fix(coding-agent): reserve stdout in print and json mode closes #2482

packages/coding-agent/src/core/output-guard.ts

@@ -0,0 +1,74 @@
+interface StdoutTakeoverState {
+	rawStdoutWrite: (chunk: string, callback?: (error?: Error | null) => void) => boolean;
+	rawStderrWrite: (chunk: string, callback?: (error?: Error | null) => void) => boolean;
+	originalStdoutWrite: typeof process.stdout.write;
+}
+
+let stdoutTakeoverState: StdoutTakeoverState | undefined;
+
+export function takeOverStdout(): void {
+	if (stdoutTakeoverState) {
+		return;
+	}
+
+	const rawStdoutWrite = process.stdout.write.bind(process.stdout) as StdoutTakeoverState["rawStdoutWrite"];
+	const rawStderrWrite = process.stderr.write.bind(process.stderr) as StdoutTakeoverState["rawStderrWrite"];
+	const originalStdoutWrite = process.stdout.write;
+
+	process.stdout.write = ((
+		chunk: string | Uint8Array,
+		encodingOrCallback?: BufferEncoding | ((error?: Error | null) => void),
+		callback?: (error?: Error | null) => void,
+	): boolean => {
+		if (typeof encodingOrCallback === "function") {
+			return rawStderrWrite(String(chunk), encodingOrCallback);
+		}
+		return rawStderrWrite(String(chunk), callback);
+	}) as typeof process.stdout.write;
+
+	stdoutTakeoverState = {
+		rawStdoutWrite,
+		rawStderrWrite,
+		originalStdoutWrite,
+	};
+}
+
+export function restoreStdout(): void {
+	if (!stdoutTakeoverState) {
+		return;
+	}
+
+	process.stdout.write = stdoutTakeoverState.originalStdoutWrite;
+	stdoutTakeoverState = undefined;
+}
+
+export function isStdoutTakenOver(): boolean {
+	return stdoutTakeoverState !== undefined;
+}
+
+export function writeRawStdout(text: string): void {
+	if (stdoutTakeoverState) {
+		stdoutTakeoverState.rawStdoutWrite(text);
+		return;
+	}
+	process.stdout.write(text);
+}
+
+export async function flushRawStdout(): Promise<void> {
+	if (stdoutTakeoverState) {
+		await new Promise<void>((resolve, reject) => {
+			stdoutTakeoverState?.rawStdoutWrite("", (err) => {
+				if (err) reject(err);
+				else resolve();
+			});
+		});
+		return;
+	}
+
+	await new Promise<void>((resolve, reject) => {
+		process.stdout.write("", (err) => {
+			if (err) reject(err);
+			else resolve();
+		});
+	});
+}

packages/coding-agent/src/core/package-manager.ts

@@ -7,6 +7,7 @@ import ignore from "ignore";
 import { minimatch } from "minimatch";
 import { CONFIG_DIR_NAME } from "../config.js";
 import { type GitSource, parseGitUrl } from "../utils/git.js";
+import { isStdoutTakenOver } from "./output-guard.js";
 import type { PackageSource, SettingsManager } from "./settings-manager.js";
 
 const NETWORK_TIMEOUT_MS = 10000;
@@ -2091,7 +2092,7 @@ export class DefaultPackageManager implements PackageManager {
 		return new Promise((resolvePromise, reject) => {
 			const child = spawn(command, args, {
 				cwd: options?.cwd,
-				stdio: "inherit",
+				stdio: isStdoutTakenOver() ? ["ignore", 2, 2] : "inherit",
 				shell: process.platform === "win32",
 			});
 			child.on("error", reject);