Made change to the override mechanism to simplify it. Already existin…

…g resource should set overwrite to true by default and let the terraform lifecycle rule handle the update of the resource. Otherwise, overwrite is false by default unless explicitly specified through override parameter.

aws/resource_aws_ssm_parameter.go

@@ -150,11 +150,13 @@ func resourceAwsSsmParameterPut(d *schema.ResourceData, meta interface{}) error
 
 	log.Printf("[INFO] Creating SSM Parameter: %s", d.Get("name").(string))
 
+	// Overwrite is set to true if the ressource already exists in the state or
+	// if it has been explicitly specified
 	paramInput := &ssm.PutParameterInput{
 		Name:           aws.String(d.Get("name").(string)),
 		Type:           aws.String(d.Get("type").(string)),
 		Value:          aws.String(d.Get("value").(string)),
-		Overwrite:      aws.Bool(shouldUpdateSsmParameter(d)),
+		Overwrite:      aws.Bool(!d.IsNewResource() || d.Get("overwrite").(bool)),
 		AllowedPattern: aws.String(d.Get("allowed_pattern").(string)),
 	}
 
@@ -184,14 +186,3 @@ func resourceAwsSsmParameterPut(d *schema.ResourceData, meta interface{}) error
 
 	return resourceAwsSsmParameterRead(d, meta)
 }
-
-func shouldUpdateSsmParameter(d *schema.ResourceData) bool {
-	// If the user has specified a preference, return their preference
-	if value, ok := d.GetOkExists("overwrite"); ok {
-		return value.(bool)
-	}
-
-	// Since the user has not specified a preference, obey lifecycle rules
-	// if it is not a new resource, otherwise overwrite should be set to false.
-	return !d.IsNewResource()
-}

aws/resource_aws_ssm_parameter_test.go

@@ -277,35 +277,3 @@ resource "aws_kms_key" "test_key" {
 }
 `, rName, rName, value)
 }
-
-func TestAWSSSMParameterShouldUpdate(t *testing.T) {
-	data := resourceAwsSsmParameter().TestResourceData()
-	failure := false
-
-	if !shouldUpdateSsmParameter(data) {
-		t.Logf("Existing resources should be overwritten if the values don't match!")
-		failure = true
-	}
-
-	data.MarkNewResource()
-	if shouldUpdateSsmParameter(data) {
-		t.Logf("New resources must never be overwritten, this will overwrite parameters created outside of the system")
-		failure = true
-	}
-
-	data = resourceAwsSsmParameter().TestResourceData()
-	data.Set("overwrite", true)
-	if !shouldUpdateSsmParameter(data) {
-		t.Logf("Resources should always be overwritten if the user requests it")
-		failure = true
-	}
-
-	data.Set("overwrite", false)
-	if shouldUpdateSsmParameter(data) {
-		t.Logf("Resources should never be overwritten if the user requests it")
-		failure = true
-	}
-	if failure {
-		t.Fail()
-	}
-}

website/docs/r/ssm_parameter.html.markdown

@@ -62,7 +62,7 @@ The following arguments are supported:
 * `value` - (Required) The value of the parameter.
 * `description` - (Optional) The description of the parameter.
 * `key_id` - (Optional) The KMS key id or arn for encrypting a SecureString.
-* `overwrite` - (Optional) Overwrite an existing parameter. If not specified, will default to `false` if the resource has not been created by terraform to avoid overwrite of existing resource and will default to `true` otherwise (terraform lifecycle rules should then be used to manage the update behavior).
+* `overwrite` - (Optional) Default `false`. Force overwrite of an existing parameter that is not yet handled by terraform. Terraform lifecycle rules apply on resources that are already in the state file.
 * `allowed_pattern` - (Optional) A regular expression used to validate the parameter value.
 * `tags` - (Optional) A mapping of tags to assign to the object.