builder/amazon: Add helper function for checking against AWSError

Replace all straight forward occurrences of `if err, ok := err.(awserr.Error)` with the `isAWSErr` helper function

builder/amazon/common/access_config.go

@@ -11,7 +11,6 @@ import (
 	"strings"
 
 	"github.com/aws/aws-sdk-go/aws"
-	"github.com/aws/aws-sdk-go/aws/awserr"
 	"github.com/aws/aws-sdk-go/aws/credentials"
 	"github.com/aws/aws-sdk-go/aws/session"
 	"github.com/aws/aws-sdk-go/service/ec2"
@@ -181,15 +180,17 @@ func (c *AccessConfig) Session() (*session.Session, error) {
 	c.session = sess
 
 	cp, err := c.session.Config.Credentials.Get()
+
+	if isAWSErr(err, "NoCredentialProviders", "") {
+		return nil, fmt.Errorf("No valid credential sources found for AWS Builder. " +
+			"Please see https://www.packer.io/docs/builders/amazon.html#specifying-amazon-credentials " +
+			"for more information on providing credentials for the AWS Builder.")
+	}
+
 	if err != nil {
-		if awsErr, ok := err.(awserr.Error); ok && awsErr.Code() == "NoCredentialProviders" {
-			return nil, fmt.Errorf("No valid credential sources found for AWS Builder. " +
-				"Please see https://www.packer.io/docs/builders/amazon.html#specifying-amazon-credentials " +
-				"for more information on providing credentials for the AWS Builder.")
-		} else {
-			return nil, fmt.Errorf("Error loading credentials for AWS Provider: %s", err)
-		}
+		return nil, fmt.Errorf("Error loading credentials for AWS Provider: %s", err)
 	}
+
 	log.Printf("[INFO] AWS Auth provider used: %q", cp.ProviderName)
 
 	if c.DecodeAuthZMessages {

builder/amazon/common/helper_funcs.go

@@ -3,11 +3,14 @@ package common
 import (
 	"fmt"
 	"log"
+	"strings"
 
 	"github.com/aws/aws-sdk-go/aws"
+	"github.com/aws/aws-sdk-go/aws/awserr"
 	"github.com/aws/aws-sdk-go/service/ec2"
 )
 
+// DestroyAMIs deregisters the AWS machine images in imageids from an active AWS account
 func DestroyAMIs(imageids []*string, ec2conn *ec2.EC2) error {
 	resp, err := ec2conn.DescribeImages(&ec2.DescribeImagesInput{
 		ImageIds: imageids,
@@ -47,3 +50,14 @@ func DestroyAMIs(imageids []*string, ec2conn *ec2.EC2) error {
 	}
 	return nil
 }
+
+// Returns true if the error matches all these conditions:
+//  * err is of type awserr.Error
+//  * Error.Code() matches code
+//  * Error.Message() contains message
+func isAWSErr(err error, code string, message string) bool {
+	if err, ok := err.(awserr.Error); ok {
+		return err.Code() == code && strings.Contains(err.Message(), message)
+	}
+	return false
+}

builder/amazon/common/step_create_tags.go

@@ -6,7 +6,6 @@ import (
 	"time"
 
 	"github.com/aws/aws-sdk-go/aws"
-	"github.com/aws/aws-sdk-go/aws/awserr"
 	"github.com/aws/aws-sdk-go/aws/session"
 	"github.com/aws/aws-sdk-go/service/ec2"
 	"github.com/hashicorp/packer/common/retry"
@@ -91,17 +90,12 @@ func (s *StepCreateTags) Run(ctx context.Context, state multistep.StateBag) mult
 		snapshotTags.Report(ui)
 
 		// Retry creating tags for about 2.5 minutes
-		err = retry.Config{
-			Tries: 11,
-			ShouldRetry: func(error) bool {
-				if awsErr, ok := err.(awserr.Error); ok {
-					switch awsErr.Code() {
-					case "InvalidAMIID.NotFound", "InvalidSnapshot.NotFound":
-						return true
-					}
-				}
-				return false
-			},
+		err = retry.Config{Tries: 11, ShouldRetry: func(error) bool {
+			if isAWSErr(err, "InvalidAMIID.NotFound", "") || isAWSErr(err, "InvalidSnapshot.NotFound", "") {
+				return true
+			}
+			return false
+		},
 			RetryDelay: (&retry.Backoff{InitialBackoff: 200 * time.Millisecond, MaxBackoff: 30 * time.Second, Multiplier: 2}).Linear,
 		}.Run(ctx, func(ctx context.Context) error {
 			// Tag images and snapshots

builder/amazon/common/step_pre_validate.go

@@ -7,7 +7,6 @@ import (
 	"time"
 
 	"github.com/aws/aws-sdk-go/aws"
-	"github.com/aws/aws-sdk-go/aws/awserr"
 	"github.com/aws/aws-sdk-go/service/ec2"
 	"github.com/hashicorp/packer/common/retry"
 	"github.com/hashicorp/packer/helper/multistep"
@@ -36,7 +35,7 @@ func (s *StepPreValidate) Run(ctx context.Context, state multistep.StateBag) mul
 			err := retry.Config{
 				Tries: 11,
 				ShouldRetry: func(err error) bool {
-					if awsErr, ok := err.(awserr.Error); ok && awsErr.Code() == "AuthFailure" {
+					if isAWSErr(err, "AuthFailure", "") {
 						log.Printf("Waiting for Vault-generated AWS credentials" +
 							" to pass authentication... trying again.")
 						return true

builder/amazon/common/step_run_source_instance.go

@@ -9,7 +9,6 @@ import (
 	"time"
 
