Avoid Public Dependency Coupling

RUST-AVOID-PUBLIC-DEPENDENCY-COUPLING

Summary

Keep dependency types out of public APIs unless interoperability is the purpose. This preserves semver freedom and avoids forcing downstream users onto implementation choices.

Rule

Avoid leaking dependency types in public APIs unless integration is the point.

Why

Public APIs that expose dependency types force downstream users to care about that dependency version, feature set, and semantics. Leak those types only when integration with the dependency is the point of the API, not as an implementation convenience.

Helps

Helps preserve semver freedom by keeping implementation dependencies from becoming downstream compile-time, feature, and version requirements.

Limits

Expose dependency types when interoperability is the purpose, such as adapters, trait integrations, ecosystem standard types, or APIs explicitly built around that dependency.

Agent Instruction

Avoid leaking dependency types in public APIs unless integration is the point; exposed dependency
types make downstream users care about that dependency's version, features, and semantics.

Mechanisms

Use local wrapper types, conversion traits, feature-gated integration modules, borrowed standard types, or private dependency types behind stable public contracts.