klubok_gleam

Do notation pipes for functions which easy to mock
Inspired by fp-ts/Effect bind Do-notation, but much more small and simple
Primarly created for easy mocking of functions, which allows to write tons of unit tests

gleam add klubok_gleam

import gleam/option.{None, Some}
import gleam/set
import klubok_gleam.{use_klubok2, eff}

type Cat {
  Cat(name: String, age: Int)
}

fn cat_birthday(mock, only) {
  // Make this function pipable
  // Need to use correct arity by count of `eff` usage, 2 in this example
  use <- use_klubok2(mock, only)

  // This function mockable
  use cat <- eff(fn() {
    // some IO implementation which fetching cat
    Cat("Barsik", 5)
  })

  // This function mockable
  use aged_cat <- eff(fn() { Cat(..cat, age: cat.age + 1) })

  aged_cat
}

pub fn main() {
  // Pass Option.None to mock and only
  // Should be used on production code
  cat_birthday(None, None) // Cat("Barsik", 6)

  // Mock first `eff` with another hardcoded cat
  // Should be used in unit tests
  cat_birthday(#(fn() { Cat("Marfa", 10) } |> Some, None) |> Some, None) // Cat("Marfa", 11)

  // Call only second `eff` and first IO ignored
  // Also our birthday fn is mocked and our cat is kiten again
  //❗`only` is type unsafe and can lead to runtime errors when `Nil` passed instead of actual `eff` value
  cat_birthday(
    #(None, fn() { Cat("Barsik", 1) } |> Some) |> Some,
    set.from_list([1]) |> Some
  ) // Cat("Barsik", 1)
}

Further documentation can be found at https://hexdocs.pm/klubok_gleam.

Development

gleam run   # Run the project
gleam test  # Run the tests

See also

• Klubok - TS implementation of Klubok