# Changelog for Elixir v1.21 ## v1.21.0-dev ### 1. Enhancements #### EEx * [EEx] Support splitting middle expressions across EEx clauses #### Elixir * [Access] Add support for keyword lists in `Access.key/2` and `Access.key!/1` * [Code] Add support for the `:erlc_options` compiler option * [Code.Formatter] Add a `:migrate_atom_interpolations` option * [Kernel] Improve performance of type constructors and complex intersections * [Kernel] Warn on binary patterns with segments that are not byte-aligned * [Kernel.ParallelCompiler] Add a hint when spawned processes cannot load modules defined during compilation * [Keyword] Optimize `Keyword.pop/3`, `Keyword.pop!/2`, and `Keyword.pop_lazy/3` * [List] Add `List.to_existing_atom/2` and `List.to_unsafe_atom/1` * [MapSet] Optimize `MapSet.symmetric_difference/2` when set sizes differ * [Path] Add `Path.safe_join/2` * [Registry] Optimize exact key matching in lookups * [String] Optimize `String.bag_distance/2` * [String] Add `String.to_existing_atom/2` and `String.to_unsafe_atom/1` * [URI] Optimize percent-decoding and `URI.to_string/1` #### ExUnit * [ExUnit.Assertions] Add `trace/3` helper ### 2. Bug fixes #### Elixir * [Calendar] Fix `Calendar.strftime/3` formatting of negative years with `%y` * [Calendar] Fix rounding for `:day`, `:hour`, and `:minute` units in `DateTime.diff/3`, `NaiveDateTime.diff/3`, and `Time.diff/3` * [Calendar.ISO] Fix `Calendar.ISO.valid_time?/4` to reject non-integer microsecond precision * [Calendar.ISO] Reject negative zero UTC offsets in basic formats * [Code.Formatter] Fix rendering calls where `do` is followed by non-block keyword arguments * [Code.Fragment] Fix cursor completion when operator keywords such as `in`, `when`, `and`, `or`, and `not` follow another operator * [Date] Preserve the `:format` option in `Date.to_iso8601/2` with custom calendars * [Date.Range] Fix slicing date ranges with stepped ranges * [Duration] Reject duplicate seconds in `Duration.from_iso8601/1` * [Enum] Fix `Enum.min/2,3` and `Enum.max/2,3` with custom sorters on ranges * [IO.ANSI.Docs] Recognize additional punctuation delimiters when rendering Markdown * [Kernel] Fix expansion of rebound variables in bitstring size expressions * [Kernel] Expand `defguard` macros separately in guard and body contexts, preserving `and`/`or` error semantics outside guards * [Kernel] Fix inferred stacktrace types to allow arbitrary keyword metadata * [Kernel] Fix inferred types for functions with non-returning clauses * [Kernel] Fix map field type inference in the presence of empty map types * [Kernel] Fix tuple fetch and deletion type operations across equivalent tuple types * [Kernel] Fix variables defined in one default argument leaking into subsequent default arguments * [Kernel] Improve the error message for non-atom struct keys * [Kernel] Raise when `|` is used in guards * [Kernel.Typespec] Preserve metadata when proxying to Elixir typespecs * [Keyword] Delete duplicate keys when `Keyword.get_and_update/3` and `Keyword.get_and_update!/3` return `:pop` * [Macro] Properly escape C1 control characters and Unicode noncharacters * [NaiveDateTime] Fix `NaiveDateTime.diff/3` over-counting incomplete units * [Range] Fix `Range.disjoint?/2` for ranges beyond floating-point precision * [Range] Fix `Range.disjoint?/2` for single-element ranges with a negative step * [String] Fix `String.reverse/1` grapheme ordering around invalid UTF-8 bytes * [String] Return `1.0` from `String.bag_distance/2` for two empty strings * [Time] Validate microseconds in `Time.from_seconds_after_midnight/3` #### ExUnit * [ExUnit.Assertions] Fix `refute_in_delta/4` at the delta boundary and with negative deltas * [ExUnit.CaptureIO] Stop `StringIO` processes when capturing a named device fails #### IEx * [IEx.Autocomplete] Fix completion crashes on maps with non-atom keys * [IEx.Evaluator] Recognize `**` and `not in` as continuation operators * [IEx.Helpers] Fix `r/1` when multiple modules are defined in the same file * [IEx.Helpers] Fix heap and stack memory calculations in `process_info/1` #### Mix * [Mix] Prevent synchronization lock files from being overwritten with empty contents * [Mix.Release] Accept chardata paths in `Mix.Release.make_boot_script/4` * [Mix.SCM.Git] Raise if Git refspecs start with `-` * [mix deps] Recompile path and fetchable dependencies when one of the dependencies they were compiled with is removed * [mix deps] Mark fetchable dependencies for compilation when their build exists but their SCM manifest is missing * [mix deps.compile] Preserve code paths and compiler options across OS partitions * [mix format] Pass `:sigils` to plugins invoked for sigils, allowing nested sigils to be formatted * [mix new] Avoid trailing whitespace in generated files ### 3. Hard deprecations #### Elixir * [Macro.Env] `Macro.Env.fetch_alias/2` and `Macro.Env.fetch_macro_alias/2` are deprecated, use `Macro.Env.expand_alias/4` instead ### 4. Soft deprecations #### Elixir * [Kernel] Atom interpolation (`:"foo_#{bar}"`) is deprecated in favor of explicit `String.to_unsafe_atom/1` * [List] `List.to_atom/1` is deprecated in favor of `List.to_unsafe_atom/1` * [String] `String.to_atom/1` is deprecated in favor of `String.to_unsafe_atom/1` ## v1.20 The CHANGELOG for v1.20 releases can be found [in the v1.20 branch](https://github.com/elixir-lang/elixir/blob/v1.20/CHANGELOG.md).