refactor: deprecate plan field in cluster resource

docs/resources/cluster.md

@@ -79,7 +79,7 @@ resource "zillizcloud_cluster" "enterprise_plan_cluster" {
 - `desired_status` (String) The desired status of the cluster. Possible values are RUNNING and SUSPENDED. Defaults to RUNNING.
 - `labels` (Map of String) A map of labels to assign to the cluster. Labels are key-value pairs that can be used to organize and categorize clusters.
 - `load_balancer_security_groups` (Set of String, Deprecated) A set of security group IDs to associate with the load balancer of the cluster.
-- `plan` (String) The plan tier of the Zilliz Cloud service. Available options are Serverless, Standard and Enterprise.
+- `plan` (String, Deprecated) The plan tier of the Zilliz Cloud service. Available options are Serverless, Standard and Enterprise.
 - `region_id` (String) The ID of the region where the cluster exists.
 - `replica` (Number) The number of replicas for the cluster. Defaults to 1.
 - `replica_settings` (Attributes) Query compute unit configuration for the cluster. The cu_settings and cu_size cannot be set simultaneously. (see [below for nested schema](#nestedatt--replica_settings))

internal/cluster/cluster_resource.go

@@ -27,6 +27,7 @@ import (
 	"github.com/hashicorp/terraform-plugin-log/tflog"
 	zilliz "github.com/zilliztech/terraform-provider-zillizcloud/client"
 	util "github.com/zilliztech/terraform-provider-zillizcloud/client/retry"
+	customplanmodifier "github.com/zilliztech/terraform-provider-zillizcloud/internal/planmodifier"
 	customvalidator "github.com/zilliztech/terraform-provider-zillizcloud/internal/validator"
 )
 
@@ -100,6 +101,10 @@ func (r *ClusterResource) Schema(ctx context.Context, req resource.SchemaRequest
 				MarkdownDescription: "The plan tier of the Zilliz Cloud service. Available options are Serverless, Standard and Enterprise.",
 				Optional:            true,
 				Computed:            true,
+				DeprecationMessage:  "The plan field is deprecated and will be removed in a future major version. The plan is determined automatically based on cu_size and cu_type.",
+				PlanModifiers: []planmodifier.String{
+					customplanmodifier.IgnoreChangesString(),
+				},
 				Validators: []validator.String{
 					stringvalidator.OneOf(FreePlan, ServerlessPlan, StandardPlan, EnterprisePlan, BusinessCriticalPlan),
 				},
@@ -534,7 +539,10 @@ func (r *ClusterResource) Read(ctx context.Context, req resource.ReadRequest, re
 	state.ConnectAddress = cluster.ConnectAddress
 	state.PrivateLinkAddress = cluster.PrivateLinkAddress
 	state.CreateTime = cluster.CreateTime
-	state.Plan = cluster.Plan
+	// plan field is deprecated - only set from API if state is empty (first read after import)
+	if state.Plan.IsNull() || state.Plan.IsUnknown() {
+		state.Plan = cluster.Plan
+	}
 	state.Replica = cluster.Replica
 	state.CuSize = cluster.CuSize
 	state.CuType = cluster.CuType

internal/planmodifier/ignore_changes_string.go

@@ -0,0 +1,38 @@
+package planmodifier
+
+import (
+	"context"
+
+	"github.com/hashicorp/terraform-plugin-framework/resource/schema/planmodifier"
+)
+
+// ignoreChangesString implements a PlanModifier that suppresses all diffs
+// for deprecated fields by keeping the prior state value.
+type ignoreChangesString struct{}
+
+func (m ignoreChangesString) Description(ctx context.Context) string {
+	return "Ignore any configuration changes by keeping the prior state value."
+}
+
+func (m ignoreChangesString) MarkdownDescription(ctx context.Context) string {
+	return m.Description(ctx)
+}
+
+func (m ignoreChangesString) PlanModifyString(ctx context.Context, req planmodifier.StringRequest, resp *planmodifier.StringResponse) {
+	// If the resource already exists (state is not null/unknown), keep the state value
+	// This completely suppresses any diff for this field
+	if !req.StateValue.IsNull() && !req.StateValue.IsUnknown() {
+		resp.PlanValue = req.StateValue
+		return
+	}
+
+	// For new resources: use the config value (or null if not set)
+	// This allows the first apply to write a value to state, which is then preserved
+	resp.PlanValue = req.ConfigValue
+}
+
+// IgnoreChangesString returns a PlanModifier that suppresses all diffs
+// by keeping the prior state value. Use this for deprecated fields.
+func IgnoreChangesString() planmodifier.String {
+	return ignoreChangesString{}
+}