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//! This modules contains various "assists": suggestions for source code edits
//! which are likely to occur at a given cursor positon. For example, if the
//! cursor is on the `,`, a possible assist is swapping the elements around the
//! comma.
mod flip_comma;
mod add_derive;
mod add_impl;
mod introduce_variable;
mod change_visibility;
mod split_import;
mod replace_if_let_with_match;
use ra_text_edit::{TextEdit, TextEditBuilder};
use ra_syntax::{
Direction, SyntaxNode, TextUnit, TextRange, SourceFile, AstNode,
algo::{find_leaf_at_offset, find_node_at_offset, find_covering_node, LeafAtOffset},
};
use itertools::Itertools;
use crate::formatting::leading_indent;
pub use self::{
flip_comma::flip_comma,
add_derive::add_derive,
add_impl::add_impl,
introduce_variable::introduce_variable,
change_visibility::change_visibility,
split_import::split_import,
replace_if_let_with_match::replace_if_let_with_match,
};
/// Return all the assists applicable at the given position.
pub fn assists(file: &SourceFile, range: TextRange) -> Vec<LocalEdit> {
let ctx = AssistCtx::new(file, range);
[
flip_comma,
add_derive,
add_impl,
introduce_variable,
change_visibility,
split_import,
replace_if_let_with_match,
]
.iter()
.filter_map(|&assist| ctx.clone().apply(assist))
.collect()
}
#[derive(Debug)]
pub struct LocalEdit {
pub label: String,
pub edit: TextEdit,
pub cursor_position: Option<TextUnit>,
}
fn non_trivia_sibling(node: &SyntaxNode, direction: Direction) -> Option<&SyntaxNode> {
node.siblings(direction)
.skip(1)
.find(|node| !node.kind().is_trivia())
}
/// `AssistCtx` allows to apply an assist or check if it could be applied.
///
/// Assists use a somewhat overengeneered approach, given the current needs. The
/// assists workflow consists of two phases. In the first phase, a user asks for
/// the list of available assists. In the second phase, the user picks a
/// particular assist and it gets applied.
///
/// There are two peculiarities here:
///
/// * first, we ideally avoid computing more things then neccessary to answer
/// "is assist applicable" in the first phase.
/// * second, when we are appling assist, we don't have a gurantee that there
/// weren't any changes between the point when user asked for assists and when
/// they applied a particular assist. So, when applying assist, we need to do
/// all the checks from scratch.
///
/// To avoid repeating the same code twice for both "check" and "apply"
/// functions, we use an approach remeniscent of that of Django's function based
/// views dealing with forms. Each assist receives a runtime parameter,
/// `should_compute_edit`. It first check if an edit is applicable (potentially
/// computing info required to compute the actual edit). If it is applicable,
/// and `should_compute_edit` is `true`, it then computes the actual edit.
///
/// So, to implement the original assists workflow, we can first apply each edit
/// with `should_compute_edit = false`, and then applying the selected edit
/// again, with `should_compute_edit = true` this time.
///
/// Note, however, that we don't actually use such two-phase logic at the
/// moment, because the LSP API is pretty awkward in this place, and it's much
/// easier to just compute the edit eagarly :-)
#[derive(Debug, Clone)]
pub struct AssistCtx<'a> {
source_file: &'a SourceFile,
range: TextRange,
should_compute_edit: bool,
}
#[derive(Debug)]
pub enum Assist {
Applicable,
Edit(LocalEdit),
}
#[derive(Default)]
struct AssistBuilder {
edit: TextEditBuilder,
cursor_position: Option<TextUnit>,
}
impl<'a> AssistCtx<'a> {
pub fn new(source_file: &'a SourceFile, range: TextRange) -> AssistCtx {
AssistCtx {
source_file,
range,
should_compute_edit: false,
}
}
pub fn apply(mut self, assist: fn(AssistCtx) -> Option<Assist>) -> Option<LocalEdit> {
self.should_compute_edit = true;
match assist(self) {
None => None,
Some(Assist::Edit(e)) => Some(e),
Some(Assist::Applicable) => unreachable!(),
}
}
pub fn check(mut self, assist: fn(AssistCtx) -> Option<Assist>) -> bool {
self.should_compute_edit = false;
match assist(self) {
None => false,
Some(Assist::Edit(_)) => unreachable!(),
Some(Assist::Applicable) => true,
}
}
fn build(self, label: impl Into<String>, f: impl FnOnce(&mut AssistBuilder)) -> Option<Assist> {
if !self.should_compute_edit {
return Some(Assist::Applicable);
}
let mut edit = AssistBuilder::default();
f(&mut edit);
Some(Assist::Edit(LocalEdit {
label: label.into(),
edit: edit.edit.finish(),
cursor_position: edit.cursor_position,
}))
}
pub(crate) fn leaf_at_offset(&self) -> LeafAtOffset<&'a SyntaxNode> {
find_leaf_at_offset(self.source_file.syntax(), self.range.start())
}
pub(crate) fn node_at_offset<N: AstNode>(&self) -> Option<&'a N> {
find_node_at_offset(self.source_file.syntax(), self.range.start())
}
pub(crate) fn covering_node(&self) -> &'a SyntaxNode {
find_covering_node(self.source_file.syntax(), self.range)
}
}
impl AssistBuilder {
fn replace(&mut self, range: TextRange, replace_with: impl Into<String>) {
self.edit.replace(range, replace_with.into())
}
fn replace_node_and_indent(&mut self, node: &SyntaxNode, replace_with: impl Into<String>) {
let mut replace_with = replace_with.into();
if let Some(indent) = leading_indent(node) {
replace_with = reindent(&replace_with, indent)
}
self.replace(node.range(), replace_with)
}
#[allow(unused)]
fn delete(&mut self, range: TextRange) {
self.edit.delete(range)
}
fn insert(&mut self, offset: TextUnit, text: impl Into<String>) {
self.edit.insert(offset, text.into())
}
fn set_cursor(&mut self, offset: TextUnit) {
self.cursor_position = Some(offset)
}
}
fn reindent(text: &str, indent: &str) -> String {
let indent = format!("\n{}", indent);
text.lines().intersperse(&indent).collect()
}
#[cfg(test)]
fn check_assist(assist: fn(AssistCtx) -> Option<Assist>, before: &str, after: &str) {
crate::test_utils::check_action(before, after, |file, off| {
let range = TextRange::offset_len(off, 0.into());
AssistCtx::new(file, range).apply(assist)
})
}
#[cfg(test)]
fn check_assist_range(assist: fn(AssistCtx) -> Option<Assist>, before: &str, after: &str) {
crate::test_utils::check_action_range(before, after, |file, range| {
AssistCtx::new(file, range).apply(assist)
})
}
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