View Source Code.Fragment (Elixir v1.15.4)
This module provides conveniences for analyzing fragments of textual code and extract available information whenever possible.
This module should be considered experimental.
Summary
Functions
Receives a string and returns a quoted expression with the cursor AST position within its parent expression.
Receives a string and returns the cursor context.
Receives a string and returns the surround context.
Types
@type position() :: {line :: pos_integer(), column :: pos_integer()}
Functions
@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], []}]}}
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
- whentrue
, attach a:column
key to the quoted metadata. Defaults tofalse
.:token_metadata
- whentrue
, includes token-related metadata in the expression AST, such as metadata fordo
andend
tokens, for closing tokens, end of expressions, as well as delimiters for sigils. SeeMacro.metadata/0
. Defaults tofalse
.:literal_encoder
- a function to encode literals in the AST. See the documentation forCode.string_to_quoted/2
for more information.
@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()} | {: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()}
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, 'hello_wor'}
Return values
{:alias, charlist}
- the context is an alias, potentially a nested one, such asHello.Wor
orHelloWor
{:alias, inside_alias, charlist}
- the context is an alias, potentially a nested one, whereinside_alias
is an expression{:module_attribute, charlist}
or{:local_or_var, charlist}
andcharlist
is a static part Examples are__MODULE__.Submodule
or@hello.Submodule
{:dot, inside_dot, charlist}
- the context is a dot whereinside_dot
is either a{:var, charlist}
,{:alias, charlist}
,{:module_attribute, charlist}
,{:unquoted_atom, charlist}
or adot
itself. If a var is given, this may either be a remote call or a map field access. Examples areHello.wor
,:hello.wor
,hello.wor
,Hello.nested.wor
,hello.nested.wor
, and@hello.world
. Ifcharlist
is empty andinside_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 whereinside_dot
is either a{:var, charlist}
,{:alias, charlist}
,{:module_attribute, charlist}
,{:unquoted_atom, charlist}
or adot
itself. If a var is given, it must be a remote arity. Examples areHello.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. whereinside_dot
is either a{:var, charlist}
,{:alias, charlist}
,{:module_attribute, charlist}
,{:unquoted_atom, charlist}
or adot
itself. If a var is given, it must be a remote call. Examples areHello.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 ashello_wor
{:local_arity, charlist}
- the context is a local (import or local) arity, such ashello_world/
{:local_call, charlist}
- the context is a local (import or local) call, such ashello_world(
andhello_world
{: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 aswhen
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/
orwhen/
{:operator_call, charlist}
- the context is an operator call, which is an operator followed by space, such asleft +
,not
orx 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 acharlist
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.
surround_context(fragment, position, options \\ [])
View Source (since 1.13.0)@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()}, inside_dot: {:alias, charlist()} | {:alias, inside_alias, charlist()} | {:dot, inside_dot, charlist()} | {:module_attribute, charlist()} | {:unquoted_atom, charlist()} | {:var, charlist()}, 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, '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
andoperator_call
/operator_arity
are collapsed intodot
andoperator
contexts respectively as there aren't any meaningful distinctions between themOn the other hand, this function still makes a distinction between
local_call
/local_arity
andlocal_or_var
, since the latter can be a local or variable@
when not followed by any identifier is returned as{:operator, '@'}
(in contrast to{:module_attribute, ''}
incursor_context/2
This function never returns empty sigils
{:sigil, ''}
or empty structs{:struct, ''}
as contextThis function returns keywords as
{:keyword, '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.