mirror of https://github.com/tailscale/tailscale/
util/multierr: new package
github.com/go-multierror/multierror served us well. But we need a few feature from it (implement Is), and it's not worth maintaining a fork of such a small module. Instead, I did a clean room implementation inspired by its API. Signed-off-by: Josh Bleecher Snyder <josh@tailscale.com>pull/3140/head
Josh Bleecher Snyder
3 years ago
committed by
Josh Bleecher Snyder
parent
17b5782b3a
commit
3fd5f4380f
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// Copyright (c) 2021 Tailscale Inc & AUTHORS All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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// Package multierr provides a simple multiple-error type.
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// It was inspired by github.com/go-multierror/multierror.
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package multierr
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import (
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"errors"
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"strings"
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)
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// An Error represents multiple errors.
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type Error struct {
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errs []error
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}
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// Error implements the error interface.
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func (e Error) Error() string {
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s := new(strings.Builder)
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s.WriteString("multiple errors:")
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for _, err := range e.errs {
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s.WriteString("\n\t")
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s.WriteString(err.Error())
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}
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return s.String()
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}
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// Errors returns a slice containing all errors in e.
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func (e Error) Errors() []error {
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return append(e.errs[:0:0], e.errs...)
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}
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// New returns an error composed from errs.
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// Some errors in errs get special treatment:
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// * nil errors are discarded
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// * errors of type Error are expanded into the top level
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// If the resulting slice has length 0, New returns nil.
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// If the resulting slice has length 1, New returns that error.
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// If the resulting slice has length > 1, New returns that slice as an Error.
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func New(errs ...error) error {
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dst := make([]error, 0, len(errs))
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for _, e := range errs {
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switch e := e.(type) {
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case nil:
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continue
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case Error:
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dst = append(dst, e.errs...)
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default:
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dst = append(dst, e)
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}
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}
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// dst has been filtered and splatted.
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switch len(dst) {
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case 0:
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return nil
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case 1:
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return dst[0]
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}
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// Zero any remaining elements of dst left over from errs, for GC.
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tail := dst[len(dst):cap(dst)]
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for i := range tail {
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tail[i] = nil
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}
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return Error{errs: dst}
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}
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// Is reports whether any error in e matches target.
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func (e Error) Is(target error) bool {
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for _, err := range e.errs {
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if errors.Is(err, target) {
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return true
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}
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}
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return false
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}
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// As finds the first error in e that matches target, and if any is found,
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// sets target to that error value and returns true. Otherwise, it returns false.
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func (e Error) As(target interface{}) bool {
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for _, err := range e.errs {
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if ok := errors.As(err, target); ok {
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return true
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}
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}
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return false
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}
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@ -0,0 +1,80 @@
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// Copyright (c) 2021 Tailscale Inc & AUTHORS All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package multierr_test
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import (
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"errors"
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"testing"
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qt "github.com/frankban/quicktest"
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"github.com/google/go-cmp/cmp/cmpopts"
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"tailscale.com/util/multierr"
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)
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func TestAll(t *testing.T) {
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C := qt.New(t)
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eqErr := qt.CmpEquals(cmpopts.EquateErrors())
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type E = []error
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N := multierr.New
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a := errors.New("a")
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b := errors.New("b")
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c := errors.New("c")
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d := errors.New("d")
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x := errors.New("x")
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abcd := E{a, b, c, d}
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tests := []struct {
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In E // input to New
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WantNil bool // want nil returned?
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WantSingle error // if non-nil, want this single error returned
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WantErrors []error // if non-nil, want an Error composed of these errors returned
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}{
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{In: nil, WantNil: true},
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{In: E{nil}, WantNil: true},
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{In: E{nil, nil}, WantNil: true},
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{In: E{a}, WantSingle: a},
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{In: E{a, nil}, WantSingle: a},
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{In: E{nil, a}, WantSingle: a},
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{In: E{nil, a, nil}, WantSingle: a},
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{In: E{a, b}, WantErrors: E{a, b}},
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{In: E{nil, a, nil, b, nil}, WantErrors: E{a, b}},
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{In: E{a, b, N(c, d)}, WantErrors: E{a, b, c, d}},
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{In: E{a, N(b, c), d}, WantErrors: E{a, b, c, d}},
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{In: E{N(a, b), c, d}, WantErrors: E{a, b, c, d}},
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{In: E{N(a, b), N(c, d)}, WantErrors: E{a, b, c, d}},
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{In: E{nil, N(a, nil, b), nil, N(c, d)}, WantErrors: E{a, b, c, d}},
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{In: E{N(a, N(b, N(c, N(d))))}, WantErrors: E{a, b, c, d}},
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{In: E{N(N(N(N(a), b), c), d)}, WantErrors: E{a, b, c, d}},
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{In: E{N(abcd...)}, WantErrors: E{a, b, c, d}},
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{In: E{N(abcd...), N(abcd...)}, WantErrors: E{a, b, c, d, a, b, c, d}},
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}
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for _, test := range tests {
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got := multierr.New(test.In...)
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if test.WantNil {
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C.Assert(got, qt.IsNil)
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continue
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}
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if test.WantSingle != nil {
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C.Assert(got, eqErr, test.WantSingle)
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continue
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}
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ee, _ := got.(multierr.Error)
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C.Assert(ee.Errors(), eqErr, test.WantErrors)
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for _, e := range test.WantErrors {
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C.Assert(ee.Is(e), qt.IsTrue)
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}
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C.Assert(ee.Is(x), qt.IsFalse)
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}
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}
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