The Tor Browser: toolkit/mozapps/extensions/test/xpcshell/test_DeferredSave.js@6474c204b198 (annotated)

toolkit/mozapps/extensions/test/xpcshell/test_DeferredSave.js@6474c204b198 (annotated)

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

Wed, 31 Dec 2014 06:09:35 +0100

author: Michael Schloh von Bennewitz <michael@schloh.com>
date: Wed, 31 Dec 2014 06:09:35 +0100
changeset 0: 6474c204b198
permissions: -rw-r--r--

Cloned upstream origin tor-browser at tor-browser-31.3.0esr-4.5-1-build1
revision ID fc1c9ff7c1b2defdbc039f12214767608f46423f for hacking purpose.

 /* 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);
 });