View Source Changelog for Elixir v1.11

Over the last releases, the Elixir team has been focusing on the compiler, both in terms of catching more mistakes at compilation time and making it faster. Elixir v1.11 has made excellent progress on both fronts. This release also includes many other goodies, such as tighter Erlang integration, support for more guard expressions, built-in datetime formatting, and other calendar enhancements.

Tighter Erlang integration

Following Elixir v1.10, we have further integrated with Erlang's new logger by adding four new log levels: notice, critical, alert, and emergency, matching all log levels found in the Syslog standard. The Logger module now supports structured logging by passing maps and keyword lists to its various functions. It is also possible to specify the log level per module, via the Logger.put_module_level/2 function. Log levels per application will be added in future releases.

IEx also has been improved to show the documentation for Erlang modules directly from your Elixir terminal. This works with Erlang/OTP 23+ and requires Erlang modules to have been compiled with documentation chunks.

Compiler checks: application boundaries

Elixir v1.11 builds on top of the recently added compilation tracers to track application boundaries. From this release, Elixir will warn if you invoke a function from an existing module but this module does not belong to any of your listed dependencies.

These two conditions may seem contradictory. After all, if a module is available, it must have come from a dependency. This is not true in two scenarios:

  • Modules from Elixir and Erlang/OTP are always available - even if their applications are not explicitly listed as a dependency

  • In an umbrella project, because all child applications are compiled within the same VM, you may have a module from a sibling project available, even if you don't depend on said sibling

This new compiler check makes sure that all modules that you invoke are listed as part of your dependencies, emitting a warning like below otherwise:

:ssl.connect/2 defined in application :ssl is used by the current
application but the current application does not directly depend
on :ssl. To fix this, you must do one of:

  1. If :ssl is part of Erlang/Elixir, you must include it under
     :extra_applications inside "def application" in your mix.exs

  2. If :ssl is a dependency, make sure it is listed under "def deps"
     in your mix.exs

  3. In case you don't want to add a requirement to :ssl, you may
     optionally skip this warning by adding [xref: [exclude: :ssl]
     to your "def project" in mix.exs

This comes with extra benefits in umbrella projects, as it requires child applications to explicitly list their dependencies, completely rejecting cyclic dependencies between siblings.

Compiler checks: data constructors

In Elixir v1.11, the compiler also tracks structs and maps fields across a function body. For example, imagine you wanted to write this code:

def drive?(%User{age: age}), do: age >= 18

If there is either a typo on the :age field or the :age field was not yet defined, the compiler will fail accordingly. However, if you wrote this code:

def drive?(%User{} = user), do: user.age >= 18

The compiler would not catch the missing field and an error would only be raised at runtime. With v1.11, Elixir will track the usage of all maps and struct fields within the same function, emitting warnings for cases like above:

warning: undefined field `age` in expression:

    # example.exs:7

expected one of the following fields: name, address

where "user" was given the type %User{} in:

    # example.exs:7
    %User{} = user

Conflict found at

The compiler also checks binary constructors. Consider you have to send a string over the wire with length-based encoding, where the string is prefixed by its length, up to 4MBs. Your initial attempt may be this:

def run_length(string) when is_binary(string) do
  <<byte_size(string)::32, string>>

However, the code above has a bug. Each segment given between <<>> must be an integer, unless specified otherwise. With Elixir v1.11, the compiler will let you know so:

warning: incompatible types:

    binary() !~ integer()

in expression:

    <<byte_size(string)::integer()-size(32), string>>

where "string" was given the type integer() in:

    # foo.exs:4
    <<byte_size(string)::integer()-size(32), string>>

where "string" was given the type binary() in:

    # foo.exs:3

HINT: all expressions given to binaries are assumed to be of type integer()
unless said otherwise. For example, <<expr>> assumes "expr" is an integer.
Pass a modifier, such as <<expr::float>> or <<expr::binary>>, to change the
default behaviour.

Conflict found at
  foo.exs:4: Check.run_length/1

Which can be fixed by adding ::binary to the second component:

def run_length(string) when is_binary(string) do
  <<byte_size(string)::32, string::binary>>

While some of those warnings could be automatically fixed by the compiler, future versions will also perform those checks across functions and potentially across modules, where automatic fixes wouldn't be desired (nor possible).

