[Performance] Memoize isWsl

packages/cli-kit/src/public/node/system.test.ts

@@ -1,6 +1,6 @@
 import * as system from './system.js'
 import {execa} from 'execa'
-import {describe, expect, test, vi} from 'vitest'
+import {describe, expect, test, vi, beforeEach} from 'vitest'
 import which from 'which'
 import {Readable} from 'stream'
 
@@ -353,6 +353,38 @@ describe('isStdinPiped', () => {
   })
 })
 
+describe('isWsl', () => {
+  beforeEach(() => {
+    system._resetIsWsl()
+  })
+
+  test('returns the value from is-wsl', async () => {
+    // Given
+    vi.doMock('is-wsl', () => ({
+      default: true,
+    }))
+
+    // When
+    const got = await system.isWsl()
+
+    // Then
+    expect(got).toBe(true)
+  })
+
+  test('memoizes the result', async () => {
+    // Given
+    const isWslModule = await import('is-wsl')
+    const spy = vi.spyOn(isWslModule, 'default', 'get').mockReturnValue(true)
+
+    // When
+    await system.isWsl()
+    await system.isWsl()
+
+    // Then
+    expect(spy).toHaveBeenCalledTimes(1)
+  })
+})
+
 describe('readStdinString', () => {
   test('returns undefined when stdin is not piped', async () => {
     // Given

packages/cli-kit/src/public/node/system.ts

@@ -354,14 +354,29 @@ export function isCI(): boolean {
   return isTruthy(process.env.CI)
 }
 
+/**
+ * Memoized promise for the WSL check.
+ */
+let memoizedIsWsl: Promise<boolean> | undefined
+
 /**
  * Check if the current environment is a WSL environment.
  *
  * @returns True if the current environment is a WSL environment.
  */
-export async function isWsl(): Promise<boolean> {
-  const wsl = await import('is-wsl')
-  return wsl.default
+export function isWsl(): Promise<boolean> {
+  memoizedIsWsl ??= (async () => {
+    const wsl = await import('is-wsl')
+    return wsl.default
+  })()
+  return memoizedIsWsl
+}
+
+/**
+ * Resets the memoized WSL check.
+ */
+export function _resetIsWsl(): void {
+  memoizedIsWsl = undefined
 }
 
 /**