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

packages/coding-agent/test/stdout-cleanliness.test.ts

@@ -0,0 +1,102 @@
+import { spawn } from "node:child_process";
+import { mkdirSync, mkdtempSync, rmSync, writeFileSync } from "node:fs";
+import { tmpdir } from "node:os";
+import { join, resolve } from "node:path";
+import { afterEach, describe, expect, it } from "vitest";
+import { ENV_AGENT_DIR } from "../src/config.js";
+
+const cliPath = resolve(__dirname, "../src/cli.ts");
+const tsxPath = resolve(__dirname, "../../../node_modules/tsx/dist/cli.mjs");
+
+const tempDirs: string[] = [];
+
+afterEach(() => {
+	for (const dir of tempDirs.splice(0)) {
+		rmSync(dir, { recursive: true, force: true });
+	}
+});
+
+function createTempDir(): string {
+	const dir = mkdtempSync(join(tmpdir(), "pi-stdout-clean-"));
+	tempDirs.push(dir);
+	return dir;
+}
+
+async function runCli(args: string[]): Promise<{ stdout: string; stderr: string; code: number | null }> {
+	const tempRoot = createTempDir();
+	const agentDir = join(tempRoot, "agent");
+	const projectDir = join(tempRoot, "project");
+	const projectConfigDir = join(projectDir, ".pi");
+	mkdirSync(agentDir, { recursive: true });
+	mkdirSync(projectConfigDir, { recursive: true });
+
+	const fakeNpmPath = join(tempRoot, "fake-npm.mjs");
+	writeFileSync(
+		fakeNpmPath,
+		[
+			'console.log("changed 1 package in 471ms");',
+			'console.log("found 0 vulnerabilities");',
+			"process.exit(0);",
+		].join("\n"),
+		"utf-8",
+	);
+
+	writeFileSync(
+		join(projectConfigDir, "settings.json"),
+		JSON.stringify(
+			{
+				packages: ["npm:fake-package"],
+				npmCommand: [process.execPath, fakeNpmPath],
+			},
+			null,
+			2,
+		),
+		"utf-8",
+	);
+
+	return await new Promise((resolvePromise, reject) => {
+		const child = spawn(process.execPath, [tsxPath, cliPath, ...args], {
+			cwd: projectDir,
+			env: {
+				...process.env,
+				[ENV_AGENT_DIR]: agentDir,
+			},
+			stdio: ["ignore", "pipe", "pipe"],
+		});
+
+		let stdout = "";
+		let stderr = "";
+		child.stdout.on("data", (chunk) => {
+			stdout += chunk.toString();
+		});
+		child.stderr.on("data", (chunk) => {
+			stderr += chunk.toString();
+		});
+		child.on("error", reject);
+		child.on("close", (code) => {
+			resolvePromise({ stdout, stderr, code });
+		});
+	});
+}
+
+describe("stdout cleanliness in non-interactive modes", () => {
+	it("keeps stdout empty for --mode json --help while routing startup chatter to stderr", async () => {
+		const result = await runCli(["--mode", "json", "--help"]);
+
+		expect(result.code).toBe(0);
+		expect(result.stdout).toBe("");
+		expect(result.stderr).toContain("changed 1 package in 471ms");
+		expect(result.stderr).toContain("found 0 vulnerabilities");
+		expect(result.stderr).toContain("Usage:");
+	});
+
+	it("keeps stdout empty for -p --help while routing startup chatter to stderr", async () => {
+		const result = await runCli(["-p", "--help"]);
+
+		expect(result.code).toBe(0);
+		expect(result.stdout).toBe("");
+		expect(result.stderr).toContain("changed 1 package in 471ms");
+		expect(result.stderr).toContain("found 0 vulnerabilities");
+		expect(result.stderr).toContain("Usage:");
+	});
+});