View Source Changelog for Elixir v1.15

This release requires Erlang/OTP 24 and later.

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

Finally, you will also find additional convenience functions in Map, Keyword, all Calendar modules, and many more.


Compile and boot-time improvements

The last several releases brought improvements to compilation time and this version is no different. In particular, this version 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 end-up being 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 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.

In this release, we will now prune the code paths to only the ones listed as dependencies. Previously if you attempted to use an Erlang/OTP or Elixir module without adding its dependency, we would warn. Now the module won't be found altogether, which is also the behaviour you see if you ran your application as a mix release. If you are using an application that does not correctly lists its dependencies, they will have to be updated accordingly (as previously warned).

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 15%.


Compiler warnings and errors



Integration with Erlang/OTP logger

This provides additional features such as global logger metadata and file logging (with rotation and compactation) out-of-the-box! See the Logger documentation for more information.

TODO: Mention :console vs Logger.Backends.Console




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 to 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.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.Formatter] Implement the Erlang Logger formatter API
  • [Logger.Formatter] Add support for ports in Logger metadata


  • [Mix.Project] Support def cli to unify all CLI defaults in a single place
  • [mix eval] Allow passing additional arguments
  • [mix compile] Set --all-warnings by default
  • [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.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 format] Allow multiple formatters per file extension and sigil
  • [mix format] Show diffs whenever --check-formatted fails
  • [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


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
  • [File] Do not raise if there are file system race conditions in File.cp/2
  • [Kernel] Expand macros on the left side of -> in try/rescue
  • [Kernel] Raise on misplaced ... inside typespecs
  • [Kernel.ParallelCompiler] Make sure compiler doesn't crash when there are stray messages in the inbox
  • [Kernel.ParallelCompiler] Track compile and runtime warnings separately
  • [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 release] Fix Windows service when invoking erlsrv.exe in path with spaces


3. Soft deprecations (no warnings emitted)


  • [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


4. Hard deprecations





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