ketrab2004-roblox / rbxts-transformer-simpleswitch

Transformer for converting switch cases to simple ifelse blocks so luau can better optimize them

rbxts-transformer-switchcase

Converts switch cases into simple if else blocks, to make it faster and to make it more legible.

Example

Input typescript

let a = 2

switch (a) {
    case 1:
        print("one");
        break;

    case 2:
        print("two");
        break;

    default:
        print("uhh what??");
        break;
}

Output luau without the transformer

local a = 2
repeat
    if a == 1 then
        print("one")
        break
    end
    if a == 2 then
        print("two")
        break
    end
    print("uhh what??")
    break
until true

Output luau with the transformer

local a = 2
-- switch
if a == 1 then
    print("one")
    -- break
elseif a == 2 then
    print("two")
    -- break
else
    print("uhh what??")
    -- break
end

How to use

1. Install by running npm i rbxts-transformer-switchcase --save-dev

2. Add it as a plugin to your tsconfig.json, see options here

   {
       "compilerOptions": {
           ...
           "plugins": [
               {
                   "transform": "rbxts-transformer-switchcase",
                   ...
               }
           ]
       }
   }

3. Try it out

Settings

In the tsconfig.json you can add settings for the plugin.

Example

{
    "compilerOptions": {
        ...
        "plugins": [
            {
                "transform": "rbxts-transformer-switchcase",
                "disableSwitchComments": false,
                "disableBreakComments": true
            }
        ]
    }
}

Identifier	Type	Default	Description
disableSwitchComments	boolean	false	whether or not --switch should be added in front of if statements generated by the transformer
disableBreakComments	boolean	false	whether or not removed break statements should get a --break in their place

Building

Setup

Install dependencies using npm i.

Build the transformer

Run npm run build in the root of the project.

Build the example

Run npm run build in /example.

Run tests

Run npm run test for quick and simple tests and npm run test:fancy for more readable results.

rbxts-transformer-simpleswitch's Issues

No proof that this is faster

In the readme it says that it's faster(?), but there is no proof.

Github action for testing

Make a github action that runs the tests automatically

Test for nested switches fails

No tests for special edge cases

• Nested switches
  • inner switch is missing a break
  • outer switch is missing a break
  • both are missing a break
  • (the above/previous but with more than 2 switches!)
• With invalid code
  • multiple default clauses
  • code after a break statement

Example

Create an example to show how you can use it (and to test if it even works)

Return and continue should also work

Currently

let a = 2;

switch (a) {
    case 1:
        return "one";

    case 2:
        return "two";

    default:
        return "uhhmmm???";
}

doesn't get converted to if else while it should.

• Return and continue should also work
• Create tests for return and continue
• Throw should also work

Ability to hide `switch` comment

Using transformer config,
also option to add comments in the place where removed break statements were.

Test fails

TypeError: Cannot read properties of undefined (reading 'updateJsxExpression') in src/index.test.ts at line 19