add completion relevance score

5 files changed, 82 insertions, 37 deletions

diff --git a/crates/ide/src/lib.rs b/crates/ide/src/lib.rs
index d1a250d48..16302eb2f 100644
--- a/crates/ide/src/lib.rs
+++ b/crates/ide/src/lib.rs
@@ -87,8 +87,8 @@ pub use crate::{
 pub use hir::{Documentation, Semantics};
 pub use ide_assists::{Assist, AssistConfig, AssistId, AssistKind};
 pub use ide_completion::{
-    CompletionConfig, CompletionItem, CompletionItemKind, CompletionScore, ImportEdit,
-    InsertTextFormat,
+    CompletionConfig, CompletionItem, CompletionItemKind, CompletionRelevance, CompletionScore,
+    ImportEdit, InsertTextFormat,
 };
 pub use ide_db::{
     base_db::{
diff --git a/crates/ide_completion/src/item.rs b/crates/ide_completion/src/item.rs
index cf1aaa131..9a4dc915c 100644
--- a/crates/ide_completion/src/item.rs
+++ b/crates/ide_completion/src/item.rs
@@ -70,7 +70,7 @@ pub struct CompletionItem {
     /// Note that Relevance ignores fuzzy match score. We compute Relevance for
     /// all possible items, and then separately build an ordered completion list
     /// based on relevance and fuzzy matching with the already typed identifier.
-    relevance: Relevance,
+    relevance: CompletionRelevance,
 
     /// Indicates that a reference or mutable reference to this variable is a
     /// possible match.
@@ -107,9 +107,11 @@ impl fmt::Debug for CompletionItem {
         if self.deprecated {
             s.field("deprecated", &true);
         }
-        if self.relevance.is_relevant() {
+
+        if self.relevance != CompletionRelevance::default() {
             s.field("relevance", &self.relevance);
         }
+
         if let Some(mutability) = &self.ref_match {
             s.field("ref_match", &format!("&{}", mutability.as_keyword_for_ref()));
         }
@@ -129,7 +131,7 @@ pub enum CompletionScore {
 }
 
 #[derive(Debug, Clone, Copy, Ord, PartialOrd, Eq, PartialEq, Default)]
-pub struct Relevance {
+pub struct CompletionRelevance {
     /// This is set in cases like these:
     ///
     /// ```
@@ -152,9 +154,34 @@ pub struct Relevance {
     pub exact_type_match: bool,
 }
 
-impl Relevance {
+impl CompletionRelevance {
+    /// Provides a relevance score. Higher values are more relevant.
+    ///
+    /// The absolute value of the relevance score is not meaningful, for
+    /// example a value of 0 doesn't mean "not relevant", rather
+    /// it means "least relevant". The score value should only be used
+    /// for relative ordering.
+    ///
+    /// See is_relevant if you need to make some judgement about score
+    /// in an absolute sense.
+    pub fn score(&self) -> u8 {
+        let mut score = 0;
+
+        if self.exact_name_match {
+            score += 1;
+        }
+        if self.exact_type_match {
+            score += 1;
+        }
+
+        score
+    }
+
+    /// Returns true when the score for this threshold is above
+    /// some threshold such that we think it is especially likely
+    /// to be relevant.
     pub fn is_relevant(&self) -> bool {
-        self != &Relevance::default()
+        self.score() > 0
     }
 }
 
@@ -249,7 +276,7 @@ impl CompletionItem {
             text_edit: None,
             deprecated: false,
             trigger_call_info: None,
-            relevance: Relevance::default(),
+            relevance: CompletionRelevance::default(),
             ref_match: None,
             import_to_add: None,
         }
@@ -292,7 +319,7 @@ impl CompletionItem {
         self.deprecated
     }
 
-    pub fn relevance(&self) -> Relevance {
+    pub fn relevance(&self) -> CompletionRelevance {
         self.relevance
     }
 
@@ -300,8 +327,14 @@ impl CompletionItem {
         self.trigger_call_info
     }
 
