elixir-lang/elixir v1.19.0

on GitHub

Official announcement: https://elixir-lang.org/blog/2025/10/16/elixir-v1-19-0-released/

1. Enhancements

Elixir

• [Access] Add Access.values/0 for traversing maps and keyword lists values
• [Base] Add functions to verify if an encoding is valid, such as valid16?, valid64?, and so forth
• [Calendar] Support 2-arity options for Calendar.strftime/3 which receives the whole data type
• [Code] Add :migrate_call_parens_on_pipe formatter option
• [Code] Add :indentation option to Code.string_to_quoted/2
• [Code.Fragment] Preserve more block content around cursor in container_cursor_to_quoted
• [Code.Fragment] Add :block_keyword_or_binary_operator to Code.Fragment for more precise suggestions after operators and closing terminators
• [Code.Fragment] Add Code.Fragment.lines/1
• [Enum] Provide more information on Enum.OutOfBoundsError
• [Inspect] Allow optional: :all when deriving Inspect
• [Inspect.Algebra] Add optimistic/pessimistic groups as a simplified implementation of next_break_fits
• [IO.ANSI] Add ANSI codes to turn off conceal and crossed_out
• [Kernel] Raise when U+2028 and U+2029 characters are present in comments and strings to avoid line spoofing attacks
• [Kernel] Include the line for the previous clause in errors/warnings related to conflicts between defaults on function definitions
• [Kernel] Support min/2 and max/2 as guards
• [Kernel.ParallelCompiler] Add each_long_verification_threshold which invokes a callback when type checking a module takes too long
• [Kernel.ParallelCompiler] Include lines in == Compilation error in file ... == slogans
• [Macro] Print debugging results from Macro.dbg/3 as they happen, instead of once at the end
• [Macro] Add __escape__/1 callback so structs can escape references and other runtime data types in Macro.escape/1
• [Module] Do not automatically load modules after their compilation, guaranteeing a more consistent compile time experience and drastically improving compilation times
• [OptionParser] Support the :regex type
• [OptionParser] Enhance parsing error to display available options
• [Protocol] Type checking of protocols dispatch and implementations
• [Regex] Add Regex.to_embed/2 which returns an embeddable representation of regex in another regex
• [Regex] Raise error message when regexes are used as default values in struct fields for compatibility with Erlang/OTP 28
• [Registry] Add key-based partitioning of duplicate registries
• [String] Add String.count/2 to count occurrences of a pattern
• [String] Update to Unicode 17.0.0

ExUnit

• [ExUnit] Set a process label for each test
• [ExUnit.CaptureLog] Parallelize log dispatch when multiple processes are capturing log
• [ExUnit.Case] Add :test_group to the test context
• [ExUnit.Doctest] Support ellipsis in doctest exceptions to match the remaining of the exception
• [ExUnit.Doctest] Add :inspect_opts option for doctest

IEx

• [IEx] Support multi-line prompts (due to this feature, :continuation_prompt and :alive_continuation_prompt are no longer supported as IEx configuration)
• [IEx.Autocomplete] Functions annotated with @doc group: "Name" metadata will appear within their own groups in autocompletion

Logger

• [Logger] Accept any enumerable in Logger.metadata/1

Mix

• [mix] Add support for MIX_PROFILE_FLAGS to configure MIX_PROFILE
• [mix compile] Debug the compiler and type checker PID when MIX_DEBUG=1 and compilation/verification thresholds are met
• [mix compile] Add Mix.Tasks.Compiler.reenable/1
• [mix deps.compile] Support MIX_OS_DEPS_COMPILE_PARTITION_COUNT for compiling deps concurrently across multiple operating system processes
• [mix help] Add mix help Mod, mix help :mod, mix help Mod.fun, mix help Mod.fun/arity, and mix help app:package
• [mix format] Add options to mix format to allow excluding of files
• [mix test] Add --name-pattern option to mix test
• [mix test] Allow to distinguish the exit status between warnings as errors and test failures
• [mix xref graph] Add support for --format json
• [mix xref graph] Emit a warning if --source is part of a cycle
• [Mix] Support the :compilers option
• [Mix.Task.Compiler] Add Mix.Task.Compiler.run/2

