40% CPU and Gigs of memory used parsing a map

[mjbvz]

From @bootstraponline on November 23, 2017 1:25

• VSCode Version: 1.18.1
• OS Version: Windows 10 Version 1709 (OS Build 16299.19)

Steps to Reproduce:

1. git clone https://github.com/bootstraponline/hex.git
2. git checkout dbf422b1856d054b01bd28193ca52ed9c4033ceb
3. Open hex/ts/ in Visual Studio Code
4. Change anything in the TypeScript files
5. Observe gigs of memory used.

Reproduces without extensions: Yes

• codes.ts

I have a large map. That appears to make TypeScript crazy. I'm not sure if there's a way to disable processing on a per file basis. This issue does not happen when using JSON instead of a map.

export let codes = new Map([
   ['03310001', ['Potion', 'Battle Items [0]', true]],
   // ...
]);

Copied from original issue: microsoft/vscode#38993

[mjbvz]

From @KuromiAK on November 26, 2017 0:28

Change the code in this way seems to help?

export let codes = new Map<string, [string, string, boolean]>([
   ['03310001', ['Potion', 'Battle Items [0]', true]],
   // ...
]);

[mjbvz]

From @bootstraponline on November 26, 2017 3:9

This helped the most. I'm not sure what causes gigs of memory usage. Maybe giant arrays in the constructor is an edge case.

// Use map to preserve iteration order. Object.keys is undefined
export let codes: Map<string, [string, string, boolean]> = new Map();
export function initCodes() {
  if (codes.size > 0) { return; }

  codes.set('03310001', ['Potion', 'Battle Items [0]', true]);
  codes.set('74500001', ['Power Ex', 'Battle Items [0]', true]);
  
...

[mjbvz]

I confirmed that the TS Server process has the high cpu usage. The server logs don't have any helpful info