Add vscode support for range in SyntaxTreeParams

This enables the client to use a command to either show the live-updating
version of the syntax tree for the current file. Or optionally when a selected
range is provided, we then provide a snapshot of the syntax tree for the range.

3 files changed, 41 insertions, 11 deletions

diff --git a/editors/code/package.json b/editors/code/package.json
index d4ce2ae2c..fda411810 100644
--- a/editors/code/package.json
+++ b/editors/code/package.json
@@ -75,7 +75,7 @@
         "commands": [
             {
                 "command": "rust-analyzer.syntaxTree",
-                "title": "Show syntax tree for current file",
+                "title": "Show Syntax Tree",
                 "category": "Rust Analyzer"
             },
             {
diff --git a/editors/code/src/commands/syntaxTree.ts b/editors/code/src/commands/syntaxTree.ts
index c0baf08c5..7200ae823 100644
--- a/editors/code/src/commands/syntaxTree.ts
+++ b/editors/code/src/commands/syntaxTree.ts
@@ -1,5 +1,5 @@
 import * as vscode from 'vscode';
-import { TextDocumentIdentifier } from 'vscode-languageclient';
+import { Range, TextDocumentIdentifier } from 'vscode-languageclient';
 
 import { Server } from '../server';
 
@@ -17,8 +17,21 @@ export class TextDocumentContentProvider
         if (editor == null) {
             return '';
         }
+
+        let range: Range | undefined;
+
+        // When the range based query is enabled we take the range of the selection
+        if (uri.query === 'range=true') {
+            range = editor.selection.isEmpty
+                ? undefined
+                : Server.client.code2ProtocolConverter.asRange(
+                      editor.selection
+                  );
+        }
+
         const request: SyntaxTreeParams = {
-            textDocument: { uri: editor.document.uri.toString() }
+            textDocument: { uri: editor.document.uri.toString() },
+            range
         };
         return Server.client.sendRequest<SyntaxTreeResult>(
             'rust-analyzer/syntaxTree',
@@ -33,6 +46,7 @@ export class TextDocumentContentProvider
 
 interface SyntaxTreeParams {
     textDocument: TextDocumentIdentifier;
+    range?: Range;
 }
 
 type SyntaxTreeResult = string;
@@ -40,11 +54,23 @@ type SyntaxTreeResult = string;
 // Opens the virtual file that will show the syntax tree
 //
 // The contents of the file come from the `TextDocumentContentProvider`
-export async function handle() {
-    const document = await vscode.workspace.openTextDocument(syntaxTreeUri);
-    return vscode.window.showTextDocument(
-        document,
-        vscode.ViewColumn.Two,
-        true
-    );
+export function createHandle(provider: TextDocumentContentProvider) {
+    return async () => {
+        const editor = vscode.window.activeTextEditor;
+        const rangeEnabled = !!(editor && !editor.selection.isEmpty);
+
+        const uri = rangeEnabled
+            ? vscode.Uri.parse(`${syntaxTreeUri.toString()}?range=true`)
+            : syntaxTreeUri;
+
+        const document = await vscode.workspace.openTextDocument(uri);
+
+        provider.eventEmitter.fire(uri);
+
+        return vscode.window.showTextDocument(
+            document,
+            vscode.ViewColumn.Two,
+            true
+        );
+    };
 }
diff --git a/editors/code/src/extension.ts b/editors/code/src/extension.ts
index 8b332eeb2..5134bb258 100644
--- a/editors/code/src/extension.ts
+++ b/editors/code/src/extension.ts
@@ -52,7 +52,6 @@ export function activate(context: vscode.ExtensionContext) {
     registerCommand('rust-analyzer.collectGarbage', () =>
         Server.client.sendRequest<null>('rust-analyzer/collectGarbage', null)
     );
-    registerCommand('rust-analyzer.syntaxTree', commands.syntaxTree.handle);
     registerCommand(
         'rust-analyzer.extendSelection',
         commands.extendSelection.handle
@@ -109,6 +108,11 @@ export function activate(context: vscode.ExtensionContext) {
         )
     );
 
+    registerCommand(
+        'rust-analyzer.syntaxTree',
+        commands.syntaxTree.createHandle(textDocumentContentProvider)
+    );
+
     vscode.workspace.onDidChangeTextDocument(
         events.changeTextDocument.createHandler(textDocumentContentProvider),
         null,