feat: Implement oneof tag (#103)

* move custom tag check to inside userDefinedArray (following similar pattern to the other userDefined<type> functions); rearrange and add tests;

* go fmt fixes; add support for 'oneof' tag for strings; add one basic test;

* add error check and error return for malformed tag; add extra tests to validate these scenarios

* added support for a tag called oneof for strings and ints

* update the creation of the custom types (not using the underlying types)

* update examples; add const for convenience

* go fmt

* update documentation examples; add TrimSpace to ensure space between colon separated values doesn't matter;

* update readme with caveat about 'oneof' tag

* linter fixes

* clean up duplicate if conditions

* finish fixing merge conflicts

* update example to be correct. use ':' to separate arguments not ','

* update example comments for clarity

* ensure comma separated arguments to oneof tag; add several more tests and a new error;

* update documentation examples

* remove useless if statement that is never true

Co-authored-by: altair <[email protected]>

README.md

@@ -12,7 +12,7 @@ Faker will generate you a fake data based on your Struct.
 [![License](https://img.shields.io/github/license/mashape/apistatus.svg)](https://github.com/bxcodec/faker/blob/master/LICENSE)
 [![GoDoc](https://godoc.org/github.com/bxcodec/faker?status.svg)](https://godoc.org/github.com/bxcodec/faker)
 [![Go.Dev](https://img.shields.io/badge/go.dev-reference-007d9c?logo=go&logoColor=white)](https://pkg.go.dev/github.com/bxcodec/faker/v3?tab=doc)
- 
+
 ## Index
 
 * [Support](#support)
@@ -38,16 +38,16 @@ go get -u github.com/bxcodec/faker/v3
 # Example
 
 ---
- 
- - Using Struct's tag: 
+
+ - Using Struct's tag:
    - [basic tags: example_with_tags_test.go](/example_with_tags_test.go)
    - [length and bounds: example_with_tags_lenbounds_test.go](/example_with_tags_lenbounds_test.go)
    - [language: example_with_tags_lang_test.go](/example_with_tags_lang_test.go)
    - [unique: example_with_tags_unique_test.go](example_with_tags_unique_test.go)
  - Custom Struct's tag (define your own faker data): [example_custom_faker_test.go](/example_custom_faker_test.go)
  - Without struct's tag: [example_without_tag_test.go](/example_without_tag_test.go)
  - Single Fake Data Function: [example_single_fake_data_test.go](/example_single_fake_data_test.go)
- 
+
 ## DEMO
 
 ---
@@ -94,6 +94,7 @@ Unfortunately this library has some limitation
 * It does not support the `map[interface{}]interface{}`, `map[any_type]interface{}` & `map[interface{}]any_type` data types. Once again, we cannot generate values for an unknown data type.
 * Custom types are not fully supported. However some custom types are already supported: we are still investigating how to do this the correct way. For now, if you use `faker`, it's safer not to use any custom types in order to avoid panics.
 * Some extra custom types can be supported IF AND ONLY IF extended with [AddProvider()](https://github.com/bxcodec/faker/blob/9169c33ae9926e5b8f8732909790ee20b10b736a/faker.go#L320) please see [example](example_custom_faker_test.go#L46)
+* The `oneof` tag currently only supports `string` & `int`. Further support is coming soon. See [example](example_with_tags_test.go#L53) for usage.
 
 ## Contribution
 

example_custom_faker_test.go

@@ -42,7 +42,7 @@ func CustomGenerator() {
 	})
 
 	_ = faker.AddProvider("customUUID", func(v reflect.Value) (interface{}, error) {
-		s := []byte{
+		s := CustomUUID{
 			0, 8, 7, 2, 3,
 		}
 		return s, nil

example_with_tags_test.go

@@ -50,6 +50,8 @@ type SomeStructWithTags struct {
 	UUIDHypenated      string  `faker:"uuid_hyphenated"`
 	UUID               string  `faker:"uuid_digit"`
 	Skip               string  `faker:"-"`
+	PaymentMethod      string  `faker:"oneof: cc, paypal, check, money order"` // oneof will randomly pick one of the comma-separated values supplied in the tag
+	AccountID          int     `faker:"oneof: 15, 27, 61"`                     // use commas to separate the values for now. Future support for other separator characters may be added
 }
 
 func Example_withTags() {
@@ -104,6 +106,8 @@ func Example_withTags() {
 			AmountWithCurrency: XBB 49257.100000,
 			UUIDHypenated: 8f8e4463-9560-4a38-9b0c-ef24481e4e27,
 			UUID: 90ea6479fd0e4940af741f0a87596b73,
+			PaymentMethod: paypal,
+			AccountID: 61
 			Skip:
 		}
 	*/

faker.go

@@ -113,6 +113,9 @@ const (
 	BoundaryEnd           = "boundary_end"
 	Equals                = "="
 	comma                 = ","
+	colon                 = ":"
+	ONEOF                 = "oneof"
+	// period                = "."
 )
 
 var defaultTag = map[string]string{
@@ -233,6 +236,9 @@ var (
 	ErrWrongFormattedTag       = "Tag \"%s\" is not written properly"
 	ErrUnknownType             = "Unknown Type"
 	ErrNotSupportedTypeForTag  = "Type is not supported by tag."
+	ErrUnsupportedTagArguments = "Tag arguments are not compatible with field type."
+	ErrDuplicateSeparator      = "Duplicate separator for tag arguments."
+	ErrNotEnoughTagArguments   = "Not enough arguments for tag."
 )
 
