@spec container_cursor_to_quoted(
  List.Chars.t(),
  keyword()
) ::
  {:ok, Macro.t()}
  | {:error, {location :: keyword(), binary() | {binary(), binary()}, binary()}}

Receives a string and returns a quoted expression with the cursor AST position within its parent expression.

This function receives a string with an Elixir code fragment, representing a cursor position, and converts such string to AST with the inclusion of special __cursor__() node representing the cursor position within its container (i.e. its parent).

For example, take this code, which would be given as input:

max(some_value,

This function will return the AST equivalent to:

max(some_value, __cursor__())

In other words, this function is capable of closing any open brackets and insert the cursor position. Other content at the cursor position which is not a parent is discarded. For example, if this is given as input:

max(some_value, another_val

It will return the same AST:

max(some_value, __cursor__())

Similarly, if only this is given:

max(some_va

Then it returns:

max(__cursor__())

Calls without parenthesis are also supported, as we assume the brackets are implicit.

Tuples, lists, maps, and binaries all retain the cursor position:

max(some_value, [1, 2,

Returns the following AST:

max(some_value, [1, 2, __cursor__()])

Keyword lists (and do-end blocks) are also retained. The following:

if(some_value, do:
if(some_value, do: :token
if(some_value, do: 1 + val

all return:

if(some_value, do: __cursor__())

For multi-line blocks, all previous lines are preserved.

The AST returned by this function is not safe to evaluate but it can be analyzed and expanded.

Examples

Function call:

iex> Code.Fragment.container_cursor_to_quoted("max(some_value, ")
{:ok, {:max, [line: 1], [{:some_value, [line: 1], nil}, {:__cursor__, [line: 1], []}]}}

Containers (for example, a list):

iex> Code.Fragment.container_cursor_to_quoted("[some, value")
{:ok, [{:some, [line: 1], nil}, {:__cursor__, [line: 1], []}]}

If an expression is complete, then the whole expression is discarded and only the parent is returned:

iex> Code.Fragment.container_cursor_to_quoted("if(is_atom(var)")
{:ok, {:if, [line: 1], [{:__cursor__, [line: 1], []}]}}

this means complete expressions themselves return only the cursor:

iex> Code.Fragment.container_cursor_to_quoted("if(is_atom(var))")
{:ok, {:__cursor__, [line: 1], []}}

Operators are also included from Elixir v1.15:

iex> Code.Fragment.container_cursor_to_quoted("foo +")
{:ok, {:+, [line: 1], [{:foo, [line: 1], nil}, {:__cursor__, [line: 1], []}]}}

In order to parse the left-side of -> properly, which appears both in anonymous functions and do-end blocks, the trailing fragment option must be given with the rest of the contents:

iex> Code.Fragment.container_cursor_to_quoted("fn x", trailing_fragment: " -> :ok end")
{:ok, {:fn, [line: 1], [{:->, [line: 1], [[{:__cursor__, [line: 1], []}], :ok]}]}}

Options

• :file - the filename to be reported in case of parsing errors. Defaults to "nofile".

• :line - the starting line of the string being parsed. Defaults to 1.

• :column - the starting column of the string being parsed. Defaults to 1.

• :columns - when true, attach a :column key to the quoted metadata. Defaults to false.

• :token_metadata - when true, includes token-related metadata in the expression AST, such as metadata for do and end tokens, for closing tokens, end of expressions, as well as delimiters for sigils. See Macro.metadata/0. Defaults to false.

• :literal_encoder - a function to encode literals in the AST. See the documentation for Code.string_to_quoted/2 for more information.

• :trailing_fragment (since v1.18.0) - the rest of the contents after the cursor. This is necessary to correctly complete anonymous functions and the left-hand side of ->

