refactor to use Tag.Lookup and add tests for empty tags

internal/reflect/helpers.go

@@ -79,50 +79,54 @@ func getStructTags(ctx context.Context, typ reflect.Type, path path.Path) (map[s
 		// This index sequence is the location of the field within the struct.
 		// For promoted fields from an embedded struct, the length of this sequence will be > 1
 		fieldIndexSequence := []int{i}
-		tag := field.Tag.Get(`tfsdk`)
-
-		switch tag {
-		// "tfsdk" tags can only be omitted on embedded structs
-		case "":
-			if field.Anonymous {
-				embeddedTags, err := getStructTags(ctx, field.Type, path)
-				if err != nil {
-					return nil, fmt.Errorf(`error retrieving embedded struct %q field tags: %w`, field.Name, err)
-				}
-				for k, v := range embeddedTags {
-					if other, ok := tags[k]; ok {
-						otherField := typ.FieldByIndex(other)
-						return nil, fmt.Errorf("embedded struct %q promotes a field with a duplicate tfsdk tag %q, conflicts with %q tfsdk tag", field.Name, k, otherField.Name)
-					}
-
-					tags[k] = append(fieldIndexSequence, v...)
-				}
-				continue
-			}
-
-			return nil, fmt.Errorf(`%s: need a struct tag for "tfsdk" on %s`, path, field.Name)
+		tag, tagExists := field.Tag.Lookup(`tfsdk`)
 
 		// "tfsdk" tags with "-" are being explicitly excluded
-		case "-":
+		if tag == "-" {
 			continue
+		}
 
-		// validate the "tfsdk" tag and ensure there are no duplicates before storing
-		default:
-			path := path.AtName(tag)
-			if field.Anonymous {
-				return nil, fmt.Errorf(`%s: embedded struct field %s cannot have tfsdk tag`, path, field.Name)
+		// Handle embedded structs
+		if field.Anonymous {
+			if tagExists {
+				return nil, fmt.Errorf(`%s: embedded struct field %s cannot have tfsdk tag`, path.AtName(tag), field.Name)
 			}
-			if !isValidFieldName(tag) {
-				return nil, fmt.Errorf("%s: invalid tfsdk tag, must only use lowercase letters, underscores, and numbers, and must start with a letter", path)
+
+			embeddedTags, err := getStructTags(ctx, field.Type, path)
+			if err != nil {
+				return nil, fmt.Errorf(`error retrieving embedded struct %q field tags: %w`, field.Name, err)
 			}
-			if other, ok := tags[tag]; ok {
-				otherField := typ.FieldByIndex(other)
-				return nil, fmt.Errorf("%s: can't use tfsdk tag %q for both %s and %s fields", path, tag, otherField.Name, field.Name)
+			for k, v := range embeddedTags {
+				if other, ok := tags[k]; ok {
+					otherField := typ.FieldByIndex(other)
+					return nil, fmt.Errorf("embedded struct %q promotes a field with a duplicate tfsdk tag %q, conflicts with %q tfsdk tag", field.Name, k, otherField.Name)
+				}
+
+				tags[k] = append(fieldIndexSequence, v...)
 			}
+			continue
+		}
+
+		// All non-embedded fields must have a tfsdk tag
+		if !tagExists {
+			return nil, fmt.Errorf(`%s: need a struct tag for "tfsdk" on %s`, path, field.Name)
+		}
 
-			tags[tag] = fieldIndexSequence
+		// Ensure the tfsdk tag has a valid name
+		path := path.AtName(tag)
+		if !isValidFieldName(tag) {
+			return nil, fmt.Errorf("%s: invalid tfsdk tag, must only use lowercase letters, underscores, and numbers, and must start with a letter", path)
 		}
+
+		// Ensure there are no duplicate tfsdk tags
+		if other, ok := tags[tag]; ok {
+			otherField := typ.FieldByIndex(other)
+			return nil, fmt.Errorf("%s: can't use tfsdk tag %q for both %s and %s fields", path, tag, otherField.Name, field.Name)
+		}
+
+		tags[tag] = fieldIndexSequence
 	}
+
 	return tags, nil
 }
 

internal/reflect/helpers_test.go

@@ -84,6 +84,18 @@ func TestGetStructTags(t *testing.T) {
 			in:          StructWithInvalidTag{},
 			expectedErr: errors.New(`*()-: invalid tfsdk tag, must only use lowercase letters, underscores, and numbers, and must start with a letter`),
 		},
+		"struct-err-missing-tfsdk-tag": {
+			in: struct {
+				ExampleField string
+			}{},
+			expectedErr: errors.New(`: need a struct tag for "tfsdk" on ExampleField`),
+		},
+		"struct-err-empty-tfsdk-tag": {
+			in: struct {
+				ExampleField string `tfsdk:""`
+			}{},
+			expectedErr: errors.New(`: invalid tfsdk tag, must only use lowercase letters, underscores, and numbers, and must start with a letter`),
+		},
 		"ignore-embedded-struct": {
 			in: struct {
 				ExampleStruct `tfsdk:"-"`
@@ -134,6 +146,12 @@ func TestGetStructTags(t *testing.T) {
 				"field5":     {1},
 			},
 		},
+		"embedded-struct-err-cannot-have-empty-tfsdk-tag": {
+			in: struct {
+				ExampleStruct `tfsdk:""` // Can't put a tfsdk tag here
+			}{},
+			expectedErr: errors.New(`: embedded struct field ExampleStruct cannot have tfsdk tag`),
+		},
 		"embedded-struct-err-cannot-have-tfsdk-tag": {
 			in: struct {
 				ExampleStruct `tfsdk:"example_field"` // Can't put a tfsdk tag here
@@ -185,6 +203,12 @@ func TestGetStructTags(t *testing.T) {
 				"field5":     {1},
 			},
 		},
+		"embedded-struct-ptr-err-cannot-have-empty-tfsdk-tag": {
+			in: struct {
+				*ExampleStruct `tfsdk:""` // Can't put a tfsdk tag here
+			}{},
+			expectedErr: errors.New(`: embedded struct field ExampleStruct cannot have tfsdk tag`),
+		},
 		"embedded-struct-ptr-err-cannot-have-tfsdk-tag": {
 			in: struct {
 				*ExampleStruct `tfsdk:"example_field"` // Can't put a tfsdk tag here

