Switch to go-multierror

It seems there are 4 locations left that use the `helper/multierror`
package, where the rest is TF settled on the `hashicorp/go-multierror`
package.

Functionally this doesn’t change anything, so I suggest to delete the
builtin version as it can only cause confusion (both packages have the
same name, but are still different types according to Go’s type system.

builtin/providers/aws/config.go

@@ -5,7 +5,7 @@ import (
 	"log"
 	"strings"
 
-	"github.com/hashicorp/terraform/helper/multierror"
+	"github.com/hashicorp/go-multierror"
 
 	"github.com/aws/aws-sdk-go/aws"
 	"github.com/aws/aws-sdk-go/aws/awserr"

builtin/providers/aws/resource_aws_db_security_group.go

@@ -9,8 +9,8 @@ import (
 	"github.com/aws/aws-sdk-go/aws"
 	"github.com/aws/aws-sdk-go/aws/awserr"
 	"github.com/aws/aws-sdk-go/service/rds"
+	"github.com/hashicorp/go-multierror"
 	"github.com/hashicorp/terraform/helper/hashcode"
-	"github.com/hashicorp/terraform/helper/multierror"
 	"github.com/hashicorp/terraform/helper/resource"
 	"github.com/hashicorp/terraform/helper/schema"
 )

builtin/providers/heroku/resource_heroku_app.go

@@ -5,7 +5,7 @@ import (
 	"log"
 
 	"github.com/cyberdelia/heroku-go/v3"
-	"github.com/hashicorp/terraform/helper/multierror"
+	"github.com/hashicorp/go-multierror"
 	"github.com/hashicorp/terraform/helper/schema"
 )
 

config/config.go

@@ -8,10 +8,10 @@ import (
 	"strconv"
 	"strings"
 
+	"github.com/hashicorp/go-multierror"
 	"github.com/hashicorp/terraform/config/lang"
 	"github.com/hashicorp/terraform/config/lang/ast"
 	"github.com/hashicorp/terraform/flatmap"
-	"github.com/hashicorp/terraform/helper/multierror"
 	"github.com/mitchellh/mapstructure"
 	"github.com/mitchellh/reflectwalk"
 )

helper/multierror/error.go

@@ -1,54 +0,0 @@
-package multierror
-
-import (
-	"fmt"
-	"strings"
-)
-
-// Error is an error type to track multiple errors. This is used to
-// accumulate errors in cases such as configuration parsing, and returning
-// them as a single error.
-type Error struct {
-	Errors []error
-}
-
-func (e *Error) Error() string {
-	points := make([]string, len(e.Errors))
-	for i, err := range e.Errors {
-		points[i] = fmt.Sprintf("* %s", err)
-	}
-
-	return fmt.Sprintf(
-		"%d error(s) occurred:\n\n%s",
-		len(e.Errors), strings.Join(points, "\n"))
-}
-
-func (e *Error) GoString() string {
-	return fmt.Sprintf("*%#v", *e)
-}
-
-// ErrorAppend is a helper function that will append more errors
-// onto an Error in order to create a larger multi-error. If the
-// original error is not an Error, it will be turned into one.
-func ErrorAppend(err error, errs ...error) *Error {
-	if err == nil {
-		err = new(Error)
-	}
-
-	switch err := err.(type) {
-	case *Error:
-		if err == nil {
-			err = new(Error)
-		}
-
-		err.Errors = append(err.Errors, errs...)
-		return err
-	default:
-		newErrs := make([]error, len(errs)+1)
-		newErrs[0] = err
-		copy(newErrs[1:], errs)
-		return &Error{
-			Errors: newErrs,
-		}
-	}
-}

helper/multierror/error_test.go

@@ -1,56 +0,0 @@
-package multierror
-
-import (
-	"errors"
-	"testing"
-)
-
-func TestError_Impl(t *testing.T) {
-	var raw interface{}
-	raw = &Error{}
-	if _, ok := raw.(error); !ok {
-		t.Fatal("Error must implement error")
-	}
-}
-
-func TestErrorError(t *testing.T) {
-	expected := `2 error(s) occurred:
-
-* foo
-* bar`
-
-	errors := []error{
-		errors.New("foo"),
-		errors.New("bar"),
-	}
-
-	multi := &Error{errors}
-	if multi.Error() != expected {
-		t.Fatalf("bad: %s", multi.Error())
-	}
-}
-
-func TestErrorAppend_Error(t *testing.T) {
-	original := &Error{
-		Errors: []error{errors.New("foo")},
-	}
-
-	result := ErrorAppend(original, errors.New("bar"))
-	if len(result.Errors) != 2 {
-		t.Fatalf("wrong len: %d", len(result.Errors))
-	}
-
-	original = &Error{}
-	result = ErrorAppend(original, errors.New("bar"))
-	if len(result.Errors) != 1 {
-		t.Fatalf("wrong len: %d", len(result.Errors))
-	}
-}
-
-func TestErrorAppend_NonError(t *testing.T) {
-	original := errors.New("foo")
-	result := ErrorAppend(original, errors.New("bar"))
-	if len(result.Errors) != 2 {
-		t.Fatalf("wrong len: %d", len(result.Errors))
-	}
-}