CHANGELOG.md

Changelog for Elixir v1.2

v1.2 brings enhancements, bug fixes, performance improvements and more into Elixir. Elixir v1.2 relies on many features in Erlang 18, requiring at least Erlang 18+. Upgrading to Erlang 18 is therefore necessary before upgrading Elixir.

Erlang 18 support

We have brought many features specific to Erlang 18:

• Maps can now scale from dozens to millions of keys. Therefore, usage of the modules Dict and HashDict is now discouraged and will be deprecated in future releases, instead use Map. Similarly, Set and HashSet will be deprecated in favor of MapSet
• Compilation times are faster due to improvements on both Elixir and Erlang compilers
• Dialyzer now emits less false negative warnings thanks to new annotations available in the Erlang compiler
• And many more

Language improvements

This release includes four notable language improvements:

• The addition of multi aliases/imports/require:

  alias MyApp.{Foo, Bar, Baz}
  

• Support for variables in map keys:

  %{key => value}
  

• Support for pin operator in map keys and function clauses:

  %{^key => value} = %{key => value}
  fn ^key -> :ok end
  

• Addition of the with special form to match on multiple expressions:

  with {:ok, contents} <- File.read("my_file.ex"),
       {res, binding} <- Code.eval_string(contents),
       do: {:ok, res}
  

Those improvements aim to make the language more consistent and expressive.

Getting started experience

At the same time we improved the language, we have improved both parser and compiler to be even more aware of language constructs, emitting warnings on common pitfalls like when piping to expressions without parenthesis or when defining unsafe variables.

We have also introduced the i/1 helper in IEx, which allows developers to retrieve information about any data type. This will help newcomers explore the language values while providing experienced developers with crucial information about the value they are introspecting.

Workflow improvements

Umbrella applications are now able to share both build and configuration files. This aims to drastically reduce compilation times in umbrella projects by adding the following configuration to each umbrella app's mix.exs file:

build_path: "../../_build",
config_path: "../../config/config.exs",

Finally, Mix will now always consolidated protocols as we are now able to consolidate in parallel and cache the consolidation results, providing the best performance across all environments without affecting compilation times.

Those are great additions on top of the faster compilation times we have achieved when migrating to Erlang 18.

v1.2.0-dev

1. Enhancements

Elixir

• [Application] Add spec/1 and spec/2 to retrieve application specification
• [Application] Add get_application/1 to retrieve the application a given module belongs to
• [Base] Optimize encode and decode operations about 10 times
• [Enum] Use the faster and auto-seeding :rand instead of :random in Enum.shuffle/1 and Enum.random/1 and Enum.take_random/2
• [GenServer] Add GenServer.stop/1 for reliably shutting servers down
• [Kernel] Support multiple aliases in alias, import, require and use. For example, alias MyApp.{Foo, Bar, Baz}
• [Kernel] Add struct!/2. Similar to struct/2 but raises on invalid keys
• [Kernel] Warn if @doc/@typedoc/@moduledoc attributes are redefined
• [Kernel] Warn if non-variables are used in defdelegate/2 (as they have no effect)
• [Kernel] Mark quoted expressions as generated avoiding false positives on dialyzer
• [Kernel] Allow variables as map keys on creation %{key => value} and on matches %{^key => value}
• [Kernel] Allow the pin operator ^ in fn clauses and on the left side of <- in for comprehensions
• [Kernel] Introduce with as a special form that allows matching on right side parameters
• [Kernel] Raise when right hand side of -> does not provide any expression
• [Kernel] Warn if the Elixir was compiled with a different endianness than the one currently available at runtime
• [Kernel] Warn if a variable is used after being defined exclusively in a nested context
• [Kernel] Warn if piping into an expression without parenthesis
• [Macro] Add Macro.traverse/4 that performs pre and post-walk at once
• [Macro] Add Macro.camelize/1 and Macro.underscore/1
• [Process] Add Process.get_keys/0
• [String] Introduce String.replace_{prefix,suffix,leading,trailing}/2. The first two will replace only the first occurrence of the given match in string. The last two will replace all occurrences of the given match
• [String] Support String.normalize/2 and String.equivalent?/2 that perform NFD and NFC normalization
• [Task] Add Task.Supervisor.async_nolink/1/3 that spawns a supervised task without linking to the caller process
• [Task] Introduce Task.yield_many/2
• [Task] Raise an error when a task is queried from a non-owning process (instead of waiting forever)

ExUnit

• [ExUnit] Allow one test to raise multiple errors. The goal is to enable tools in the ecosystem to emit multiple failure reports from the same test
• [ExUnit] Support @tag report: [:foo, :bar] which will include the values for tags :foo and :bar whenever a test fails

IEx

• [IEx] Display type docs for t(Module.type) and t(Module.type/arity)
• [IEx] Add i/1 helper that prints information about any data type
• [IEx] Show source code snippet whenever there is a request to pry a given process

Logger

• [Logger] Add file to logger metadata

Mix

• [Mix] Cache and always consolidate protocols
• [Mix] Add warn_test_pattern to mix test that will warn on potentially misconfigured test files
• [Mix] Introduce MIX_QUIET environment variable that configures the underlying Mix task to output only error messages
• [Mix] Validate git options and warn on conflicting ref, branch or tags
• [Mix] New umbrella applications will now share configuration and build files

2. Bug fixes

Kernel

• [Kernel] Change __ENV__.file if @file is set for the given function
• [Kernel] Make Kernel.ParallelRequire aware of :warning_as_errors
• [Kernel] Improve error message for invalid do/do:

IEx

• [IEx] Do not start apps on recompile helper if --no-start was given
• [IEx] Avoid copying of data when evaluating every expression in IEx

Mix

• [Mix] Always run non-recursive tasks at the umbrella root
• [Mix] Ensure rebar projects work on directory names that contain non-latin characters
• [Mix] Ignore directories inside apps in umbrellas that do not have a mix.exs file
• [Mix] Ensure Mix can be used with path dependencies where the app name is different than the path basename

ExUnit

• [ExUnit] Include file and line in all compilation errors for doctests

3. Soft deprecations (no warnings emitted)

Kernel

• [Dict] Dict and HashDict are soft deprecated in favor of Map
• [Keyword] Keyword.size/1 is deprecated in favor of length/1
• [Map] Map.size/1 is deprecated in favor of map_size/1
• [Set] Set and HashSet are soft deprecated in favor of MapSet

Mix

• [Mix] Mix.Utils.camelize/1 and Mix.Utils.underscore/1 are soft deprecated in favor of Macro.camelize/1 and Macro.underscore/1