[Performance] Memoize isWsl result

This change memoizes the result of the `isWsl` function in `@shopify/cli-kit`.
Since `isWsl` involves a dynamic import and potential filesystem checks,
memoizing the promise ensures that these operations are only performed once
per process. This is particularly beneficial in high-frequency paths like
analytics collection.

A `_resetIsWsl` function is also provided for test isolation.
Added regression tests in `system.test.ts`.

Author: gonzaloriestra

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

@@ -393,3 +393,32 @@ describe('readStdinString', () => {
     await expect(got).rejects.toThrow('Stdin input exceeded the maximum allowed size.')
   })
 })
+
+describe('isWsl', () => {
+  test('memoizes the result', async () => {
+    // Given
+    // We need to use the real isWsl but since it's already exported from system.js
+    // we can check if it returns the same promise.
+
+    // When
+    const promise1 = system.isWsl()
+    const promise2 = system.isWsl()
+
+    // Then
+    expect(promise1).toBe(promise2)
+    await promise1
+  })
+
+  test('can be reset', async () => {
+    // Given
+    const promise1 = system.isWsl()
+
+    // When
+    ;(system as any)._resetIsWsl()
+    const promise2 = system.isWsl()
+
+    // Then
+    expect(promise1).not.toBe(promise2)
+    await Promise.all([promise1, promise2])
+  })
+})

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

@@ -354,14 +354,29 @@ export function isCI(): boolean {
   return isTruthy(process.env.CI)
 }
 
+/**
+ * Memoized value 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> {
+  return (memoizedIsWsl ??= (async () => {
+    const wsl = await import('is-wsl')
+    return wsl.default
+  })())
+}
+
+/**
+ * Resets the memoized value of isWsl.
+ * This is only used for testing.
+ */
+export function _resetIsWsl() {
+  memoizedIsWsl = undefined
 }
 
 /**