View Source Macro.Env (Elixir v1.18.0)

A struct that holds compile time environment information.

The current environment can be accessed at any time as __ENV__/0. Inside macros, the caller environment can be accessed as __CALLER__/0.

The majority of the functions in this module are provided for low-level tools, which need to integrate with the Elixir compiler, such as language servers and embedded languages. For regular usage in Elixir code and macros, you must use the Macro module instead. In particular, avoid modifying the Macro.Env struct directly and prefer to use high-level constructs, such as a import, aliases, and so forth to build your own environment. For example, to build a custom environment, you can define a function such as:

def make_custom_env do
  import SomeModule, only: [some_function: 2], warn: false
  alias A.B.C, warn: false
  __ENV__
end

Struct fields

The Macro.Env struct contains the following fields:

context - the context of the environment; it can be nil (default context), :guard (inside a guard) or :match (inside a match)
context_modules - a list of modules defined in the current context
file - the current absolute file name as a binary
function - a tuple as {atom, integer}, where the first element is the function name and the second its arity; returns nil if not inside a function
line - the current line as an integer
module - the current module name

The following fields are private to Elixir's macro expansion mechanism and must not be accessed directly:

aliases
functions
macro_aliases
macros
lexical_tracker
requires
tracers
versioned_vars

Summary

Types

context()

context_modules()

file()

line()

name_arity()

t()

variable()

Functions

define_alias(env, meta, module, opts \\ [])

Defines the given as an alias to module in the environment.

define_import(env, meta, module, opts \\ [])

Defines the given module as imported in the environment.

define_require(env, meta, module, opts \\ [])

Defines the given module as required in the environment.

expand_alias(env, meta, list, opts \\ [])

Expands an alias given by the alias segments.

expand_import(env, meta, name, arity, opts \\ [])

Expands an import given by name and arity.

expand_require(env, meta, module, name, arity, opts \\ [])

Expands a require given by module, name, and arity.

has_var?(env, var)

Checks if a variable belongs to the environment.

in_guard?(env)

Returns whether the compilation environment is currently inside a guard.

in_match?(env)

Returns whether the compilation environment is currently inside a match clause.

location(env)

Returns a keyword list containing the file and line information as keys.

lookup_alias_as(env, atom)

Returns the names of any aliases for the given module or atom.

lookup_import(env, name_arity)

Returns the modules from which the given {name, arity} was imported.

prepend_tracer(env, tracer)

Prepend a tracer to the list of tracers in the environment.

prune_compile_info(env)

Prunes compile information from the environment.

required?(env, module)

Returns true if the given module has been required.

stacktrace(env)

Returns the environment stacktrace.

to_guard(env)

Returns an environment in the guard context.

to_match(env)

Returns an environment in the match context.

vars(env)

Returns a list of variables in the current environment.

Types

context()

@type context() :: :match | :guard | nil

context_modules()

@type context_modules() :: [module()]

file()

@type file() :: binary()

line()

@type line() :: non_neg_integer()

name_arity()

@type name_arity() :: {atom(), arity()}

t()

@type t() :: %Macro.Env{
  aliases: aliases(),
  context: context(),
  context_modules: context_modules(),
  file: file(),
  function: name_arity() | nil,
  functions: functions(),
  lexical_tracker: lexical_tracker(),
  line: line(),
  macro_aliases: macro_aliases(),
  macros: macros(),
  module: module(),
  requires: requires(),
  tracers: tracers(),
  versioned_vars: versioned_vars()
}

variable()

@type variable() :: {atom(), atom() | term()}

Functions

define_alias(env, meta, module, opts \\ [])

(since 1.17.0)

@spec define_alias(t(), Macro.metadata(), module(), keyword()) ::
  {:ok, t()} | {:error, String.t()}

Defines the given as an alias to module in the environment.

This is used by tools which need to mimic the Elixir compiler. The appropriate :alias compiler tracing event will be emitted.

