Debugger setup

package.json

@@ -7,7 +7,8 @@
   "categories": [
     "Programming Languages",
     "Snippets",
-    "Formatters"
+    "Formatters",
+    "Debuggers"
   ],
   "keywords": [
     "cairo",
@@ -87,6 +88,31 @@
         "category": "Cairo"
       }
     ],
+    "breakpoints": [
+      {
+        "language": "cairo"
+      }
+    ],
+    "debuggers": [
+      {
+        "type": "cairo",
+        "languages": [
+          "cairo"
+        ],
+        "label": "Cairo Debug",
+        "configurationAttributes": {
+          "launch": {
+            "properties": {
+              "program": {
+                "type": "string",
+                "description": "Program to run to start debugging",
+                "default": "cairo-debugger"
+              }
+            }
+          }
+        }
+      }
+    ],
     "menus": {
       "commandPalette": [
         {

src/debugger.ts

@@ -0,0 +1,55 @@
+import * as vscode from "vscode";
+import { Context } from "./context";
+import { ChildProcess, spawn } from "child_process";
+import * as readline from "node:readline";
+import { Readable } from "node:stream";
+
+export function enableLaunchingDebugger(ctx: Context) {
+  const factory = new CairoDebugAdapterServerDescriptorFactory();
+  ctx.extension.subscriptions.push(
+    vscode.debug.registerDebugAdapterDescriptorFactory("cairo", factory),
+  );
+}
+
+class CairoDebugAdapterServerDescriptorFactory implements vscode.DebugAdapterDescriptorFactory {
+  private debugAdapterProcesses: ChildProcess[] = [];
+
+  createDebugAdapterDescriptor(
+    session: vscode.DebugSession,
+  ): vscode.ProviderResult<vscode.DebugAdapterDescriptor> {
+    const program = session.configuration["program"] as string;
+    const adapterProcess = spawn(program, { stdio: "pipe", env: process.env });
+    this.debugAdapterProcesses.push(adapterProcess);
+
+    return this.waitForFreePort(adapterProcess.stdout).then(
+      (port) => new vscode.DebugAdapterServer(port),
+    );
+  }
+
+  async waitForFreePort(adapterStdout: Readable): Promise<number> {
+    const lineReader = readline.createInterface({ input: adapterStdout });
+
+    // Wait for the server to print the port number it is listening on.
+    for await (let line of lineReader) {
+      line = line.trim();
+      const matches = line.match("DEBUGGER PORT: ([0-9]*)");
+      if (matches !== null) {
+        const port = parseInt(matches[1]!, 10);
+        return Promise.resolve(port);
+      }
+    }
+
+    throw Error("Have not received a port number from the adapter");
+  }
+
+  dispose(): void {
+    for (const process of this.debugAdapterProcesses) {
+      process.kill();
+    }
+
+    for (const process of this.debugAdapterProcesses) {
+      // For good measure.
+      if (process.exitCode === undefined) process.kill("SIGKILL");
+    }
+  }
+}

src/extension.ts

@@ -2,10 +2,13 @@ import * as vscode from "vscode";
 import * as lc from "vscode-languageclient/node";
 import { Context } from "./context";
 import { CairoExtensionManager } from "./extensionManager";
+import { enableLaunchingDebugger } from "./debugger";
 
 export async function activate(extensionContext: vscode.ExtensionContext) {
   const ctx = Context.create(extensionContext);
 
+  enableLaunchingDebugger(ctx);
+
   if (ctx.config.get("enableLanguageServer")) {
     const extensionManager = CairoExtensionManager.fromContext(ctx);
     await extensionManager.tryStartClient();