iam/policy: Allow IAM policy leading whitespace

.changelog/36597.txt

@@ -0,0 +1,39 @@
+```release-note:enhancement
+resource/aws_glacier_vault_lock: Allow `policy` to have leading whitespace
+```
+
+```release-note:enhancement
+resource/aws_iam_group_policy: Allow `policy` to have leading whitespace
+```
+
+```release-note:enhancement
+resource/aws_iam_policy: Allow `policy` to have leading whitespace
+```
+
+```release-note:enhancement
+resource/aws_iam_role_policy: Allow `policy` to have leading whitespace
+```
+
+```release-note:enhancement
+resource/aws_iam_role: Allow `assume_role_policy` and `inline_policy.*.policy` to have leading whitespace
+```
+
+```release-note:enhancement
+resource/aws_iam_user_policy: Allow `policy` to have leading whitespace
+```
+
+```release-note:enhancement
+resource/aws_media_store_container_policy: Allow `policy` to have leading whitespace
+```
+
+```release-note:enhancement
+resource/aws_ssoadmin_permission_set_inline_policy: Allow `inline_policy` to have leading whitespace
+```
+
+```release-note:enhancement
+resource/aws_transfer_access: Allow `policy` to have leading whitespace
+```
+
+```release-note:enhancement
+resource/aws_transfer_user: Allow `policy` to have leading whitespace
+```

internal/service/iam/policy_test.go

@@ -83,6 +83,44 @@ func TestAccIAMPolicy_description(t *testing.T) {
 	})
 }
 
+func TestAccIAMPolicy_whitespace(t *testing.T) {
+	ctx := acctest.Context(t)
+	var out iam.Policy
+	rName := sdkacctest.RandomWithPrefix(acctest.ResourcePrefix)
+	resourceName := "aws_iam_policy.test"
+
+	resource.ParallelTest(t, resource.TestCase{
+		PreCheck:                 func() { acctest.PreCheck(ctx, t) },
+		ErrorCheck:               acctest.ErrorCheck(t, names.IAMServiceID),
+		ProtoV5ProviderFactories: acctest.ProtoV5ProviderFactories,
+		CheckDestroy:             testAccCheckPolicyDestroy(ctx),
+		Steps: []resource.TestStep{
+			{
+				Config: testAccPolicyConfig_whitespace(rName, "", "", ""),
+				Check: resource.ComposeTestCheckFunc(
+					testAccCheckPolicyExists(ctx, resourceName, &out),
+				),
+			},
+			{
+				Config:   testAccPolicyConfig_whitespace(rName, " ", "", ""),
+				PlanOnly: true,
+			},
+			{
+				Config:   testAccPolicyConfig_whitespace(rName, " ", "\n", ""),
+				PlanOnly: true,
+			},
+			{
+				Config:   testAccPolicyConfig_whitespace(rName, " ", "\n", " "),
+				PlanOnly: true,
+			},
+			{
+				Config:   testAccPolicyConfig_whitespace(rName, " \n", "\n", "\t "),
+				PlanOnly: true,
+			},
+		},
+	})
+}
+
 func TestAccIAMPolicy_disappears(t *testing.T) {
 	ctx := acctest.Context(t)
 	var out iam.Policy
@@ -408,6 +446,29 @@ EOF
 `, rName)
 }
 
+func testAccPolicyConfig_whitespace(rName, ws1, ws2, ws3 string) string {
+	return fmt.Sprintf(`
+resource "aws_iam_policy" "test" {
+  name = %[1]q
+
+  policy = <<EOF
+%[2]s{
+  "Version": "2012-10-17",%[3]s
+  "Statement": [
+    {
+      "Action": [
+        "ec2:Describe*"
+      ],
+      "Effect": %[3]s"Allow",
+      "Resource": "*"
+    }
+  ]
+}
+EOF
+}
+`, rName, ws1, ws2, ws3)
+}
+
 func testAccPolicyConfig_namePrefix(namePrefix string) string {
 	return fmt.Sprintf(`
 resource "aws_iam_policy" "test" {

