Errorf

Errorf is a common naming convention for a function that constructs an error value by formatting a message. It is widely used in programming libraries to produce descriptive, human-readable error text that can be propagated up call stacks.

In the Go programming language, a representative example is the function fmt.Errorf. This function takes a format string along with a variadic list of arguments and returns a value that implements the error interface. The formatted message is created according to the standard formatting rules, with verbs like %s, %d, and others. Since Go 1.13, fmt.Errorf can also wrap an existing error using the %w verb, enabling error unwrapping with errors.Is and errors.As. For instance, a call like fmt.Errorf("operation failed: %w", err) attaches the original error while producing a new, descriptive message.

Errorf-style functions are used to create errors at points of failure, to add context to existing errors, and to propagate errors through layers of a program. They help produce consistent and actionable messages, often including both a high-level description and the underlying cause.

Outside of Go, other languages and libraries may provide similarly named helpers that format messages before returning an error object or exception. While the exact syntax varies, the underlying idea remains the same: generate informative, formatted error messages that aid debugging and error handling.

See also: error interface, error wrapping, error handling patterns.