forc-node build fails: ethers-contract abigen! macro cannot find ethers crate in Nix sandbox

[JoshuaBatty]

Summary

When building forc-node in the Nix sandbox, the build fails because fuel-core-relayer uses the ethers-contract::abigen! macro, which cannot locate the ethers crate.

Related Issue

This is related to but separate from #196. Issue #196 documents the fuel-core-wasm-executor network access problem. This issue documents a different blocker.

Root Cause

The abigen! macro from ethers-contract uses the proc-macro-crate library to detect crate names at compile time. It generates code with paths like ::ethers::core::types::*. However, fuel-core-relayer only depends on individual ethers sub-crates (ethers-contract, ethers-core, ethers-providers), not the umbrella ethers crate.

In a normal cargo build, proc-macro-crate can read Cargo.toml and detect the sub-crates. But in Nix's sandboxed/vendored build environment, this detection fails, causing compilation errors like:

error[E0433]: failed to resolve: could not find `ethers` in the list of imported crates

This is a known issue with the ethers ecosystem in sandboxed builds:

• chore: merging TokenWithRefunds with Token AztecProtocol/aztec-packages#8042

Attempted Fix

We attempted to fix this by:

1. Adding ethers = { version = "2.0", default-features = false } to the forc workspace
2. Patching Cargo.lock to include ethers and its dependencies
3. Patching the vendored fuel-core-relayer Cargo.toml in preBuild

However, this led to cargo resolution errors looking for ethers-etherscan even with default-features = false, likely due to how cargo resolves features in offline/sandboxed mode.

Potential Solutions

1. Patch fuel-core-relayer upstream to add the umbrella ethers crate as a dependency
2. Vendor a pre-patched version of fuel-core-relayer
3. Use Nix overlays to modify the ethers crate's feature resolution
4. Patch the vendored crates more aggressively during the Nix build

Affects

• forc-node >= 0.70.x (both sway and forc repo versions)