Memorize shell documentation lookup

Every onHover or completion result takes ~10 ms to look up on a new Macbook. Let us save those CPU cycles for something better.

Author: skovhus

server/src/util/__tests__/sh.test.ts

@@ -491,3 +491,24 @@ BSD                             April 12, 2003                             BSD`)
     ).toMatchSnapshot()
   })
 })
+
+describe('memorize', () => {
+  it('memorizes a function', async () => {
+    const fnRaw = jest.fn(async args => args)
+    const arg1 = { one: '1' }
+    const arg2 = { another: { word: 'word' } }
+    const fnMemorized = sh.memorize(fnRaw)
+
+    const arg1CallResult1 = await fnMemorized(arg1)
+    const arg1CallResult2 = await fnMemorized(arg1)
+
+    const arg2CallResult1 = await fnMemorized(arg2)
+    const arg2CallResult2 = await fnMemorized(arg2)
+
+    expect(fnRaw).toHaveBeenCalledTimes(2)
+    expect(fnRaw).toHaveBeenCalledWith(arg2)
+
+    expect(arg1CallResult1).toBe(arg1CallResult2)
+    expect(arg2CallResult1).toBe(arg2CallResult2)
+  })
+})

server/src/util/sh.ts

@@ -27,7 +27,7 @@ export function execShellScript(body: string): Promise<string> {
 /**
  * Get documentation for the given word by usingZZ help and man.
  */
-export async function getShellDocumentation({
+export async function getShellDocumentationWithoutCache({
   word,
 }: {
   word: string
@@ -84,3 +84,27 @@ export function formatManOutput(manOutput: string): string {
 
   return formattedManOutput
 }
+
+/**
+ * Only works for one-parameter (serializable) functions.
+ */
+export function memorize<T extends Function>(func: T): T {
+  const cache = new Map()
+
+  const returnFunc = async function(arg: any) {
+    const cacheKey = JSON.stringify(arg)
+
+    if (cache.has(cacheKey)) {
+      return cache.get(cacheKey)
+    }
+
+    const result = await func(arg)
+
+    cache.set(cacheKey, result)
+    return result
+  }
+
+  return returnFunc as any
+}
+
+export const getShellDocumentation = memorize(getShellDocumentationWithoutCache)