@spec cursor_context(
  List.Chars.t(),
  keyword()
) ::
  {:alias, charlist()}
  | {:alias, inside_alias, charlist()}
  | {:dot, inside_dot, charlist()}
  | {:dot_arity, inside_dot, charlist()}
  | {:dot_call, inside_dot, charlist()}
  | :expr
  | {:local_or_var, charlist()}
  | {:local_arity, charlist()}
  | {:local_call, charlist()}
  | {:anonymous_call, inside_caller}
  | {:module_attribute, charlist()}
  | {:operator, charlist()}
  | {:operator_arity, charlist()}
  | {:operator_call, charlist()}
  | :none
  | {:sigil, charlist()}
  | {:struct, inside_struct}
  | {:unquoted_atom, charlist()}
when inside_dot:
       {:alias, charlist()}
       | {:alias, inside_alias, charlist()}
       | {:dot, inside_dot, charlist()}
       | {:module_attribute, charlist()}
       | {:unquoted_atom, charlist()}
       | {:var, charlist()}
       | :expr,
     inside_alias: {:local_or_var, charlist()} | {:module_attribute, charlist()},
     inside_struct:
       charlist()
       | {:alias, inside_alias, charlist()}
       | {:local_or_var, charlist()}
       | {:module_attribute, charlist()}
       | {:dot, inside_dot, charlist()},
     inside_caller: {:var, charlist()} | {:module_attribute, charlist()}

Receives a string and returns the cursor context.

This function receives a string with an Elixir code fragment, representing a cursor position, and based on the string, it provides contextual information about the latest token. The return of this function can then be used to provide tips, suggestions, and autocompletion functionality.

This function performs its analyses on tokens. This means it does not understand how constructs are nested within each other. See the "Limitations" section below.

Consider adding a catch-all clause when handling the return type of this function as new cursor information may be added in future releases.

Examples

iex> Code.Fragment.cursor_context("")
:expr

iex> Code.Fragment.cursor_context("hello_wor")
{:local_or_var, ~c"hello_wor"}

Return values

• {:alias, charlist} - the context is an alias, potentially a nested one, such as Hello.Wor or HelloWor

• {:alias, inside_alias, charlist} - the context is an alias, potentially a nested one, where inside_alias is an expression {:module_attribute, charlist} or {:local_or_var, charlist} and charlist is a static part Examples are __MODULE__.Submodule or @hello.Submodule

• {:dot, inside_dot, charlist} - the context is a dot where inside_dot is either a {:var, charlist}, {:alias, charlist}, {:module_attribute, charlist}, {:unquoted_atom, charlist} or a dot itself. If a var is given, this may either be a remote call or a map field access. Examples are Hello.wor, :hello.wor, hello.wor, Hello.nested.wor, hello.nested.wor, and @hello.world. If charlist is empty and inside_dot is an alias, then the autocompletion may either be an alias or a remote call.

• {:dot_arity, inside_dot, charlist} - the context is a dot arity where inside_dot is either a {:var, charlist}, {:alias, charlist}, {:module_attribute, charlist}, {:unquoted_atom, charlist} or a dot itself. If a var is given, it must be a remote arity. Examples are Hello.world/, :hello.world/, hello.world/2, and @hello.world/2

• {:dot_call, inside_dot, charlist} - the context is a dot call. This means parentheses or space have been added after the expression. where inside_dot is either a {:var, charlist}, {:alias, charlist}, {:module_attribute, charlist}, {:unquoted_atom, charlist} or a dot itself. If a var is given, it must be a remote call. Examples are Hello.world(, :hello.world(, Hello.world, hello.world(, hello.world, and @hello.world(

• :expr - may be any expression. Autocompletion may suggest an alias, local or var

• {:local_or_var, charlist} - the context is a variable or a local (import or local) call, such as hello_wor

• {:local_arity, charlist} - the context is a local (import or local) arity, such as hello_world/

• {:local_call, charlist} - the context is a local (import or local) call, such as hello_world( and hello_world

• {:anonymous_call, inside_caller} - the context is an anonymous call, such as fun.( and @fun.(.

• {:module_attribute, charlist} - the context is a module attribute, such as @hello_wor

• {:operator, charlist} - the context is an operator, such as + or ==. Note textual operators, such as when do not appear as operators but rather as :local_or_var. @ is never an :operator and always a :module_attribute

• {:operator_arity, charlist} - the context is an operator arity, which is an operator followed by /, such as +/, not/ or when/

• {:operator_call, charlist} - the context is an operator call, which is an operator followed by space, such as left +, not or x when

• :none - no context possible

• {:sigil, charlist} - the context is a sigil. It may be either the beginning of a sigil, such as ~ or ~s, or an operator starting with ~, such as ~> and ~>>

• {:struct, inside_struct} - the context is a struct, such as %, %UR or %URI. inside_struct can either be a charlist in case of a static alias or an expression {:alias, inside_alias, charlist}, {:module_attribute, charlist}, {:local_or_var, charlist}, {:dot, inside_dot, charlist}

• {:unquoted_atom, charlist} - the context is an unquoted atom. This can be any atom or an atom representing a module

We recommend looking at the test suite of this function for a complete list of examples and their return values.

