TODO.

• Type inference of patterns (typing inference of guards will be part of an upcoming release)

• Type checking of all language constructs, including local and remote calls, except for, with, and closures

• Type checking of all Kernel and conversion functions inlined by the compiler

• Support for tuples and lists as composite types as well as type checking of their basic operations

• Detection of clauses and patterns that will never match from case, cond, and =

• Detection of unused clauses from private functions

ExUnit now supports parameterized tests to run the same test module multiple times under different parameters.

For example, Elixir ships a local, decentralized and scalable key-value process storage called Registry. The registry can be partitioned and its implementation differs depending if partitioning is enabled or not. Therefore, during tests, we want to ensure both modes are exercised. With Elixir v1.18, we can achieve this by writing:

defmodule Registry.Test do
  use ExUnit.Case,
    async: true,
    parameterize: [
      %{partitions: 1},
      %{partitions: 8}
    ]

  # ... the actual tests ...
end

ExUnit parameterizes whole test modules. If your modules are configured to run concurrently, as above, so will the parameterized ones.

ExUnit also comes with the ability of specifying test groups. While ExUnit supports running tests concurrently, those tests must not have shared state between them. However, in large applications, it may be common for some tests to depend on some shared state, and other tests to depend on a completely separate state. For example, part of your tests may depend on Cassandra, while others depend on Redis. Prior to Elixir v1.18, these tests could not run concurrently, but in v1.18 they might as long as they are assigned to different groups. Tests modules within the same group do not run concurrently, but across groups, they might.

With features like async tests, suite partitioning, and now grouping, Elixir developers have plenty of flexibility to make the most use of their machine resources, both in development and in CI.

TODO.

This release no longer supports WERL (a graphical user interface on Windows used by Erlang 25 and earlier). For a better user experience on Windows terminals, use Erlang/OTP 26+.

Furthermore, in order to support inference of patterns, Elixir will raise if it finds recursive variable definitions. This means patterns that never match, such as this one, will no longer compile:

def foo(x = {:ok, y}, x = y)

However, recursion of root variables (where variables directly point to each other), will also fail to compile:

def foo(x = y, y = z, z = x)

While the definition above could succeed (as long as all three arguments are equal), the cycle is not necessary and could be removed, as below:

def foo(x = y, y = z, z)

You may also prefer to write using guards:

def foo(x, y, z) when x == y and y == z

• [CLI] Add experimental PowerShell scripts for elixir, elixirc, and mix on Windows. Those provide a safer entry point for running Elixir from other platforms
• [Code] Support several migration options in Code.format_string!/2
• [Code] Add parenthesis around -- and --- in Code.format_string!/2 to make precedence clearer
• [Code] Include more metadata in Code.string_to_quoted/2 when token_metadata: true to help compute ranges from the AST
• [Code.Fragment] Have :capture_arg as its own entry in Code.Fragment.surround_context/2
• [Config] Add Config.read_config/1
• [Enumerable] Add Enum.product_by/2 and Enum.sum_by/2
• [Exception] Add MissingApplicationsError exception to denote missing applications
• [Kernel] Update source code parsing to match UTS #55 latest recommendations. In particular, mixed script is allowed in identifiers as long as they are separate by underscores (_), such as http_сервер. Previously allowed highly restrictive identifiers, which mixed Latin and other scripts, such as the japanese word for t-shirt, Tシャツ, now require the underscore as well
• [Kernel] Warn on bidirectional confusability in identifiers
• [Kernel] Now verify the type of the binary generators
• [Kernel] Track the type of tuples in patterns and inside elem/2
• [Kernel] Perform validation of root AST nodes in unquote and unquote_splicing to catch bugs earlier
• [Kernel] Add source, behaviour, and record information to Docs chunk metadata
• [Kernel] Support deterministic builds in tandem with Erlang by setting ERL_COMPILER_OPTIONS=deterministic. Keep in mind deterministic builds strip source and other compile time information, which may be relevant for programs
• [List] Add List.ends_with?/2
• [Macro] Improve dbg handling of if/2, with/1 and of code blocks
• [Macro] Add Macro.struct_info!/2 to return struct information mirroring mod.__info__(:struct)
• [Registry] Add Registry.lock/3 for local locking
• [PartitionSupervisor] Add PartitionSupervisor.resize!/2 to resize the number of partitions in a supervisor (up to the limit it was started with)
• [Process] Handle arbitrarily high integer values in Process.sleep/1
• [String] Inspect special whitespace and zero-width characters using their Unicode representation

• [ExUnit] Support parameterized tests on ExUnit.Case
• [ExUnit] Support test groups: tests in the same group never run concurrently

• [IEx] Add :dot_iex support to IEx.configure/1
• [IEx] Add report for normal/shutdown exits in IEx

• [mix compile] Ensure only a single operating system process can compile at a given time
• [mix deps.get] Ensure only a single operating system process can fetch deps at a given time
• [mix format] Add mix format --migrate to migrate from deprecated functionality
• [mix test] Taint failure manifest if requiring or compiling tests fail
• [Mix.Project] Add a :listeners configuration to listen to compilation events from the current and other operating system processes
• [Mix.Task.Compiler] Add API for fetching all persisted compiler diagnostics
• [Mix.Task.Compiler] Add API for fetching all compiler tasks

• [Code] Fix delimiter metadata for single quoted atoms and remote calls in Code.string_to_quoted/2
• [Code.Formatter] Fix formatter adding extra escapes to quoted remote calls
• [Code.Fragment] Properly handle keyword keys as their own entry
• [Inspect.Algebra] Ensure next_break_fits respects line_length
• [Module] Include module attribute line and name when tracing its aliases
• [Stream] Do not halt streams twice in Stream.transform/5
• [URI] Fix a bug when a schemaless URI is given to URI.merge/2

• [ExUnit.Assertions] Raise if guards are used in assert/1 with =

• [IEx.Helpers] IEx.Helpers.recompile/0 will reload modules changed by other operating system processes

• [mix compile] Ensure warnings from external resources are emitted with --all-warnings when files do not change
• [mix deps.compile] Fix escaping issues when invoking rebar3 in some cases
• [mix escript] Fix escript layout and support storing priv directories
• [mix release] Make .app files deterministic in releases

• [Inspect.Algebra] color/3 is deprecated in favor of color_doc/3
• [Inspect.Algebra] fold_doc/2 is deprecated in favor of fold/2
• [Kernel] Deprecate unless in favor of if. Use mix format --migrate to automate the migration
• [Macro] Macro.struct!/2 is deprecated in favor of Macro.struct_info!/2

• [EEx] <%# is deprecated in favor of <%!-- or <% #
• [EEx] c:EEx.handle_text/2 is deprecated in favor of c:EEx.handle_text/3

• [Code] Setting :warnings_as_errors is deprecated via Code.put_compiler_option/2. This must not affect developers, as the :warnings_as_errors option is managed by Mix tasks, and not directly used via the Code module
• [Enumerable] Deprecate returning a two-arity function in Enumerable.slice/1
• [List] List.zip/1 is deprecated in favor of Enum.zip/1
• [Module] Deprecate Module.eval_quoted/3 in favor of Code.eval_quoted/3
• [Range] Deprecate inferring negative ranges on Range.new/2
• [Tuple] Tuple.append/2 is deprecated, use Tuple.insert_at/3 instead

• [mix cmd] Deprecate mix cmd --app APP in favor of mix do --app APP
• [Mix.Tasks.Compile] Deprecate compilers/0 in favor of Mix.Task.Compiler.compilers/0

The CHANGELOG for v1.17 releases can be found in the v1.17 branch.