internal/reflect/struct_test.go

@@ -223,6 +223,26 @@ func TestNewStruct_errors(t *testing.T) {
 				"error retrieving field names from struct tags: %w",
 				errors.New("invalidTag: invalid tfsdk tag, must only use lowercase letters, underscores, and numbers, and must start with a letter")),
 		},
+		"struct-has-empty-tag": {
+			typ: types.ObjectType{
+				AttrTypes: map[string]attr.Type{
+					"a": types.StringType,
+				},
+			},
+			objVal: tftypes.NewValue(tftypes.Object{
+				AttributeTypes: map[string]tftypes.Type{
+					"a": tftypes.String,
+				},
+			}, map[string]tftypes.Value{
+				"a": tftypes.NewValue(tftypes.String, "hello"),
+			}),
+			targetVal: reflect.ValueOf(struct {
+				A string `tfsdk:""`
+			}{}),
+			expectedError: fmt.Errorf(
+				"error retrieving field names from struct tags: %w",
+				errors.New(": invalid tfsdk tag, must only use lowercase letters, underscores, and numbers, and must start with a letter")),
+		},
 		"embedded-struct-has-invalid-tags": {
 			typ: types.ObjectType{
 				AttrTypes: map[string]attr.Type{
@@ -332,6 +352,26 @@ func TestNewStruct_errors(t *testing.T) {
 					"Error: reflect: indirection through nil pointer to embedded struct field embedSingleField",
 			),
 		},
+		"embedded-struct-has-empty-tfsdk-tag": {
+			typ: types.ObjectType{
+				AttrTypes: map[string]attr.Type{
+					"attr_1": types.StringType,
+				},
+			},
+			objVal: tftypes.NewValue(tftypes.Object{
+				AttributeTypes: map[string]tftypes.Type{
+					"attr_1": tftypes.String,
+				},
+			}, map[string]tftypes.Value{
+				"attr_1": tftypes.NewValue(tftypes.String, "hello"),
+			}),
+			targetVal: reflect.ValueOf(struct {
+				embedSingleField `tfsdk:""`
+			}{}),
+			expectedError: errors.New(
+				"error retrieving field names from struct tags: : embedded struct field embedSingleField cannot have tfsdk tag",
+			),
+		},
 		"embedded-struct-has-tfsdk-tag": {
 			typ: types.ObjectType{
 				AttrTypes: map[string]attr.Type{
@@ -1803,6 +1843,27 @@ func TestFromStruct_errors(t *testing.T) {
 				),
 			},
 		},
+		"struct-has-empty-tag": {
+			typ: types.ObjectType{
+				AttrTypes: map[string]attr.Type{
+					"test": types.StringType,
+				},
+			},
+			val: reflect.ValueOf(
+				struct {
+					Test types.String `tfsdk:""`
+				}{},
+			),
+			expectedDiags: diag.Diagnostics{
+				diag.NewAttributeErrorDiagnostic(
+					path.Root("test"),
+					"Value Conversion Error",
+					"An unexpected error was encountered trying to convert from struct value. "+
+						"This is always an error in the provider. Please report the following to the provider developer:\n\n"+
+						"error retrieving field names from struct tags: test.: invalid tfsdk tag, must only use lowercase letters, underscores, and numbers, and must start with a letter",
+				),
+			},
+		},
 		"embedded-struct-has-invalid-tags": {
 			typ: types.ObjectType{
 				AttrTypes: map[string]attr.Type{
@@ -2016,6 +2077,27 @@ func TestFromStruct_errors(t *testing.T) {
 				),
 			},
 		},
+		"embedded-struct-has-empty-tfsdk-tag": {
+			typ: types.ObjectType{
+				AttrTypes: map[string]attr.Type{
+					"attr_1": types.StringType,
+				},
+			},
+			val: reflect.ValueOf(
+				struct {
+					embedSingleField `tfsdk:""`
+				}{},
+			),
+			expectedDiags: diag.Diagnostics{
+				diag.NewAttributeErrorDiagnostic(
+					path.Root("test"),
+					"Value Conversion Error",
+					"An unexpected error was encountered trying to convert from struct value. "+
+						"This is always an error in the provider. Please report the following to the provider developer:\n\n"+
+						"error retrieving field names from struct tags: test.: embedded struct field embedSingleField cannot have tfsdk tag",
+				),
+			},
+		},
 		"embedded-struct-has-tfsdk-tag": {
 			typ: types.ObjectType{
 				AttrTypes: map[string]attr.Type{