withstack.go

// Copyright 2019 The Cockroach Authors.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
// implied. See the License for the specific language governing
// permissions and limitations under the License.

package withstack

import (
	"fmt"

	"github.com/cockroachdb/errors/errbase"
)

// This file mirrors the WithStack functionality from
// github.com/pkg/errors. We would prefer to reuse the withStack
// struct from that package directly (the library recognizes it well)
// unfortunately github.com/pkg/errors does not enable client code to
// customize the depth at which the stack trace is captured.

// WithStack annotates err with a stack trace at the point WithStack was called.
func WithStack(err error) error {
	// Skip the frame of WithStack itself, this mirrors the behavior
	// of WithStack() in github.com/pkg/errors.
	return WithStackDepth(err, 1)
}

// WithStackDepth annotates err with a stack trace starting from the
// given call depth. The value zero identifies the caller
// of WithStackDepth itself.
func WithStackDepth(err error, depth int) error {
	if err == nil {
		return nil
	}
	return &withStack{cause: err, stack: callers(depth + 1)}
}

type withStack struct {
	cause error

	*stack
}

func (w *withStack) Error() string { return w.cause.Error() }
func (w *withStack) Cause() error  { return w.cause }
func (w *withStack) Unwrap() error { return w.cause }

func (w *withStack) Format(s fmt.State, verb rune) {
	switch verb {
	case 'v':
		if s.Flag('+') {
			fmt.Fprintf(s, "%+v", w.Cause())
			fmt.Fprintf(s, "\n-- stack trace:\n")
			w.stack.Format(s, verb)
			return
		}
		fallthrough
	case 's', 'q':
		errbase.FormatError(s, verb, w.cause)
	}
}

func (w *withStack) SafeDetails() []string {
	return []string{fmt.Sprintf("%+v", w.StackTrace())}
}