Simplify assists resolution API

Assist vs UnresolvedAssist split doesn't really pull its weight. This
is especially bad if we want to include `Assist` as a field of
diagnostics, where we'd have to make the thing generic.

6 files changed, 69 insertions, 120 deletions

diff --git a/crates/assists/src/assist_context.rs b/crates/assists/src/assist_context.rs
index 80cf9aba1..4f59d39a9 100644
--- a/crates/assists/src/assist_context.rs
+++ b/crates/assists/src/assist_context.rs
@@ -19,7 +19,7 @@ use text_edit::{TextEdit, TextEditBuilder};
 
 use crate::{
     assist_config::{AssistConfig, SnippetCap},
-    Assist, AssistId, AssistKind, GroupLabel, ResolvedAssist,
+    Assist, AssistId, AssistKind, GroupLabel,
 };
 
 /// `AssistContext` allows to apply an assist or check if it could be applied.
@@ -105,46 +105,23 @@ impl<'a> AssistContext<'a> {
 pub(crate) struct Assists {
     resolve: bool,
     file: FileId,
-    buf: Vec<(Assist, Option<SourceChange>)>,
+    buf: Vec<Assist>,
     allowed: Option<Vec<AssistKind>>,
 }
 
 impl Assists {
-    pub(crate) fn new_resolved(ctx: &AssistContext) -> Assists {
+    pub(crate) fn new(ctx: &AssistContext, resolve: bool) -> Assists {
         Assists {
-            resolve: true,
+            resolve,
             file: ctx.frange.file_id,
             buf: Vec::new(),
             allowed: ctx.config.allowed.clone(),
         }
     }
 
-    pub(crate) fn new_unresolved(ctx: &AssistContext) -> Assists {
-        Assists {
-            resolve: false,
-            file: ctx.frange.file_id,
-            buf: Vec::new(),
-            allowed: ctx.config.allowed.clone(),
-        }
-    }
-
-    pub(crate) fn finish_unresolved(self) -> Vec<Assist> {
-        assert!(!self.resolve);
-        self.finish()
-            .into_iter()
-            .map(|(label, edit)| {
-                assert!(edit.is_none());
-                label
-            })
-            .collect()
-    }
-
-    pub(crate) fn finish_resolved(self) -> Vec<ResolvedAssist> {
-        assert!(self.resolve);
-        self.finish()
-            .into_iter()
-            .map(|(label, edit)| ResolvedAssist { assist: label, source_change: edit.unwrap() })
-            .collect()
+    pub(crate) fn finish(mut self) -> Vec<Assist> {
+        self.buf.sort_by_key(|assist| assist.target.len());
+        self.buf
     }
 
     pub(crate) fn add(
@@ -158,7 +135,7 @@ impl Assists {
             return None;
         }
         let label = Label::new(label.into());
-        let assist = Assist { id, label, group: None, target };
+        let assist = Assist { id, label, group: None, target, source_change: None };
         self.add_impl(assist, f)
     }
 
@@ -174,11 +151,11 @@ impl Assists {
             return None;
         }
         let label = Label::new(label.into());
-        let assist = Assist { id, label, group: Some(group.clone()), target };
+        let assist = Assist { id, label, group: Some(group.clone()), target, source_change: None };
         self.add_impl(assist, f)
     }
 
-    fn add_impl(&mut self, assist: Assist, f: impl FnOnce(&mut AssistBuilder)) -> Option<()> {
+    fn add_impl(&mut self, mut assist: Assist, f: impl FnOnce(&mut AssistBuilder)) -> Option<()> {
         let source_change = if self.resolve {
             let mut builder = AssistBuilder::new(self.file);
             f(&mut builder);
@@ -186,16 +163,12 @@ impl Assists {
         } else {
             None
         };
+        assist.source_change = source_change.clone();
 
-        self.buf.push((assist, source_change));
+        self.buf.push(assist);
         Some(())
     }
 
