Add planmodify util package

pagerdutyplugin/resource_pagerduty_service.go

@@ -10,6 +10,7 @@ import (
 	"github.com/PagerDuty/go-pagerduty"
 	"github.com/PagerDuty/terraform-provider-pagerduty/util"
 	"github.com/PagerDuty/terraform-provider-pagerduty/util/enumtypes"
+	"github.com/PagerDuty/terraform-provider-pagerduty/util/planmodify"
 	"github.com/PagerDuty/terraform-provider-pagerduty/util/tztypes"
 	"github.com/PagerDuty/terraform-provider-pagerduty/util/validate"
 	"github.com/hashicorp/terraform-plugin-framework-validators/listvalidator"
@@ -237,6 +238,7 @@ func (r *resourceService) Schema(ctx context.Context, req resource.SchemaRequest
 				PlanModifiers: []planmodifier.List{
 					listplanmodifier.RequiresReplace(),
 					listplanmodifier.UseStateForUnknown(),
+					planmodify.UseNullForRemovedWithState(),
 				},
 				Validators: []validator.List{
 					listvalidator.SizeBetween(1, 1),

util/planmodify/use_null_for_removed_with_state.go

@@ -0,0 +1,37 @@
+package planmodify
+
+import (
+	"context"
+
+	"github.com/hashicorp/terraform-plugin-framework/resource/schema/planmodifier"
+)
+
+// UseNullForRemovedWithState sets plan to null if the list has an state, but
+// the configuration is now null
+func UseNullForRemovedWithState() planmodifier.List {
+	return useNullForRemovedWithStateModifier{}
+}
+
+type useNullForRemovedWithStateModifier struct{}
+
+func (m useNullForRemovedWithStateModifier) Description(_ context.Context) string {
+	return "Removes the value if the list has an state, but the configuration changes to null"
+}
+
+func (m useNullForRemovedWithStateModifier) MarkdownDescription(_ context.Context) string {
+	return "Removes the value if the list has an state, but the configuration changes to null"
+}
+
+func (m useNullForRemovedWithStateModifier) PlanModifyList(_ context.Context, req planmodifier.ListRequest, resp *planmodifier.ListResponse) {
+	// Do nothing if there is no state value.
+	if req.StateValue.IsNull() {
+		return
+	}
+
+	// Do nothing if there is a known or an unknown configuration value.
+	if !req.ConfigValue.IsNull() {
+		return
+	}
+
+	resp.PlanValue = req.ConfigValue
+}