tagexpr

package module
v2.9.11 Latest Latest
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 Go to latest Published: Oct 10, 2023 License: Apache-2.0 Imports: 16 Imported by: 1

README

go-tagexpr report card GoDoc

An interesting go struct tag expression syntax for field validation, etc.

Usage

  • Validator: A powerful validator that supports struct tag expression

  • Binding: A powerful HTTP request parameters binder that supports struct tag expression

Feature

  • Support for a variety of common operator
  • Support for accessing arrays, slices, members of the dictionary
  • Support access to any field in the current structure
  • Support access to nested fields, non-exported fields, etc.
  • Support registers function expression
  • Built-in len, sprintf, regexp functions
  • Support single mode and multiple mode to define expression
  • Parameter check subpackage
  • Use offset pointers to directly take values, better performance
  • Required go version ≥1.9

Example

package tagexpr_test

import (
	"fmt"

	tagexpr "github.com/bytedance/go-tagexpr/v2"
)

func Example() {
	type T struct {
		A  int             `tagexpr:"$<0||$>=100"`
		B  string          `tagexpr:"len($)>1 && regexp('^\\w*$')"`
		C  bool            `tagexpr:"expr1:(f.g)$>0 && $; expr2:'C must be true when T.f.g>0'"`
		d  []string        `tagexpr:"@:len($)>0 && $[0]=='D'; msg:sprintf('invalid d: %v',$)"`
		e  map[string]int  `tagexpr:"len($)==$['len']"`
		e2 map[string]*int `tagexpr:"len($)==$['len']"`
		f  struct {
			g int `tagexpr:"$"`
		}
	}

	vm := tagexpr.New("tagexpr")
	t := &T{
		A:  107,
		B:  "abc",
		C:  true,
		d:  []string{"x", "y"},
		e:  map[string]int{"len": 1},
		e2: map[string]*int{"len": new(int)},
		f: struct {
			g int `tagexpr:"$"`
		}{1},
	}

	tagExpr, err := vm.Run(t)
	if err != nil {
		panic(err)
	}

	fmt.Println(tagExpr.Eval("A"))
	fmt.Println(tagExpr.Eval("B"))
	fmt.Println(tagExpr.Eval("C@expr1"))
	fmt.Println(tagExpr.Eval("C@expr2"))
	if !tagExpr.Eval("d").(bool) {
		fmt.Println(tagExpr.Eval("d@msg"))
	}
	fmt.Println(tagExpr.Eval("e"))
	fmt.Println(tagExpr.Eval("e2"))
	fmt.Println(tagExpr.Eval("f.g"))

	// Output:
	// true
	// true
	// true
	// C must be true when T.f.g>0
	// invalid d: [x y]
	// true
	// false
	// 1
}

Syntax

Struct tag syntax spec:

type T struct {
	// Single model
    Field1 T1 `tagName:"expression"`
	// Multiple model
    Field2 T2 `tagName:"exprName:expression; [exprName2:expression2;]..."`
	// Omit it
    Field3 T3 `tagName:"-"`
    // Omit it when it is nil
    Field4 T4 `tagName:"?"`
    ...
}

NOTE: The exprName under the same struct field cannot be the same！

Operator or Operand Explain
true false boolean
0 0.0 float64 "0"
'' String
\\' Escape ' delims in string
\" Escape " delims in string
nil nil, undefined
! not
+ Digital addition or string splicing
- Digital subtraction or negative
* Digital multiplication
/ Digital division
% division remainder, as: float64(int64(a)%int64(b))
== eq
!= ne
> gt
>= ge
< lt
<= le
&& Logic and
|| Logic or
() Expression group
(X)$ Struct field value named X
(X.Y)$ Struct field value named X.Y
$ Shorthand for (X)$, omit (X) to indicate current struct field value
(X)$['A'] Map value with key A or struct A sub-field in the struct field X
(X)$[0] The 0th element or sub-field of the struct field X(type: map, slice, array, struct)
len((X)$) Built-in function len, the length of struct field X
mblen((X)$) the length of string field X (character number)
regexp('^\\w*$', (X)$) Regular match the struct field X, return boolean
regexp('^\\w*$') Regular match the current struct field, return boolean
sprintf('X value: %v', (X)$) fmt.Sprintf, format the value of struct field X
range(KvExpr, forEachExpr) Iterate over an array, slice, or dictionary
- #k is the element key var
- #v is the element value var
- ## is the number of elements
- e.g. example
in((X)$, enum_1, ...enum_n) Check if the first parameter is one of the enumerated parameters

