From c2eebcaab4edc44a678b2205382a86ab65b52251 Mon Sep 17 00:00:00 2001
From: Mark Probst <mark.probst@gmail.com>
Date: Mon, 20 Jul 2026 18:18:28 -0400
Subject: [PATCH] fix(cli): exit cleanly instead of crashing on EPIPE (#864)

Piping quicktype's output into a program that closes the pipe early
(e.g. `... | head -n 4`) left an unhandled 'error' event on
process.stdout/stderr. Node treated the resulting EPIPE as an
uncaught exception, printing a raw stack trace and exiting with code
1 instead of exiting quietly like well-behaved Unix CLIs do.

Add EPIPE error handlers on process.stdout/stderr in the CLI entry
point that exit(0) on EPIPE and rethrow any other stream error.

Co-Authored-By: gpt-5.6-sol via pi <noreply@openai.com>
---
 src/index.ts                | 11 +++++++
 test/unit/cli-epipe.test.ts | 57 +++++++++++++++++++++++++++++++++++++
 2 files changed, 68 insertions(+)
 create mode 100644 test/unit/cli-epipe.test.ts

diff --git a/src/index.ts b/src/index.ts
index 6ae510e25b..7383ef03bd 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -1272,6 +1272,17 @@ export async function main(
 }
 
 if (require.main === module) {
+    const exitOnEPIPE = (error: NodeJS.ErrnoException): void => {
+        if (error.code === "EPIPE") {
+            process.exit(0);
+        }
+
+        throw error;
+    };
+
+    process.stdout.on("error", exitOnEPIPE);
+    process.stderr.on("error", exitOnEPIPE);
+
     main(process.argv.slice(2)).catch((e) => {
         if (e instanceof Error) {
             console.error(`Error: ${e.message}.`);
diff --git a/test/unit/cli-epipe.test.ts b/test/unit/cli-epipe.test.ts
new file mode 100644
index 0000000000..460dbe36eb
--- /dev/null
+++ b/test/unit/cli-epipe.test.ts
@@ -0,0 +1,57 @@
+import { spawn } from "node:child_process";
+import * as path from "node:path";
+
+import { describe, expect, test } from "vitest";
+
+const repositoryRoot = process.cwd();
+
+function runWithClosedStdout(): Promise<{
+    code: number | null;
+    signal: NodeJS.Signals | null;
+    stderr: string;
+}> {
+    return new Promise((resolve, reject) => {
+        const child = spawn(
+            process.execPath,
+            [
+                path.join(repositoryRoot, "dist", "index.js"),
+                "--src-lang",
+                "schema",
+                "--lang",
+                "swift",
+                "--just-types",
+                path.join(
+                    repositoryRoot,
+                    "test",
+                    "inputs",
+                    "schema",
+                    "vega-lite.schema",
+                ),
+            ],
+            { stdio: ["ignore", "pipe", "pipe"] },
+        );
+        let stderr = "";
+
+        child.stderr.setEncoding("utf8");
+        child.stderr.on("data", (chunk: string) => {
+            stderr += chunk;
+        });
+        child.on("error", reject);
+        child.on("close", (code, signal) => {
+            resolve({ code, signal, stderr });
+        });
+
+        child.stdout.destroy();
+    });
+}
+
+describe("CLI output", () => {
+    test("exits successfully when stdout is closed early", async () => {
+        const result = await runWithClosedStdout();
+
+        expect(result.signal).toBeNull();
+        expect(result.code).toBe(0);
+        expect(result.stderr).not.toContain("Error: write EPIPE");
+        expect(result.stderr).not.toContain("Unhandled 'error' event");
+    });
+});