error(badDataError);
+badDataError = "badDataProvider called twice";
+throw err;
+}
+// Handle cases where data provider throws
+// First, throws during a normal save
+add_task(function data_throw() {
+setQuickMockTimer();
+badDataError = expectedDataError;
+let tester = DeferredSaveTester(badDataProvider);
+yield tester.save("data_throw").then(
+count => do_throw("Expected serialization failure"),
+error => do_check_eq(error.message, expectedDataError));
+});
+// Now, throws during flush
+add_task(function data_throw_during_flush() {
+badDataError = expectedDataError;
+let tester = DeferredSaveTester(badDataProvider);
+let firstCallback_happened = false;
+setPromiseMockTimer();
+// Write callback should never be called
+tester.save("data_throw_during_flush", disabled_write_callback).then(
+count => do_throw("Expected serialization failure"),
+error => {
+do_check_false(firstCallback_happened);
+do_check_eq(error.message, expectedDataError);
+firstCallback_happened = true;
+});
+// flush() will cancel the timer
+yield tester.flush(disabled_write_callback).then(
+count => do_throw("Expected serialization failure"),
+error => do_check_eq(error.message, expectedDataError)
+);
+do_check_true(firstCallback_happened);
+});
+// Try to reproduce race condition. The observed sequence of events:
+// saveChanges
+// start writing
+// saveChanges
+// finish writing (need to restart delayed timer)
+// saveChanges
+// flush
+// write starts
+// actually restart timer for delayed write
+// write completes
+// delayed timer goes off, throws error because DeferredSave has been torn down
+add_task(function delay_flush_race() {
+let timerPromise = setPromiseMockTimer();
+let tester = DeferredSaveTester();
+let firstData = "First save";
+let secondData = "Second save";
+let thirdData = "Third save";
+let writeStarted = Promise.defer();
+function writeCallback(aTester) {
+writeStarted.resolve(aTester.waDeferred);
+}
+// This promise won't resolve until after writeStarted
+let firstSave = tester.save(firstData, writeCallback);
+(yield timerPromise).callback();
+let writer = yield writeStarted.promise;
+// the first write has started
+// dirty the data and request another save
+let secondSave = tester.save(secondData);
+// complete the first write
+writer.resolve(firstData.length);
+yield firstSave;
+do_check_eq(tester.writtenData, firstData);
+tester.save(thirdData);
+let flushing = tester.flush();
+yield secondSave;
+do_check_eq(tester.writtenData, thirdData);
+yield flushing;
+do_check_eq(tester.writtenData, thirdData);
+// Our DeferredSave should not have a _timer here; if it
+// does, the bug caused a reschedule
+do_check_eq(null, tester.saver._timer);
+});