Bug: forge flatten does not account for as keyword in imports

[transmissions11]

Component

Forge

Have you ensured that all of these are up to date?

• Foundry
• Foundryup

What version of Foundry are you on?

latest

What command(s) is the bug in?

forge flatten

Operating System

macOS (M1)

Describe the bug

the as keyword, used to remap imports like

import {FixedPointMath as Math} from "..."

Math.mul()

is ignored by forge flatten, which just indiscriminately pastes FixedPointMath in and fails to rename/alias it to Math

this results in the output of forge flatten failing to compile because the compiler does not know what Math is if FixedPointMath is not alias'd/renamed, while the input could be a perfectly valid contract like above

[mattsse]

@rkrasiuk perhaps we're using the offset of the wrong identifier?

[rkrasiuk]

@mattsse so i've fixed parsing aliases using solang and our regex fallback. now the only question is how do we want to proceed with fixing the aliases in the flattened file. both renaming import target to the alias and renaming the alias back to the original import name have the edge cases that break the flattened file.
i.e. if we chose to rename the import target

// FixedPointMath.sol
library FixedPointMath { }

// Calculator1.sol
import {FixedPointMath as Math} from "./FixedPointMath.sol";

Math.mul();

// Calculator2.sol
import {FixedPointMath} from "./FixedPointMath.sol";

FixedPointMath.mul(); // this is where it would break

[mattsse]

hmm, this not ideal but not really solvable until we have proper formatting.
But I think this limitation is negligible and would even highlight inconsistent import pattern.
so perhaps the right approach for now is to simply resolve the alias. and replace Math with FixedPointMath in the node's content?
wdyt?

[rkrasiuk]

sgtm, just want to make sure that these edge cases are acknowledged. so, you suggest replacing the alias with the original import name, not the other way around, right?

[mattsse]

sgtm, just want to make sure that these edge cases are acknowledged. so, you suggest replacing the alias with the original import name, not the other way around, right?

can we replace per node or only once we've flattened everything?

the other way around would include renaming the library as well, right?

I'd think replacing the more verbose lib name with the alias could be more accurate but I don't think we should rename the library.

so, I'd say let's replace alias Math with actual name FixedPointMath.

[rkrasiuk]

we can replace per node, the only caveat is identifying correctly the token to replace. we either regex it on flattening or traverse the solang result and store information about various tokens used inside every file

[mattsse]

I think regexing should be sufficient :)

[mattsse]

closed by gakonst/ethers-rs#1192