Impl simple completion

lsp/src/state.rs

@@ -1,7 +1,7 @@
 use crate::vfs::{Vfs, VfsPath};
 use crossbeam_channel::Sender;
 use lsp_types::{self as lsp, notification as notif, request as req, OneOf, Url};
-use nil::{Analysis, AnalysisHost, Change, FilePos, InFile};
+use nil::{Analysis, AnalysisHost, Change, CompletionItemKind, FilePos, InFile};
 use std::sync::{Arc, RwLock};
 use text_size::TextRange;
 
@@ -15,6 +15,10 @@ pub fn server_capabilities() -> lsp::ServerCapabilities {
             },
         )),
         definition_provider: Some(OneOf::Left(true)),
+        completion_provider: Some(lsp::CompletionOptions {
+            trigger_characters: Some(vec![".".into()]),
+            ..Default::default()
+        }),
         ..Default::default()
     }
 }
@@ -80,6 +84,36 @@ impl State {
                     None => Some(lsp::GotoDefinitionResponse::Array(Vec::new())),
                 }
             })
+            .on::<req::Completion>(|st, params| {
+                let pos = get_file_pos(&st.vfs.read().unwrap(), &params.text_document_position)?;
+                let items = st.analysis.completions(pos).ok()??;
+                let vfs = st.vfs.read().unwrap();
+                let items = items
+                    .into_iter()
+                    .filter_map(|item| {
+                        let kind = match item.kind {
+                            // FIXME: More specific?
+                            CompletionItemKind::Builtin => lsp::CompletionItemKind::KEYWORD,
+                            CompletionItemKind::Binding => lsp::CompletionItemKind::VARIABLE,
+                        };
+                        Some(lsp::CompletionItem {
+                            label: item.label.into(),
+                            kind: Some(kind),
+                            insert_text: None,
+                            insert_text_format: Some(lsp::InsertTextFormat::PLAIN_TEXT),
+                            // We don't support indentation yet.
+                            insert_text_mode: Some(lsp::InsertTextMode::ADJUST_INDENTATION),
+                            text_edit: Some(lsp::CompletionTextEdit::Edit(lsp::TextEdit {
+                                range: to_lsp_range(&vfs, pos.map(|_| item.source_range))?,
+                                new_text: item.replace.into(),
+                            })),
+                            // TODO
+                            ..Default::default()
+                        })
+                    })
+                    .collect::<Vec<_>>();
+                Some(lsp::CompletionResponse::Array(items))
+            })
             .finish();
     }
 
@@ -159,11 +193,14 @@ fn get_file_pos(vfs: &Vfs, params: &lsp::TextDocumentPositionParams) -> Option<F
 
 fn to_lsp_location(vfs: &Vfs, pos: InFile<TextRange>) -> Option<lsp::Location> {
     let url = vfs.file_path(pos.file_id)?.try_into().ok()?;
+    Some(lsp::Location::new(url, to_lsp_range(vfs, pos)?))
+}
+
+fn to_lsp_range(vfs: &Vfs, pos: InFile<TextRange>) -> Option<lsp::Range> {
     let (_, line1, col1) = vfs.get_file_line_col(pos.map(|range| range.start()))?;
     let (_, line2, col2) = vfs.get_file_line_col(pos.map(|range| range.end()))?;
-    let range = lsp::Range::new(
+    Some(lsp::Range::new(
         lsp::Position::new(line1, col1),
         lsp::Position::new(line2, col2),
-    );
-    Some(lsp::Location::new(url, range))
+    ))
 }

src/ide/completion.rs

@@ -0,0 +1,79 @@
+use crate::{
+    builtin,
+    def::{AstPtr, DefDatabase},
+    FileId,
+};
+use rowan::ast::AstNode;
+use smol_str::SmolStr;
+use syntax::{ast, match_ast, SyntaxKind, TextRange, TextSize, T};
+
+/// A single completion variant in the editor pop-up.
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct CompletionItem {
+    /// The label to show in the completion menu.
+    pub label: SmolStr,
+    /// Range of identifier that is being completed.
+    pub source_range: TextRange,
+    /// What content replaces the source range when user selects this item.
+    pub replace: SmolStr,
+    /// What item (struct, function, etc) are we completing.
+    pub kind: CompletionItemKind,
+}
+
+/// The type of the completion item.
+#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord)]
+pub enum CompletionItemKind {
+    Builtin,
+    Binding,
+}
+
+pub(crate) fn completions(
+    db: &dyn DefDatabase,
+    file_id: FileId,
+    pos: TextSize,
+) -> Option<Vec<CompletionItem>> {
+    let parse = db.parse(file_id).value;
+
+    let tok = parse.syntax_node().token_at_offset(pos).left_biased()?;
+    let source_range = match tok.kind() {
+        T![.] => TextRange::empty(pos),
+        SyntaxKind::IDENT => tok.text_range(),
+        _ => return None,
+    };
+
+    let ref_node = tok.parent_ancestors().find_map(|node| {
+        match_ast! {
+            match node {
+                ast::Ref(n) => Some(n),
+                _ => None,
+            }
+        }
+    })?;
+    let source_map = db.source_map(file_id);
+    let expr_id = source_map.node_expr(AstPtr::new(ref_node.syntax()))?;
+    let scopes = db.scopes(file_id);
+    let scope_id = scopes.scope_by_expr(expr_id)?;
+
+    // TODO: Better sorting.
+    let mut items = scopes
+        .ancestors(scope_id)
+        .filter_map(|scope| scope.as_name_defs())
+        .flat_map(|scope| scope.keys())
+        .map(|name| CompletionItem {
+            label: name.clone(),
+            source_range,
+            replace: name.clone(),
+            kind: CompletionItemKind::Binding,
+        })
+        .chain(builtin::NAMES.iter().map(|name| CompletionItem {
+            label: name.into(),
+            source_range,
+            replace: name.into(),
+            kind: CompletionItemKind::Builtin,
+        }))
+        .collect::<Vec<_>>();
+    items.sort_by(|lhs, rhs| lhs.label.cmp(&rhs.label));
+    items.dedup_by(|lhs, rhs| lhs.label == rhs.label);
+
+    Some(items)
+}

src/ide/mod.rs

@@ -1,9 +1,12 @@
+mod completion;
+mod goto_definition;
+
 use crate::{base::SourceDatabaseStorage, def::DefDatabaseStorage, Change, FileId, FilePos};
 use rowan::TextRange;
 use salsa::{Cancelled, Database, Durability, ParallelDatabase};
 use std::fmt;
 
-mod goto_definition;
+pub use completion::{CompletionItem, CompletionItemKind};
 
 #[derive(Debug, Clone, PartialEq, Eq)]
 pub struct NavigationTarget {
@@ -78,4 +81,8 @@ impl Analysis {
     pub fn goto_definition(&self, pos: FilePos) -> Cancellable<Option<Vec<NavigationTarget>>> {
         self.with_db(|db| goto_definition::goto_definition(db, pos.file_id, pos.value))
     }
+
+    pub fn completions(&self, pos: FilePos) -> Cancellable<Option<Vec<CompletionItem>>> {
+        self.with_db(|db| completion::completions(db, pos.file_id, pos.value))
+    }
 }

src/lib.rs

@@ -9,4 +9,6 @@ mod tests;
 
 pub use base::{Change, FileId, FilePos, FileRange, InFile};
 pub use diagnostic::Diagnostic;
-pub use ide::{Analysis, AnalysisHost, RootDatabase};
+pub use ide::{
+    Analysis, AnalysisHost, CompletionItem, CompletionItemKind, NavigationTarget, RootDatabase,
+};