2. Bug fixes

Elixir

• [Code] Return error on invalid unicode sequences in Code.string_to_quoted/2 instead of raising
• [Code] Properly handle column annotation for in in not in expressions
• [DateTime] Do not truncate microseconds regardless of precision in DateTime.diff/3
• [Enum] Fix infinite loop on Enum.take/2 with negative index on empty enumerable
• [File] Properly handle permissions errors cascading from parent in File.mkdir_p/1
• [Inspect] Inspect ill-formed structs as maps
• [Kernel] Properly increment metadata newline when ? is followed by a literal newline character
• [Kernel] not_a_map.key now raises BadMapError for consistency with other map operations
• [Protocol] defstruct/1 and defexception/1 are now disabled inside defprotocol as to not allow defining structs/exceptions alongside a protocol
• [Regex] Fix Regex.split/2 returning too many results when the chunk being split on was empty (which can happen when using features such as /K)
• [Stream] Ensure Stream.transform/5 respects suspend command when its inner stream halts
• [URI] Several fixes to URI.merge/2 related to trailing slashes, trailing dots, and hostless base URIs

ExUnit

• [ExUnit.Assertions] Fix order of pinned variables in failure reports
• [ExUnit.Assertions] Raise if attempting to raise an assertion error with invalid message (not a binary)
• [ExUnit.Case] Do not crash on empty test unit groups

IEx

• [IEx] Abort pipelines when there is an error in any step along the way

Mix

• [mix cmd] Preserve argument quoting in subcommands by no longer performing shell expansion. To revert to the previous behaviour, pass --shell before the command name
• [mix compile] Fix bug where reverting changes to an external resource (such as HEEx template) after a compilation error would make it so the source module would not be compiled
• [mix compile] Avoid failures when locking compilation across different users
• [mix compile] Fix race condition when renaming files used by the compilation lock
• [mix format] Ensure the formatter does not go over the specified limit in certain corner cases
• [mix release] Fix RELEASE_SYS_CONFIG for Windows 11
• [mix test] Ensure modules are preloaded in mix test --slowest-modules=N
• [mix xref graph] Provide more consistent output by considering strong connected components only when computing graphs

3. Soft deprecations (no warnings emitted)

Elixir

• [Inspect.Algebra] next_break_fits is deprecated in favor of optimistic/pessimistic groups
• [Node] Node.start/2-3 is deprecated in favor of Node.start/2 with a keyword list

Mix

• [mix compile] --no-protocol-consolidation is deprecated in favor of --no-consolidate-protocols for consistency with mix.exs configuration
• [mix compile.protocols] Protocol consolidation is now part of compile.elixir and the task itself has no effect

4. Hard deprecations

Elixir

• [Code] Warn if line-break characters outside of \r and \r\n are found in strings according to UX#55. This warning will be fast-tracked into an error for security reasons in Elixir v1.20, following a similar rule to bidirectional control characters. They will already raise if found in comments
• [Code] The on_undefined_variable: :warn is deprecated. Relying on undefined variables becoming function calls will not be supported in the future
• [File] Passing a callback as third argument to File.cp/3 is deprecated, pass it as a on_conflict: callback option instead
• [File] Passing a callback as third argument to File.cp_r/3 is deprecated, pass it as a on_conflict: callback option instead
• [Kernel] The struct update syntax, such as %URI{uri | path: "/foo/bar"}, now requires the given variable (or expression) to explicitly pattern match on the struct before it can be updated. This is because, thanks to the type system, pattern matching on structs can find more errors, more reliably, and we want to promote its usage. Once pattern matching is added, you may optionally convert the struct update syntax into the map update syntax %{uri | path: "/foo/bar"} with no less of typing guarantees
• [Kernel.ParallelCompiler] Passing return_diagnostics: true as an option is required on compile, compile_to_path and require

Logger

• [Logger] The :backends configuration is deprecated, either set the :default_handler to false or start backends in your application start callback

Mix

• [mix] The :default_task, :preferred_cli_env, and :preferred_cli_target configuration inside def project in your mix.exs has been deprecated in favor of :default_task, :preferred_envs and :preferred_targets inside the def cli function
• [mix do] Using commas as task separator in mix do (such as mix do foo, bar) is deprecated, use + instead (as in mix do foo + bar)