Deprecation of Ember.Logger
This RFC recommends the deprecation and eventual removal of
There are a variety of features of Ember designed to support old browsers,
features that are no longer needed.
Ember.Logger came into being because
the browser support for the console was inconsistent. In some browsers,
like Internet Explorer 9, the console only existed when the developer tools
panel was open, which caused null references and program crashes when run
with the console closed.
Ember.Logger provided methods that would route to
the console when it was available.
With Ember 3.x, Ember no longer supports these older browsers, and hence this feature no longer serves a purpose. Removing it will make Ember smaller and lighter.
For the most part, this is a 1:1 substitution of the global
Node only added support for
console.debug in Node version 9. Where we wish
to support earlier versions of Node, we will need to use
console.log, rather than
console.debug, as the replacement for
Logger.debug. Apps and addons
which don't care about Node or are specifying Node version 9 as their minimum can
Internet Explorer 11 and Edge both require console methods to be bound to the console object when the developer tools are not showing. This diverges from the expectations of other browsers. Direct calls to console methods will work correctly, but constructs which involve explicitly or implicitly binding the console methods to other objects or using them unbound will fail. This is straightforward to work around.
You can address the issue by binding the method to the console object:
// Before - assigning raw method to a variable for later use var print = Logger.log; // assigning method to variable print('Message'); // After - assigning console-bound method to variable for later use var print = console.log.bind(console); print('Message');
In some cases, you can use rest parameter syntax to avoid the issue entirely:
// Before Logger.info.apply(undefined, arguments); // or Logger.info.apply(null, arguments); // or Logger.info.apply(this, arguments); // or // After console.info(...arguments);
Within the framework
Remove the following direct uses of
Ember.Logger from the ember.js and
- deprecate (
- debug (
- warn (
- deprecate (
- transitioned to -
- preparing to transition to -
- intermediate-transitioned to -
- transitioned to -
- Testing paused (
- Catch-all handler (
- Testing paused (
Adjust all test code that redirects logging and sets it back:
Note: None of the uses of
Ember.debug, so that issue doesn't affect the Ember.js code directly.
Add deprecation warnings to the implementation:
Bear in mind that
ember-debug currently calls
Logger.warn, so the
ember-debug code should be changed first or adding
the deprecation warning will create a deep recursion.
Ember.deprecate methods suppress their output on production builds.
However, they are suppressing them in the
ember-debug module, which
Ember.Logger, not by
Ember.Logger itself. Hence,
replacing calls to
Ember.Logger with direct calls to the console will not
affect this behavior.
The following high-impact add-ons (9 or 10 or a * on EmberObserver) use
Ember.Logger and should probably be given an early heads-up to adjust
their code to use
console before this RFC is implemented. This will limit
the level of pain that their users experience when the deprecation is released.
Add-ons that need to also support Ember 2.x will need to make their console references conditional on console being "truthy", of course, to support Internet Explorer 9.
In the order of their number of references to
For details, see https://emberobserver.com/code-search?codeQuery=Ember.Logger.
How we teach this
Communication of change
We need to inform users that
Ember.Logger will be deprecated and in what
release it will occur.
Official code bases and documentation
We do not currently actively teach the use of
Ember.Logger. We will need to
remove any passing references to
Ember.Logger from the Ember guides
from the Super Rentals tutorial, and anywhere else it appears on the website.
Once it is gone from the code, we also need to verify it no longer appears in the API listings.
We must provide an entry in the deprecation guide for this change:
- describing relevant divergences remaining in the handling of the console in Internet Explorer 11 and Edge browsers.
- describing the issue with using console.debug on node versions earlier than Node 9.
- describing alternative ways of dealing with eslint's
191 add-ons in Ember Inspector are using
Ember.Logger. It has been there and
documented for a long time. So this deprecation will cause some level of change
on many projects.
This, of course, can be said for almost any deprecation, and Ember's
disciplined approach to deprecation has been repeatedly shown to ease things.
These particular changes are proving easy to locate and replace by hand. Also,
only twenty of those add-ons have more than six references to
If this is characteristic of the user base, the level of effort to make
the change, even by hand, should be very small for most users.
Logger.debug as something different from
Logger.log may have
at least a theoretical concern. Under the covers
Logger.debug only calls
console.debug if it exists, calling
console.log otherwise. The only
platform where the difference between the two is visible in the console is on
Safari. We can encourage folks with a tangible, practical concern about this to
speak up during the comment period, but I don't anticipate this will have much
Leave things as they are, perhaps providing an
Ember.Loggerinto its own (tiny)
@ember/consolepackage as a shim for users.
None at this point. The answers from prior drafts have been promoted into the text.