Add JSON validation to the aws_sns_topic resource.

This commit adds support for new helper function which is used to
normalise and validate JSON string.

This commit also removes unnecessary code from the StateFunc function,
and reduces it so that it only uses the normalizeJsonString helper.

Signed-off-by: Krzysztof Wilczynski <krzysztof.wilczynski@linux.com>

builtin/providers/aws/resource_aws_sns_topic.go

@@ -1,19 +1,17 @@
 package aws
 
 import (
-	"bytes"
-	"encoding/json"
 	"fmt"
 	"log"
 	"strings"
 	"time"
 
-	"github.com/hashicorp/terraform/helper/resource"
-	"github.com/hashicorp/terraform/helper/schema"
-
 	"github.com/aws/aws-sdk-go/aws"
 	"github.com/aws/aws-sdk-go/aws/awserr"
 	"github.com/aws/aws-sdk-go/service/sns"
+	"github.com/hashicorp/errwrap"
+	"github.com/hashicorp/terraform/helper/resource"
+	"github.com/hashicorp/terraform/helper/schema"
 )
 
 // Mutable attributes
@@ -49,21 +47,11 @@ func resourceAwsSnsTopic() *schema.Resource {
 				Type:             schema.TypeString,
 				Optional:         true,
 				Computed:         true,
+				ValidateFunc:     validateJsonString,
 				DiffSuppressFunc: suppressEquivalentAwsPolicyDiffs,
 				StateFunc: func(v interface{}) string {
-					s, ok := v.(string)
+					json, _ := normalizeJsonString(v)
-					if !ok || s == "" {
+					return json
-						return ""
-					}
-					jsonb := []byte(s)
-					buffer := new(bytes.Buffer)
-					if err := json.Compact(buffer, jsonb); err != nil {
-						log.Printf("[WARN] Error compacting JSON for Policy in SNS Topic")
-						return ""
-					}
-					value := normalizeJson(buffer.String())
-					log.Printf("[DEBUG] topic policy before save: %s", value)
-					return value
 				},
 			},
 			"delivery_policy": &schema.Schema{
@@ -191,7 +179,10 @@ func resourceAwsSnsTopicRead(d *schema.ResourceData, meta interface{}) error {
 				if resource.Schema[iKey] != nil {
 					var value string
 					if iKey == "policy" {
-						value = normalizeJson(*attrmap[oKey])
+						value, err = normalizeJsonString(*attrmap[oKey])
+						if err != nil {
+							return errwrap.Wrapf("policy contains an invalid JSON: {{err}}", err)
+						}
 					} else {
 						value = *attrmap[oKey]
 					}