[Internal] Add maxItem=1 validator for object types in plugin framewo…

…rk schema (#4094)

## Changes
<!-- Summary of your changes that are easy to understand -->
- Added `object` tag for object types in tfsdk struct
- Added `maxItem=1` validator for object types in the plugin framework
schema

## Tests
<!-- 
How is this tested? Please see the checklist below and also describe any
other relevant tests
-->

- [x] `make test` run locally
- [x] relevant change in `docs/` folder
- [x] covered with integration tests in `internal/acceptance`
- [x] relevant acceptance tests are passing
- [x] using Go SDK

.codegen/model.go.tmpl

@@ -31,7 +31,7 @@ type {{.PascalName}} struct {
 {{end}}
 
 {{- define "field-tag" -}}
-	{{if .IsJson}}tfsdk:"{{if and (ne .Entity.Terraform nil) (ne .Entity.Terraform.Alias "") }}{{.Entity.Terraform.Alias}}{{else}}{{.Name}}{{end}}" tf:"{{if not .Required}}optional{{end}}"{{else}}tfsdk:"-"{{end -}}
+  {{if .IsJson}}tfsdk:"{{if and (ne .Entity.Terraform nil) (ne .Entity.Terraform.Alias "") }}{{.Entity.Terraform.Alias}}{{else}}{{.Name}}{{end}}" tf:"{{- $first := true -}}{{- if not .Required -}}{{- if not $first -}},{{end}}optional{{- $first = false -}}{{- end -}}{{- if .Entity.IsObject -}}{{- if not $first -}},{{end}}object{{- $first = false -}}{{- end -}}"{{else}}tfsdk:"-"{{end -}}
 {{- end -}}
 
 {{- define "type" -}}

go.mod

@@ -52,6 +52,7 @@ require (
 	github.com/hashicorp/logutils v1.0.0 // indirect
 	github.com/hashicorp/terraform-exec v0.21.0 // indirect
 	github.com/hashicorp/terraform-json v0.22.1 // indirect
+	github.com/hashicorp/terraform-plugin-framework-validators v0.13.0 // indirect
 	github.com/hashicorp/terraform-registry-address v0.2.3 // indirect
 	github.com/hashicorp/terraform-svchost v0.1.1 // indirect
 	github.com/hashicorp/yamux v0.1.1 // indirect

go.sum

@@ -134,6 +134,8 @@ github.com/hashicorp/terraform-json v0.22.1 h1:xft84GZR0QzjPVWs4lRUwvTcPnegqlyS7
 github.com/hashicorp/terraform-json v0.22.1/go.mod h1:JbWSQCLFSXFFhg42T7l9iJwdGXBYV8fmmD6o/ML4p3A=
 github.com/hashicorp/terraform-plugin-framework v1.11.0 h1:M7+9zBArexHFXDx/pKTxjE6n/2UCXY6b8FIq9ZYhwfE=
 github.com/hashicorp/terraform-plugin-framework v1.11.0/go.mod h1:qBXLDn69kM97NNVi/MQ9qgd1uWWsVftGSnygYG1tImM=
+github.com/hashicorp/terraform-plugin-framework-validators v0.13.0 h1:bxZfGo9DIUoLLtHMElsu+zwqI4IsMZQBRRy4iLzZJ8E=
+github.com/hashicorp/terraform-plugin-framework-validators v0.13.0/go.mod h1:wGeI02gEhj9nPANU62F2jCaHjXulejm/X+af4PdZaNo=
 github.com/hashicorp/terraform-plugin-go v0.23.0 h1:AALVuU1gD1kPb48aPQUjug9Ir/125t+AAurhqphJ2Co=
 github.com/hashicorp/terraform-plugin-go v0.23.0/go.mod h1:1E3Cr9h2vMlahWMbsSEcNrOCxovCZhOOIXjFHbjc/lQ=
 github.com/hashicorp/terraform-plugin-log v0.9.0 h1:i7hOA+vdAItN1/7UrfBqBwvYPQ9TFvymaRGZED3FCV0=

internal/providers/pluginfw/tfschema/customizable_schema_test.go

@@ -13,9 +13,10 @@ import (
 )
 
 type TestTfSdk struct {
-	Description types.String            `tfsdk:"description" tf:""`
-	Nested      *NestedTfSdk            `tfsdk:"nested" tf:"optional"`
-	Map         map[string]types.String `tfsdk:"map" tf:"optional"`
+	Description       types.String            `tfsdk:"description" tf:""`
+	Nested            *NestedTfSdk            `tfsdk:"nested" tf:"optional"`
+	NestedSliceObject []NestedTfSdk           `tfsdk:"nested_slice_object" tf:"optional,object"`
+	Map               map[string]types.String `tfsdk:"map" tf:"optional"`
 }
 
