From a7d819c26c3f6b79cdc5414736d720e80c7a2ed7 Mon Sep 17 00:00:00 2001
From: JJordan0C <69581081+JJordan0C@users.noreply.github.com>
Date: Fri, 14 Aug 2026 10:30:20 +0200
Subject: [PATCH] fix: support TypeScript project references

---
 src/index.js                                  |  3 +++
 test/unit.test.js                             | 10 +++++----
 test/unit/ts-project-references/app/input.ts  |  3 +++
 .../ts-project-references/app/tsconfig.json   | 12 +++++++++++
 test/unit/ts-project-references/lib/index.ts  |  3 +++
 .../ts-project-references/lib/tsconfig.json   |  6 ++++++
 test/unit/ts-project-references/opt.json      |  4 ++++
 .../ts-project-references/output-coverage.js  | 21 +++++++++++++++++++
 test/unit/ts-project-references/output.js     | 21 +++++++++++++++++++
 9 files changed, 79 insertions(+), 4 deletions(-)
 create mode 100644 test/unit/ts-project-references/app/input.ts
 create mode 100644 test/unit/ts-project-references/app/tsconfig.json
 create mode 100644 test/unit/ts-project-references/lib/index.ts
 create mode 100644 test/unit/ts-project-references/lib/tsconfig.json
 create mode 100644 test/unit/ts-project-references/opt.json
 create mode 100644 test/unit/ts-project-references/output-coverage.js
 create mode 100644 test/unit/ts-project-references/output.js

diff --git a/src/index.js b/src/index.js
index 8db368791..880d3bf3c 100644
--- a/src/index.js
+++ b/src/index.js
@@ -369,6 +369,9 @@ function ncc (
                 module: 'esnext',
                 target: 'esnext',
                 ...fullTsconfig.compilerOptions,
+                // ncc bundles the root project and its dependencies as one compilation.
+                // Disable composite's implicit rootDir so referenced sources are included.
+                composite: false,
                 allowSyntheticDefaultImports: true,
                 noEmit: false,
                 outDir: '//'
diff --git a/test/unit.test.js b/test/unit.test.js
index e01ca242a..07720192d 100644
--- a/test/unit.test.js
+++ b/test/unit.test.js
@@ -26,11 +26,13 @@ for (const unitTest of fs.readdirSync(`${__dirname}/unit`)) {
       opts = JSON.parse(opts);
     } catch (_) {}
 
-    // set env variable so tsconfig-paths can find the config
-    process.env.TS_NODE_PROJECT = `${testDir}/tsconfig.json`;
     // find the name of the input file (e.g input.ts)
-    const inputFile = fs.readdirSync(testDir).find(file => file.includes("input"));
-    await ncc(`${testDir}/${inputFile}`, Object.assign({
+    const rootInput = fs.readdirSync(testDir).find(file => file.includes("input"));
+    const inputDir = rootInput ? testDir : `${testDir}/app`;
+    const inputFile = rootInput || fs.readdirSync(inputDir).find(file => file.includes("input"));
+    // set env variable so tsconfig-paths can find the config
+    process.env.TS_NODE_PROJECT = `${inputDir}/tsconfig.json`;
+    await ncc(`${inputDir}/${inputFile}`, Object.assign({
       assetBuilds: true,
       transpileOnly: true,
       customEmit (path) {
diff --git a/test/unit/ts-project-references/app/input.ts b/test/unit/ts-project-references/app/input.ts
new file mode 100644
index 000000000..20a97dc70
--- /dev/null
+++ b/test/unit/ts-project-references/app/input.ts
@@ -0,0 +1,3 @@
+import { hello } from '../lib/index';
+
+console.log(hello());
diff --git a/test/unit/ts-project-references/app/tsconfig.json b/test/unit/ts-project-references/app/tsconfig.json
new file mode 100644
index 000000000..8ca9a2ef8
--- /dev/null
+++ b/test/unit/ts-project-references/app/tsconfig.json
@@ -0,0 +1,12 @@
+{
+  "compilerOptions": {
+    "composite": true,
+    "outDir": "dist"
+  },
+  "include": ["input.ts"],
+  "references": [
+    {
+      "path": "../lib"
+    }
+  ]
+}
diff --git a/test/unit/ts-project-references/lib/index.ts b/test/unit/ts-project-references/lib/index.ts
new file mode 100644
index 000000000..64884ae96
--- /dev/null
+++ b/test/unit/ts-project-references/lib/index.ts
@@ -0,0 +1,3 @@
+export function hello() {
+  return 'Hello, World!';
+}
diff --git a/test/unit/ts-project-references/lib/tsconfig.json b/test/unit/ts-project-references/lib/tsconfig.json
new file mode 100644
index 000000000..679a56a61
--- /dev/null
+++ b/test/unit/ts-project-references/lib/tsconfig.json
@@ -0,0 +1,6 @@
+{
+  "compilerOptions": {
+    "composite": true,
+    "outDir": "dist"
+  }
+}
diff --git a/test/unit/ts-project-references/opt.json b/test/unit/ts-project-references/opt.json
new file mode 100644
index 000000000..548f583b4
--- /dev/null
+++ b/test/unit/ts-project-references/opt.json
@@ -0,0 +1,4 @@
+{
+  "cache": false,
+  "transpileOnly": false
+}
diff --git a/test/unit/ts-project-references/output-coverage.js b/test/unit/ts-project-references/output-coverage.js
new file mode 100644
index 000000000..113adba41
--- /dev/null
+++ b/test/unit/ts-project-references/output-coverage.js
@@ -0,0 +1,21 @@
+/******/ (() => { // webpackBootstrap
+/******/ 	"use strict";
+/******/ 	/* webpack/runtime/compat */
+/******/ 	
+/******/ 	if (typeof __nccwpck_require__ !== 'undefined') __nccwpck_require__.ab = __dirname + "/";
+/******/ 	
+/************************************************************************/
+var __webpack_exports__ = {};
+
+;// CONCATENATED MODULE: ./test/unit/ts-project-references/lib/index.ts
+function hello() {
+    return 'Hello, World!';
+}
+
+;// CONCATENATED MODULE: ./test/unit/ts-project-references/app/input.ts
+
+console.log(hello());
+
+module.exports = __webpack_exports__;
+/******/ })()
+;
diff --git a/test/unit/ts-project-references/output.js b/test/unit/ts-project-references/output.js
new file mode 100644
index 000000000..113adba41
--- /dev/null
+++ b/test/unit/ts-project-references/output.js
@@ -0,0 +1,21 @@
+/******/ (() => { // webpackBootstrap
+/******/ 	"use strict";
+/******/ 	/* webpack/runtime/compat */
+/******/ 	
+/******/ 	if (typeof __nccwpck_require__ !== 'undefined') __nccwpck_require__.ab = __dirname + "/";
+/******/ 	
+/************************************************************************/
+var __webpack_exports__ = {};
+
+;// CONCATENATED MODULE: ./test/unit/ts-project-references/lib/index.ts
+function hello() {
+    return 'Hello, World!';
+}
+
+;// CONCATENATED MODULE: ./test/unit/ts-project-references/app/input.ts
+
+console.log(hello());
+
+module.exports = __webpack_exports__;
+/******/ })()
+;