-    fn finish(mut self) -> Vec<(Assist, Option<SourceChange>)> {
-        self.buf.sort_by_key(|(label, _edit)| label.target.len());
-        self.buf
-    }
-
     fn is_allowed(&self, id: &AssistId) -> bool {
         match &self.allowed {
             Some(allowed) => allowed.iter().any(|kind| kind.contains(id.1)),
diff --git a/crates/assists/src/lib.rs b/crates/assists/src/lib.rs
index 6b89b2d04..fdec886e9 100644
--- a/crates/assists/src/lib.rs
+++ b/crates/assists/src/lib.rs
@@ -73,45 +73,32 @@ pub struct Assist {
     /// 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 target: TextRange,
-}
-
-#[derive(Debug, Clone)]
-pub struct ResolvedAssist {
-    pub assist: Assist,
-    pub source_change: SourceChange,
+    /// Computing source change sometimes is much more costly then computing the
+    /// other fields. Additionally, the actual change is not required to show
+    /// the lightbulb UI, it only is needed when the user tries to apply an
+    /// assist. So, we compute it lazily: the API allow requesting assists with
+    /// or without source change. We could (and in fact, used to) distinguish
+    /// between resolved and unresolved assists at the type level, but this is
+    /// cumbersome, especially if you want to embed an assist into another data
+    /// structure, such as a diagnostic.
+    pub source_change: Option<SourceChange>,
 }
 
 impl Assist {
     /// Return all the assists applicable at the given position.
-    ///
-    /// Assists are returned in the "unresolved" state, that is only labels are
-    /// returned, without actual edits.
-    pub fn unresolved(db: &RootDatabase, config: &AssistConfig, range: FileRange) -> Vec<Assist> {
-        let sema = Semantics::new(db);
-        let ctx = AssistContext::new(sema, config, range);
-        let mut acc = Assists::new_unresolved(&ctx);
-        handlers::all().iter().for_each(|handler| {
-            handler(&mut acc, &ctx);
-        });
-        acc.finish_unresolved()
-    }
-
-    /// Return all the assists applicable at the given position.
-    ///
-    /// Assists are returned in the "resolved" state, that is with edit fully
-    /// computed.
-    pub fn resolved(
+    pub fn get(
         db: &RootDatabase,
         config: &AssistConfig,
+        resolve: bool,
         range: FileRange,
-    ) -> Vec<ResolvedAssist> {
+    ) -> Vec<Assist> {
         let sema = Semantics::new(db);
         let ctx = AssistContext::new(sema, config, range);
-        let mut acc = Assists::new_resolved(&ctx);
+        let mut acc = Assists::new(&ctx, resolve);
         handlers::all().iter().for_each(|handler| {
             handler(&mut acc, &ctx);
         });
-        acc.finish_resolved()
+        acc.finish()
     }
 }
 
diff --git a/crates/assists/src/tests.rs b/crates/assists/src/tests.rs
index b41f4874a..21e448fb8 100644
--- a/crates/assists/src/tests.rs
+++ b/crates/assists/src/tests.rs
@@ -48,24 +48,25 @@ fn check_doc_test(assist_id: &str, before: &str, after: &str) {
     let before = db.file_text(file_id).to_string();
     let frange = FileRange { file_id, range: selection.into() };
 
-    let assist = Assist::resolved(&db, &AssistConfig::default(), frange)
+    let assist = Assist::get(&db, &AssistConfig::default(), true, frange)
         .into_iter()
-        .find(|assist| assist.assist.id.0 == assist_id)
+        .find(|assist| assist.id.0 == assist_id)
         .unwrap_or_else(|| {
             panic!(
                 "\n\nAssist is not applicable: {}\nAvailable assists: {}",
                 assist_id,
-                Assist::resolved(&db, &AssistConfig::default(), frange)
+                Assist::get(&db, &AssistConfig::default(), false, frange)
                     .into_iter()
-                    .map(|assist| assist.assist.id.0)
+                    .map(|assist| assist.id.0)
                     .collect::<Vec<_>>()
                     .join(", ")
             )
         });
 