Additional options

It accepts the same options as Kernel.SpecialForm.alias/2 plus:

:trace - when set to false, it disables compilation tracers and lexical tracker. This option must only be used by language servers and other tools that need to introspect code without affecting how it is compiled. Disabling tracer inside macros or regular code expansion is extremely discouraged as it blocks the compiler from accurately tracking dependencies

Examples

iex> env = __ENV__
iex> Macro.Env.expand_alias(env, [], [:Baz])
:error
iex> {:ok, env} = Macro.Env.define_alias(env, [line: 10], Foo.Bar, as: Baz)
iex> Macro.Env.expand_alias(env, [], [:Baz])
{:alias, Foo.Bar}
iex> Macro.Env.expand_alias(env, [], [:Baz, :Bat])
{:alias, Foo.Bar.Bat}

If no :as option is given, the alias will be inferred from the module:

iex> env = __ENV__
iex> {:ok, env} = Macro.Env.define_alias(env, [line: 10], Foo.Bar)
iex> Macro.Env.expand_alias(env, [], [:Bar])
{:alias, Foo.Bar}

If it is not possible to infer one, an error is returned:

iex> Macro.Env.define_alias(__ENV__, [line: 10], :an_atom)
{:error,
 "alias cannot be inferred automatically for module: :an_atom, " <>
   "please use the :as option. Implicit aliasing is only supported with Elixir modules"}

define_import(env, meta, module, opts \\ [])

(since 1.17.0)

@spec define_import(t(), Macro.metadata(), module(), keyword()) ::
  {:ok, t()} | {:error, String.t()}

Defines the given module as imported in the environment.

It assumes module is available. This is used by tools which need to mimic the Elixir compiler. The appropriate :import compiler tracing event will be emitted.

Additional options

It accepts the same options as Kernel.SpecialForm.import/2 plus:

:emit_warnings - emit warnings found when defining imports
:trace - when set to false, it disables compilation tracers and lexical tracker. This option must only be used by language servers and other tools that need to introspect code without affecting how it is compiled. Disabling tracer inside macros or regular code expansion is extremely discouraged as it blocks the compiler from accurately tracking dependencies
:info_callback - a function to use instead of Module.__info__/1. The function will be invoked with :functions or :macros argument. It has to return a list of {function, arity} key value pairs. If it fails, it defaults to using module metadata based on module_info/1.

Examples

iex> env = __ENV__
iex> Macro.Env.lookup_import(env, {:flatten, 1})
[]
iex> {:ok, env} = Macro.Env.define_import(env, [line: 10], List)
iex> Macro.Env.lookup_import(env, {:flatten, 1})
[{:function, List}]

It accepts the same options as Kernel.SpecialForm.import/2:

iex> env = __ENV__
iex> Macro.Env.lookup_import(env, {:is_odd, 1})
[]
iex> {:ok, env} = Macro.Env.define_import(env, [line: 10], Integer, only: :macros)
iex> Macro.Env.lookup_import(env, {:is_odd, 1})
[{:macro, Integer}]

Info callback override

iex> env = __ENV__
iex> Macro.Env.lookup_import(env, {:flatten, 1})
[]
iex> {:ok, env} = Macro.Env.define_import(env, [line: 10], SomeModule, [info_callback: fn :functions -> [{:flatten, 1}]; :macros -> [{:some, 2}]; end])
iex> Macro.Env.lookup_import(env, {:flatten, 1})
[{:function, SomeModule}]
iex> Macro.Env.lookup_import(env, {:some, 2})
[{:macro, SomeModule}]

define_require(env, meta, module, opts \\ [])

(since 1.17.0)

Defines the given module as required in the environment.

It does not check or assert the module is available. This is used by tools which need to mimic the Elixir compiler. The appropriate :require compiler tracing event will be emitted.

