zip.md

CancellableTaskValidation.zip

Namespace: FsToolkit.ErrorHandling

Function Signature:

CancellableTaskValidation<'left, 'error>
  -> CancellableTaskValidation<'right, 'error>
  -> CancellableTaskValidation<'left * 'right, 'error>

Takes two CancellableTaskValidation values, runs them serially (left then right), and returns a tuple of the results. Errors from both computations are accumulated — if both return Error, all errors are collected into a single list.

Unlike parallelZip, computations run one after the other.

Examples

Example 1

Combining two validation results into a tuple:

let validateUserAndRole (userId: UserId) : CancellableTaskValidation<User * Role, string> =
    CancellableTaskValidation.zip
        (fetchAndValidateUser userId)
        (fetchAndValidateRole userId)

Example 2

Using zip inside a larger computation expression:

let buildProfile (userId: UserId) : CancellableTaskValidation<UserProfile, string> =
    cancellableTaskValidation {
        let! user, preferences =
            CancellableTaskValidation.zip
                (fetchUser userId)
                (fetchPreferences userId)
        return UserProfile.create user preferences
    }

Example 3

Accumulating errors from two independent validations:

let validateForm (form: SignupForm) : CancellableTaskValidation<ValidEmail * ValidUsername, string> =
    CancellableTaskValidation.zip
        (validateEmail form.Email)     // e.g. Error ["Invalid email format"]
        (validateUsername form.Username) // e.g. Error ["Username too short"]
    // If both fail, result is Error ["Invalid email format"; "Username too short"]