 	"github.com/aws/aws-sdk-go/aws"
-	"github.com/aws/aws-sdk-go/aws/awserr"
 	"github.com/aws/aws-sdk-go/service/ec2"
 
 	"github.com/hashicorp/packer/common/retry"
@@ -207,17 +206,12 @@ func (s *StepRunSourceInstance) Run(ctx context.Context, state multistep.StateBa
 	// will fail. Retry a couple of times to try to mitigate that race.
 
 	var r *ec2.DescribeInstancesOutput
-	err = retry.Config{
-		Tries: 11,
-		ShouldRetry: func(err error) bool {
-			if awsErr, ok := err.(awserr.Error); ok {
-				switch awsErr.Code() {
-				case "InvalidInstanceID.NotFound":
-					return true
-				}
-			}
-			return false
-		},
+	err = retry.Config{Tries: 11, ShouldRetry: func(err error) bool {
+		if isAWSErr(err, "InvalidInstanceID.NotFound", "") {
+			return true
+		}
+		return false
+	},
 		RetryDelay: (&retry.Backoff{InitialBackoff: 200 * time.Millisecond, MaxBackoff: 30 * time.Second, Multiplier: 2}).Linear,
 	}.Run(ctx, func(ctx context.Context) error {
 		r, err = ec2conn.DescribeInstances(describeInstance)
@@ -254,17 +248,12 @@ func (s *StepRunSourceInstance) Run(ctx context.Context, state multistep.StateBa
 	if s.IsRestricted {
 		ec2Tags.Report(ui)
 		// Retry creating tags for about 2.5 minutes
-		err = retry.Config{
-			Tries: 11,
-			ShouldRetry: func(error) bool {
-				if awsErr, ok := err.(awserr.Error); ok {
-					switch awsErr.Code() {
-					case "InvalidInstanceID.NotFound":
-						return true
-					}
-				}
-				return false
-			},
+		err = retry.Config{Tries: 11, ShouldRetry: func(error) bool {
+			if isAWSErr(err, "InvalidInstanceID.NotFound", "") {
+				return true
+			}
+			return false
+		},
 			RetryDelay: (&retry.Backoff{InitialBackoff: 200 * time.Millisecond, MaxBackoff: 30 * time.Second, Multiplier: 2}).Linear,
 		}.Run(ctx, func(ctx context.Context) error {
 			_, err := ec2conn.CreateTags(&ec2.CreateTagsInput{

builder/amazon/common/step_run_spot_instance.go

@@ -9,7 +9,6 @@ import (
 	"time"
 
 	"github.com/aws/aws-sdk-go/aws"
-	"github.com/aws/aws-sdk-go/aws/awserr"
 	"github.com/aws/aws-sdk-go/service/ec2"
 	"github.com/hashicorp/packer/common/random"
 	"github.com/hashicorp/packer/common/retry"
@@ -353,17 +352,12 @@ func (s *StepRunSpotInstance) Run(ctx context.Context, state multistep.StateBag)
 	}
 
 	// Retry creating tags for about 2.5 minutes
-	err = retry.Config{
-		Tries: 11,
-		ShouldRetry: func(error) bool {
-			if awsErr, ok := err.(awserr.Error); ok {
-				switch awsErr.Code() {
-				case "InvalidInstanceID.NotFound":
-					return true
-				}
-			}
-			return false
-		},
+	err = retry.Config{Tries: 11, ShouldRetry: func(error) bool {
+		if isAWSErr(err, "InvalidInstanceID.NotFound", "") {
+			return true
+		}
+		return false
+	},
 		RetryDelay: (&retry.Backoff{InitialBackoff: 200 * time.Millisecond, MaxBackoff: 30 * time.Second, Multiplier: 2}).Linear,
 	}.Run(ctx, func(ctx context.Context) error {
 		_, err := ec2conn.CreateTags(&ec2.CreateTagsInput{

builder/amazon/common/step_stop_ebs_instance.go

@@ -5,7 +5,6 @@ import (
 	"fmt"
 	"time"
 
-	"github.com/aws/aws-sdk-go/aws/awserr"
 	"github.com/aws/aws-sdk-go/service/ec2"
 	"github.com/hashicorp/packer/common/retry"
 	"github.com/hashicorp/packer/helper/multistep"
@@ -41,17 +40,12 @@ func (s *StepStopEBSBackedInstance) Run(ctx context.Context, state multistep.Sta
 		// does not exist.
 
 		// Work around this by retrying a few times, up to about 5 minutes.
-		err := retry.Config{
-			Tries: 6,
-			ShouldRetry: func(error) bool {
-				if awsErr, ok := err.(awserr.Error); ok {
-					switch awsErr.Code() {
-					case "InvalidInstanceID.NotFound":
-						return true
-					}
-				}
-				return false
-			},
+		err := retry.Config{Tries: 6, ShouldRetry: func(error) bool {
+			if isAWSErr(err, "InvalidInstanceID.NotFound", "") {
+				return true
+			}
+			return false
+		},
 			RetryDelay: (&retry.Backoff{InitialBackoff: 10 * time.Second, MaxBackoff: 60 * time.Second, Multiplier: 2}).Linear,
 		}.Run(ctx, func(ctx context.Context) error {
 			ui.Message(fmt.Sprintf("Stopping instance"))