Foundry-ZKsync zksolc Support Policy

[dutterbutter]

To provide clarity and a consistent user experience, we are introducing a formal policy for zksolc version support within Foundry-ZKsync. This policy is designed to address issues related to backward compatibility, unexpected behaviour, and user confusion when using unsupported or deprecated versions of zksolc alongside foundry-zksync.

Background

Historically, Foundry-ZKsync has informally supported only the latest release of zksolc. While this approach ensures that users benefit from the most recent features and fixes, it can lead to breaking changes for earlier versions. For instance, changes in compiler outputs or fields across zksolc versions have highlighted the potential for breaking changes. Such instances underscore the importance of a clear and structured version support policy.

Policy Overview

Supported Versions

• Foundry-ZKsync will officially support zksolc starting from v1.5.6.
  • v1.5.6 serves as a baseline since it maintains structural compatibility.
  • Support will also extend to v1.5.7 and upcoming versions, which include post-compile-time linkage support.
  • Note: v1.5.9 is explicitly not supported due to a change where AssemblyCreate was introduced as an ErrorType rather than a WarningType, leading to potential compatibility and usability issues. Users are strongly advised to use v1.5.11 or later, which resolves this behaviour.

Deprecation Policy

• Backward compatibility will be maintained for supported versions (v1.5.6 and later) unless compelling reasons necessitate deprecation (e.g., critical security vulnerabilities or obsolete functionality).
• Earlier versions (v1.5.5 and below or zksolc = 1.5.9) will not be supported. Compilation will fail if these versions are explicitly specified.

Behaviour for Unsupported Versions

• Explicitly Specified Versions: If a user specifies an unsupported zksolc version (e.g., zksolc = 1.5.5) directly in their configuration, compilation will fail with a clear error message.
• Hardcoded Paths: If a hardcoded binary is detected with an unsupported version (e.g., zksolc = "path/to/zksolc-v1.5.5"), Foundry will emit a warning rather than failing outright. This allows users to make informed decisions while minimizing disruptions.

By defining this policy, we aim to enhance the stability and predictability of Foundry-ZKsync development while accommodating the evolving needs of the ecosystem. Feedback and contributions from the community are welcome as we implement and refine this policy.

Relevant links:

• Define and apply a zksolc version support policy. matter-labs/foundry-zksync#759
• feat: implement compiler backwards compatibility policy matter-labs/foundry-zksync#843
• Foundry-ZKsync book
• zksolc release logs