View Source Changelog for Elixir v1.15

This release requires Erlang/OTP 24 and later.

Elixir v1.15 is a smaller release with focused improvements on compilation and boot times. This release also completes our integration process with Erlang/OTP logger, bringing new features such as log rotation and compaction out of the box.

You will also find additional convenience functions in Code, Map, Keyword, all Calendar modules, and others.


Compile and boot-time improvements

The last several releases brought improvements to compilation time and this version is no different. In particular, Elixir now caches and prunes load paths before compilation, ensuring your project (and dependencies!) compile faster and in an environment closer to production.

In a nutshell the Erlang VM loads modules from code paths. Each application that ships with Erlang and Elixir plus each dependency become an entry in your code path. The larger the code path, the more work Erlang has to do in order to find a module.

In previous versions, Mix would only add entries to the load paths. Therefore, if you compiled 20 dependencies and you went to compile the 21st, the code path would have 21 entries (plus all Erlang and Elixir apps). This allowed modules from unrelated dependencies to be seen and made compilation slower the more dependencies you had. With this release, we will now prune the code paths to only the ones listed as dependencies, bringing the behaviour closer to mix release.

Furthermore, Erlang/OTP 26 allows us to start applications concurrently and cache the code path lookups, decreasing the cost of booting applications. The combination of Elixir v1.15 and Erlang/OTP 26 should reduce the boot time of applications, such as when starting iex -S mix or running a single test with mix test, from 5% to 30%.

The compiler is also smarter in several ways: @behaviour declarations no longer add compile-time dependencies and aliases in patterns and guards add no dependency whatsoever, as no dispatching happens. Furthermore, Mix now tracks the digests of @external_resource files, reducing the amount of recompilation when swapping branches. Finally, dependencies are automatically recompiled when their compile-time configuration changes.


Potential incompatibilities

Due to the code path pruning, if you have an application or dependency that does not specify its dependencies on Erlang and Elixir application, it may no longer compile successfully in Elixir v1.15. You can temporarily disable code path pruning by setting prune_code_paths: false in your mix.exs, although doing so may lead to runtime bugs that are only manifested inside a mix release.


Compiler warnings and errors

The Elixir compiler can now emit many errors for a single file, making sure more feedback is reported to developers before compilation is aborted.

In Elixir v1.14, an undefined function would be reported as:

** (CompileError) undefined function foo/0 (there is no such import)

In Elixir v1.15, the new reports will look like:

error: undefined function foo/0 (there is no such import)

** (CompileError) nofile: cannot compile file (errors have been logged)

A new function, called Code.with_diagnostics/2, has been added so this information can be leveraged by editors, allowing them to point to several errors at once.


Integration with Erlang/OTP logger

This release provides additional features such as global logger metadata and file logging (with rotation and compaction) out-of-the-box!

This release also soft-deprecates Elixir's Logger Backends in favor of Erlang's Logger handlers. Elixir will automatically convert your :console backend configuration into the new configuration. Previously, you would set:

config :logger, :console,
  level: :error,
  format: "$time $message $metadata"

Which is now translated to the equivalent:

config :logger, :default_handler,
  level: :error

config :logger, :default_formatter,
  format: "$time $message $metadata"

If you use Logger.Backends.Console or other backends, they are still fully supported and functional. If you implement your own backends, you want to consider migrating to :logger_backends in the long term.

See the new Logger documentation for more information on the new features and on compatibility.


v1.15.0-rc.1 (2022-05-29)


1. Enhancements




2. Bug fixes


  • [Code] Ensure :on_undefined_variable option works as advertised (regression)
  • [Code] Format paths in Code.with_diagnostic/2 as relative paths (regression)
  • [Kernel] Raise when macros are given to dialyzer
  • [Kernel] Support bitstring specifiers as map keys in pattern (regression)
  • [Module] Ensure that Module.get_attribute/3 returns nil and not the given default value when an attribute has been explicitly set as nil
  • [Task] Do not double log Task failure reports


  • [ExUnit.CaptureLog] Allow capturing deprecated log level (regression)
  • [ExUnit.DocTest] Ensure proper line is returned when failing to parse doctest results


  • [IEx] Fix IO operations not returning when booting IEx (regression)


  • [mix deps] Ensure dependencies with included_applications can be loaded (regression)
  • [mix format] Ensure proper formatter options are returned for files (regression)


3. Soft deprecations


  • [Kernel] Require pin variable when accessing variable inside binary size in match


v1.15.0-rc.0 (2022-05-22)


1. Enhancements


  • [EEx] Include source code snippets in syntax errors



  • [ExUnit] Add more color configuration to ExUnit CLI formatter
  • [ExUnit.Callbacks] Accept {module, function} tuples in ExUnit setup callbacks
  • [ExUnit.Doctest] Add ExUnit.DocTest.doctest_file/2
  • [ExUnit.Formatter] When comparing two anonymous functions, defined at the same place but capturing a different environment, we will now also diff the environments


