Improve quality of 'workspace/symbols' response (#311)

The new method uses a fuzzy finder instead of the simple `String::starts_with(...)` method previously used.

vhdl_ls/Cargo.toml

@@ -24,6 +24,7 @@ log = "0"
 env_logger = "0"
 clap = { version = "4", features = ["derive"] }
 lsp-server = "0"
+fuzzy-matcher = "0.3.7"
 
 [dev-dependencies]
 tempfile = "3"

vhdl_ls/src/vhdl_server.rs

@@ -17,6 +17,7 @@ use std::collections::hash_map::Entry;
 use vhdl_lang::ast::ObjectClass;
 
 use crate::rpc_channel::SharedRpcChannel;
+use fuzzy_matcher::skim::SkimMatcherV2;
 use std::io;
 use std::io::ErrorKind;
 use std::path::{Path, PathBuf};
@@ -64,6 +65,7 @@ pub struct VHDLServer {
     init_params: Option<InitializeParams>,
     config_file: Option<PathBuf>,
     severity_map: SeverityMap,
+    string_matcher: SkimMatcherV2,
 }
 
 impl VHDLServer {
@@ -77,6 +79,7 @@ impl VHDLServer {
             init_params: None,
             config_file: None,
             severity_map: SeverityMap::default(),
+            string_matcher: SkimMatcherV2::default().use_cache(true).ignore_case(),
         }
     }
 
@@ -91,6 +94,7 @@ impl VHDLServer {
             init_params: None,
             config_file: None,
             severity_map: SeverityMap::default(),
+            string_matcher: SkimMatcherV2::default(),
         }
     }
 

vhdl_ls/src/vhdl_server/workspace.rs

@@ -1,10 +1,13 @@
 use crate::vhdl_server::{srcpos_to_location, to_symbol_kind, uri_to_file_name, VHDLServer};
+use fuzzy_matcher::FuzzyMatcher;
 use lsp_types::{
     DidChangeWatchedFilesParams, OneOf, WorkspaceSymbol, WorkspaceSymbolParams,
     WorkspaceSymbolResponse,
 };
+use std::cmp::Ordering;
+use std::collections::BinaryHeap;
 use vhdl_lang::ast::Designator;
-use vhdl_lang::Message;
+use vhdl_lang::{EntRef, Message};
 
 impl VHDLServer {
     pub fn workspace_did_change_watched_files(&mut self, params: &DidChangeWatchedFilesParams) {
@@ -32,39 +35,77 @@ impl VHDLServer {
         params: &WorkspaceSymbolParams,
     ) -> Option<WorkspaceSymbolResponse> {
         let trunc_limit = 200;
-        let query = params.query.to_ascii_lowercase();
-        let mut symbols: Vec<_> = self
+        let query = params.query.clone();
+        let symbols = self
             .project
             .public_symbols()
             .filter_map(|ent| match ent.designator() {
                 Designator::Identifier(_) | Designator::Character(_) => {
-                    Some((ent, ent.designator().to_string().to_ascii_lowercase()))
+                    Some((ent, ent.designator().to_string()))
                 }
-                Designator::OperatorSymbol(op) => Some((ent, op.to_string().to_ascii_lowercase())),
+                Designator::OperatorSymbol(op) => Some((ent, op.to_string())),
                 Designator::Anonymous(_) => None,
-            })
-            .collect();
-        symbols.sort_by(|(_, n1), (_, n2)| n1.cmp(n2));
+            });
+
         Some(WorkspaceSymbolResponse::Nested(
-            symbols
-                .into_iter()
-                .filter_map(|(ent, name)| {
-                    let decl_pos = ent.decl_pos()?;
-                    if name.starts_with(&query) {
-                        Some(WorkspaceSymbol {
+            self.filter_workspace_symbols(symbols.into_iter(), &query, trunc_limit),
+        ))
+    }
+
+    /// Filters found workspace symbols according to a given query.
+    /// This uses a fuzzy matcher internally to improve the results.
+    /// Queries 'close' to the target string will score high and be included in the
+    /// returned vec, while queries 'not close' to the target string will be omitted.
+    /// The returned vec is sorted according to the score of the fuzzy matcher.
+    fn filter_workspace_symbols<'a>(
+        &self,
+        symbols: impl Iterator<Item = (EntRef<'a>, String)>,
+        query: &str,
+        trunc_limit: usize,
+    ) -> Vec<WorkspaceSymbol> {
+        #[derive(Eq, PartialEq)]
+        struct WorkspaceSymbolWithScore {
+            symbol: WorkspaceSymbol,
+            score: i64,
+        }
+
+        impl PartialOrd<Self> for WorkspaceSymbolWithScore {
+            fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
+                Some(self.cmp(other))
+            }
+        }
+
+        impl Ord for WorkspaceSymbolWithScore {
+            fn cmp(&self, other: &Self) -> Ordering {
+                self.score.cmp(&other.score)
+            }
+        }
+
+        let symbols_with_scores: BinaryHeap<_> = symbols
+            .into_iter()
+            .filter_map(|(ent, name)| {
+                let decl_pos = ent.decl_pos()?;
+                self.string_matcher.fuzzy_match(&name, query).map(|score| {
+                    WorkspaceSymbolWithScore {
+                        symbol: WorkspaceSymbol {
                             name: ent.describe(),
                             kind: to_symbol_kind(ent.kind()),
                             tags: None,
                             container_name: ent.parent.map(|ent| ent.path_name()),
                             location: OneOf::Left(srcpos_to_location(decl_pos)),
                             data: None,
-                        })
-                    } else {
-                        None
+                        },
+                        score,
                     }
                 })
-                .take(trunc_limit)
-                .collect(),
-        ))
+            })
+            .take(trunc_limit)
+            .collect();
+        symbols_with_scores
+            .into_sorted_vec()
+            .into_iter()
+            .rev()
+            .map(|wsws| wsws.symbol)
+            .collect()
     }
 }