Test proper input stream handling in the CLI.

Author: AndreasArvidsson

src/cli/cli.ts

@@ -1,6 +1,7 @@
 import getStdin from "get-stdin";
 import * as fs from "node:fs/promises";
 import * as process from "node:process";
+import type { Readable } from "node:stream";
 import type { CLI } from "../types.js";
 import { EXIT_ERROR, EXIT_FAIL, EXIT_OK } from "../util/constants.js";
 import { getErrorMessage } from "../util/getErrorMessage.js";
@@ -132,16 +133,12 @@ export async function formatFile(
     }
 }
 
-async function mainFormatStdin(cli: CLI, check: boolean): Promise<number> {
-    const input = await getStdin();
-    return formatStdin(cli, input, check);
-}
-
-export async function formatStdin(
+export async function mainFormatStdin(
     cli: CLI,
-    input: string,
-    check: boolean = false,
+    check: boolean,
+    stdin: Readable = process.stdin,
 ): Promise<number> {
+    const input = await getStdin({ stdin });
     const formatted = await cli.format(input, "stdin");
 
     if (check) {

src/test/cli.test.ts

@@ -2,7 +2,8 @@ import * as assert from "node:assert";
 import fs from "node:fs/promises";
 import os from "node:os";
 import path from "node:path";
-import { formatFile, formatFiles, formatStdin } from "../cli/cli.js";
+import { PassThrough } from "node:stream";
+import { formatFile, formatFiles, mainFormatStdin } from "../cli/cli.js";
 import type { CLI, ParsedArgs } from "../types.js";
 import { EXIT_FAIL, EXIT_OK } from "../util/constants.js";
 import { parseArgs } from "../util/parseArgs.js";
@@ -108,7 +109,7 @@ suite("CLI", () => {
     test("writes formatted stdin to stdout", async () => {
         const cli = createCLI((text) => `${text} updated`);
         const output = await captureStreamWrite(process.stdout, async () =>
-            formatStdin(cli, "content"),
+            readAndFormatStdin(cli, "content"),
         );
 
         assert.equal(output.result, EXIT_OK);
@@ -118,7 +119,7 @@ suite("CLI", () => {
     test("reports stdin formatting issues to stderr in check mode", async () => {
         const cli = createCLI((text) => `${text} updated`);
         const output = await captureStreamWrite(process.stderr, async () =>
-            formatStdin(cli, "content", true),
+            readAndFormatStdin(cli, "content", true),
         );
 
         assert.equal(output.result, EXIT_FAIL);
@@ -128,10 +129,10 @@ suite("CLI", () => {
     test("returns success for unchanged stdin in check mode", async () => {
         const cli = createCLI((text) => text);
         const stderr = await captureStreamWrite(process.stderr, async () =>
-            formatStdin(cli, "content", true),
+            readAndFormatStdin(cli, "content", true),
         );
         const stdout = await captureStreamWrite(process.stdout, async () =>
-            formatStdin(cli, "content", true),
+            readAndFormatStdin(cli, "content", true),
         );
 
         assert.equal(stderr.result, EXIT_OK);
@@ -195,6 +196,18 @@ function createCLI(format: (text: string) => string | Promise<string>): CLI {
     };
 }
 
+async function readAndFormatStdin(
+    cli: CLI,
+    input: string,
+    check: boolean = false,
+): Promise<number> {
+    const stdin = new PassThrough();
+    Object.defineProperty(stdin, "isTTY", { value: false });
+    const result = mainFormatStdin(cli, check, stdin);
+    stdin.end(input);
+    return result;
+}
+
 async function captureStreamWrite<T>(
     stream: NodeJS.WriteStream,
     callback: () => Promise<T>,