rust/crates/ide-assists/src/assist_context.rs

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//! See [`AssistContext`].
use hir::Semantics;
use ide_db::base_db::{FileId, FileRange};
use ide_db::{label::Label, RootDatabase};
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use syntax::{
algo::{self, find_node_at_offset, find_node_at_range},
AstNode, AstToken, Direction, SourceFile, SyntaxElement, SyntaxKind, SyntaxToken, TextRange,
TextSize, TokenAtOffset,
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};
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use crate::{
assist_config::AssistConfig, Assist, AssistId, AssistKind, AssistResolveStrategy, GroupLabel,
};
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pub(crate) use ide_db::source_change::{SourceChangeBuilder, TreeMutator};
/// `AssistContext` allows to apply an assist or check if it could be applied.
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///
/// 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
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/// 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.
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/// * 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,
/// `resolve`. It first check if an edit is applicable (potentially computing
/// info required to compute the actual edit). If it is applicable, and
/// `resolve` is `true`, it then computes the actual edit.
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///
/// So, to implement the original assists workflow, we can first apply each edit
/// with `resolve = false`, and then applying the selected edit again, with
/// `resolve = true` this time.
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///
/// 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 :-)
pub(crate) struct AssistContext<'a> {
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pub(crate) config: &'a AssistConfig,
pub(crate) sema: Semantics<'a, RootDatabase>,
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frange: FileRange,
trimmed_range: TextRange,
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source_file: SourceFile,
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}
impl<'a> AssistContext<'a> {
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pub(crate) fn new(
sema: Semantics<'a, RootDatabase>,
config: &'a AssistConfig,
frange: FileRange,
) -> AssistContext<'a> {
let source_file = sema.parse(frange.file_id);
let start = frange.range.start();
let end = frange.range.end();
let left = source_file.syntax().token_at_offset(start);
let right = source_file.syntax().token_at_offset(end);
let left =
left.right_biased().and_then(|t| algo::skip_whitespace_token(t, Direction::Next));
let right =
right.left_biased().and_then(|t| algo::skip_whitespace_token(t, Direction::Prev));
let left = left.map(|t| t.text_range().start().clamp(start, end));
let right = right.map(|t| t.text_range().end().clamp(start, end));
let trimmed_range = match (left, right) {
(Some(left), Some(right)) if left <= right => TextRange::new(left, right),
// Selection solely consists of whitespace so just fall back to the original
_ => frange.range,
};
AssistContext { config, sema, frange, source_file, trimmed_range }
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}
pub(crate) fn db(&self) -> &RootDatabase {
self.sema.db
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}
// NB, this ignores active selection.
pub(crate) fn offset(&self) -> TextSize {
self.frange.range.start()
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}
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pub(crate) fn file_id(&self) -> FileId {
self.frange.file_id
}
pub(crate) fn has_empty_selection(&self) -> bool {
self.trimmed_range.is_empty()
}
/// Returns the selected range trimmed for whitespace tokens, that is the range will be snapped
/// to the nearest enclosed token.
pub(crate) fn selection_trimmed(&self) -> TextRange {
self.trimmed_range
}
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pub(crate) fn token_at_offset(&self) -> TokenAtOffset<SyntaxToken> {
self.source_file.syntax().token_at_offset(self.offset())
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}
pub(crate) fn find_token_syntax_at_offset(&self, kind: SyntaxKind) -> Option<SyntaxToken> {
self.token_at_offset().find(|it| it.kind() == kind)
}
pub(crate) fn find_token_at_offset<T: AstToken>(&self) -> Option<T> {
self.token_at_offset().find_map(T::cast)
}
pub(crate) fn find_node_at_offset<N: AstNode>(&self) -> Option<N> {
find_node_at_offset(self.source_file.syntax(), self.offset())
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}
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pub(crate) fn find_node_at_range<N: AstNode>(&self) -> Option<N> {
find_node_at_range(self.source_file.syntax(), self.trimmed_range)
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}
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pub(crate) fn find_node_at_offset_with_descend<N: AstNode>(&self) -> Option<N> {
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self.sema.find_node_at_offset_with_descend(self.source_file.syntax(), self.offset())
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}
/// Returns the element covered by the selection range, this excludes trailing whitespace in the selection.
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pub(crate) fn covering_element(&self) -> SyntaxElement {
self.source_file.syntax().covering_element(self.selection_trimmed())
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}
}
pub(crate) struct Assists {
file: FileId,
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resolve: AssistResolveStrategy,
buf: Vec<Assist>,
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allowed: Option<Vec<AssistKind>>,
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}
impl Assists {
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pub(crate) fn new(ctx: &AssistContext<'_>, resolve: AssistResolveStrategy) -> Assists {
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Assists {
resolve,
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file: ctx.frange.file_id,
buf: Vec::new(),
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allowed: ctx.config.allowed.clone(),
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}
}
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pub(crate) fn finish(mut self) -> Vec<Assist> {
self.buf.sort_by_key(|assist| assist.target.len());
self.buf
}
pub(crate) fn add(
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&mut self,
id: AssistId,
label: impl Into<String>,
target: TextRange,
f: impl FnOnce(&mut SourceChangeBuilder),
) -> Option<()> {
let mut f = Some(f);
self.add_impl(None, id, label.into(), target, &mut |it| f.take().unwrap()(it))
}
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pub(crate) fn add_group(
&mut self,
group: &GroupLabel,
id: AssistId,
label: impl Into<String>,
target: TextRange,
f: impl FnOnce(&mut SourceChangeBuilder),
) -> Option<()> {
let mut f = Some(f);
self.add_impl(Some(group), id, label.into(), target, &mut |it| f.take().unwrap()(it))
}
fn add_impl(
&mut self,
group: Option<&GroupLabel>,
id: AssistId,
label: String,
target: TextRange,
f: &mut dyn FnMut(&mut SourceChangeBuilder),
) -> Option<()> {
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if !self.is_allowed(&id) {
return None;
}
let mut trigger_signature_help = false;
let source_change = if self.resolve.should_resolve(&id) {
let mut builder = SourceChangeBuilder::new(self.file);
f(&mut builder);
trigger_signature_help = builder.trigger_signature_help;
Some(builder.finish())
} else {
None
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};
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let label = Label::new(label);
let group = group.cloned();
self.buf.push(Assist { id, label, group, target, source_change, trigger_signature_help });
Some(())
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}
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fn is_allowed(&self, id: &AssistId) -> bool {
match &self.allowed {
Some(allowed) => allowed.iter().any(|kind| kind.contains(id.1)),
None => true,
}
}
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}