 type NestedTfSdk struct {
@@ -121,3 +122,11 @@ func TestCustomizeSchemaAddPlanModifier(t *testing.T) {
 
 	assert.True(t, len(scm.Attributes["description"].(schema.StringAttribute).PlanModifiers) == 1)
 }
+
+func TestCustomizeSchemaObjectTypeValidatorAdded(t *testing.T) {
+	scm := ResourceStructToSchema(TestTfSdk{}, func(c CustomizableSchema) CustomizableSchema {
+		return c
+	})
+
+	assert.True(t, len(scm.Blocks["nested_slice_object"].(schema.ListNestedBlock).Validators) == 1)
+}

internal/providers/pluginfw/tfschema/struct_to_schema.go

@@ -7,11 +7,19 @@ import (
 
 	"github.com/databricks/terraform-provider-databricks/common"
 	"github.com/databricks/terraform-provider-databricks/internal/tfreflect"
+	"github.com/hashicorp/terraform-plugin-framework-validators/listvalidator"
 	dataschema "github.com/hashicorp/terraform-plugin-framework/datasource/schema"
 	"github.com/hashicorp/terraform-plugin-framework/resource/schema"
+	"github.com/hashicorp/terraform-plugin-framework/schema/validator"
 	"github.com/hashicorp/terraform-plugin-framework/types"
 )
 
