Initial Import

LICENSE

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+Copyright 2022 Caleb Case <calebcase@gmail.com>
+
+Permission is hereby granted, free of charge, to any person obtaining a copy of
+this software and associated documentation files (the "Software"), to deal in
+the Software without restriction, including without limitation the rights to
+use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies
+of the Software, and to permit persons to whom the Software is furnished to do
+so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.

README.md

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+# oops
+
+[![Go Reference](https://pkg.go.dev/badge/github.com/calebcase/oops.svg)](https://pkg.go.dev/github.com/calebcase/oops)
+[![Go Report Card](https://goreportcard.com/badge/github.com/calebcase/oops)](https://goreportcard.com/report/github.com/calebcase/oops)
+
+Oops implements the batteries that are missing from [errors][errors]:
+
+* Stack traces: attach a stack trace to any error
+* Chaining: combining multiple errors into a single stack of errors (as you
+  might want when handling the errors from disposing resources like
+  [file_close][file.Close()])
+* Namespacing: create an error factory that prefixes errors with a given name
+* Shadowing: hide the exact error behind a package level error (as you might
+  want when trying to stabilize your API's supported errors)
+
+---
+
+[errors]: https://pkg.go.dev/errors
+[file_close]: https://pkg.go.dev/os#File.Close

chain.go

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+package oops
+
+import (
+	"fmt"
+	"strings"
+)
+
+// ChainError is a list of errors oldest to newest.
+type ChainError []error
+
+var _ error = ChainError{}
+var _ unwrapper = ChainError{}
+
+func (ce ChainError) Error() string {
+	return fmt.Sprintf("%v", ce)
+}
+
+func (ce ChainError) Unwrap() error {
+	if len(ce) == 0 || len(ce) == 1 {
+		return nil
+	}
+
+	if len(ce) == 2 {
+		return ce[1]
+	}
+
+	return ChainError(ce[1:])
+}
+
+// Format implements fmt.Format.
+func (ce ChainError) Format(f fmt.State, verb rune) {
+	if len(ce) == 0 {
+		return
+	}
+
+	flag := ""
+	if f.Flag(int('+')) {
+		flag = "+"
+	}
+
+	if flag == "" {
+		fmt.Fprintf(f, "%"+string(verb), ce[0])
+
+		return
+	}
+
+	errs := make([]string, 0, len(ce))
+
+	fmt.Fprintf(f, "chain:\n")
+	for i, err := range ce {
+		lines := ErrorIndent(err, "%"+flag+string(verb), "··")
+
+		errs = append(errs, fmt.Sprintf("··[%d] %s", i, lines[0]))
+
+		if len(lines) > 1 {
+			errs = append(errs, lines[1:]...)
+		}
+	}
+
+	f.Write([]byte(strings.Join(errs, "\n")))
+}
+
+// Chain combines errors into a chain of errors. nil errors are removed.
+func Chain(errs ...error) error {
+	if len(errs) == 0 {
+		return nil
+	}
+
+	if len(errs) == 1 {
+		return errs[0]
+	}
+
+	ce := ChainError{}
+
+	for _, err := range errs {
+		if err == nil {
+			continue
+		}
+
+		if peer, ok := err.(ChainError); ok {
+			ce = append(ce, peer...)
+
+			continue
+		}
+
+		ce = append(ce, err)
+	}
+
+	return ce
+}
+
+// ChainP combines errors into a chain of errors. nil errors are removed.
+func ChainP(err *error, errs ...error) {
+	if err == nil {
+		return
+	}
+
+	*err = Chain(append([]error{*err}, errs...)...)
+}