Compilation time improvements

Elixir v1.11 features many improvements to how the compiler tracks file dependencies, such that touching one file causes less files to be recompiled. In previous versions, Elixir tracked three types of dependencies:

  • compile time dependencies - if A depends on B at compile time, such as by using a macro, whenever B changes, A is recompiled
  • struct dependencies - if A depends on B's struct, whenever B's struct definition changed, A is recompiled
  • runtime dependencies - if A depends on B at runtime, A is never recompiled

However, because dependencies are transitive, if A depends on B at compile time and B depends on C at runtime, A would depend on C at compile time. Therefore, it is very important to reduce the amount of compile time dependencies.

Elixir v1.11 replaces "struct dependencies" by "exports dependencies". In other words, if A depends on B, whenever B public's interface changes, A is recompiled. B's public interface is made by its struct definition and all of its public functions and macros.

This change allows us to mark imports and requires as "exports dependencies" instead of "compile time" dependencies. This simplifies the dependency graph considerably. For example, in the project, changing the user.ex file in Elixir v1.10 would emit this:

$ touch lib/hexpm/accounts/user.ex && mix compile
Compiling 90 files (.ex)

In Elixir v1.11, we now get:

$ touch lib/hexpm/accounts/user.ex && mix compile
Compiling 16 files (.ex)

To make things even better, Elixir v1.11 also introduces a more granular file tracking for path dependencies. In previous versions, a module from a path dependency would always be treated as a compile time dependency. This often meant that if you have an umbrella project, changing an application would cause many modules in sibling applications to recompile. Fortunately, Elixir v1.11 will tag modules from dependencies as exports if appropriate, yielding dramatic improvements to those using path dependencies.

To round up the list of compiler enhancements, the --profile=time option added in Elixir v1.10 now also includes the time to compile each individual file. For example, in the Plug project, one can now get:

[profile] lib/plug/conn.ex compiled in 935ms
[profile] lib/plug/ssl.ex compiled in 147ms (plus 744ms waiting)
[profile] lib/plug/static.ex compiled in 238ms (plus 654ms waiting)
[profile] lib/plug/csrf_protection.ex compiled in 237ms (plus 790ms waiting)
[profile] lib/plug/debugger.ex compiled in 719ms (plus 947ms waiting)
[profile] Finished compilation cycle of 60 modules in 1802ms
[profile] Finished group pass check of 60 modules in 75ms

While implementing those features, we have also made the --long-compilation-threshold flag more precise. In previous versions, --long-compilation-threshold would consider both the time a file spent to compile and the time spent waiting on other files. In Elixir v1.11, it considers only the compilation time. This means less false positives and you can now effectively get all files that take longer than 2s to compile by passing --long-compilation-threshold 2.

mix xref graph improvements

To bring visibility to the compiler tracking improvements described in the previous section, we have also added new features to mix xref. mix xref is a task that describes cross-references between files in your projects. The mix xref graph subsection focuses on the dependency graph between them.

First we have made the existing --label flag to consider transitive dependencies. Using --sink FILE and --label compile can be a powerful combo to find out which files will change whenever the given FILE changes. For example, in the project, we get:

$ mix xref graph --sink lib/hexpm/accounts/user.ex --label compile
└── lib/hexpm/billing/billing.ex (compile)
└── lib/hexpm/billing/billing.ex (compile)
├── lib/hexpm/accounts/email.ex (compile)
└── lib/hexpm/accounts/user.ex (compile)
└── lib/hexpm_web/views/email_view.ex (compile)
└── lib/hexpm_web/controllers/auth_helpers.ex (compile)
└── lib/hexpm_web/controllers/auth_helpers.ex (compile)
└── lib/hexpm_web/controllers/auth_helpers.ex (compile)
└── lib/hexpm_web/controllers/auth_helpers.ex (compile)
└── lib/hexpm_web/controllers/auth_helpers.ex (compile)
└── lib/hexpm_web/controllers/auth_helpers.ex (compile)
└── lib/hexpm_web/controllers/auth_helpers.ex (compile)
└── lib/hexpm_web/controllers/auth_helpers.ex (compile)
└── lib/hexpm_web/controllers/auth_helpers.ex (compile)
└── lib/hexpm_web/views/blog_view.ex (compile)
├── lib/hexpm_web/plug_parser.ex (compile)
└── lib/hexpm_web/session.ex (compile)

All the files at the root will recompile if lib/hexpm/accounts/user.ex changes. Their children describe the why. For example, the repository_controller.ex file will recompile if user changes because it has a compile time dependency on auth_helpers.ex, which depends on user.ex. This indirect compile time dependency is often the source of recompilations and Elixir v1.11 now makes it trivial to spot them, so they can be eventually addressed.