Limitations

The analysis is based on the current token, by analysing the last line of the input. For example, this code:

iex> Code.Fragment.cursor_context("%URI{")
:expr

returns :expr, which suggests any variable, local function or alias could be used. However, given we are inside a struct, the best suggestion would be a struct field. In such cases, you can use container_cursor_to_quoted, which will return the container of the AST the cursor is currently within. You can then analyse this AST to provide completion of field names.

As a consequence of its token-based implementation, this function considers only the last line of the input. This means it will show suggestions inside strings, heredocs, etc, which is intentional as it helps with doctests, references, and more.

@spec surround_context(List.Chars.t(), position(), keyword()) ::
  %{begin: position(), end: position(), context: context} | :none
when context:
       {:alias, charlist()}
       | {:alias, inside_alias, charlist()}
       | {:dot, inside_dot, charlist()}
       | {:local_or_var, charlist()}
       | {:local_arity, charlist()}
       | {:local_call, charlist()}
       | {:module_attribute, charlist()}
       | {:operator, charlist()}
       | {:sigil, charlist()}
       | {:struct, inside_struct}
       | {:unquoted_atom, charlist()}
       | {:keyword, charlist()}
       | {:key, charlist()}
       | {:capture_arg, charlist()},
     inside_dot:
       {:alias, charlist()}
       | {:alias, inside_alias, charlist()}
       | {:dot, inside_dot, charlist()}
       | {:module_attribute, charlist()}
       | {:unquoted_atom, charlist()}
       | {:var, charlist()}
       | :expr,
     inside_alias: {:local_or_var, charlist()} | {:module_attribute, charlist()},
     inside_struct:
       charlist()
       | {:alias, inside_alias, charlist()}
       | {:local_or_var, charlist()}
       | {:module_attribute, charlist()}
       | {:dot, inside_dot, charlist()}

Receives a string and returns the surround context.

This function receives a string with an Elixir code fragment and a position. It returns a map containing the beginning and ending of the identifier alongside its context, or :none if there is nothing with a known context. This is useful to provide mouse-over and highlight functionality in editors.

The difference between cursor_context/2 and surround_context/3 is that the former assumes the expression in the code fragment is incomplete. For example, do in cursor_context/2 may be a keyword or a variable or a local call, while surround_context/3 assumes the expression in the code fragment is complete, therefore do would always be a keyword.

The position contains both the line and column, both starting with the index of 1. The column must precede the surrounding expression. For example, the expression foo, will return something for the columns 1, 2, and 3, but not 4:

foo
^ column 1

foo
 ^ column 2

foo
  ^ column 3

foo
   ^ column 4

The returned map contains the column the expression starts and the first column after the expression ends.

Similar to cursor_context/2, this function is also token-based and may not be accurate under all circumstances. See the "Return values" and "Limitations" section under cursor_context/2 for more information.

Examples

iex> Code.Fragment.surround_context("foo", {1, 1})
%{begin: {1, 1}, context: {:local_or_var, ~c"foo"}, end: {1, 4}}

Differences to cursor_context/2

Because surround_context/3 attempts to capture complex expressions, it has some differences to cursor_context/2:

• dot_call/dot_arity and operator_call/operator_arity are collapsed into dot and operator contexts respectively as there aren't any meaningful distinctions between them

• On the other hand, this function still makes a distinction between local_call/local_arity and local_or_var, since the latter can be a local or variable

• @ when not followed by any identifier is returned as {:operator, ~c"@"} (in contrast to {:module_attribute, ~c""} in cursor_context/2

• This function never returns empty sigils {:sigil, ~c""} or empty structs {:struct, ~c""} as context

• This function returns keywords as {:keyword, ~c"do"}

• This function never returns :expr

We recommend looking at the test suite of this function for a complete list of examples and their return values.