IO

Represents a capability to perform I/O operations. The capability should be part of the signature of any method, which either performs I/O operations, or calls other methods which perform I/O operations. For example:

 def readFromFile(path: String)(using IO): String = ...
 def writeToFile(path: String, content: String)(using IO): Unit = ...
 def transform(path: String)(f: String => String)(using IO): Unit =
   writeToFile(path, f(readFromFile(path)))

The capability can be introduced using IO.unsafe or by import ox.IO.globalForTesting.given.

Take care not to capture the capability e.g. using constructors (unless you are sure such usage is safe), as this might circumvent the tracking of I/O operations. Similarly, the capability might be captured by lambdas, which might later be used when the IO capability is not in scope. In future Scala and Ox releases, these problems should be detected at compile-time using the upcoming capture checker.