+type structTag struct {
+	optional     bool
+	computed     bool
+	singleObject bool
+}
+
 func typeToSchema(v reflect.Value) NestedBlockObject {
 	scmAttr := map[string]AttributeBuilder{}
 	scmBlock := map[string]BlockBuilder{}
@@ -30,8 +38,7 @@ func typeToSchema(v reflect.Value) NestedBlockObject {
 		if fieldName == "-" {
 			continue
 		}
-		isOptional := fieldIsOptional(typeField)
-		isComputed := fieldIsComputed(typeField)
+		structTag := getStructTag(typeField)
 		kind := typeField.Type.Kind()
 		value := field.Value
 		typeFieldType := typeField.Type
@@ -52,42 +59,47 @@ func typeToSchema(v reflect.Value) NestedBlockObject {
 			case reflect.TypeOf(types.Bool{}):
 				scmAttr[fieldName] = ListAttributeBuilder{
 					ElementType: types.BoolType,
-					Optional:    isOptional,
-					Required:    !isOptional,
-					Computed:    isComputed,
+					Optional:    structTag.optional,
+					Required:    !structTag.optional,
+					Computed:    structTag.computed,
 				}
 			case reflect.TypeOf(types.Int64{}):
 				scmAttr[fieldName] = ListAttributeBuilder{
 					ElementType: types.Int64Type,
-					Optional:    isOptional,
-					Required:    !isOptional,
-					Computed:    isComputed,
+					Optional:    structTag.optional,
+					Required:    !structTag.optional,
+					Computed:    structTag.computed,
 				}
 			case reflect.TypeOf(types.Float64{}):
 				scmAttr[fieldName] = ListAttributeBuilder{
 					ElementType: types.Float64Type,
-					Optional:    isOptional,
-					Required:    !isOptional,
-					Computed:    isComputed,
+					Optional:    structTag.optional,
+					Required:    !structTag.optional,
+					Computed:    structTag.computed,
 				}
 			case reflect.TypeOf(types.String{}):
 				scmAttr[fieldName] = ListAttributeBuilder{
 					ElementType: types.StringType,
-					Optional:    isOptional,
-					Required:    !isOptional,
-					Computed:    isComputed,
+					Optional:    structTag.optional,
+					Required:    !structTag.optional,
+					Computed:    structTag.computed,
 				}
 			default:
 				// Nested struct
 				nestedScm := typeToSchema(reflect.New(elemType).Elem())
+				var validators []validator.List
+				if structTag.singleObject {
+					validators = append(validators, listvalidator.SizeAtMost(1))
+				}
 				scmBlock[fieldName] = ListNestedBlockBuilder{
 					NestedObject: NestedBlockObject{
 						Attributes: nestedScm.Attributes,
 						Blocks:     nestedScm.Blocks,
 					},
-					Optional: isOptional,
-					Required: !isOptional,
-					Computed: isComputed,
+					Optional:   structTag.optional,
+					Required:   !structTag.optional,
+					Computed:   structTag.computed,
+					Validators: validators,
 				}
 			}
 		} else if kind == reflect.Map {
@@ -102,30 +114,30 @@ func typeToSchema(v reflect.Value) NestedBlockObject {
 			case reflect.TypeOf(types.Bool{}):
 				scmAttr[fieldName] = MapAttributeBuilder{
 					ElementType: types.BoolType,
-					Optional:    isOptional,
-					Required:    !isOptional,
-					Computed:    isComputed,
+					Optional:    structTag.optional,
+					Required:    !structTag.optional,
+					Computed:    structTag.computed,
 				}
 			case reflect.TypeOf(types.Int64{}):
 				scmAttr[fieldName] = MapAttributeBuilder{
 					ElementType: types.Int64Type,
-					Optional:    isOptional,
-					Required:    !isOptional,
-					Computed:    isComputed,
+					Optional:    structTag.optional,
+					Required:    !structTag.optional,
+					Computed:    structTag.computed,
 				}
 			case reflect.TypeOf(types.Float64{}):
 				scmAttr[fieldName] = MapAttributeBuilder{
 					ElementType: types.Float64Type,
-					Optional:    isOptional,
-					Required:    !isOptional,
-					Computed:    isComputed,
+					Optional:    structTag.optional,
+					Required:    !structTag.optional,
+					Computed:    structTag.computed,
 				}
 			case reflect.TypeOf(types.String{}):
 				scmAttr[fieldName] = MapAttributeBuilder{
 					ElementType: types.StringType,
-					Optional:    isOptional,
-					Required:    !isOptional,
-					Computed:    isComputed,
+					Optional:    structTag.optional,
+					Required:    !structTag.optional,
+					Computed:    structTag.computed,
 				}
 			default:
 				// Nested struct
@@ -134,36 +146,36 @@ func typeToSchema(v reflect.Value) NestedBlockObject {
 					NestedObject: NestedAttributeObject{
 						Attributes: nestedScm.Attributes,
 					},
-					Optional: isOptional,
-					Required: !isOptional,
-					Computed: isComputed,
+					Optional: structTag.optional,
+					Required: !structTag.optional,
+					Computed: structTag.computed,
 				}
 			}
 		} else if kind == reflect.Struct {
 			switch value.Interface().(type) {
 			case types.Bool:
 				scmAttr[fieldName] = BoolAttributeBuilder{
-					Optional: isOptional,
-					Required: !isOptional,
-					Computed: isComputed,
+					Optional: structTag.optional,
+					Required: !structTag.optional,
+					Computed: structTag.computed,
 				}
 			case types.Int64:
 				scmAttr[fieldName] = Int64AttributeBuilder{
-					Optional: isOptional,
-					Required: !isOptional,
-					Computed: isComputed,
+					Optional: structTag.optional,
+					Required: !structTag.optional,
+					Computed: structTag.computed,
 				}
 			case types.Float64:
 				scmAttr[fieldName] = Float64AttributeBuilder{
-					Optional: isOptional,
-					Required: !isOptional,
-					Computed: isComputed,
+					Optional: structTag.optional,
+					Required: !structTag.optional,
+					Computed: structTag.computed,
 				}
 			case types.String:
 				scmAttr[fieldName] = StringAttributeBuilder{
-					Optional: isOptional,
-					Required: !isOptional,
-					Computed: isComputed,
+					Optional: structTag.optional,
+					Required: !structTag.optional,
+					Computed: structTag.computed,
 				}
 			case types.List:
 				panic(fmt.Errorf("types.List should never be used in tfsdk structs. %s", common.TerraformBugErrorMessage))
@@ -176,9 +188,9 @@ func typeToSchema(v reflect.Value) NestedBlockObject {
 				nestedScm := typeToSchema(sv)
 				scmBlock[fieldName] = ListNestedBlockBuilder{
 					NestedObject: nestedScm,
-					Optional:     isOptional,
-					Required:     !isOptional,
-					Computed:     isComputed,
+					Optional:     structTag.optional,
+					Required:     !structTag.optional,
+					Computed:     structTag.computed,
 				}
 			}
 		} else {
@@ -188,14 +200,13 @@ func typeToSchema(v reflect.Value) NestedBlockObject {
 	return NestedBlockObject{Attributes: scmAttr, Blocks: scmBlock}
 }
 
-func fieldIsComputed(field reflect.StructField) bool {
+func getStructTag(field reflect.StructField) structTag {
 	tagValue := field.Tag.Get("tf")
-	return strings.Contains(tagValue, "computed")
-}
-
-func fieldIsOptional(field reflect.StructField) bool {
-	tagValue := field.Tag.Get("tf")
-	return strings.Contains(tagValue, "optional")
+	return structTag{
+		optional:     strings.Contains(tagValue, "optional"),
+		computed:     strings.Contains(tagValue, "computed"),
+		singleObject: strings.Contains(tagValue, "object"),
+	}
 }
 
 // ResourceStructToSchema builds a resource schema from a tfsdk struct, with custoimzations applied.