Added remove_current_attachment_association attribute to ec2_transit_gateway_route_table_association

.changelog/31452.txt

@@ -0,0 +1,3 @@
+```release-note:enhancement
+resource/ec2_transit_gateway_route_table_association: added `remove_current_attachment_association` attribute to allow for disassociating a transit gateways currently associated route table before associating the new route table
+```

internal/service/ec2/transitgateway_route_table_association.go

@@ -49,6 +49,12 @@ func ResourceTransitGatewayRouteTableAssociation() *schema.Resource {
 				ForceNew:     true,
 				ValidateFunc: validation.NoZeroValues,
 			},
+			"remove_current_attachment_association": {
+				Type:     schema.TypeBool,
+				Optional: true,
+				ForceNew: true,
+				Default:  false,
+			},
 		},
 	}
 }
@@ -60,6 +66,15 @@ func resourceTransitGatewayRouteTableAssociationCreate(ctx context.Context, d *s
 	transitGatewayAttachmentID := d.Get("transit_gateway_attachment_id").(string)
 	transitGatewayRouteTableID := d.Get("transit_gateway_route_table_id").(string)
 	id := TransitGatewayRouteTableAssociationCreateResourceID(transitGatewayRouteTableID, transitGatewayAttachmentID)
+
+	removeCurrentAttachmentAssociation := d.Get("remove_current_attachment_association").(bool)
+	if removeCurrentAttachmentAssociation {
+		err := transitGatewayDisassociateLinkedRouteTable(ctx, conn, transitGatewayAttachmentID)
+		if err != nil {
+			return sdkdiag.AppendErrorf(diags, "disassociating existing EC2 Transit Gateway Route Table from Gateway Attachment (%s %s): %s", transitGatewayAttachmentID, transitGatewayRouteTableID, err)
+		}
+	}
+
 	input := &ec2.AssociateTransitGatewayRouteTableInput{
 		TransitGatewayAttachmentId: aws.String(transitGatewayAttachmentID),
 		TransitGatewayRouteTableId: aws.String(transitGatewayRouteTableID),
@@ -200,6 +215,40 @@ func transitGatewayRouteTableAssociationUpdate(ctx context.Context, conn *ec2.EC
 	return nil
 }
 
+// transitGatewayDisassociateLinkedRouteTable is used to disassociate the currently linked route table to a Gateway Attachment without knowledge of the Route Table ID.
+func transitGatewayDisassociateLinkedRouteTable(ctx context.Context, conn *ec2.EC2, transitGatewayAttachmentID string) error {
+	transitGatewayAttachment, err := FindTransitGatewayAttachmentByID(ctx, conn, transitGatewayAttachmentID)
+	if err != nil {
+		return err
+	}
+
+	if transitGatewayAttachment.Association == nil {
+		return nil // If no Association object was found then Gateway Attachment is not linked to a Route Table
+	}
+	transitGatewayRouteTableID := *transitGatewayAttachment.Association.TransitGatewayRouteTableId
+
+	if *transitGatewayAttachment.Association.State != ec2.AssociationStatusCodeAssociated {
+		return fmt.Errorf("associated Route Table with Transit Gateway Attachment is not in correct state (%s): expected attachment in %s state got %s", transitGatewayAttachmentID, ec2.AssociationStatusCodeAssociated, *transitGatewayAttachment.Association.State)
+	}
+
+	disassociateInput := &ec2.DisassociateTransitGatewayRouteTableInput{
+		TransitGatewayAttachmentId: aws.String(transitGatewayAttachmentID),
+		TransitGatewayRouteTableId: aws.String(transitGatewayRouteTableID),
+	}
+
+	_, err = conn.DisassociateTransitGatewayRouteTableWithContext(ctx, disassociateInput)
+	if err != nil {
+		return fmt.Errorf("failed to disassociate Route Table with Transit Gateway Attachment (%s %s): %w", transitGatewayRouteTableID, transitGatewayAttachmentID, err)
+	}
+
+	_, err = WaitTransitGatewayRouteTableAssociationDeleted(ctx, conn, transitGatewayRouteTableID, transitGatewayAttachmentID)
+	if err != nil {
+		return fmt.Errorf("waiting for EC2 Transit Gateway Route Table Association (%s %s) delete: %s", transitGatewayRouteTableID, transitGatewayAttachmentID, err)
+	}
+
+	return nil
+}
+
 const transitGatewayRouteTableAssociationIDSeparator = "_"
 
 func TransitGatewayRouteTableAssociationCreateResourceID(transitGatewayRouteTableID, transitGatewayAttachmentID string) string {

internal/service/ec2/transitgateway_route_table_association_test.go

@@ -37,6 +37,7 @@ func testAccTransitGatewayRouteTableAssociation_basic(t *testing.T) {
 					resource.TestCheckResourceAttrSet(resourceName, "resource_type"),
 					resource.TestCheckResourceAttrPair(resourceName, "transit_gateway_attachment_id", transitGatewayVpcAttachmentResourceName, "id"),
 					resource.TestCheckResourceAttrPair(resourceName, "transit_gateway_route_table_id", transitGatewayRouteTableResourceName, "id"),
+					resource.TestCheckResourceAttrSet(resourceName, "remove_current_attachment_association"),
 				),
 			},
 			{

website/docs/r/ec2_transit_gateway_route_table_association.html.markdown

@@ -25,6 +25,7 @@ The following arguments are supported:
 
 * `transit_gateway_attachment_id` - (Required) Identifier of EC2 Transit Gateway Attachment.
 * `transit_gateway_route_table_id` - (Required) Identifier of EC2 Transit Gateway Route Table.
+* `remove_current_attachment_association` - (Optional) Boolean whether the Gateway Attachment should remove its current Route Table association before associating with the new Route Table. Default value: `false`.
 
 ## Attributes Reference