V02 Compare contract versions

Use your current course session. Preparation and course runner · R script ↓

Optional deep dive. Enable only the options named in each block, after preparing its packages or services.

V02a Add descriptive metadata

Goal: Document ownership and grain.

Prerequisites: H04; extras.

Descriptive metadata does not enforce access control or approval policies.

training_step(
  "V02a",
  {
    owned_contract <- policy_contract |>
      dr_contract_meta(
        owner = "Risk Analytics",
        description = "Synthetic training policies",
        grain = "One policy"
      )
    print(owned_contract)
  },
  needs = c("H04"),
  enabled = training_options$extras,
  optional = TRUE
)

Expected result: Owner and grain are documented.

Task: Does owner grant read access?

V02b Choose a validation policy

Goal: Allow extra columns deliberately.

Prerequisites: V02a.

Contract policy should be explicit, rather than hidden in transformations.

training_step(
  "V02b",
  {
    flexible_contract <- owned_contract |>
      dr_contract_policy(allow_extra = TRUE)
    print(flexible_contract$allow_extra)
  },
  needs = c("V02a"),
  enabled = training_options$extras,
  optional = TRUE
)

Expected result: Additional columns are allowed; declared keys remain binding.

Task: Should every delivery use this policy?

V02 Compare contract versions

Goal: Review a change before using it.

Prerequisites: V02b.

A new version makes the revision explicit. A diff may require review instead of declaring every change compatible.

training_step(
  "V02",
  {
    contract_v2 <- dr_contract_update(
      owned_contract,
      version = "2.0.0",
      columns = c(channel = "character")
    )
    print(dr_contract_diff(owned_contract, contract_v2))
    stopifnot(!"channel" %in% names(owned_contract$columns))
  },
  needs = c("V02b"),
  enabled = training_options$extras,
  optional = TRUE
)

Expected result: The diff shows the change; the old contract is unchanged.

Task: Is a newly added column automatically required?