Create a simple Errors struct to replace multierror

This creates a simple Errors struct that implements error to aggregate multiple errors as a single error.  This simplifies the dependency structure of this otherwise nearly leaf package.

Fixes: #205

estargz/build.go

@@ -36,7 +36,6 @@ import (
 	"strings"
 	"sync"
 
-	"github.com/hashicorp/go-multierror"
 	digest "github.com/opencontainers/go-digest"
 	"github.com/pkg/errors"
 	"golang.org/x/sync/errgroup"
@@ -431,19 +430,20 @@ func (tf *tempFiles) TempFile(dir, pattern string) (*os.File, error) {
 	return f, nil
 }
 
-func (tf *tempFiles) CleanupAll() (allErr error) {
+func (tf *tempFiles) CleanupAll() error {
 	tf.filesMu.Lock()
 	defer tf.filesMu.Unlock()
+	var allErr *Errors
 	for _, f := range tf.files {
 		if err := f.Close(); err != nil {
-			allErr = multierror.Append(allErr, err)
+			allErr = allErr.Append(err)
 		}
 		if err := os.Remove(f.Name()); err != nil {
-			allErr = multierror.Append(allErr, err)
+			allErr = allErr.Append(err)
 		}
 	}
 	tf.files = nil
-	return nil
+	return allErr
 }
 
 func newCountReader(r io.ReaderAt) (*countReader, error) {

estargz/errors.go

@@ -0,0 +1,46 @@
+/*
+   Copyright The containerd 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 estargz
+
+import (
+	"fmt"
+	"strings"
+)
+
+// Errors provides an abstraction for accumulating multiple errors.
+type Errors []error
+
+// Append adds an error to the Errors
+func (e *Errors) Append(err error) *Errors {
+	if e == nil {
+		return &Errors{err}
+	}
+	errs := append(*e, err)
+	return &errs
+}
+
+// Error implements error
+func (e *Errors) Error() string {
+	points := make([]string, len(*e)+1)
+	points[0] = fmt.Sprintf("%d error(s) occurred:", len(*e))
+	for i, err := range *e {
+		points[i+1] = fmt.Sprintf("* %s", err)
+	}
+	return strings.Join(points, "\n\t")
+}
+
+var _ error = (*Errors)(nil)

estargz/errors_test.go

@@ -0,0 +1,48 @@
+/*
+   Copyright The containerd 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 estargz
+
+import (
+	"testing"
+
+	"github.com/pkg/errors"
+)
+
+func TestErrors(t *testing.T) {
+	var err0 *Errors
+
+	err1 := err0.Append(errors.New("foo"))
+	err2 := err1.Append(errors.New("bar"))
+	err3 := err2.Append(errors.New("baz"))
+
+	want := `3 error(s) occurred:
+	* foo
+	* bar
+	* baz`
+
+	if got := err3.Error(); want != got {
+		t.Errorf("Error() = %v, wanted %v", got, want)
+	}
+
+	want = `2 error(s) occurred:
+	* foo
+	* bar`
+
+	if got := err2.Error(); want != got {
+		t.Errorf("Error() = %v, wanted %v", got, want)
+	}
+}

estargz/estargz.go

@@ -42,7 +42,6 @@ import (
 	"sync"
 	"time"
 
-	"github.com/hashicorp/go-multierror"
 	digest "github.com/opencontainers/go-digest"
 	"github.com/pkg/errors"
 )
@@ -739,11 +738,13 @@ func footerBytes(tocOff int64) []byte {
 }
 
 func parseFooter(p []byte) (tocOffset int64, footerSize int64, rErr error) {
+	var allErr *Errors
+
 	tocOffset, err := parseEStargzFooter(p)
 	if err == nil {
 		return tocOffset, FooterSize, nil
 	}
-	rErr = multierror.Append(rErr, err)
+	allErr = allErr.Append(err)
 
 	pad := len(p) - legacyFooterSize
 	if pad < 0 {
@@ -753,8 +754,7 @@ func parseFooter(p []byte) (tocOffset int64, footerSize int64, rErr error) {
 	if err == nil {
 		return tocOffset, legacyFooterSize, nil
 	}
-	rErr = multierror.Append(rErr, err)
-	return
+	return 0, 0, allErr.Append(err)
 }
 
 func parseEStargzFooter(p []byte) (tocOffset int64, err error) {

estargz/go.mod

@@ -3,7 +3,6 @@ module github.com/containerd/stargz-snapshotter/estargz
 go 1.13
 
 require (
-	github.com/hashicorp/go-multierror v1.1.0
 	github.com/opencontainers/go-digest v1.0.0
 	github.com/pkg/errors v0.9.1
 	golang.org/x/sync v0.0.0-20201207232520-09787c993a3a

estargz/go.sum

@@ -1,7 +1,3 @@
-github.com/hashicorp/errwrap v1.0.0 h1:hLrqtEDnRye3+sgx6z4qVLNuviH3MR5aQ0ykNJa/UYA=
-github.com/hashicorp/errwrap v1.0.0/go.mod h1:YH+1FKiLXxHSkmPseP+kNlulaMuP3n2brvKWEqk/Jc4=
-github.com/hashicorp/go-multierror v1.1.0 h1:B9UzwGQJehnUY1yNrnwREHc3fGbC2xefo8g4TbElacI=
-github.com/hashicorp/go-multierror v1.1.0/go.mod h1:spPvp8C1qA32ftKqdAHm4hHTbPw+vmowP0z+KUhOZdA=
 github.com/opencontainers/go-digest v1.0.0 h1:apOUWs51W5PlhuyGyz9FCeeBIOUDA/6nW8Oi/yOhh5U=
 github.com/opencontainers/go-digest v1.0.0/go.mod h1:0JzlMkj0TRzQZfJkVvzbP0HBR3IKzErnv2BNG4W4MAM=
 github.com/pkg/errors v0.9.1 h1:FEBLx1zS214owpjy7qsBeixbURkuhQAwrK5UwLGTwt4=