Add truncated flag to RunResult for output exceeding 256 KB

Callers can now distinguish between normal output and silently truncated
output. Two new tests verify the flag for small and oversized output.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: georgeglarson

RestaurantReviews/src/server/__tests__/runner.test.ts

@@ -128,4 +128,19 @@ describe("spawnAndCapture", () => {
     expect(result.stdout).toBe("");
     expect(result.stderr).toBe("");
   });
+
+  it("sets truncated to false for small output", async () => {
+    const result = await spawnAndCapture("/bin/echo", ["hello"]);
+    expect(result.truncated).toBe(false);
+  });
+
+  it("sets truncated to true when stdout exceeds 256 KB", async () => {
+    // Generate 300 KB of output via dd
+    const result = await spawnAndCapture("/bin/dd", [
+      "if=/dev/zero",
+      "bs=1024",
+      "count=300",
+    ]);
+    expect(result.truncated).toBe(true);
+  });
 });

RestaurantReviews/src/server/exercises/runner.ts

@@ -10,6 +10,7 @@ export interface RunResult {
   stdout: string;
   stderr: string;
   exitCode: number;
+  truncated: boolean;
 }
 
 /**
@@ -23,7 +24,7 @@ export async function runWithFile(
   options: { interpreter?: string; timeout?: number } = {}
 ): Promise<RunResult> {
   if (Buffer.byteLength(input, "utf-8") > MAX_INPUT_BYTES) {
-    return { stdout: "", stderr: "Input too large", exitCode: 1 };
+    return { stdout: "", stderr: "Input too large", exitCode: 1, truncated: false };
   }
 
   const dir = await mkdtemp(path.join(tmpdir(), "exercise-"));
@@ -70,6 +71,7 @@ export function spawnAndCapture(
         stdout: Buffer.concat(stdoutChunks).toString("utf-8"),
         stderr: Buffer.concat(stderrChunks).toString("utf-8"),
         exitCode: code ?? 1,
+        truncated: stdoutLen > MAX_OUTPUT_BYTES || stderrLen > MAX_OUTPUT_BYTES,
       });
     });
   });