Another improvement to mix xref graph is the addition of --format cycles, which will print all cycles in your compilation dependency graph. A --min-cycle-size flag can be used if you want to discard short cycles.

config/runtime.exs and mix app.config

Elixir v1.9 introduced a new configuration file, specific to releases, called config/releases.exs. A release is a self-contained artifact with the Erlang VM, Elixir and your application, ready to run in production.

The addition of config/releases.exs has been a very useful one but, unfortunately, it applies only to releases. Developers not using releases must use the config/config.exs file, which often loaded too early at compilation time. For any dynamic configuration, developers had to resort to third-party tools or workarounds to achieve the desired results.

Elixir v1.11 addresses this issue by introducing a new configuration file, called config/runtime.exs. This new configuration file is loaded exactly before your application starts, when the code is already fully compiled. It is loaded in development, test, and production, regardless if you are using Mix or releases. Therefore it provides a unified API for runtime configuration in Elixir.

config/runtime.exs works the same as any other configuration file. However, given config/runtime.exs is meant to run with or without Mix, developers must not use Mix.env() or in config/runtime.exs. Instead, they must use the new config_env() and config_target(), which have been added to the Config module.

While config/releases.exs will continue to be supported, developers can migrate to config/runtime.exs without loss of functionality. For example, a config/releases.exs file such as this one

# config/releases.exs
import Config

config :foo, ...
config :bar, ...

could run as is as config/runtime.exs. However, given config/runtime.exs runs in all environments, you may want to restrict part of your configuration to the :prod environment:

# config/runtime.exs
import Config

if config_env() == :prod do
  config :foo, ...
  config :bar, ...

If both files are available, releases will pick the now preferred config/runtime.exs instead of config/releases.exs.

To wrap it all up, Mix also includes a new task called mix app.config. This task loads all applications and configures them, without starting them. Whenever you write your own Mix tasks, you will typically want to invoke either mix app.start or mix app.config before running your own code. Which one is better depends if you want your applications running or only configured.

Other improvements

Elixir v1.11 adds the is_struct/2, is_exception/1, and is_exception/2 guards. It also adds support for the map.field syntax in guards.

The Calendar module ships with a new Calendar.strftime/3 function, which provides datetime formatting based on the strftime format. The Date module got new functions for working with weeks and months, such as Date.beginning_of_month/1 and Date.end_of_week/2. Finally, all calendar types got conversion functions from and to gregorian timestamps, such as Date.from_gregorian_days/2 and NaiveDateTime.to_gregorian_seconds/1.

Mix also includes two new tasks: mix app.config, for application runtime configuration, and mix test.coverage, which generates aggregated coverage reports for umbrella projects and for test suites partitioned across processes.

v1.11.0 (2020-10-06)

1. Enhancements


  • [EEx] Track column information in EEx templates when enabled in the compiler
  • [EEx] Show column information in EEx error messages
  • [EEx] Support :indentation option when compiling EEx templates for proper column tracking



  • [ExUnit] Add support for coloring on Windows 10 consoles/shells
  • [ExUnit] Add ExUnit.fetch_test_supervisor/0
  • [ExUnit] Add @tag :tmp_dir support to ExUnit. The temporary directory is automatically created and pruned before each test
  • [ExUnit] Add file and line to ExUnit's --trace
  • [ExUnit.Assertion] Allow receive timeouts to be computed at runtime
  • [ExUnit.Case] Add register_test/6 to speed up compilation of custom tests
  • [ExUnit.Doctest] Allow users to add tags to doctests


  • [IEx] Add support for coloring on Windows 10 consoles/shells
  • [IEx.Helpers] Show docs from Erlang modules that have been compiled with the docs chunk


  • [Logger] Add notice, critical, alert, and emergency log levels
  • [Logger] Support structured logging by logging maps or keyword lists
  • [Logger] Allow level to be set per module with Logger.put_module_level/2
  • [Logger] Include erl_level in Logger's metadata