internal/verify/validate.go

@@ -165,9 +165,13 @@ func ValidCIDRNetworkAddress(v interface{}, k string) (ws []string, errors []err
 func ValidIAMPolicyJSON(v interface{}, k string) (ws []string, errors []error) {
 	// IAM Policy documents need to be valid JSON, and pass legacy parsing
 	value := v.(string)
+	value = strings.TrimSpace(value)
 	if len(value) < 1 {
 		errors = append(errors, fmt.Errorf("%q is an empty string, which is not a valid JSON value", k))
-	} else if first := value[:1]; first != "{" {
+		return //nolint:nakedret // Naked return due to legacy, non-idiomatic Go function, error handling
+	}
+
+	if first := value[:1]; first != "{" {
 		switch value[:1] {
 		case " ", "\t", "\r", "\n":
 			errors = append(errors, fmt.Errorf("%q contains an invalid JSON policy: leading space characters are not allowed", k))
@@ -193,14 +197,21 @@ func ValidIAMPolicyJSON(v interface{}, k string) (ws []string, errors []error) {
 			// Generic error for if we didn't find something more specific to say.
 			errors = append(errors, fmt.Errorf("%q contains an invalid JSON policy: not a JSON object", k))
 		}
-	} else if _, err := structure.NormalizeJsonString(v); err != nil {
+		return //nolint:nakedret // Naked return due to legacy, non-idiomatic Go function, error handling
+	}
+
+	if _, err := structure.NormalizeJsonString(v); err != nil {
 		errStr := err.Error()
 		if err, ok := errs.As[*json.SyntaxError](err); ok {
 			errStr = fmt.Sprintf("%s, at byte offset %d", errStr, err.Offset)
 		}
 		errors = append(errors, fmt.Errorf("%q contains an invalid JSON policy: %s", k, errStr))
-	} else if err := basevalidation.JSONNoDuplicateKeys(value); err != nil {
+		return //nolint:nakedret // Naked return due to legacy, non-idiomatic Go function, error handling
+	}
+
+	if err := basevalidation.JSONNoDuplicateKeys(value); err != nil {
 		errors = append(errors, fmt.Errorf("%q contains duplicate JSON keys: %s", k, err))
+		return //nolint:nakedret // Naked return due to legacy, non-idiomatic Go function, error handling
 	}
 
 	return //nolint:nakedret // Just a long function.

website/docs/r/iam_policy.html.markdown

@@ -10,6 +10,8 @@ description: |-
 
 Provides an IAM policy.
 
+~> **NOTE:** We suggest using [`jsonencode()`](https://developer.hashicorp.com/terraform/language/functions/jsonencode) when assigning a value to `policy`. This function seamlessly translates Terraform language into JSON, enabling you to maintain consistency within your configuration without the need for context switches. By employing `jsonencode()`, you can sidestep potential complications arising from formatting discrepancies, whitespace inconsistencies, and other nuances inherent to JSON.
+
 ## Example Usage
 
 ```terraform
@@ -40,24 +42,19 @@ resource "aws_iam_policy" "policy" {
 This resource supports the following arguments:
 
 * `description` - (Optional, Forces new resource) Description of the IAM policy.
-* `name` - (Optional, Forces new resource) The name of the policy. If omitted, Terraform will assign a random, unique name.
 * `name_prefix` - (Optional, Forces new resource) Creates a unique name beginning with the specified prefix. Conflicts with `name`.
-* `path` - (Optional, default "/") Path in which to create the policy.
-  See [IAM Identifiers](https://docs.aws.amazon.com/IAM/latest/UserGuide/Using_Identifiers.html) for more information.
-* `policy` - (Required) The policy document. This is a JSON formatted string. For more information about building AWS IAM policy documents with Terraform, see the [AWS IAM Policy Document Guide](https://learn.hashicorp.com/terraform/aws/iam-policy)
+* `name` - (Optional, Forces new resource) Name of the policy. If omitted, Terraform will assign a random, unique name.
+* `path` - (Optional, default "/") Path in which to create the policy. See [IAM Identifiers](https://docs.aws.amazon.com/IAM/latest/UserGuide/Using_Identifiers.html) for more information.
+* `policy` - (Required) Policy document. This is a JSON formatted string. For more information about building AWS IAM policy documents with Terraform, see the [AWS IAM Policy Document Guide](https://learn.hashicorp.com/terraform/aws/iam-policy)
 * `tags` - (Optional) Map of resource tags for the IAM Policy. If configured with a provider [`default_tags` configuration block](https://registry.terraform.io/providers/hashicorp/aws/latest/docs#default_tags-configuration-block) present, tags with matching keys will overwrite those defined at the provider-level.
 
 ## Attribute Reference
 
 This resource exports the following attributes in addition to the arguments above:
 
-* `id` - The ARN assigned by AWS to this policy.
-* `arn` - The ARN assigned by AWS to this policy.
-* `description` - The description of the policy.
-* `name` - The name of the policy.
-* `path` - The path of the policy in IAM.
-* `policy` - The policy document.
-* `policy_id` - The policy's ID.
+* `arn` - ARN assigned by AWS to this policy.
+* `id` - ARN assigned by AWS to this policy.
+* `policy_id` - Policy's ID.
 * `tags_all` - A map of tags assigned to the resource, including those inherited from the provider [`default_tags` configuration block](https://registry.terraform.io/providers/hashicorp/aws/latest/docs#default_tags-configuration-block).
 
 ## Import