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//! This module defines `AssistCtx` -- the API surface that is exposed to assists.
use hir::db::HirDatabase;
use ra_db::FileRange;
use ra_fmt::{leading_indent, reindent};
use ra_syntax::{
algo::{self, find_covering_element, find_node_at_offset},
AstNode, SourceFile, SyntaxElement, SyntaxKind, SyntaxNode, SyntaxToken, TextRange, TextUnit,
TokenAtOffset,
};
use ra_text_edit::TextEditBuilder;
use crate::{AssistAction, AssistId, AssistLabel};
#[derive(Clone, Debug)]
pub(crate) enum Assist {
Unresolved { label: AssistLabel },
Resolved { label: AssistLabel, action: AssistAction },
}
/// `AssistCtx` allows to apply an assist or check if it could be applied.
///
/// Assists use a somewhat over-engineered 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 necessary to answer
/// "is assist applicable" in the first phase.
/// * second, when we are applying assist, we don't have a guarantee 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 reminiscent 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 eagerly :-)#[derive(Debug, Clone)]
#[derive(Debug)]
pub(crate) struct AssistCtx<'a, DB> {
pub(crate) db: &'a DB,
pub(crate) frange: FileRange,
source_file: SourceFile,
should_compute_edit: bool,
}
impl<'a, DB> Clone for AssistCtx<'a, DB> {
fn clone(&self) -> Self {
AssistCtx {
db: self.db,
frange: self.frange,
source_file: self.source_file.clone(),
should_compute_edit: self.should_compute_edit,
}
}
}
impl<'a, DB: HirDatabase> AssistCtx<'a, DB> {
pub(crate) fn with_ctx<F, T>(db: &DB, frange: FileRange, should_compute_edit: bool, f: F) -> T
where
F: FnOnce(AssistCtx<DB>) -> T,
{
let parse = db.parse(frange.file_id);
let ctx = AssistCtx { db, frange, source_file: parse.tree(), should_compute_edit };
f(ctx)
}
pub(crate) fn add_assist(
self,
id: AssistId,
label: impl Into<String>,
f: impl FnOnce(&mut AssistBuilder),
) -> Option<Assist> {
let label = AssistLabel { label: label.into(), id };
let assist = if self.should_compute_edit {
let action = {
let mut edit = AssistBuilder::default();
f(&mut edit);
edit.build()
};
Assist::Resolved { label, action }
} else {
Assist::Unresolved { label }
};
Some(assist)
}
pub(crate) fn token_at_offset(&self) -> TokenAtOffset<SyntaxToken> {
self.source_file.syntax().token_at_offset(self.frange.range.start())
}
pub(crate) fn find_token_at_offset(&self, kind: SyntaxKind) -> Option<SyntaxToken> {
self.token_at_offset().find(|it| it.kind() == kind)
}
pub(crate) fn find_node_at_offset<N: AstNode>(&self) -> Option<N> {
find_node_at_offset(self.source_file.syntax(), self.frange.range.start())
}
pub(crate) fn covering_element(&self) -> SyntaxElement {
find_covering_element(self.source_file.syntax(), self.frange.range)
}
pub(crate) fn covering_node_for_range(&self, range: TextRange) -> SyntaxElement {
find_covering_element(self.source_file.syntax(), range)
}
}
#[derive(Default)]
pub(crate) struct AssistBuilder {
edit: TextEditBuilder,
cursor_position: Option<TextUnit>,
target: Option<TextRange>,
}
impl AssistBuilder {
/// Replaces specified `range` of text with a given string.
pub(crate) fn replace(&mut self, range: TextRange, replace_with: impl Into<String>) {
self.edit.replace(range, replace_with.into())
}
/// Replaces specified `node` of text with a given string, reindenting the
/// string to maintain `node`'s existing indent.
// FIXME: remove in favor of ra_syntax::edit::IndentLevel::increase_indent
pub(crate) 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.text_range(), replace_with)
}
/// Remove specified `range` of text.
#[allow(unused)]
pub(crate) fn delete(&mut self, range: TextRange) {
self.edit.delete(range)
}
/// Append specified `text` at the given `offset`
pub(crate) fn insert(&mut self, offset: TextUnit, text: impl Into<String>) {
self.edit.insert(offset, text.into())
}
/// Specify desired position of the cursor after the assist is applied.
pub(crate) fn set_cursor(&mut self, offset: TextUnit) {
self.cursor_position = Some(offset)
}
/// Specify that the assist should be active withing the `target` range.
///
/// Target ranges are used to sort assists: the smaller the target range,
/// the more specific assist is, and so it should be sorted first.
pub(crate) fn target(&mut self, target: TextRange) {
self.target = Some(target)
}
/// Get access to the raw `TextEditBuilder`.
pub(crate) fn text_edit_builder(&mut self) -> &mut TextEditBuilder {
&mut self.edit
}
pub(crate) fn replace_ast<N: AstNode>(&mut self, old: N, new: N) {
algo::diff(old.syntax(), new.syntax()).into_text_edit(&mut self.edit)
}
fn build(self) -> AssistAction {
AssistAction {
edit: self.edit.finish(),
cursor_position: self.cursor_position,
target: self.target,
}
}
}
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