Don't allow empty content in note widget (#607)

If the note_definition of a widget is empty, it will fail JSON
serialization. Let's make sure it fails validation instead.

Closes #574

Co-authored-by: Jiri Kuncar <jiri.kuncar@datadoghq.com>

datadog/resource_datadog_dashboard.go

@@ -8,6 +8,7 @@ import (
 	datadogV1 "github.com/DataDog/datadog-api-client-go/api/v1/datadog"
 	"github.com/hashicorp/terraform-plugin-sdk/helper/resource"
 	"github.com/hashicorp/terraform-plugin-sdk/helper/schema"
+	"github.com/hashicorp/terraform-plugin-sdk/helper/validation"
 )
 
 func resourceDatadogDashboard() *schema.Resource {
@@ -2905,8 +2906,9 @@ func buildTerraformManageStatusDefinition(datadogDefinition datadogV1.MonitorSum
 func getNoteDefinitionSchema() map[string]*schema.Schema {
 	return map[string]*schema.Schema{
 		"content": {
-			Type:     schema.TypeString,
-			Required: true,
+			Type:         schema.TypeString,
+			Required:     true,
+			ValidateFunc: validation.StringIsNotEmpty,
 		},
 		"background_color": {
 			Type:     schema.TypeString,

datadog/resource_datadog_dashboard_note_test.go

@@ -1,7 +1,10 @@
 package datadog
 
 import (
+	"regexp"
 	"testing"
+
+	"github.com/hashicorp/terraform-plugin-sdk/helper/resource"
 )
 
 // JSON export used as test scenario
@@ -62,6 +65,21 @@ resource "datadog_dashboard" "note_dashboard" {
 }
 `
 
+const datadogDashboardNoteConfigNoContent = `
+resource "datadog_dashboard" "note_dashboard" {
+	title         = "Acceptance Test Notes Widget Dashboard"
+	description   = "Created using the Datadog provider in Terraform"
+	layout_type   = "ordered"
+	is_read_only  = "true"
+
+	widget {
+		note_definition {
+			content = ""
+		}
+	}
+}
+`
+
 var datadogDashboardNoteAsserts = []string{
 	"description = Created using the Datadog provider in Terraform",
 	"widget.0.note_definition.0.content = This is a note widget",
@@ -83,3 +101,19 @@ func TestAccDatadogDashboardNote(t *testing.T) {
 func TestAccDatadogDashboardNote_import(t *testing.T) {
 	testAccDatadogDashboardWidgetUtil_import(t, datadogDashboardNoteConfig, "datadog_dashboard.note_dashboard")
 }
+
+func TestAccDatadogDashboardNoteContentError(t *testing.T) {
+	accProviders, cleanup := testAccProviders(t, initRecorder(t))
+	defer cleanup(t)
+
+	resource.Test(t, resource.TestCase{
+		PreCheck:  func() { testAccPreCheck(t) },
+		Providers: accProviders,
+		Steps: []resource.TestStep{
+			{
+				Config:      datadogDashboardNoteConfigNoContent,
+				ExpectError: regexp.MustCompile("expected \"widget.0.note_definition.0.content\" to not be an empty string"),
+			},
+		},
+	})
+}