Create touch and getBootTime utility functions

Change-type: patch

src/lib/fs-utils.ts

@@ -3,6 +3,7 @@ import { promises as fs } from 'fs';
 import * as path from 'path';
 import { exec as execSync } from 'child_process';
 import { promisify } from 'util';
+import { uptime } from 'os';
 
 import * as constants from './constants';
 
@@ -82,3 +83,26 @@ export async function unlinkAll(...paths: string[]): Promise<void> {
 export function getPathOnHost(...paths: string[]): string[] {
 	return paths.map((p: string) => path.join(constants.rootMountPoint, p));
 }
+
+/**
+ * Change modification and access time of the given file.
+ * It creates an empty file if it does not exist
+ */
+export const touch = (file: string, time = new Date()) =>
+	// set both access time and modified time to the value passed
+	// as argument (default to `now`)
+	fs.utimes(file, time, time).catch((e) =>
+		// only create the file if it doesn't exist,
+		// if some other error happens is probably better to not touch it
+		e.code === 'ENOENT'
+			? fs
+					.open(file, 'w')
+					.then((fd) => fd.close())
+					// If date is custom we need to change the file atime and mtime
+					.then(() => fs.utimes(file, time, time))
+			: e,
+	);
+
+// Get the system boot time as a Date object
+export const getBootTime = () =>
+	new Date(new Date().getTime() - uptime() * 1000);

test/src/lib/fs-utils.spec.ts

@@ -15,8 +15,14 @@ describe('lib/fs-utils', () => {
 
 	const mockFs = () => {
 		mock({
-			[testFile1]: 'foo',
-			[testFile2]: 'bar',
+			[testFile1]: mock.file({
+				content: 'foo',
+				mtime: new Date('2022-01-04T00:00:00'),
+			}),
+			[testFile2]: mock.file({
+				content: 'bar',
+				mtime: new Date('2022-01-04T00:00:00'),
+			}),
 		});
 	};
 
@@ -154,4 +160,41 @@ describe('lib/fs-utils', () => {
 			).to.deep.equal([testFile1, testFile2]);
 		});
 	});
+
+	describe('touch', () => {
+		beforeEach(mockFs);
+		afterEach(unmockFs);
+
+		it('creates the file if it does not exist', async () => {
+			await fsUtils.touch('somefile');
+			expect(await fsUtils.exists('somefile')).to.be.true;
+		});
+
+		it('updates the file mtime if file already exists', async () => {
+			const statsBefore = await fs.stat(testFile1);
+			await fsUtils.touch(testFile1);
+			const statsAfter = await fs.stat(testFile1);
+
+			// Mtime should be different
+			expect(statsAfter.mtime.getTime()).to.not.equal(
+				statsBefore.mtime.getTime(),
+			);
+		});
+
+		it('allows setting a custom time for existing files', async () => {
+			const customTime = new Date('1981-11-24T12:00:00');
+			await fsUtils.touch(testFile1, customTime);
+			const statsAfter = await fs.stat(testFile1);
+
+			expect(statsAfter.mtime.getTime()).to.be.equal(customTime.getTime());
+		});
+
+		it('allows setting a custom time for newly created files', async () => {
+			const customTime = new Date('1981-11-24T12:00:00');
+			await fsUtils.touch('somefile', customTime);
+			const statsAfter = await fs.stat('somefile');
+
+			expect(statsAfter.mtime.getTime()).to.be.equal(customTime.getTime());
+		});
+	});
 });