From 4bbdc4bce84a549ad6828c26d43c4aa29235e5cd Mon Sep 17 00:00:00 2001
From: Christoph Knittel <ck@cca.io>
Date: Sat, 5 Oct 2024 19:31:51 +0200
Subject: [PATCH 1/2] rescript format: process files in batches

---
 cli/rescript_format.js | 42 ++++++++++++++++++++++++++++++++++--------
 1 file changed, 34 insertions(+), 8 deletions(-)

diff --git a/cli/rescript_format.js b/cli/rescript_format.js
index 51037f2580..0873b95bbb 100644
--- a/cli/rescript_format.js
+++ b/cli/rescript_format.js
@@ -1,5 +1,7 @@
 //@ts-check
+var os = require("os");
 var arg = require("./rescript_arg.js");
+
 var format_usage = `Usage: rescript format <options> [files]
 
 \`rescript format\` formats the current directory
@@ -67,6 +69,27 @@ async function readStdin() {
   return Buffer.concat(chunks).toString("utf8");
 }
 
+const numThreads = os.cpus().length;
+
+/**
+ * Splits an array into smaller chunks of a specified size.
+ *
+ * @template T
+ * @param {T[]} array - The array to split into chunks.
+ * @param {number} chunkSize - The size of each chunk.
+ * @returns {T[][]} - An array of chunks, where each chunk is an array of type T.
+ */
+function chunkArray(array, chunkSize) {
+  /** @type {T[][]} */
+  const result = [];
+
+  for (let i = 0; i < array.length; i += chunkSize) {
+    result.push(array.slice(i, i + chunkSize));
+  }
+
+  return result;
+}
+
 /**
  * @param {string[]} files
  * @param {string} bsc_exe
@@ -74,11 +97,15 @@ async function readStdin() {
  * @param {boolean} checkFormatting
  */
 async function formatFiles(files, bsc_exe, isSupportedFile, checkFormatting) {
-  var incorrectlyFormattedFiles = 0;
+  const supportedFiles = files.filter(isSupportedFile);
+  const batchSize = 4 * os.cpus().length;
+  const batches = chunkArray(supportedFiles, batchSize);
+
+  let incorrectlyFormattedFiles = 0;
   try {
-    const _promises = await Promise.all(
-      files.map(async file => {
-        if (isSupportedFile(file)) {
+    for (const batch of batches) {
+      await Promise.all(
+        batch.map(async file => {
           const flags = checkFormatting
             ? ["-format", file]
             : ["-o", file, "-format", file];
@@ -90,10 +117,9 @@ async function formatFiles(files, bsc_exe, isSupportedFile, checkFormatting) {
               incorrectlyFormattedFiles++;
             }
           }
-        }
-        return null;
-      }),
-    );
+        }),
+      );
+    }
   } catch (err) {
     console.error(err);
     process.exit(2);

From 3d321b0b0b5d9e0c2a7e6a94971e6df48624c5bc Mon Sep 17 00:00:00 2001
From: Christoph Knittel <ck@cca.io>
Date: Sat, 5 Oct 2024 20:51:00 +0200
Subject: [PATCH 2/2] CHANGELOG

---
 CHANGELOG.md | 1 +
 1 file changed, 1 insertion(+)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index b144bb80c8..a8e756cbf2 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -29,6 +29,7 @@
 
 - Fix tuple coercion. https://github.com/rescript-lang/rescript-compiler/pull/7024
 - Fix attribute printing. https://github.com/rescript-lang/rescript-compiler/pull/7025
+- Fix "rescript format" with many files. https://github.com/rescript-lang/rescript-compiler/pull/7081
 
 #### :nail_care: Polish