Improve handling of "set variable" failure (e.g. on consts)

Signed-off-by: itowlson <ivan.towlson@fermyon.com>

Author: itowlson

debugger/vscode-dap-extension/shared/messages.ts

@@ -155,10 +155,15 @@ export interface VariablesResponse {
   type: 'variables',
   value: ReadonlyArray<IRuntimeVariable>,
 }
-export interface VariableSetResponse {
-  type: 'variableSet',
-  value: IRuntimeVariable,
-}
+export type VariableSetResponse = TypedErrorable<'variableSet', IRuntimeVariable>;
+// export interface VariableSetResponse {
+//   type: 'variableSet',
+//   value: IRuntimeVariable,
+// }
+// export interface VariableSetErrorResponse {
+//   type: 'variableSet',
+//   error: string,
+// }
 export interface EvaluateResponse {
   type: 'evaluate';
   value: {
@@ -173,3 +178,12 @@ export interface IRuntimeVariable {
   variablesReference: number;
 }
 
+export function succeeded<M, V>(message: TypedErrorable<M, V>): message is { type: M, value: V } {
+  return !failed(message);
+}
+export function failed<T>(e: Errorable<T>): e is { error: string } {
+  return (<{ error?: string }>e).error !== undefined;
+}
+
+export type TypedErrorable<M, V> = { type: M, value: V } | { type: M, error: string };
+export type Errorable<V> = V | { error: string };

debugger/vscode-dap-extension/src/starlingMonkeyDebugger.ts

@@ -17,6 +17,7 @@ import {
   StarlingMonkeyRuntime,
   FileAccessor,
 } from "./starlingMonkeyRuntime.js";
+import { failed } from "../shared/messages.js";
 
 interface ILaunchRequestArguments extends DebugProtocol.LaunchRequestArguments {
   program: string;
@@ -316,7 +317,12 @@ export class StarlingMonkeyDebugSession extends LoggingDebugSession {
       args.name,
       args.value
     );
-    response.body = { value: message.value, type: message.type, variablesReference: message.variablesReference };
+    if (failed(message)) {
+      response.success = false;
+      response.message = message.error;
+    } else {
+      response.body = { value: message.value, type: message.type, variablesReference: message.variablesReference };
+    }
     this.sendResponse(response);
   }
 

debugger/vscode-dap-extension/src/starlingMonkeyRuntime.ts

@@ -6,7 +6,7 @@ import { Signal } from "./signals.js";
 import { Terminal, TerminalShellExecution, window } from "vscode";
 import { SourceLocation, SourceMaps } from "./sourcemaps/sourceMaps.js";
 import { dirname } from "path";
-import { BreakpointSetResponse, BreakpointsForLineResponse, EvaluateResponse, InstanceToRuntimeMessage, IRuntimeBreakpoint, IRuntimeStackFrame, IRuntimeVariable, RuntimeToInstanceMessage, ScopesResponse, StackResponse, VariableSetResponse, VariablesResponse } from '../shared/messages';
+import { BreakpointSetResponse, BreakpointsForLineResponse, EvaluateResponse, InstanceToRuntimeMessage, IRuntimeBreakpoint, IRuntimeStackFrame, IRuntimeVariable, RuntimeToInstanceMessage, ScopesResponse, StackResponse, succeeded, VariableSetResponse, VariablesResponse } from '../shared/messages';
 
 export interface FileAccessor {
   isWindows: boolean;
@@ -633,7 +633,7 @@ export class StarlingMonkeyRuntime extends EventEmitter<RuntimeEventMap> {
     variablesReference: number,
     name: string,
     value: string
-  ): Promise<IRuntimeVariable> {
+  ): Promise<IRuntimeVariable | { error: string }> {
     const jsValue: unknown = JSON.parse(value);
     this.sendMessage(
       { type: "setVariable", value: {
@@ -644,7 +644,11 @@ export class StarlingMonkeyRuntime extends EventEmitter<RuntimeEventMap> {
     );
 
     const message = await this._variableSet.wait();
-    return message.value;
+    if (succeeded(message)) {
+      return message.value;
+    } else {
+      return { error: message.error };
+    }
   }
 
   public async evaluate(expression: string): Promise<{

debugger/vscode-dap-extension/starling-debugger/debugger.ts

@@ -493,7 +493,12 @@ try {
     } else {
       assert(currentFrame);
       let frame = findFrame(currentFrame, variablesReference - 1);
-      frame.environment.setVariable(name, value);
+      try {
+        frame.environment.setVariable(name, value);
+      } catch (e) {
+        sendMessage({ type: 'variableSet', error: `${e}` });
+        return;
+      }
       newValue = { name, ...formatValue(frame.environment.getVariable(name)) };
     }
 

debugger/vscode-dap-extension/tests/spin-ts/src/index.ts

@@ -1,6 +1,5 @@
-
 function handle(_request: Request): Response {
-  let thingy = 'world';
+  const thingy = 'world';
   let message = `Hello, ${thingy}`;
   return new Response(message, {
     status: 200,