remove usage of github.com/hashicorp/go-multierror

The internal replacement is a simpler implementation which only supports enough
functionality for the places where github.com/hashicorp/go-multierror was used
before.

Not depending on github.com/hashicorp/go-multierror and thus
github.com/hashicorp/errwrap makes it easier to use CDI in Kubernetes because
we don't need to add those other dependencies.

Signed-off-by: Patrick Ohly <[email protected]>

go.mod

@@ -4,7 +4,6 @@ go 1.17
 
 require (
 	github.com/fsnotify/fsnotify v1.5.1
-	github.com/hashicorp/go-multierror v1.1.1
 	github.com/opencontainers/runc v1.1.2
 	github.com/opencontainers/runtime-spec v1.0.3-0.20210326190908-1c3f411f0417
 	github.com/opencontainers/runtime-tools v0.0.0-20190417131837-cd1349b7c47e
@@ -21,6 +20,7 @@ require (
 	github.com/blang/semver v3.5.1+incompatible // indirect
 	github.com/davecgh/go-spew v1.1.1 // indirect
 	github.com/hashicorp/errwrap v1.0.0 // indirect
+	github.com/hashicorp/go-multierror v1.1.1 // indirect
 	github.com/inconshreveable/mousetrap v1.0.0 // indirect
 	github.com/opencontainers/selinux v1.10.0 // indirect
 	github.com/pmezard/go-difflib v1.0.0 // indirect

internal/multierror/multierror.go

@@ -0,0 +1,84 @@
+/*
+   Copyright © 2022 The CDI 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 multierror
+
+import (
+	"strings"
+)
+
+// New combines several errors into a single error. Parameters that are nil are
+// ignored. If no errors are passed in or all parameters are nil, then the
+// result is also nil.
+func New(errors ...error) error {
+	// Filter out nil entries.
+	numErrors := 0
+	for _, err := range errors {
+		if err != nil {
+			errors[numErrors] = err
+			numErrors++
+		}
+	}
+	if numErrors == 0 {
+		return nil
+	}
+	return multiError(errors[0:numErrors])
+}
+
+// multiError is the underlying implementation used by New. It can be instantiated
+// directly to get access to the Append method or to cast a plain slice of
+// errors to get a single error.
+//
+// Beware that a null multiError is not the same as a nil error.
+type multiError []error
+
+// multiError returns all individual error strings concatenated with "\n"
+func (e multiError) Error() string {
+	var builder strings.Builder
+	for i, err := range e {
+		if i > 0 {
+			_, _ = builder.WriteString("\n")
+		}
+		_, _ = builder.WriteString(err.Error())
+	}
+	return builder.String()
+}
+
+// Append returns a new multi error all errors concatenated. Errors that are
+// multi errors get flattened, nil is ignored.
+func Append(err error, errors ...error) error {
+	var result multiError
+	if m, ok := err.(multiError); ok {
+		result = m
+	} else if err != nil {
+		result = append(result, err)
+	}
+
+	for _, e := range errors {
+		if e == nil {
+			continue
+		}
+		if m, ok := e.(multiError); ok {
+			result = append(result, m...)
+		} else {
+			result = append(result, e)
+		}
+	}
+	if len(result) == 0 {
+		return nil
+	}
+	return result
+}

internal/multierror/multierror_test.go

@@ -0,0 +1,38 @@
+/*
+   Copyright © 2022 The CDI 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 multierror
+
+import (
+	"testing"
+	"errors"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestNew(t *testing.T) {
+	assert.Equal(t, nil, New())
+	assert.Equal(t, nil, New(nil))
+	assert.Equal(t, "hello\nworld", New(errors.New("hello"), errors.New("world")).Error())
+}
+
+func TestAppend(t *testing.T) {
+	assert.Equal(t, nil, Append(nil))
+	assert.Equal(t, nil, Append(nil, nil))
+	assert.Equal(t, multiError{errors.New("hello"), errors.New("world"), errors.New("x"), errors.New("y")},
+		Append(New(errors.New("hello"), errors.New("world")), New(errors.New("x"), errors.New("y"))))
+
+}

pkg/cdi/cache.go

@@ -26,9 +26,9 @@ import (
 
 	stderr "errors"
 
+	"github.com/container-orchestrated-devices/container-device-interface/internal/multierror"
 	cdi "github.com/container-orchestrated-devices/container-device-interface/specs-go"
 	"github.com/fsnotify/fsnotify"
-	"github.com/hashicorp/go-multierror"
 	oci "github.com/opencontainers/runtime-spec/specs-go"
 	"github.com/pkg/errors"
 )
@@ -127,8 +127,8 @@ func (c *Cache) Refresh() error {
 
 	// collect and return cached errors, much like refresh() does it
 	var result error
-	for _, err := range c.errors {
-		result = multierror.Append(result, err...)
+	for _, errors := range c.errors {
+		result = multierror.Append(result, errors...)
 	}
 	return result
 }
@@ -198,11 +198,7 @@ func (c *Cache) refresh() error {
 	c.devices = devices
 	c.errors = specErrors
 
-	if len(result) > 0 {
-		return multierror.Append(nil, result...)
-	}
-
-	return nil
+	return multierror.New(result...)
 }
 
 // RefreshIfRequired triggers a refresh if necessary.

schema/schema.go

@@ -25,10 +25,11 @@ import (
 	"net/http"
 	"path/filepath"
 	"strings"
+	"fmt"
 
 	"sigs.k8s.io/yaml"
 
-	"github.com/hashicorp/go-multierror"
+	"github.com/container-orchestrated-devices/container-device-interface/internal/multierror"
 	"github.com/pkg/errors"
 	schema "github.com/xeipuuv/gojsonschema"
 )
@@ -227,17 +228,17 @@ func (s *Schema) validate(doc schema.JSONLoader) error {
 	return &Error{Result: docErr}
 }
 
-// Error returns the given Result's error as a multierror(.Error()).
+// Error returns the given Result's errors as a single error string.
 func (e *Error) Error() string {
 	if e == nil || e.Result == nil || e.Result.Valid() {
 		return ""
 	}
 
 	var multi error
 	for _, err := range e.Result.Errors() {
-		multi = multierror.Append(multi, errors.Errorf("%v", err))
+		multi = multierror.Append(multi, fmt.Errorf("%v", err))
 	}
-	return strings.TrimRight(multi.Error(), "\n")
+	return multi.Error()
 }
 
 var (