Operator priority(high -> low):

  • () ! bool float64 string nil
  • * / %
  • + -
  • < <= > >=
  • == !=
  • &&
  • ||

Field Selector

field_lv1.field_lv2...field_lvn

Expression Selector

  • If expression is single model or exprName is @:
field_lv1.field_lv2...field_lvn
  • If expression is multiple model and exprName is not @:
field_lv1.field_lv2...field_lvn@exprName

Benchmark

goos: darwin
goarch: amd64
pkg: github.com/bytedance/go-tagexpr
BenchmarkTagExpr-4   	10000000	       148 ns/op	      32 B/op	       3 allocs/op
BenchmarkReflect-4   	10000000	       182 ns/op	      16 B/op	       2 allocs/op
PASS

Go to test code

Documentation

Overview

Package tagexpr is an interesting go struct tag expression syntax for field validation, etc.

Copyright 2019 Bytedance Inc. All Rights Reserved.

Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at 

http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.

Example 
package main

import (
	"fmt"

	tagexpr "github.com/bytedance/go-tagexpr/v2"
)

func main() {
	type T struct {
		A  int             `tagexpr:"$<0||$>=100"`
		B  string          `tagexpr:"len($)>1 && regexp('^\\w*$')"`
		C  bool            `tagexpr:"expr1:(f.g)$>0 && $; expr2:'C must be true when T.f.g>0'"`
		d  []string        `tagexpr:"@:len($)>0 && $[0]=='D'; msg:sprintf('invalid d: %v',$)"`
		e  map[string]int  `tagexpr:"len($)==$['len']"`
		e2 map[string]*int `tagexpr:"len($)==$['len']"`
		f  struct {
			g int `tagexpr:"$"`
		}
	}

	vm := tagexpr.New("tagexpr")
	t := &T{
		A:  107,
		B:  "abc",
		C:  true,
		d:  []string{"x", "y"},
		e:  map[string]int{"len": 1},
		e2: map[string]*int{"len": new(int)},
		f: struct {
			g int `tagexpr:"$"`
		}{1},
	}

	tagExpr, err := vm.Run(t)
	if err != nil {
		panic(err)
	}

	fmt.Println(tagExpr.Eval("A"))
	fmt.Println(tagExpr.Eval("B"))
	fmt.Println(tagExpr.Eval("C@expr1"))
	fmt.Println(tagExpr.Eval("C@expr2"))
	if !tagExpr.Eval("d").(bool) {
		fmt.Println(tagExpr.Eval("d@msg"))
	}
	fmt.Println(tagExpr.Eval("e"))
	fmt.Println(tagExpr.Eval("e2"))
	fmt.Println(tagExpr.Eval("f.g"))

}

Output:

true
true
true
C must be true when T.f.g>0
invalid d: [x y]
true
false
1

Index

Examples

Constants

View Source 
const (
	// FieldSeparator in the expression selector,
	// the separator between field names
	FieldSeparator = "."
	// ExprNameSeparator in the expression selector,
	// the separator of the field name and expression name
	ExprNameSeparator = "@"
	// DefaultExprName the default name of single model expression
	DefaultExprName = ExprNameSeparator
)

Variables

This section is empty.