 // Compiled regexp
@@ -636,21 +642,6 @@ func setDataWithTag(v reflect.Value, tag string) error {
 		reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Float32, reflect.Float64:
 		return userDefinedNumber(v, tag)
 	case reflect.Slice, reflect.Array:
-		/**
-		 * check for added Provider tag first before
-		 * defaulting to userDefinedArray()
-		 * this way the user at least has the
-		 * option of a custom tag working
-		 */
-		_, tagExists := mapperTag[tag]
-		if tagExists {
-			res, err := mapperTag[tag](v)
-			if err != nil {
-				return err
-			}
-			v.Set(reflect.ValueOf(res))
-			return nil
-		}
 		return userDefinedArray(v, tag)
 	case reflect.Map:
 		return userDefinedMap(v, tag)
@@ -720,6 +711,15 @@ func getValueWithTag(t reflect.Type, tag string) (interface{}, error) {
 }
 
 func userDefinedArray(v reflect.Value, tag string) error {
+	_, tagExists := mapperTag[tag]
+	if tagExists {
+		res, err := mapperTag[tag](v)
+		if err != nil {
+			return err
+		}
+		v.Set(reflect.ValueOf(res))
+		return nil
+	}
 	len := randomSliceAndMapSize()
 	if shouldSetNil && len == 0 {
 		v.Set(reflect.Zero(v.Type()))
@@ -787,7 +787,8 @@ func extractStringFromTag(tag string) (interface{}, error) {
 	var err error
 	strlen := randomStringLen
 	strlng := &lang
-	if !strings.Contains(tag, Length) && !strings.Contains(tag, Language) {
+	isOneOfTag := strings.Contains(tag, ONEOF)
+	if !strings.Contains(tag, Length) && !strings.Contains(tag, Language) && !isOneOfTag {
 		return nil, fmt.Errorf(ErrTagNotSupported, tag)
 	}
 	if strings.Contains(tag, Length) {
@@ -803,6 +804,22 @@ func extractStringFromTag(tag string) (interface{}, error) {
 			return nil, fmt.Errorf(ErrWrongFormattedTag, tag)
 		}
 	}
+	if isOneOfTag {
+		items := strings.Split(tag, colon)
+		argsList := items[1:]
+		if len(argsList) != 1 {
+			return nil, fmt.Errorf(ErrUnsupportedTagArguments)
+		}
+		if strings.Contains(argsList[0], ",,") {
+			return nil, fmt.Errorf(ErrDuplicateSeparator)
+		}
+		args := strings.Split(argsList[0], comma)
+		if len(args) < 2 {
+			return nil, fmt.Errorf(ErrNotEnoughTagArguments)
+		}
+		toRet := args[rand.Intn(len(args))]
+		return strings.TrimSpace(toRet), nil
+	}
 	res := randomString(strlen, strlng)
 	return res, nil
 }
@@ -826,9 +843,42 @@ func extractLangFromTag(tag string) (*langRuneBoundary, error) {
 }
 
 func extractNumberFromTag(tag string, t reflect.Type) (interface{}, error) {
-	if !strings.Contains(tag, BoundaryStart) || !strings.Contains(tag, BoundaryEnd) {
+	hasOneOf := strings.Contains(tag, ONEOF)
+	hasBoundaryStart := strings.Contains(tag, BoundaryStart)
+	hasBoundaryEnd := strings.Contains(tag, BoundaryEnd)
+	usingOneOfTag := hasOneOf && (!hasBoundaryStart && !hasBoundaryEnd)
+	usingBoundariesTags := !hasOneOf && (hasBoundaryStart && hasBoundaryEnd)
+	if !usingOneOfTag && !usingBoundariesTags {
 		return nil, fmt.Errorf(ErrTagNotSupported, tag)
 	}
+
+	// handling oneof tag
+	if usingOneOfTag {
+		argsList := strings.Split(tag, colon)[1:]
+		if len(argsList) != 1 {
+			return nil, fmt.Errorf(ErrUnsupportedTagArguments)
+		}
+		if strings.Contains(argsList[0], ",,") {
+			return nil, fmt.Errorf(ErrDuplicateSeparator)
+		}
+		args := strings.Split(argsList[0], comma)
+		if len(args) < 2 {
+			return nil, fmt.Errorf(ErrNotEnoughTagArguments)
+		}
+		var numberValues []int
+		for _, i := range args {
+			k := strings.TrimSpace(i)
+			j, err := strconv.Atoi(k)
+			if err != nil {
+				return nil, fmt.Errorf(ErrUnsupportedTagArguments)
+			}
+			numberValues = append(numberValues, j)
+		}
+		toRet := numberValues[rand.Intn(len(numberValues))]
+		return toRet, nil
+	}
+
+	// handling boundary tags
 	valuesStr := strings.SplitN(tag, comma, -1)
 	if len(valuesStr) != 2 {
 		return nil, fmt.Errorf(ErrWrongFormattedTag, tag)