Additional options

It accepts the same options as Kernel.SpecialForm.require/2 plus:

:trace - when set to false, it disables compilation tracers and lexical tracker. This option must only be used by language servers and other tools that need to introspect code without affecting how it is compiled. Disabling tracer inside macros or regular code expansion is extremely discouraged as it blocks the compiler from accurately tracking dependencies

Examples

iex> env = __ENV__
iex> Macro.Env.required?(env, Integer)
false
iex> {:ok, env} = Macro.Env.define_require(env, [line: 10], Integer)
iex> Macro.Env.required?(env, Integer)
true

If the :as option is given, it will also define an alias:

iex> env = __ENV__
iex> {:ok, env} = Macro.Env.define_require(env, [line: 10], Foo.Bar, as: Baz)
iex> Macro.Env.expand_alias(env, [], [:Baz])
{:alias, Foo.Bar}

expand_alias(env, meta, list, opts \\ [])

(since 1.17.0)

@spec expand_alias(t(), keyword(), [atom()], keyword()) :: {:alias, atom()} | :error

Expands an alias given by the alias segments.

It returns {:alias, alias} if the segments is a list of atoms and an alias was found. Returns :error otherwise.

This expansion may emit the :alias_expansion trace event but it does not emit the :alias_reference one.

Options

:trace - when set to false, it disables compilation tracers and lexical tracker. This option must only be used by language servers and other tools that need to introspect code without affecting how it is compiled. Disabling tracer inside macros or regular code expansion is extremely discouraged as it blocks the compiler from accurately tracking dependencies

Examples

iex> alias List, as: MyList
iex> Macro.Env.expand_alias(__ENV__, [], [:MyList])
{:alias, List}
iex> Macro.Env.expand_alias(__ENV__, [], [:MyList, :Nested])
{:alias, List.Nested}

If there is no alias or the alias starts with Elixir. (which disables aliasing), then :error is returned:

iex> alias List, as: MyList
iex> Macro.Env.expand_alias(__ENV__, [], [:Elixir, MyList])
:error
iex> Macro.Env.expand_alias(__ENV__, [], [:AnotherList])
:error

expand_import(env, meta, name, arity, opts \\ [])

(since 1.17.0)

@spec expand_import(t(), keyword(), atom(), arity(), keyword()) ::
  {:macro, module(), (Macro.metadata(), args :: [Macro.t()] -> Macro.t())}
  | {:function, module(), atom()}
  | {:error, :not_found | {:conflict, module()} | {:ambiguous, [module()]}}

Expands an import given by name and arity.

If the import points to a macro, it returns a tuple with the module and a function that expands the macro. The function expects the metadata to be attached to the expansion and the arguments of the macro.

If the import points to a function, it returns a tuple with the module and the function name.

If any import is found, the appropriate compiler tracing event will be emitted.

Otherwise returns {:error, reason}.

Options

:allow_locals - when set to false, it does not attempt to capture local macros defined in the current module in env
:check_deprecations - when set to false, does not check for deprecations when expanding macros
:trace - when set to false, it disables compilation tracers and lexical tracker. This option must only be used by language servers and other tools that need to introspect code without affecting how it is compiled. Disabling tracer inside macros or regular code expansion is extremely discouraged as it blocks the compiler from accurately tracking dependencies

expand_require(env, meta, module, name, arity, opts \\ [])

(since 1.17.0)

@spec expand_require(t(), keyword(), module(), atom(), arity(), keyword()) ::
  {:macro, module(), (Macro.metadata(), args :: [Macro.t()] -> Macro.t())}
  | :error

Expands a require given by module, name, and arity.

If the require points to a macro and the module has been required, it returns a tuple with the module and a function that expands the macro. The function expects the metadata to be attached to the expansion and the arguments of the macro. The appropriate :remote_macro compiler tracing event will be emitted if a macro is found (note a :remote_function event is not emitted in :error cases).

Otherwise returns :error.

Options

:check_deprecations - when set to false, does not check for deprecations when expanding macros
:trace - when set to false, it disables compilation tracers and lexical tracker. This option must only be used by language servers and other tools that need to introspect code without affecting how it is compiled. Disabling tracer inside macros or regular code expansion is extremely discouraged as it blocks the compiler from accurately tracking dependencies

has_var?(env, var)

(since 1.7.0)

@spec has_var?(t(), variable()) :: boolean()

Checks if a variable belongs to the environment.