-    pub fn ref_match(&self) -> Option<Mutability> {
-        self.ref_match
+    pub fn ref_match(&self) -> Option<(Mutability, CompletionRelevance)> {
+        // Relevance of the ref match should be the same as the original
+        // match, but with exact type match set because self.ref_match
+        // is only set if there is an exact type match.
+        let mut relevance = self.relevance;
+        relevance.exact_type_match = true;
+
+        self.ref_match.map(|mutability| (mutability, relevance))
     }
 
     pub fn import_to_add(&self) -> Option<&ImportEdit> {
@@ -349,7 +382,7 @@ pub(crate) struct Builder {
     text_edit: Option<TextEdit>,
     deprecated: bool,
     trigger_call_info: Option<bool>,
-    relevance: Relevance,
+    relevance: CompletionRelevance,
     ref_match: Option<Mutability>,
 }
 
@@ -457,7 +490,7 @@ impl Builder {
         self.deprecated = deprecated;
         self
     }
-    pub(crate) fn set_relevance(&mut self, relevance: Relevance) -> &mut Builder {
+    pub(crate) fn set_relevance(&mut self, relevance: CompletionRelevance) -> &mut Builder {
         self.relevance = relevance;
         self
     }
diff --git a/crates/ide_completion/src/lib.rs b/crates/ide_completion/src/lib.rs
index d46f521a0..21e489755 100644
--- a/crates/ide_completion/src/lib.rs
+++ b/crates/ide_completion/src/lib.rs
@@ -24,8 +24,8 @@ use crate::{completions::Completions, context::CompletionContext, item::Completi
 pub use crate::{
     config::CompletionConfig,
     item::{
-        CompletionItem, CompletionItemKind, CompletionScore, ImportEdit, InsertTextFormat,
-        Relevance,
+        CompletionItem, CompletionItemKind, CompletionRelevance, CompletionScore, ImportEdit,
+        InsertTextFormat,
     },
 };
 
diff --git a/crates/ide_completion/src/render.rs b/crates/ide_completion/src/render.rs
index f7f9084d9..db31896e5 100644
--- a/crates/ide_completion/src/render.rs
+++ b/crates/ide_completion/src/render.rs
@@ -20,7 +20,7 @@ use ide_db::{
 use syntax::TextRange;
 
 use crate::{
-    item::{ImportEdit, Relevance},
+    item::{CompletionRelevance, ImportEdit},
     CompletionContext, CompletionItem, CompletionItemKind, CompletionKind,
 };
 
@@ -322,9 +322,9 @@ impl<'a> Render<'a> {
     }
 }
 
-fn compute_relevance(ctx: &RenderContext, ty: &Type, name: &str) -> Option<Relevance> {
+fn compute_relevance(ctx: &RenderContext, ty: &Type, name: &str) -> Option<CompletionRelevance> {
     let (expected_name, expected_type) = ctx.expected_name_and_type()?;
-    let mut res = Relevance::default();
+    let mut res = CompletionRelevance::default();
     res.exact_type_match = ty == &expected_type;
     res.exact_name_match = name == &expected_name;
     Some(res)
@@ -338,7 +338,7 @@ mod tests {
 
     use crate::{
         test_utils::{check_edit, do_completion, get_all_items, TEST_CONFIG},
-        CompletionKind, Relevance,
+        CompletionKind, CompletionRelevance,
     };
 
     fn check(ra_fixture: &str, expect: Expect) {
@@ -347,12 +347,14 @@ mod tests {
     }
 
     fn check_relevance(ra_fixture: &str, expect: Expect) {
-        fn display_relevance(relevance: Relevance) -> &'static str {
+        fn display_relevance(relevance: CompletionRelevance) -> &'static str {
             match relevance {
-                Relevance { exact_type_match: true, exact_name_match: true } => "[type+name]",
-                Relevance { exact_type_match: true, exact_name_match: false } => "[type]",
-                Relevance { exact_type_match: false, exact_name_match: true } => "[name]",
-                Relevance { exact_type_match: false, exact_name_match: false } => "[]",
+                CompletionRelevance { exact_type_match: true, exact_name_match: true } => {
+                    "[type+name]"
+                }
+                CompletionRelevance { exact_type_match: true, exact_name_match: false } => "[type]",
+                CompletionRelevance { exact_type_match: false, exact_name_match: true } => "[name]",
+                CompletionRelevance { exact_type_match: false, exact_name_match: false } => "[]",
             }
         }
 
