[macro] How likely TypeScript will consider adding macro in the future

[Bistard]

Suggestion

I believe the team of TypeScript definitely has considered related topics about macro in the past. Since we do not have macro right now in TypeScript, there must be some concerns or flaws about macro. I am actually kind of curious and want to know a few reasons why not having macro today.

I can guess a few points so far:

1. It is against the design idea of TypeScript just like enum because it changes the actual behaviour.
2. It is hard to do type-checking while using macro.
3. macro used across different JavaScript files can resolve weird type-checking behaviours.

I personally wish to have macro to increase readability while writing TypeScript.

🔍 Search Terms

macro

✅ Viability Checklist

My suggestion meets these guidelines:

• This wouldn't be a breaking change in existing TypeScript/JavaScript code
• This wouldn't change the runtime behavior of existing JavaScript code
• This could be implemented without emitting different JS based on the types of the expressions
• This isn't a runtime feature (e.g. library functionality, non-ECMAScript syntax with JavaScript output, new syntax sugar for JS, etc.)
• This feature would agree with the rest of TypeScript's Design Goals.

📃 Motivating Example

TBD

💻 Use Cases

TBD

[jcalz]

Polo?

[xiBread]

Assuming you mean macro, then #4892.

[fatcerberus]

I initially assumed this is about macros too, but the phrasing is... very odd.

related topics about Marco
concerns ... about Marco
having Marco
using Marco
I personally wish to have Marco

Given the commitment to this odd phrasing (and conspicuous capitalization of Marco) in an otherwise well-written issue, I'm left to ask either or both of these questions:

1. Who is Marco?
2. Is this a joke?

[Bistard]

I initially assumed this is about macros too, but the phrasing is... very odd.

related topics about Marco
concerns ... about Marco
having Marco
using Marco
I personally wish to have Marco

Given the commitment to this odd phrasing in an otherwise well-written issue, I'm left to ask either or both of these questions:

1. Who is Marco?
2. Is this a joke?

nah, I just typed everything wrong. Didn't mean't Macro Poll.

[fatcerberus]

Macro Poll

Okay, now you're just doing it on purpose. 😉

[fatcerberus]

This isn't a runtime feature (e.g. library functionality, non-ECMAScript syntax with JavaScript output, new syntax sugar for JS, etc.)

I think macros probably fall under "non-ECMAScript syntax with JavaScript output", but I'm not positive. It does seem like a bit of a gray area w.r.t. the TS design goals.

[Bistard]

Assuming you mean macro, then #4892.

Thanks for sharing (just realized the reason I didn't find related issues on macros is that I typed it as marcos). I read through the issue and found some related topics or comments on this one:

• inline function support Feature request: inline function #661
• comment 1 - Feature Request: Macros #4892 (comment)
• comment 2 - Feature Request: Macros #4892 (comment)
• existing plugin - https://github.com/LeDDGroup/typescript-transform-macros

After reading through the above issue still haven't found any positive or negative responses from the team 😭 I guess this proposal is already been refused a long time ago.

[MartinJohns]

I'm confused. You correctly identified

It is against the design idea of TypeScript

but then you check

[x] This feature would agree with the rest of TypeScript's Design Goals.

in the viability checklist.

---

Besides that, I find it highly unlikely to expect anything like this in the next 5 years, if ever.

[RyanCavanaugh]

The most likely outcome, by a very large margin, is that macros are not happening. We've looked into this in the past and it doesn't seem like there's any tractable path that doesn't violate critical design constraints. If you macro with existing syntax (like how C's preprocessor works), there's a violation of the "all JS is TS" principle, plus it's super weird (what happens if you indirect a macro function?). If you macro with novel syntax, then there's a problem of how you even parse a file, especially in contexts like tooling where you expect to be able to open a TS file and get reasonable behavior without knowing the entire project context.

[alshdavid]

#60645