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mops check-candid

Check Candid interface compatibility between two Candid files

mops check-candid <new-candid> <original-candid>

Verifies that a new Candid interface is compatible with an original interface. Compatibility means that clients using the original interface will continue to work with the new interface.

Examples​

Check if a new interface is compatible with the original

mops check-candid ./build/backend.did ./src/backend.did

Arguments​

<new-candid>​

Path to the new Candid interface file (the candidate interface to validate).

<original-candid>​

Path to the original Candid interface file (the baseline for compatibility).

Compatibility Rules​

Compatible changes:

  • Add new optional fields to records
  • Add new variant options
  • Make function parameters optional
  • Add new methods
  • Extend return types

Breaking changes:

  • Remove fields from records
  • Remove variant options
  • Change field types incompatibly
  • Remove methods
  • Make optional parameters required
info

The mops build command automatically runs Candid compatibility checks when a candid field is specified in the canister configuration.