     let actual = {
+        let source_change = assist.source_change.unwrap();
         let mut actual = before;
-        for source_file_edit in assist.source_change.source_file_edits {
+        for source_file_edit in source_change.source_file_edits {
             if source_file_edit.file_id == file_id {
                 source_file_edit.edit.apply(&mut actual)
             }
@@ -90,18 +91,18 @@ fn check(handler: Handler, before: &str, expected: ExpectedResult, assist_label:
     let sema = Semantics::new(&db);
     let config = AssistConfig::default();
     let ctx = AssistContext::new(sema, &config, frange);
-    let mut acc = Assists::new_resolved(&ctx);
+    let mut acc = Assists::new(&ctx, true);
     handler(&mut acc, &ctx);
-    let mut res = acc.finish_resolved();
+    let mut res = acc.finish();
 
     let assist = match assist_label {
-        Some(label) => res.into_iter().find(|resolved| resolved.assist.label == label),
+        Some(label) => res.into_iter().find(|resolved| resolved.label == label),
         None => res.pop(),
     };
 
     match (assist, expected) {
         (Some(assist), ExpectedResult::After(after)) => {
-            let mut source_change = assist.source_change;
+            let mut source_change = assist.source_change.unwrap();
             assert!(!source_change.source_file_edits.is_empty());
             let skip_header = source_change.source_file_edits.len() == 1
                 && source_change.file_system_edits.len() == 0;
@@ -138,7 +139,7 @@ fn check(handler: Handler, before: &str, expected: ExpectedResult, assist_label:
             assert_eq_text!(after, &buf);
         }
         (Some(assist), ExpectedResult::Target(target)) => {
-            let range = assist.assist.target;
+            let range = assist.target;
             assert_eq_text!(&text_without_caret[range], target);
         }
         (Some(_), ExpectedResult::NotApplicable) => panic!("assist should not be applicable!"),
@@ -155,14 +156,11 @@ fn assist_order_field_struct() {
     let (before_cursor_pos, before) = extract_offset(before);
     let (db, file_id) = with_single_file(&before);
     let frange = FileRange { file_id, range: TextRange::empty(before_cursor_pos) };
-    let assists = Assist::resolved(&db, &AssistConfig::default(), frange);
+    let assists = Assist::get(&db, &AssistConfig::default(), false, frange);
     let mut assists = assists.iter();
 
-    assert_eq!(
-        assists.next().expect("expected assist").assist.label,
-        "Change visibility to pub(crate)"
-    );
-    assert_eq!(assists.next().expect("expected assist").assist.label, "Add `#[derive]`");
+    assert_eq!(assists.next().expect("expected assist").label, "Change visibility to pub(crate)");
+    assert_eq!(assists.next().expect("expected assist").label, "Add `#[derive]`");
 }
 
 #[test]
@@ -178,11 +176,11 @@ fn assist_order_if_expr() {
     let (range, before) = extract_range(before);
     let (db, file_id) = with_single_file(&before);
     let frange = FileRange { file_id, range };
-    let assists = Assist::resolved(&db, &AssistConfig::default(), frange);
+    let assists = Assist::get(&db, &AssistConfig::default(), false, frange);
     let mut assists = assists.iter();
 
-    assert_eq!(assists.next().expect("expected assist").assist.label, "Extract into variable");
-    assert_eq!(assists.next().expect("expected assist").assist.label, "Replace with match");
+    assert_eq!(assists.next().expect("expected assist").label, "Extract into variable");
+    assert_eq!(assists.next().expect("expected assist").label, "Replace with match");
 }
 
 #[test]
@@ -203,27 +201,27 @@ fn assist_filter_works() {
         let mut cfg = AssistConfig::default();
         cfg.allowed = Some(vec![AssistKind::Refactor]);
 
