Changed attributes in Terraform Plugin Framework

I'm creating a custom terraform provider with the new Terraform Plugin Framework.

I want to save objects like this to terraform state:

	"attributes": {
		"name_servers": {
		"ns1": {
			"host": "host1",
			"id": 100,
			"ip": "",
			"is_used": true
		},
		"ns2": {
			"host": "host2",
			"id": 101,
			"ip": "",
			"is_used": true,
		}
		},
		"domain": "example.com"
	},

And it's working with following terraform resource:

	...
	type FooResourceModel struct {
		Domain types.String                `tfsdk:"domain"`
		NameServers map[string]NameServersModel `tfsdk:"name_servers"`
	}

	type NameServersModel struct {
		ID       types.Int64  `tfsdk:"id"`
		Host     types.String `tfsdk:"host"`
		IP       types.String `tfsdk:"ip"`
		IsUsed   types.Bool   `tfsdk:"is_used"`
	}


	func (r *FooNSResource) Schema(ctx context.Context, req resource.SchemaRequest, resp *resource.SchemaResponse) {
		resp.Schema = schema.Schema{
			Attributes: map[string]schema.Attribute{
				"domain": schema.StringAttribute{
					Required:            true,
				},
				"name_servers": schema.MapNestedAttribute{
					Required: true,
					NestedObject: schema.NestedAttributeObject{
						Attributes: map[string]schema.Attribute{
							"id": schema.Int64Attribute{
								Computed: true,
							},
							"host": schema.StringAttribute{
								Optional: true,
								Computed: true,
							},
							"ip": schema.StringAttribute{
								Optional: true,
								Computed: true,
							},
							"is_used": schema.BoolAttribute{
								Computed: true,
							},
						},
					},
				},
			},
		}
	}

	func (r *FooNSResource) Read(ctx context.Context, req resource.ReadRequest, resp *resource.ReadResponse) {
		var data *FooNSResourceModel
		diags := req.State.Get(ctx, &data)
		resp.Diagnostics.Append(diags...)
		if resp.Diagnostics.HasError() {
			return
		}

		serviceName := data.ServiceName.ValueString()
		// Read Terraform prior state data into the model
		resp.Diagnostics.Append(req.State.Get(ctx, &data)...)

		if resp.Diagnostics.HasError() {
			return
		}

		nameServers, err := getNs(r, serviceName)

		data.NameServers = nameServers

		diags = resp.State.Set(ctx, &data)
		resp.Diagnostics.Append(diags...)
		if resp.Diagnostics.HasError() {
			return
		}
	}

	func getNs(r *FooNSResource, domain string) (map[string]NameServersModel, error) {
		nameServers := make(map[string]NameServersModel)
		var ids []uint64

		err := r.client.Get(domain, &ids)
		if err != nil {
			return nil, err
		}

		for key, id := range ids {
			nsResponse := NameServerResponse{}
			err := r.client.Get(id, &nsResponse)
			if err != nil {
				return nil, err
			}

			nameServers["ns"+strconv.Itoa(key+1)] = NameServersModel{
				ID:       types.Int64Value(int64(nsResponse.Id)),
				Host:     types.StringValue(nsResponse.GetHost()),
				IP:       types.StringValue(nsResponse.GetIP()),
				IsUsed:   types.BoolValue(nsResponse.IsUsed),
			}
		}

		return nameServers, nil
	}

	func (r *FooNSResource) ImportState(ctx context.Context, req resource.ImportStateRequest, resp *resource.ImportStateResponse) {
		serviceName := req.ID
		nameServers, err := getNs(r, serviceName)

		resp.Diagnostics.Append(resp.State.SetAttribute(ctx, path.Root("domain"), serviceName)...)
		resp.Diagnostics.Append(resp.State.SetAttribute(ctx, path.Root("name_servers"), nameServers)...)
	}
	...

So when I'm importing data from API, it saves it into terraform state.

I have this in my Terraform file:

	...
	resource "my_custom_provider" "my-server" {
		service_name = "example.com"
	
		name_servers = {
		"ns1" = {
			host = "host1"
		},
		"ns2" = {
			host = "host2"
		},
		}
	}
	...

And when I run terraform plan, it says everything is fine:

No changes. Your infrastructure matches the configuration.

But when I add ip value:

	...
	resource "my_custom_provider" "my-server" {
		service_name = "example.com"
	
		name_servers = {
		"ns1" = {
			host = "host1"
		},
		"ns2" = {
			host = "host2"
			ip = "127.0.0.1"
		},
		}
	}
	...

then Terraform wants to update everything:

	Terraform will perform the following actions:

	# my_custom_provider.my-server will be updated in-place
	~ resource "my_custom_provider" "my-server" {
		~ name_servers = {
			~ "ns1" = {
				~ id        = 100 -> (known after apply)
				~ ip        = "" -> (known after apply)
				~ is_used   = true -> (known after apply)
					# (1 unchanged attribute hidden)
				},
			~ "ns2" = {
				~ id        = 101 -> (known after apply)
				~ ip        = "" -> "127.0.0.1"
				~ is_used   = true -> (known after apply)
					# (1 unchanged attribute hidden)
				},
			}
			# (1 unchanged attribute hidden)
		}

	Plan: 0 to add, 1 to change, 0 to destroy.

The unchanged attribute in name_servers is my host.

The question is:
Why Terraform thinks that everything will be changed? How can I prevent it, so only ns1 or ns2 values host/ip are going to be updated?

I've found a solution - PlanModifier: https://developer.hashicorp.com/terraform/plugin/framework/resources/plan-modification#common-use-case-attribute-plan-modifiers

Use PlanModifier with UseStateForUnknown() function:

>UseStateForUnknown(): Copies the prior state value, if not null. This is useful for reducing (known after apply) plan outputs for computed attributes which are known to not change over time.

The Schema looks like this right now:

    NestedObject: schema.NestedAttributeObject{
        Attributes: map[string]schema.Attribute{
            "id": schema.Int64Attribute{
                Computed: true,
                PlanModifiers: []planmodifier.Int64{
                    int64planmodifier.UseStateForUnknown(),
                },
            },
            "host": schema.StringAttribute{
                Optional: true,
                Computed: true,
                PlanModifiers: []planmodifier.String{
                    stringplanmodifier.UseStateForUnknown(),
                },
            },
            "ip": schema.StringAttribute{
                Optional: true,
                Computed: true,
                PlanModifiers: []planmodifier.String{
                    stringplanmodifier.UseStateForUnknown(),
                },
            },
            "is_used": schema.BoolAttribute{
                Computed: true,
                PlanModifiers: []planmodifier.Bool{
                    boolplanmodifier.UseStateForUnknown(),
                },
            },
        },
    },

For every attribute I've added the plan modifier, and now output in terraform plan looks as it should.

I don't know if its a best solution, but it works Tested on Terraform 1.4.2.