From d89390b75e3e9993f347387a49b0ac5550f45c7f Mon Sep 17 00:00:00 2001
From: Barrie Treloar <baerrach@gmail.com>
Date: Sun, 29 Sep 2019 13:34:53 +0930
Subject: [PATCH] Fix: use async reading of stdin in bin/eslint.js (fixes
 #12212) (#12230)

---
 bin/eslint.js       | 37 ++++++++++++++++++++++++++++++++-----
 tests/bin/eslint.js |  9 +++++++++
 2 files changed, 41 insertions(+), 5 deletions(-)

diff --git a/bin/eslint.js b/bin/eslint.js
index 82bcc1e033b..a9f51f1d7d4 100755
--- a/bin/eslint.js
+++ b/bin/eslint.js
@@ -59,13 +59,40 @@ process.once("uncaughtException", err => {
 if (useStdIn) {
 
     /*
-     * Note: `process.stdin.fd` is not used here due to https://github.com/nodejs/node/issues/7439.
-     * Accessing the `process.stdin` property seems to modify the behavior of file descriptor 0, resulting
-     * in an error when stdin is piped in asynchronously.
+     * Note: See
+     * - https://github.com/nodejs/node/blob/master/doc/api/process.md#processstdin
+     * - https://github.com/nodejs/node/blob/master/doc/api/process.md#a-note-on-process-io
+     * - https://lists.gnu.org/archive/html/bug-gnu-emacs/2016-01/msg00419.html
+     * - https://github.com/nodejs/node/issues/7439 (historical)
+     *
+     * On Windows using `fs.readFileSync(STDIN_FILE_DESCRIPTOR, "utf8")` seems
+     * to read 4096 bytes before blocking and never drains to read further data.
+     *
+     * The investigation on the Emacs thread indicates:
+     *
+     * > Emacs on MS-Windows uses pipes to communicate with subprocesses; a
+     * > pipe on Windows has a 4K buffer. So as soon as Emacs writes more than
+     * > 4096 bytes to the pipe, the pipe becomes full, and Emacs then waits for
+     * > the subprocess to read its end of the pipe, at which time Emacs will
+     * > write the rest of the stuff.
+     *
+     * Using the nodejs code example for reading from stdin.
      */
-    const STDIN_FILE_DESCRIPTOR = 0;
+    let contents = "",
+        chunk = "";
 
-    process.exitCode = cli.execute(process.argv, fs.readFileSync(STDIN_FILE_DESCRIPTOR, "utf8"));
+    process.stdin.setEncoding("utf8");
+    process.stdin.on("readable", () => {
+
+        // Use a loop to make sure we read all available data.
+        while ((chunk = process.stdin.read()) !== null) {
+            contents += chunk;
+        }
+    });
+
+    process.stdin.on("end", () => {
+        process.exitCode = cli.execute(process.argv, contents, "utf8");
+    });
 } else if (init) {
     const configInit = require("../lib/init/config-initializer");
 
diff --git a/tests/bin/eslint.js b/tests/bin/eslint.js
index b6254fa5ff1..932dd9ec451 100644
--- a/tests/bin/eslint.js
+++ b/tests/bin/eslint.js
@@ -163,6 +163,15 @@ describe("bin/eslint.js", () => {
                 return assertExitCode(child, 0);
             });
         });
+
+        it("successfully handles more than 4k data via stdin", () => {
+            const child = runESLint(["--stdin", "--no-eslintrc"]);
+            const large = fs.createReadStream(`${__dirname}/../bench/large.js`, "utf8");
+
+            large.pipe(child.stdin);
+
+            return assertExitCode(child, 0);
+        });
     });
 
     describe("running on files", () => {