Functions

func FakeBool 

func FakeBool(v interface{}) bool

FakeBool fakes any type as a boolean.

func JoinExprSelector 

func JoinExprSelector(pathFields []string, exprName string) string

JoinExprSelector creates a expression selector.

func JoinFieldSelector 

func JoinFieldSelector(path ...string) string

JoinFieldSelector creates a field selector.

func MustRegFunc added in v2.9.8 

func MustRegFunc(funcName string, fn func(...interface{}) interface{}, force ...bool)

MustRegFunc registers function expression. NOTE: 

example: len($), regexp("\\d") or regexp("\\d",$);
If @force=true, allow to cover the existed same @funcName;
The go number types always are float64;
The go string types always are string;
Panic if there is an error.

func RegFunc 

func RegFunc(funcName string, fn func(...interface{}) interface{}, force ...bool) error

RegFunc registers function expression. NOTE: 

example: len($), regexp("\\d") or regexp("\\d",$);
If @force=true, allow to cover the existed same @funcName;
The go number types always are float64;
The go string types always are string.

Types

type Boolean 

type Boolean = bool

Internally unified data types

type Expr 

type Expr struct {
	// contains filtered or unexported fields
}

Expr expression

type ExprHandler 

type ExprHandler struct {
	// contains filtered or unexported fields
}

ExprHandler expr handler

func (*ExprHandler) Eval 

func (e *ExprHandler) Eval() interface{}

Eval evaluate the value of the struct tag expression. NOTE: 

result types: float64, string, bool, nil

func (*ExprHandler) EvalBool 

func (e *ExprHandler) EvalBool() bool

EvalBool evaluates the value of the struct tag expression. NOTE: 

If the expression value is not 0, '' or nil, return true.

func (*ExprHandler) EvalFloat 

func (e *ExprHandler) EvalFloat() float64

EvalFloat evaluates the value of the struct tag expression. NOTE: 

If the expression value type is not float64, return 0.

func (*ExprHandler) EvalString 

func (e *ExprHandler) EvalString() string

EvalString evaluates the value of the struct tag expression. NOTE: 

If the expression value type is not string, return "".

func (*ExprHandler) ExprSelector 

func (e *ExprHandler) ExprSelector() ExprSelector

ExprSelector returns the expression selector of ExprSelector type.

func (*ExprHandler) Path 

func (e *ExprHandler) Path() string

Path returns the path description of the expression.

func (*ExprHandler) StringSelector 

func (e *ExprHandler) StringSelector() string

StringSelector returns the expression selector of string type.

func (*ExprHandler) TagExpr 

func (e *ExprHandler) TagExpr() *TagExpr

TagExpr returns the *TagExpr.

type ExprNode 

type ExprNode interface {
	SetParent(ExprNode)
	Parent() ExprNode
	LeftOperand() ExprNode
	RightOperand() ExprNode
	SetLeftOperand(ExprNode)
	SetRightOperand(ExprNode)
	String() string
	Run(context.Context, string, *TagExpr) interface{}
}

ExprNode expression interface

type ExprSelector 

type ExprSelector string

ExprSelector expression selector

func (ExprSelector) Field 

func (e ExprSelector) Field() string

Field returns the field selector it belongs to.

func (ExprSelector) Name 

func (e ExprSelector) Name() string

Name returns the name of the expression.

func (ExprSelector) ParentField 

func (e ExprSelector) ParentField() (string, bool)

ParentField returns the parent field selector it belongs to.

func (ExprSelector) Split 

func (e ExprSelector) Split() (field FieldSelector, name string)

Split returns the field selector and the expression name.

func (ExprSelector) String 

func (e ExprSelector) String() string

String returns string type value.

type FieldHandler 

type FieldHandler struct {
	// contains filtered or unexported fields
}

FieldHandler field handler

func (*FieldHandler) EvalFuncs 

func (f *FieldHandler) EvalFuncs() map[ExprSelector]func() interface{}

EvalFuncs returns the tag expression eval functions.

func (*FieldHandler) FieldSelector 

func (f *FieldHandler) FieldSelector() FieldSelector

FieldSelector returns the field selector of FieldSelector type.

func (*FieldHandler) StringSelector 

func (f *FieldHandler) StringSelector() string

StringSelector returns the field selector of string type.

func (*FieldHandler) StructField 

func (f *FieldHandler) StructField() reflect.StructField

StructField returns the field StructField object.

func (*FieldHandler) Value 

func (f *FieldHandler) Value(initZero bool) reflect.Value

Value returns the field value. NOTE: 

