From 914052aadcc37764030c56b9139482a115146cb4 Mon Sep 17 00:00:00 2001
From: BM Cho <bm1016bm@gmail.com>
Date: Fri, 17 Jul 2026 17:07:36 +0800
Subject: [PATCH] fix: support comments in .nvmrc files

---
 __tests__/main.test.ts   | 29 +++++++++++++++++++++++++++++
 dist/cache-save/index.js | 15 +++++++++++++--
 dist/setup/index.js      | 15 +++++++++++++--
 src/util.ts              | 20 ++++++++++++++++++--
 4 files changed, 73 insertions(+), 6 deletions(-)

diff --git a/__tests__/main.test.ts b/__tests__/main.test.ts
index 382d8b196..4a96d2863 100644
--- a/__tests__/main.test.ts
+++ b/__tests__/main.test.ts
@@ -216,6 +216,35 @@ describe('main tests', () => {
 
       expect(util.getNodeVersionFromFile('file')).toBe(expected);
     });
+
+    each`
+      name                                      | contents                                                       | expected
+      ${'ignores blank lines and comments'}     | ${'# use the version below\n\n  20.16.0 # maintenance release\n'} | ${'20.16.0'}
+      ${'strips an inline comment'}             | ${'v20.16.0 # maintenance release'}                            | ${'20.16.0'}
+      ${'preserves an alias before a comment'}  | ${'lts/* # use the latest LTS'}                                | ${'lts/*'}
+      ${'rejects a comment-only file'}          | ${'# comment only'}                                            | ${null}
+      ${'rejects comments and whitespace only'} | ${'#\r\n  # another comment\r\n'}                            | ${null}
+    `.it('$name', ({contents, expected}: any) => {
+      const existsSpy = jest.spyOn(fs, 'existsSync');
+      existsSpy.mockImplementation(() => true);
+
+      const readFileSpy = jest.spyOn(fs, 'readFileSync');
+      readFileSpy.mockImplementation(() => contents);
+
+      expect(util.getNodeVersionFromFile('.nvmrc')).toBe(expected);
+    });
+
+    it('preserves .tool-versions parsing', () => {
+      const existsSpy = jest.spyOn(fs, 'existsSync');
+      existsSpy.mockImplementation(() => true);
+
+      const readFileSpy = jest.spyOn(fs, 'readFileSync');
+      readFileSpy.mockImplementation(
+        () => 'ruby 3.3.0\nnodejs 20.16.0\npython 3.12.0'
+      );
+
+      expect(util.getNodeVersionFromFile('.tool-versions')).toBe('20.16.0');
+    });
   });
 
   describe('printEnvDetailsAndSetOutput', () => {
diff --git a/dist/cache-save/index.js b/dist/cache-save/index.js
index 49820c5df..8852f9d1b 100644
--- a/dist/cache-save/index.js
+++ b/dist/cache-save/index.js
@@ -92709,8 +92709,19 @@ function getNodeVersionFromFile(versionFilePath) {
     catch {
         core.info('Node version file is not JSON file');
     }
-    const found = contents.match(/^(?:node(js)?\s+)?v?(?<version>[^\s]+)$/m);
-    return found?.groups?.version ?? contents.trim();
+    let versionFileContents = contents;
+    if (path.basename(versionFilePath) === '.nvmrc') {
+        versionFileContents = contents
+            .split(/\r?\n/)
+            .map(line => line.replace(/#.*/, '').trim())
+            .filter(Boolean)
+            .join('\n');
+        if (!versionFileContents) {
+            return null;
+        }
+    }
+    const found = versionFileContents.match(/^(?:node(js)?\s+)?v?(?<version>[^\s]+)$/m);
+    return found?.groups?.version ?? versionFileContents.trim();
 }
 async function printEnvDetailsAndSetOutput() {
     core.startGroup('Environment details');
diff --git a/dist/setup/index.js b/dist/setup/index.js
index 105c3a9cf..8eec56b67 100644
--- a/dist/setup/index.js
+++ b/dist/setup/index.js
@@ -98103,8 +98103,19 @@ function getNodeVersionFromFile(versionFilePath) {
     catch {
         core_info('Node version file is not JSON file');
     }
-    const found = contents.match(/^(?:node(js)?\s+)?v?(?<version>[^\s]+)$/m);
-    return found?.groups?.version ?? contents.trim();
+    let versionFileContents = contents;
+    if (external_path_default().basename(versionFilePath) === '.nvmrc') {
+        versionFileContents = contents
+            .split(/\r?\n/)
+            .map(line => line.replace(/#.*/, '').trim())
+            .filter(Boolean)
+            .join('\n');
+        if (!versionFileContents) {
+            return null;
+        }
+    }
+    const found = versionFileContents.match(/^(?:node(js)?\s+)?v?(?<version>[^\s]+)$/m);
+    return found?.groups?.version ?? versionFileContents.trim();
 }
 async function printEnvDetailsAndSetOutput() {
     startGroup('Environment details');
diff --git a/src/util.ts b/src/util.ts
index 1663a4064..8186d1fb1 100644
--- a/src/util.ts
+++ b/src/util.ts
@@ -68,8 +68,24 @@ export function getNodeVersionFromFile(versionFilePath: string): string | null {
     core.info('Node version file is not JSON file');
   }
 
-  const found = contents.match(/^(?:node(js)?\s+)?v?(?<version>[^\s]+)$/m);
-  return found?.groups?.version ?? contents.trim();
+  let versionFileContents = contents;
+
+  if (path.basename(versionFilePath) === '.nvmrc') {
+    versionFileContents = contents
+      .split(/\r?\n/)
+      .map(line => line.replace(/#.*/, '').trim())
+      .filter(Boolean)
+      .join('\n');
+
+    if (!versionFileContents) {
+      return null;
+    }
+  }
+
+  const found = versionFileContents.match(
+    /^(?:node(js)?\s+)?v?(?<version>[^\s]+)$/m
+  );
+  return found?.groups?.version ?? versionFileContents.trim();
 }
 
 export async function printEnvDetailsAndSetOutput() {