Examples

iex> x = 13
iex> x
13
iex> Macro.Env.has_var?(__ENV__, {:x, nil})
true
iex> Macro.Env.has_var?(__ENV__, {:unknown, nil})
false

in_guard?(env)

@spec in_guard?(t()) :: boolean()

Returns whether the compilation environment is currently inside a guard.

in_match?(env)

@spec in_match?(t()) :: boolean()

Returns whether the compilation environment is currently inside a match clause.

location(env)

@spec location(t()) :: keyword()

Returns a keyword list containing the file and line information as keys.

lookup_alias_as(env, atom)

(since 1.15.0)

@spec lookup_alias_as(t(), atom()) :: [atom()]

Returns the names of any aliases for the given module or atom.

Examples

iex> alias Foo.Bar
iex> Bar
Foo.Bar
iex> Macro.Env.lookup_alias_as(__ENV__, Foo.Bar)
[Elixir.Bar]
iex> alias Foo.Bar, as: Baz
iex> Baz
Foo.Bar
iex> Macro.Env.lookup_alias_as(__ENV__, Foo.Bar)
[Elixir.Bar, Elixir.Baz]
iex> Macro.Env.lookup_alias_as(__ENV__, Unknown)
[]

lookup_import(env, name_arity)

(since 1.13.0)

@spec lookup_import(t(), name_arity()) :: [{:function | :macro, module()}]

Returns the modules from which the given {name, arity} was imported.

It returns a list of two element tuples in the shape of {:function | :macro, module}. The elements in the list are in no particular order and the order is not guaranteed.

Use only for introspection

This function does not emit compiler tracing events, which may block the compiler from correctly tracking dependencies. Use this function for reflection purposes but to do not use it to expand imports into qualified calls. Instead, use expand_import/5.

Examples

iex> Macro.Env.lookup_import(__ENV__, {:duplicate, 2})
[]
iex> import Tuple, only: [duplicate: 2], warn: false
iex> Macro.Env.lookup_import(__ENV__, {:duplicate, 2})
[{:function, Tuple}]
iex> import List, only: [duplicate: 2], warn: false
iex> Macro.Env.lookup_import(__ENV__, {:duplicate, 2})
[{:function, List}, {:function, Tuple}]

iex> Macro.Env.lookup_import(__ENV__, {:def, 1})
[{:macro, Kernel}]

prepend_tracer(env, tracer)

(since 1.13.0)

@spec prepend_tracer(t(), module()) :: t()

Prepend a tracer to the list of tracers in the environment.

Examples

Macro.Env.prepend_tracer(__ENV__, MyCustomTracer)

prune_compile_info(env)

(since 1.14.0)

@spec prune_compile_info(t()) :: t()

Prunes compile information from the environment.

This happens when the environment is captured at compilation time, for example, in the module body, and then used to evaluate code after the module has been defined.

required?(env, module)

(since 1.13.0)

@spec required?(t(), module()) :: boolean()

Returns true if the given module has been required.

Examples

iex> Macro.Env.required?(__ENV__, Integer)
false
iex> require Integer
iex> Macro.Env.required?(__ENV__, Integer)
true

iex> Macro.Env.required?(__ENV__, Kernel)
true

stacktrace(env)

@spec stacktrace(t()) :: list()

Returns the environment stacktrace.

to_guard(env)

(since 1.17.0)

@spec to_guard(t()) :: t()

Returns an environment in the guard context.

to_match(env)

@spec to_match(t()) :: t()

Returns an environment in the match context.

vars(env)

(since 1.7.0)

@spec vars(t()) :: [variable()]

Returns a list of variables in the current environment.

Each variable is identified by a tuple of two elements, where the first element is the variable name as an atom and the second element is its context, which may be an atom or an integer.