If initZero==true, initialize nil pointer to zero value

type FieldSelector 

type FieldSelector string

FieldSelector expression selector

func (FieldSelector) Name 

func (f FieldSelector) Name() string

Name returns the current field name.

func (FieldSelector) Parent 

func (f FieldSelector) Parent() (string, bool)

Parent returns the parent FieldSelector.

func (FieldSelector) Split 

func (f FieldSelector) Split() (paths []string, name string)

Split returns the path segments and the current field name.

func (FieldSelector) String 

func (f FieldSelector) String() string

String returns string type value.

type Null 

type Null = interface{}

Internally unified data types

type Number 

type Number = float64

Internally unified data types

type String 

type String = string

Internally unified data types

type TagExpr 

type TagExpr struct {
	// contains filtered or unexported fields
}

TagExpr struct tag expression evaluator

func (*TagExpr) Eval 

func (t *TagExpr) Eval(exprSelector string) interface{}

Eval evaluates the value of the struct tag expression by the selector expression. NOTE: 

format: fieldName, fieldName.exprName, fieldName1.fieldName2.exprName1
result types: float64, string, bool, nil

func (*TagExpr) EvalBool 

func (t *TagExpr) EvalBool(exprSelector string) bool

EvalBool evaluates the value of the struct tag expression by the selector expression. NOTE: 

If the expression value is not 0, '' or nil, return true.

func (*TagExpr) EvalFloat 

func (t *TagExpr) EvalFloat(exprSelector string) float64

EvalFloat evaluates the value of the struct tag expression by the selector expression. NOTE: 

If the expression value type is not float64, return 0.

func (*TagExpr) EvalString 

func (t *TagExpr) EvalString(exprSelector string) string

EvalString evaluates the value of the struct tag expression by the selector expression. NOTE: 

If the expression value type is not string, return "".

func (*TagExpr) Field 

func (t *TagExpr) Field(fieldSelector string) (fh *FieldHandler, found bool)

Field returns the field handler specified by the selector.

func (*TagExpr) Range 

func (t *TagExpr) Range(fn func(*ExprHandler) error) error

Range loop through each tag expression. When fn returns false, interrupt traversal and return false. NOTE: 

eval result types: float64, string, bool, nil

func (*TagExpr) RangeFields 

func (t *TagExpr) RangeFields(fn func(*FieldHandler) bool) bool

RangeFields loop through each field. When fn returns false, interrupt traversal and return false.

type VM 

type VM struct {
	// contains filtered or unexported fields
}

VM struct tag expression interpreter

func New 

func New(tagName ...string) *VM

New creates a tag expression interpreter that uses tagName as the tag name. NOTE: 

If no tagName is specified, no tag expression will be interpreted,
but still can operate the various fields.

func (*VM) MustRun 

func (vm *VM) MustRun(structOrStructPtrOrReflectValue interface{}) *TagExpr

MustRun is similar to Run, but panic when error.

func (*VM) Run 

func (vm *VM) Run(structPtrOrReflectValue interface{}) (*TagExpr, error)

Run returns the tag expression handler of the @structPtrOrReflectValue. NOTE: 

If the structure type has not been warmed up,
it will be slower when it is first called.

Disable new -d=checkptr behaviour for Go 1.14

func (*VM) RunAny 

func (vm *VM) RunAny(v interface{}, fn func(*TagExpr, error) error) error

RunAny returns the tag expression handler for the @v. NOTE: 

The @v can be structured data such as struct, map, slice, array, interface, reflcet.Value, etc.
If the structure type has not been warmed up,
it will be slower when it is first called.

Source Files

View all Source files

Directories

Path Synopsis
gjson
gjson/internal/caching
gjson/internal/rt
tidwall_gjson
Package gjson provides searching for json strings, github.com/tidwall/gjson v1.9.3
 Package gjson provides searching for json strings, github.com/tidwall/gjson v1.9.3
Package validator is a powerful validator that supports struct tag expression.
 Package validator is a powerful validator that supports struct tag expression.

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