  • [mix] Add MIX_BUILD_ROOT to config _build dir
  • [mix] Introduce MIX_XDG as a simpler mechanism to opt-in to the XDG specification
  • [mix] Allow requirements for a Mix task to be listed via the @requirements module attribute
  • [mix] Allow optional dependencies to be defined in :extra_applications and :applications
  • [mix app.config] Add new mix app.config task that compiles applications and loads runtime configuration
  • [mix archive.install] Support --repo option on Hex packages
  • [mix compile] Support the __mix_recompile__?/0 callback for custom behaviour on when Mix should recompile a given module
  • [mix compile.elixir] Mark modules for path dependencies as "Export dependencies" if they changed but their public interface is the same
  • [mix compile.elixir] Track application boundaries in the Elixir compiler. If you invoke code from Erlang or Elixir standard libraries and you don't depend on the proper applications, a warning will be emitted. A warning will also be emitted if you invoke code from an umbrella sibling that you don't depend on - effectively forbidding cyclic dependencies between apps
  • [mix deps] Sort the dependencies alphabetically before printing
  • [mix deps] Use origin/HEAD as the default Git ref in dependencies
  • [mix deps] Redact Git username/password in output log
  • [mix deps] Support rebar3's git_subdir resource type
  • [mix deps.compile] Allow local deps to be skipped on mix deps.compile
  • [mix deps.unlock] Print which dependencies get unlocked when using the --unused flag
  • [mix escript.install] Support --repo option on Hex packages
  • [mix new] Add @impl to application generated by mix new --sup
  • [mix release] Enable overriding sys.config location via RELEASE_SYS_CONFIG env var
  • [mix release] Boot a release under configuration in interactive mode and then swap to embedded mode (if running on Erlang/OTP 23+)
  • [mix release] Add rel_templates_path to configure the source of template files such as "", "vm.args.eex" and "overlays"
  • [mix release] Allow some chunks to be kept in the :strip_beams config
  • [mix test] Allow :ignore_modules inside :test_coverage option
  • [mix test.coverage] Add mix test.coverage that aggregates coverage results from umbrellas and OS partitioning
  • [mix xref] Make the --label option for mix xref graph transitive by default and add --only-direct for only direct dependencies
  • [mix xref] Add --format cycles support for mix xref graph
  • [mix xref] Add support to mix xref graph for using --source and --sink at the same time

2. Bug fixes


  • [EEx] Make trimming behaviour via the :trim option more consistent


  • [Application] Warn if non-atom keys are given to put_env, get_env, fetch_env, and delete_env
  • [Code] Do not send language keyword through the :static_atoms_encoder in Code.string_to_quoted
  • [Kernel] Validate values given to :line in quote to avoid emitting invalid ASTs
  • [Kernel] Report the correct line number when raising inside a macro
  • [Kernel] Fix an issue where elixirc would not accept paths with backslash (\) separators on Windows
  • [Kernel] Properly parse &//2 (i.e. the capture of the division operator)
  • [Kernel] Raise CompileError when trying to define reserved types
  • [Kernel] Improve compiler error message when using | in a def signature
  • [Kernel] Improve error message when trying to use invalid list operators in guards
  • [Kernel.SpecialForms] Add |/2 to the list of special forms to avoid inconsistent behaviour on overrides
  • [Keyword] Enforce keys to be atoms in Keyword.keys/1
  • [Record] Keep lexical ordering when creating records
  • [Registry] Do not crash when a process with key-value has been registered using :via and it fails to start on init
  • [URI] URI.decode_query/2 emits an empty string for parameters without values, according to URL's living standard - note this behaviour is not specified in the spec implemented by the URI module, so the living standard was chosen
  • [Version] Add defaults and enforce keys in Version struct


  • [ExUnit.CaptureIO] Fix race condition where a dead capture would still be considered as active
  • [ExUnit.Diff] Do not crash when failing to eval/inspect struct
  • [ExUnit.Diff] Properly diff numbers in respect to == and === operators


  • [IEx] Fix tokenizer emitting repeated warnings in the REPL
  • [IEx] Ensure --dot-iex is preserved when restarting the evaluator and after shell respawn
  • [IEx.Pry] Ensure IEx.pry can be triggered more than twice when invoked from the same process


  • [mix cmd] Fix a bug where only the first --app option would be executed
  • [mix compile] Fix an issue where new protocol implementations would not propagate when running mix compile from an umbrella root
  • [mix deps.compile] Use gmake instead of make when compiling deps on NetBSD/DragonFlyBSD
  • [mix release] Load .app from dependencies path when it is a project dependency
  • [mix release] Always include "rel/overlays" in the list of overlays directories if available
  • [mix release] Change erts/bin/erl binary mode to 0o755
  • [mix test] Compare to test coverage threshold inclusively


  • [Logger] Print metadata for all types that implement String.Chars

3. Soft-deprecations (no warnings emitted)



  • [Logger] warn log level is deprecated in favor of warning


  • [mix release] config/releases.exs is deprecated in favor of a more general purpose config/runtime.exs

4. Hard-deprecations



  • [Mix.Project] Deprecate Mix.Project.compile/2 in favor of"compile", args)


The CHANGELOG for v1.10 releases can be found in the v1.10 branch.