  • [IEx] Make pry opt-in on dbg with --dbg pry
  • [IEX] Support IEX_HOME
  • [IEx.Autocomplete] Only provide aliases when autocompleting alias, import, and require
  • [IEx.Autocomplete] Provide field completion on map and struct updates
  • [IEx.Helpers] Add runtime_info(:allocators)
  • [IEx.Info] Implement protocol for Range, DateTime, and Regex


  • [Logger] Add Logger.add_handlers/1 and Logger.default_formatter/1
  • [Logger] Introduce default_formatter and default_handler configuration for Logger which configures Erlang/OTP logger
  • [Logger] Add :always_evaluate_messages configuration to Logger
  • [Logger.Formatter] Implement the Erlang Logger formatter API
  • [Logger.Formatter] Add support for ports in Logger metadata


  • [mix app.start] Allow applications to be started concurrently via the :start_concurrently configuration
  • [mix compile] Set --all-warnings by default
  • [mix compile] Reduce the amount of filesystem lookups for path dependencies by storing timestamps in manifests
  • [mix compile] Track digests of @external_resources
  • [mix] Write optional_applications to .app file
  • [mix compile.elixir] Add --purge-consolidation-path-if-stale which will purge the given consolidation path if compilation is required
  • [mix deps.compile] Automatically recompile dependencies if their compile env changes
  • [mix deps.get] Automatically install Hex and Rebar on mix deps.get/mix deps.update
  • [mix deps.get] Support --check-locked which raises if changes to the lockfile are required
  • [mix eval] Allow passing additional arguments
  • [mix format] Support --no-exit option
  • [mix format] Allow multiple formatters per file extension and sigil
  • [mix format] Show diffs whenever --check-formatted fails
  • [mix format] Allow the formatting root to be configured
  • [mix loadpaths] Cache deps and archive loadpaths in Erlang/OTP 26
  • [mix profile.fprof] Support --trace-to-file to improve performance when working with large outputs
  • [mix release] Allow passing additional arguments to the eval command
  • [mix xref graph] Support --output flag
  • [Mix.Project] Support def cli to unify all CLI defaults in a single place
  • [Mix.Project] Add Mix.Project.deps_tree/1


2. Bug fixes


  • [Code.Formatter] Fix a scenario where a keyword followed by parenthesis could go above the maximum line length
  • [Code.Formatter] Remove unnecessary parens in nullary type funs
  • [Exception] Fix operator precedence when printing guards in Exception.blame/3
  • [File] Do not raise if there are file system race conditions in File.cp/2
  • [File] Do not raise when deleting write-only empty directories on File.rm_rf/1
  • [Kernel] Expand macros on the left side of -> in try/rescue
  • [Kernel] Raise on misplaced ... inside typespecs
  • [Kernel] Do not import behaviour_info and module_info functions from Erlang modules
  • [Kernel.ParallelCompiler] Make sure compiler doesn't crash when there are stray messages in the inbox
  • [Kernel.ParallelCompiler] Track compile and runtime warnings separately
  • [System] Fix race condition when a script would terminate before System.stop/1 executes
  • [URI] Make sure URI.merge/2 works accordingly with relative paths


  • [ExUnit] Fix crash when @tag capture_log: true was set to true and the Logger application was shut down in the middle of the test
  • [ExUnit] Do not merge context as tags inside the runner to reduce memory usage when emitting events to formatters
  • [ExUnit] Do not expand or collect vars from quote in ExUnit assertions


  • [IEx] Do not spawn a process to read IO. This fixes a bug where multiline paste stopped working whenever the input reader was killed
  • [IEx] Do not perform completion for prompts triggered during code evaluation


  • [mix compile] Include cwd in compiler cache key
  • [mix release] Fix Windows service when invoking erlsrv.exe in path with spaces


3. Soft deprecations (no warnings emitted)


  • [File] File.cp/3 and File.cp_r/3 with a function as third argument is deprecated in favor of a keyword list
  • [Kernel.ParallelCompiler] Require the :return_diagnostics option to be set to true when compiling or requiring code


  • [Logger] add_backend/2, remove_backend/2, and configure_backend/2 have been deprecated in favor of the new :logger_backends dependency
  • [Logger] The :console configuration has been deprecated in favor of :default_formatter
  • [Logger] The :backends configuration has been deprecated in favor of Logger.add_handlers/1


  • [Mix.Project] :preferred_cli_env is deprecated in favor of :preferred_envs in def cli
  • [Mix.Project] :preferred_cli_target is deprecated in favor of :preferred_targets in def cli
  • [mix local] The environment variable HEX_MIRROR is deprecated in favor of HEX_BUILDS_URL


4. Hard deprecations





The CHANGELOG for v1.14 releases can be found in the v1.14 branch.