init

Author: Dmitry Mandrika

LICENSE

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+MIT License
+
+Copyright (c) 2020 Dmitriy
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.

README.txt

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+Package validator implements value validations based on struct tags.
+
+In code it is often necessary to validate that a given value is valid before
+using it for something. A typical example might be something like this.
+
+	if age < 18 {
+		return error.New("age cannot be under 18")
+	}
+
+This is a simple enough example, but it can get significantly more complex,
+especially when dealing with structs.
+
+	l := len(strings.Trim(s.Username))
+	if l < 3 || l > 40  || !regexp.MatchString("^[a-zA-Z]$", s.Username) ||	s.Age < 18 || s.Password {
+		return errors.New("Invalid request")
+	}
+
+You get the idea. Package validator allows one to define valid values as
+struct tags when defining a new struct type.
+
+	type NewUserRequest struct {
+		Username string `validate:"min=3,max=40,regexp=^[a-zA-Z]$"`
+		Name string     `validate:"nonzero"`
+		Age int         `validate:"min=18"`
+		Password string `validate:"min=8"`
+	}
+
+Then validating a variable of type NewUserRequest becomes trivial.
+
+	nur := NewUserRequest{Username: "something", ...}
+	if valid, _ := validator.Validate(nur); valid {
+		// do something
+	}
+
+Builtin validator functions
+
+Here is the list of validator functions builtin in the package.
+
+	max
+		For numeric numbers, max will simply make sure that the value is
+		equal to the parameter given. For strings, it checks that
+		the string length is exactly that number of characters. For slices,
+		arrays, and maps, validates the number of items. (Usage: len=10)
+
+	max
+		For numeric numbers, max will simply make sure that the value is
+		lesser or equal to the parameter given. For strings, it checks that
+		the string length is at most that number of characters. For slices,
+		arrays, and maps, validates the number of items. (Usage: max=10)
+
+	min
+		For numeric numbers, min will simply make sure that the value is
+		greater or equal to the parameter given. For strings, it checks that
+		the string length is at least that number of characters. For slices,
+		arrays, and maps, validates the number of items. (Usage: min=10)
+
+	nonzero
+		This validates that the value is not zero. The appropriate zero value
+		is given by the Go spec (e.g. for int it's 0, for string it's "", for
+		pointers is nil, etc.) Usage: nonzero
+
+	regexp
+		Only valid for string types, it will validate that the value matches
+		the regular expression provided as parameter. (Usage: regexp=^a.*b$)
+
+	in
+		For string, int, float. Validates that the value is presented in the
+		whitelist. (Usage: in='str1,str2,str3')
+		Note: any string containing commas must be single-quoted to prevent
+		parsing failures.
+
+	type
+		Checks if the value is valid for defined type(one of: base64, timestamp).
+		(Usage: type=base64)
+
+
+Note that there are no tests to prevent conflicting validator parameters. For
+instance, these fields will never be valid.
+
+	...
+	A int     `validate:"max=0,min=1"`
+	B string  `validate:"len=10,regexp=^$"
+	...
+
+Custom validation functions
+
+It is possible to define custom validation functions by using SetValidationFunc.
+First, one needs to create a validation function.
+
+	// Very simple validation func
+	func notZZ(v interface{}, param string) error {
+		st := reflect.ValueOf(v)
+		if st.Kind() != reflect.String {
+			return validate.ErrUnsupported
+		}
+		if st.String() == "ZZ" {
+			return errors.New("value cannot be ZZ")
+		}
+		return nil
+	}
+
+Then one needs to add it to the list of validation funcs and give it a "tag" name.
+
+	validate.SetValidationFunc("notzz", notZZ)
+
+Then it is possible to use the notzz validation tag. This will print
+"Field A error: value cannot be ZZ"
+
+	type T struct {
+		A string  `validate:"nonzero,notzz"`
+	}
+	t := T{"ZZ"}
+	if valid, errs := validator.Validate(t); !valid {
+		fmt.Printf("Field A error: %s\n", errs["A"][0])
+	}
+
+To use parameters, it is very similar.
+
+	// Very simple validator with parameter
+	func notSomething(v interface{}, param string) error {
+		st := reflect.ValueOf(v)
+		if st.Kind() != reflect.String {
+			return validate.ErrUnsupported
+		}
+		if st.String() == param {
+			return errors.New("value cannot be " + param)
+		}
+		return nil
+	}
+
+And then the code below should print "Field A error: value cannot be ABC".
+
+	validator.SetValidationFunc("notsomething", notSomething)
+	type T struct {
+		A string  `validate:"notsomething=ABC"`
+	}
+	t := T{"ABC"}
+	if valid, errs := validator.Validate(t); !valid {
+		fmt.Printf("Field A error: %s\n", errs["A"][0])
+	}
+
+As well, it is possible to overwrite builtin validation functions.
+
+	validate.SetValidationFunc("min", myMinFunc)
+
+And you can delete a validation function by setting it to nil.
+
+	validate.SetValidationFunc("notzz", nil)
+	validate.SetValidationFunc("nonzero", nil)
+
+Using a non-existing validation func in a field tag will always return