@@ -975,7 +977,7 @@ fn main() {
                             Local,
                         ),
                         detail: "S",
-                        relevance: Relevance {
+                        relevance: CompletionRelevance {
                             exact_name_match: true,
                             exact_type_match: false,
                         },
diff --git a/crates/rust-analyzer/src/to_proto.rs b/crates/rust-analyzer/src/to_proto.rs
index a9846fa70..a467bc685 100644
--- a/crates/rust-analyzer/src/to_proto.rs
+++ b/crates/rust-analyzer/src/to_proto.rs
@@ -6,9 +6,10 @@ use std::{
 
 use ide::{
     Annotation, AnnotationKind, Assist, AssistKind, CallInfo, CompletionItem, CompletionItemKind,
-    Documentation, FileId, FileRange, FileSystemEdit, Fold, FoldKind, Highlight, HlMod, HlPunct,
-    HlRange, HlTag, Indel, InlayHint, InlayKind, InsertTextFormat, Markup, NavigationTarget,
-    ReferenceAccess, RenameError, Runnable, Severity, SourceChange, TextEdit, TextRange, TextSize,
+    CompletionRelevance, Documentation, FileId, FileRange, FileSystemEdit, Fold, FoldKind,
+    Highlight, HlMod, HlPunct, HlRange, HlTag, Indel, InlayHint, InlayKind, InsertTextFormat,
+    Markup, NavigationTarget, ReferenceAccess, RenameError, Runnable, Severity, SourceChange,
+    TextEdit, TextRange, TextSize,
 };
 use ide_db::SymbolKind;
 use itertools::Itertools;
@@ -213,12 +214,22 @@ pub(crate) fn completion_item(
         ..Default::default()
     };
 
-    if item.relevance().is_relevant() {
-        lsp_item.preselect = Some(true);
-        // HACK: sort preselect items first
-        lsp_item.sort_text = Some(format!(" {}", item.label()));
+    fn set_score(res: &mut lsp_types::CompletionItem, relevance: CompletionRelevance) {
+        if relevance.is_relevant() {
+            res.preselect = Some(true);
+        }
+        // The relevance needs to be inverted to come up with a sort score
+        // because the client will sort ascending.
+        let sort_score = relevance.score() ^ 0xFF;
+        // Zero pad the string to ensure values are sorted numerically
+        // even though the client is sorting alphabetically. Three
+        // characters is enough to fit the largest u8, which is the
+        // type of the relevance score.
+        res.sort_text = Some(format!("{:03}", sort_score));
     }
 
+    set_score(&mut lsp_item, item.relevance());
+
     if item.deprecated() {
         lsp_item.tags = Some(vec![lsp_types::CompletionItemTag::Deprecated])
     }
@@ -228,10 +239,9 @@ pub(crate) fn completion_item(
     }
 
     let mut res = match item.ref_match() {
-        Some(mutability) => {
+        Some((mutability, relevance)) => {
             let mut lsp_item_with_ref = lsp_item.clone();
-            lsp_item.preselect = Some(true);
-            lsp_item.sort_text = Some(format!(" {}", item.label()));
+            set_score(&mut lsp_item_with_ref, relevance);
             lsp_item_with_ref.label =
                 format!("&{}{}", mutability.as_keyword_for_ref(), lsp_item_with_ref.label);
             if let Some(lsp_types::CompletionTextEdit::Edit(it)) = &mut lsp_item_with_ref.text_edit
@@ -1107,13 +1117,13 @@ mod tests {
                 (
                     "&arg",
                     Some(
-                        " arg",
+                        "253",
                     ),
                 ),
                 (
                     "arg",
                     Some(
-                        " arg",
+                        "254",
                     ),
                 ),
             ]