chain_test.go

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+package oops_test
+
+import (
+	"context"
+	"encoding/json"
+	"errors"
+	"testing"
+
+	"github.com/calebcase/oops"
+	"github.com/stretchr/testify/require"
+)
+
+type closer struct {
+	open bool
+}
+
+func open() (*closer, error) {
+	return &closer{true}, nil
+}
+
+func (c *closer) Close(ctx context.Context) error {
+	c.open = false
+
+	return oops.New("close error")
+}
+
+func openclose() (err error) {
+	ctx := context.Background()
+
+	f, err := open()
+	if err != nil {
+		return err
+	}
+	defer func() {
+		err = oops.Chain(err, f.Close(ctx))
+	}()
+
+	return oops.New("openclose error")
+}
+
+func opencloseP() (err error) {
+	ctx := context.Background()
+
+	f, err := open()
+	if err != nil {
+		return err
+	}
+	defer func() {
+		oops.ChainP(&err, f.Close(ctx))
+	}()
+
+	return oops.New("openclose error")
+}
+
+func TestChain(t *testing.T) {
+	t.Run("Chain", func(t *testing.T) {
+		err := openclose()
+		werr := errors.Unwrap(err)
+
+		t.Logf("error: %T\n%+v\n", err, err)
+		require.Error(t, err)
+
+		t.Logf("wrapped error: %T\n%+v\n", werr, werr)
+		require.Error(t, werr)
+
+		bs, jerr := json.MarshalIndent(err, "", "  ")
+		require.NoError(t, jerr)
+		t.Log(string(bs))
+	})
+
+	t.Run("ChainP", func(t *testing.T) {
+		err := opencloseP()
+		werr := errors.Unwrap(err)
+
+		t.Logf("error: %T\n%+v\n", err, err)
+		require.Error(t, err)
+
+		t.Logf("wrapped error: %T\n%+v\n", werr, werr)
+		require.Error(t, werr)
+	})
+}

doc.go

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+// Package oops implements the batteries missing from Package errors.
+package oops

error.go

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+package oops
+
+import (
+	"encoding/json"
+	"fmt"
+	"strings"
+)
+
+// ErrorMarshalJSON uses e's json.Marshaler if it implements one otherwise it
+// uses the output from e.Error() (marshalled into a JSON string).
+func ErrorMarshalJSON(e error) (bs []byte, err error) {
+	if jm, ok := e.(json.Marshaler); ok {
+		bs, err = jm.MarshalJSON()
+	} else {
+		bs, err = json.Marshal(e.Error())
+	}
+
+	if err != nil {
+		return nil, err
+	}
+
+	return bs, nil
+}
+
+// ErrorLines returns the error's string in the given format as an array of
+// lines.
+func ErrorLines(err error, format string) []string {
+	return strings.Split(fmt.Sprintf(format, err), "\n")
+}
+
+// ErrorIndent returns the error's string prefixed by indent. The first line is
+// not indented.
+func ErrorIndent(err error, format, indent string) []string {
+	lines := ErrorLines(err, format)
+	for i, line := range lines {
+		if i == 0 {
+			continue
+		}
+
+		lines[i] = indent + line
+	}
+
+	return lines
+}

go.mod

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+module github.com/calebcase/oops
+
+go 1.19
+
+require github.com/stretchr/testify v1.8.1
+
+require (
+	github.com/davecgh/go-spew v1.1.1 // indirect
+	github.com/pmezard/go-difflib v1.0.0 // indirect
+	gopkg.in/yaml.v3 v3.0.1 // indirect
+)

go.sum

@@ -0,0 +1,17 @@
+github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
+github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
+github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
+github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
+github.com/stretchr/objx v0.4.0/go.mod h1:YvHI0jy2hoMjB+UWwv71VJQ9isScKT/TqJzVSSt89Yw=
+github.com/stretchr/objx v0.5.0/go.mod h1:Yh+to48EsGEfYuaHDzXPcE3xhTkx73EhmCGUpEOglKo=
+github.com/stretchr/testify v1.7.1/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/h/Wwjteg=
+github.com/stretchr/testify v1.8.0/go.mod h1:yNjHg4UonilssWZ8iaSj1OCr/vHnekPRkoO+kdMU+MU=
+github.com/stretchr/testify v1.8.1 h1:w7B6lhMri9wdJUVmEZPGGhZzrYTPvgJArz7wNPgYKsk=
+github.com/stretchr/testify v1.8.1/go.mod h1:w2LPCIKwWwSfY2zedu0+kehJoqGctiVI29o6fzry7u4=
+gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405 h1:yhCVgyC4o1eVCa2tZl7eS0r+SDo693bJlVdllGtEeKM=
+gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
+gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=
+gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=
+gopkg.in/yaml.v3 v3.0.1/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=