+false and with error validate.ErrUnknownTag.
+
+Finally, package validator also provides a helper function that can be used
+to validate simple variables/values.
+
+    // valid: true, errs: []
+	valid, errs = validator.Valid(42, "min=10, max=50")
+
+	// valid: false, errs: [validate.ErrZeroValue]
+	valid, errs = validator.Valid(nil, "nonzero")
+
+	// valid: false, errs: [validate.ErrMin,validate.ErrMax]
+	valid, errs = validator.Valid("hi", "nonzero,min=3,max=2")
+
+Custom tag name
+
+In case there is a reason why one would not wish to use tag 'validate' (maybe due to
+a conflict with a different package), it is possible to tell the package to use
+a different tag.
+
+	validator.SetTag("valid")
+
+Then.
+
+	Type T struct {
+		A int    `valid:"min=8, max=10"`
+		B string `valid:"nonzero"`
+	}
+
+SetTag is permanent. The new tag name will be used until it is again changed
+with a new call to SetTag. A way to temporarily use a different tag exists.
+
+	validator.WithTag("foo").Validate(t)
+	validator.WithTag("bar").Validate(t)
+	// But this will go back to using 'validate'
+	validator.Validate(t)
+
+Multiple validators
+
+You may often need to have a different set of validation
+rules for different situations. In all the examples above,
+we only used the default validator but you could create a
+new one and set specific rules for it.
+
+For instance, you might use the same struct to decode incoming JSON for a REST API
+but your needs will change when you're using it to, say, create a new instance
+in storage vs. when you need to change something.
+
+	type User struct {
+		Username string `validate:"nonzero"`
+		Name string     `validate:"nonzero"`
+		Age int         `validate:"nonzero"`
+		Password string `validate:"nonzero"`
+	}
+
+Maybe when creating a new user, you need to make sure all values in the struct are filled,
+but then you use the same struct to handle incoming requests to, say, change the password,
+in which case you only need the Username and the Password and don't care for the others.
+You might use two different validators.
+
+	type User struct {
+		Username string `creating:"nonzero" chgpw:"nonzero"`
+		Name string     `creating:"nonzero"`
+		Age int         `creating:"nonzero"`
+		Password string `creating:"nonzero" chgpw:"nonzero"`
+	}
+
+	var (
+		creationValidator = validator.NewValidator()
+		chgPwValidator = validator.NewValidator()
+	)
+
+	func init() {
+		creationValidator.SetTag("creating")
+		chgPwValidator.SetTag("chgpw")
+	}
+
+	...
+
+	func CreateUserHandler(w http.ResponseWriter, r *http.Request) {
+		var u User
+		json.NewDecoder(r.Body).Decode(&user)
+		if valid, _ := creationValidator.Validate(user); !valid {
+			// the request did not include all of the User
+			// struct fields, so send a http.StatusBadRequest
+			// back or something
+		}
+		// create the new user
+	}
+
+	func SetNewUserPasswordHandler(w http.ResponseWriter, r *http.Request) {
+		var u User
+		json.NewDecoder(r.Body).Decode(&user)
+		if valid, _ := chgPwValidator.Validate(user); !valid {
+			// the request did not Username and Password,
+			// so send a http.StatusBadRequest
+			// back or something
+		}
+		// save the new password
+	}
+
+It is also possible to do all of that using only the default validator as long
+as SetTag is always called before calling validator.Validate() or you chain the
+with WithTag().
+
+========================
+type User struct {
+    Firstname string `validate:"attr=firstname,min=3,msg_min=errors.form.too_small,max=15,msg_max=errors.form.too_big,regexp=^[a-zA-Z]$,msg_regexp=My custom message"`
+    Lastname string `validate:"attr=lastname,min=3,msg_min=errors.form.too_small,max=15,msg_max=errors.form.too_big,regexp=^[a-zA-Z]$,msg_regexp=my custom message"`
+}
+
+Результат валидации при некорректных данных будет map, где поле ключа соответствует названию атрибута (задается как "attr" в тэге), а значение - первой ошибке из списка правил валидации, если их несколько для одного поля.
+
+map[string]error{
+     "firstname" : "errors.form.too_small",
+     "lastname" : "my custom message",
+}
+
+    Добавить возможность использования кастомных сообщений об ошибках. Они должны задаваться параметром тега "msg_%rule_name%", где %rule_name% - правило валидации.
+
+    Необходимые правила валидации:
+
+    "empty" - для любого объекта (для цифровых значений 0)
+    "min", "max" - для string, slice длина, для числовых значений само значение
+    "in" - значение входит в slice типа поля, к которому относится, к примеру validate:"attr=sex,in=male,female" , для числовых значений: validate:"attr=option,in=1,9,42"
+    "compare" - значение соответствует заданному согласно типу validate:"attr=agree_terms,compare=true"
+    "type" - значение соответствует некоторому типу, пока только timestamp и base64 validate:"attr=created_at,type=timestamp"
+
+    Для правил min, max должны обрабатываться плейсхолдеры {min} {max} при генерации ошибок. msg_min=The value should be more than {min}.

go.mod

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+module github.com/censync/go-validator
+
+go 1.14