4 files changed, 62 insertions, 0 deletions

diff --git a/editors/code/package.json b/editors/code/package.json
index 1743b374c..17d9281ff 100644
--- a/editors/code/package.json
+++ b/editors/code/package.json
@@ -110,6 +110,11 @@
                 "category": "Rust Analyzer"
             },
             {
+                "command": "rust-analyzer.viewItemTree",
+                "title": "Debug ItemTree",
+                "category": "Rust Analyzer"
+            },
+            {
                 "command": "rust-analyzer.viewCrateGraph",
                 "title": "View Crate Graph",
                 "category": "Rust Analyzer"
diff --git a/editors/code/src/commands.ts b/editors/code/src/commands.ts
index 8ab259af2..0fdb9fe05 100644
--- a/editors/code/src/commands.ts
+++ b/editors/code/src/commands.ts
@@ -429,6 +429,56 @@ export function viewHir(ctx: Ctx): Cmd {
     };
 }
 
+export function viewItemTree(ctx: Ctx): Cmd {
+    const tdcp = new class implements vscode.TextDocumentContentProvider {
+        readonly uri = vscode.Uri.parse('rust-analyzer://viewItemTree/itemtree.rs');
+        readonly eventEmitter = new vscode.EventEmitter<vscode.Uri>();
+        constructor() {
+            vscode.workspace.onDidChangeTextDocument(this.onDidChangeTextDocument, this, ctx.subscriptions);
+            vscode.window.onDidChangeActiveTextEditor(this.onDidChangeActiveTextEditor, this, ctx.subscriptions);
+        }
+
+        private onDidChangeTextDocument(event: vscode.TextDocumentChangeEvent) {
+            if (isRustDocument(event.document)) {
+                // We need to order this after language server updates, but there's no API for that.
+                // Hence, good old sleep().
+                void sleep(10).then(() => this.eventEmitter.fire(this.uri));
+            }
+        }
+        private onDidChangeActiveTextEditor(editor: vscode.TextEditor | undefined) {
+            if (editor && isRustEditor(editor)) {
+                this.eventEmitter.fire(this.uri);
+            }
+        }
+
+        provideTextDocumentContent(_uri: vscode.Uri, ct: vscode.CancellationToken): vscode.ProviderResult<string> {
+            const rustEditor = ctx.activeRustEditor;
+            const client = ctx.client;
+            if (!rustEditor || !client) return '';
+
+            const params = {
+                textDocument: client.code2ProtocolConverter.asTextDocumentIdentifier(rustEditor.document),
+            };
+            return client.sendRequest(ra.viewItemTree, params, ct);
+        }
+
+        get onDidChange(): vscode.Event<vscode.Uri> {
+            return this.eventEmitter.event;
+        }
+    };
+
+    ctx.pushCleanup(vscode.workspace.registerTextDocumentContentProvider('rust-analyzer', tdcp));
+
+    return async () => {
+        const document = await vscode.workspace.openTextDocument(tdcp.uri);
+        tdcp.eventEmitter.fire(tdcp.uri);
+        void await vscode.window.showTextDocument(document, {
+            viewColumn: vscode.ViewColumn.Two,
+            preserveFocus: true
+        });
+    };
+}
+
 export function viewCrateGraph(ctx: Ctx): Cmd {
     return async () => {
         const panel = vscode.window.createWebviewPanel("rust-analyzer.crate-graph", "rust-analyzer crate graph", vscode.ViewColumn.Two);
diff --git a/editors/code/src/lsp_ext.ts b/editors/code/src/lsp_ext.ts
index aa745a65c..6d5c2ea72 100644
--- a/editors/code/src/lsp_ext.ts
+++ b/editors/code/src/lsp_ext.ts
@@ -27,6 +27,12 @@ export const syntaxTree = new lc.RequestType<SyntaxTreeParams, string, void>("ru
 
 export const viewHir = new lc.RequestType<lc.TextDocumentPositionParams, string, void>("rust-analyzer/viewHir");
 
+export interface ViewItemTreeParams {
+    textDocument: lc.TextDocumentIdentifier;
+}
+
+export const viewItemTree = new lc.RequestType<ViewItemTreeParams, string, void>("rust-analyzer/viewItemTree");
+
 export const viewCrateGraph = new lc.RequestType0<string, void>("rust-analyzer/viewCrateGraph");
 
 export interface ExpandMacroParams {
diff --git a/editors/code/src/main.ts b/editors/code/src/main.ts
index 516322d03..92c797d47 100644
--- a/editors/code/src/main.ts
+++ b/editors/code/src/main.ts
@@ -106,6 +106,7 @@ async function tryActivate(context: vscode.ExtensionContext) {
     ctx.registerCommand('parentModule', commands.parentModule);
     ctx.registerCommand('syntaxTree', commands.syntaxTree);
     ctx.registerCommand('viewHir', commands.viewHir);
+    ctx.registerCommand('viewItemTree', commands.viewItemTree);
     ctx.registerCommand('viewCrateGraph', commands.viewCrateGraph);
     ctx.registerCommand('expandMacro', commands.expandMacro);
     ctx.registerCommand('run', commands.run);