failure v2

[morikuni]

Please check docs/v1-to-v2.md for migration.
If there were something unclear or found issues, feel free to open issue or contact me on X https://twitter.com/inukirom.

What's New

Remarkable changes with v2.

Simple error chain structure

v2 has only one struct to wrap errors rather than wrapping errors for each wrapper struct.

In v1 error chain structure was like

withCode {
    code,
    withMessage {
        message,
        withCallStack {
            callstack,
            err,
        },
    },
}

But in v2 error chain structure will be like

Failure {
    fields {
        KeyCode: code,
        KeyMessage: message,
        KeyCallStack: callstack,
    },
    Failure {
        fields {
            KeyCallStack: callstack,
        },
        err,
    },
}

So no longer need wrapping too much times for each additional data.
You can simply add any key-value data in failure.

Arbitrary error code type

v1 had been requested Code interface for error codes:

type Code interface {
	// ErrorCode returns an error code in string representation.
	ErrorCode() string
}

But now, any comparable types can be used as error code in v2:

type Code comparable

So, you can use gRPC error code google.golang.org/grpc/codes with failure!

failure.New(codes.InvalidArgument)