Feature request: String.format with specifiers

[PaulRBerg]

Console logging supports format specifiers like %s and %d.

It would be helpful to have something similar for formatting strings, e.g. equivalent to Java's String.format.

As per #2313, I gather that the format specifier logic is implemented in Rust, not Solidity. But I went ahead and created this issue because I think it's a highly desirable feature, especially for use cases like NFT SVGs.

[mds1]

IIUC this seems like a cheatcode that should be implemented in foundry, so transferring this issue, but let me know if I misunderstood

[PaulRBerg]

Nah, I was referring to a pure Solidity implementation of format specifiers, meant to be used in production.

Of course, I imagine that this would be difficult to implement.

[mds1]

Production-level solidity string formatting is out of scope for forge-std since it's a development-focused repo. However, solady is being audited soon and it has a lot of string manipulation utils, so you may be able to get something like this in there then have it audited. I'll leave this open in the foundry repo since this still seems like it could be useful as a cheatcode

[zerosnacks]

Related: #6891

Could be extended to support format

[leovct]

Is this still needed? If so, I can work on that.

cc @grandizzy @zerosnacks

[grandizzy]

@leovct yes, that would be a nice addition

[leovct]

I know it's been a while, I was quite busy at work. I implemented a first tiny version, can you guys check if this is what you're expecting? cc @grandizzy @zerosnacks

[zerosnacks]

Hey @leovct, not a problem! I think this is in line with what @mds1 is proposing. One concern I have it the amount of functions there would be to sufficiently cover every case, see: https://github.com/foundry-rs/forge-std/blob/master/src/console.sol

[leovct]

Hey @leovct, not a problem! I think this is in line with what @mds1 is proposing. One concern I have it the amount of functions there would be to sufficiently cover every case, see: https://github.com/foundry-rs/forge-std/blob/master/src/console.sol

That's also a concern I have, it will require a lot of code to implement such feature. I'm not a rust expert but maybe using macros seems like a better approach to reduce code duplication?

[zerosnacks]

cc @DaniPopes do you see a clever macro trick we could do here w/ cheatcodes to avoid polluting the concise Vm.sol interface for a relatively niche feature?

[DaniPopes]

I would prefer a similar approach to console, where the full exposed API is in a separate library and Vm provides a formatRaw(string spec, string ty, bytes data), with ty + data = Vec<DynSolValue> to mimic variadics; it could even be used as "...".format() with using-for.