-        let assists = Assist::resolved(&db, &cfg, frange);
+        let assists = Assist::get(&db, &cfg, false, frange);
         let mut assists = assists.iter();
 
-        assert_eq!(assists.next().expect("expected assist").assist.label, "Extract into variable");
-        assert_eq!(assists.next().expect("expected assist").assist.label, "Replace with match");
+        assert_eq!(assists.next().expect("expected assist").label, "Extract into variable");
+        assert_eq!(assists.next().expect("expected assist").label, "Replace with match");
     }
 
     {
         let mut cfg = AssistConfig::default();
         cfg.allowed = Some(vec![AssistKind::RefactorExtract]);
-        let assists = Assist::resolved(&db, &cfg, frange);
+        let assists = Assist::get(&db, &cfg, false, frange);
         assert_eq!(assists.len(), 1);
 
         let mut assists = assists.iter();
-        assert_eq!(assists.next().expect("expected assist").assist.label, "Extract into variable");
+        assert_eq!(assists.next().expect("expected assist").label, "Extract into variable");
     }
 
     {
         let mut cfg = AssistConfig::default();
         cfg.allowed = Some(vec![AssistKind::QuickFix]);
-        let assists = Assist::resolved(&db, &cfg, frange);
+        let assists = Assist::get(&db, &cfg, false, frange);
         assert!(assists.is_empty(), "All asserts but quickfixes should be filtered out");
     }
 }
diff --git a/crates/ide/src/lib.rs b/crates/ide/src/lib.rs
index a75cc85b6..41eb139d1 100644
--- a/crates/ide/src/lib.rs
+++ b/crates/ide/src/lib.rs
@@ -79,7 +79,7 @@ pub use crate::{
         HighlightedRange,
     },
 };
-pub use assists::{Assist, AssistConfig, AssistId, AssistKind, ResolvedAssist};
+pub use assists::{Assist, AssistConfig, AssistId, AssistKind};
 pub use completion::{
     CompletionConfig, CompletionItem, CompletionItemKind, CompletionResolveCapability,
     CompletionScore, ImportEdit, InsertTextFormat,
@@ -491,22 +491,16 @@ impl Analysis {
     }
 
     /// Computes assists (aka code actions aka intentions) for the given
-    /// position. Computes enough info to show the lightbulb list in the editor,
-    /// but doesn't compute actual edits, to improve performance.
-    ///
-    /// When the user clicks on the assist, call `resolve_assists` to get the
-    /// edit.
-    pub fn assists(&self, config: &AssistConfig, frange: FileRange) -> Cancelable<Vec<Assist>> {
-        self.with_db(|db| Assist::unresolved(db, config, frange))
-    }
-
-    /// Computes resolved assists with source changes for the given position.
-    pub fn resolve_assists(
+    /// position. If `resolve == false`, computes enough info to show the
+    /// lightbulb list in the editor, but doesn't compute actual edits, to
+    /// improve performance.
+    pub fn assists(
         &self,
         config: &AssistConfig,
+        resolve: bool,
         frange: FileRange,
-    ) -> Cancelable<Vec<ResolvedAssist>> {
-        self.with_db(|db| assists::Assist::resolved(db, config, frange))
+    ) -> Cancelable<Vec<Assist>> {
+        self.with_db(|db| Assist::get(db, config, resolve, frange))
     }
 
     /// Computes the set of diagnostics for the given file.
diff --git a/crates/rust-analyzer/src/handlers.rs b/crates/rust-analyzer/src/handlers.rs
index 1207b31c4..374fb5302 100644
--- a/crates/rust-analyzer/src/handlers.rs
+++ b/crates/rust-analyzer/src/handlers.rs
@@ -946,12 +946,12 @@ pub(crate) fn handle_code_action(
 
     if snap.config.client_caps.code_action_resolve {
         for (index, assist) in
-            snap.analysis.assists(&assists_config, frange)?.into_iter().enumerate()
+            snap.analysis.assists(&assists_config, false, frange)?.into_iter().enumerate()
         {
             res.push(to_proto::unresolved_code_action(&snap, params.clone(), assist, index)?);
         }
     } else {
-        for assist in snap.analysis.resolve_assists(&assists_config, frange)?.into_iter() {
+        for assist in snap.analysis.assists(&assists_config, true, frange)?.into_iter() {
             res.push(to_proto::resolved_code_action(&snap, assist)?);
         }
     }
@@ -1014,11 +1014,11 @@ pub(crate) fn handle_code_action_resolve(
         .only
         .map(|it| it.into_iter().filter_map(from_proto::assist_kind).collect());
 
-    let assists = snap.analysis.resolve_assists(&snap.config.assist, frange)?;
+    let assists = snap.analysis.assists(&snap.config.assist, true, frange)?;
     let (id, index) = split_once(&params.id, ':').unwrap();
     let index = index.parse::<usize>().unwrap();
     let assist = &assists[index];
-    assert!(assist.assist.id.0 == id);
+    assert!(assist.id.0 == id);
     let edit = to_proto::resolved_code_action(&snap, assist.clone())?.edit;
     code_action.edit = edit;
     Ok(code_action)
diff --git a/crates/rust-analyzer/src/to_proto.rs b/crates/rust-analyzer/src/to_proto.rs
index 753aad628..1a38e79f0 100644
--- a/crates/rust-analyzer/src/to_proto.rs
+++ b/crates/rust-analyzer/src/to_proto.rs
@@ -8,8 +8,8 @@ use ide::{
     Assist, AssistKind, CallInfo, CompletionItem, CompletionItemKind, Documentation, FileId,
     FileRange, FileSystemEdit, Fold, FoldKind, Highlight, HighlightModifier, HighlightTag,
     HighlightedRange, Indel, InlayHint, InlayKind, InsertTextFormat, LineIndex, Markup,
-    NavigationTarget, ReferenceAccess, ResolvedAssist, Runnable, Severity, SourceChange,
-    SourceFileEdit, SymbolKind, TextEdit, TextRange, TextSize,
+    NavigationTarget, ReferenceAccess, Runnable, Severity, SourceChange, SourceFileEdit,
+    SymbolKind, TextEdit, TextRange, TextSize,
 };
 use itertools::Itertools;
 
@@ -780,6 +780,7 @@ pub(crate) fn unresolved_code_action(
     assist: Assist,
     index: usize,
 ) -> Result<lsp_ext::CodeAction> {
+    assert!(assist.source_change.is_none());
     let res = lsp_ext::CodeAction {
         title: assist.label.to_string(),
         group: assist.group.filter(|_| snap.config.client_caps.code_action_group).map(|gr| gr.0),
@@ -796,18 +797,14 @@ pub(crate) fn unresolved_code_action(
 
 pub(crate) fn resolved_code_action(
     snap: &GlobalStateSnapshot,
-    assist: ResolvedAssist,
+    assist: Assist,
 ) -> Result<lsp_ext::CodeAction> {
-    let change = assist.source_change;
+    let change = assist.source_change.unwrap();
     let res = lsp_ext::CodeAction {
         edit: Some(snippet_workspace_edit(snap, change)?),
-        title: assist.assist.label.to_string(),
-        group: assist
-            .assist
-            .group
-            .filter(|_| snap.config.client_caps.code_action_group)
-            .map(|gr| gr.0),
-        kind: Some(code_action_kind(assist.assist.id.1)),
+        title: assist.label.to_string(),
+        group: assist.group.filter(|_| snap.config.client_caps.code_action_group).map(|gr| gr.0),
+        kind: Some(code_action_kind(assist.id.1)),
         is_preferred: None,
         data: None,
     };