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package validation_test |
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import ( |
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"context" |
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"errors" |
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"fmt" |
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"github.com/muonsoft/validation" |
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"github.com/muonsoft/validation/it" |
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"github.com/muonsoft/validation/validator" |
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) |
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var ErrNestingLimitReached = errors.New("nesting limit reached") |
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// It is recommended to make a custom constraint to check for nesting limit. |
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type NestingLimitConstraint struct { |
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limit int |
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} |
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func (c NestingLimitConstraint) ValidateProperty(ctx context.Context, validator *validation.Validator, property *Property) error { |
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level, ok := ctx.Value(nestingLevelKey).(int) |
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if !ok { |
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// Don't forget to handle missing value. |
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return fmt.Errorf("nesting level not found in context") |
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} |
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if level >= c.limit { |
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return validator.CreateViolation(ctx, ErrNestingLimitReached, "Maximum nesting level reached.") |
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} |
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return nil |
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} |
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func ItIsNotDeeperThan(limit int) NestingLimitConstraint { |
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return NestingLimitConstraint{limit: limit} |
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} |
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// Properties can be nested. |
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type Property struct { |
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Name string |
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Properties []Property |
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} |
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// You can declare you own constraint interface to create custom constraints. |
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type PropertyConstraint interface { |
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ValidateProperty(ctx context.Context, validator *validation.Validator, property *Property) error |
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} |
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// To create your own functional argument for validation simply create a function with |
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// a typed value and use the validation.NewArgument constructor. |
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func ValidProperty(property *Property, constraints ...PropertyConstraint) validation.ValidatorArgument { |
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return validation.NewArgument(func(ctx context.Context, validator *validation.Validator) (*validation.ViolationList, error) { |
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violations := validation.NewViolationList() |
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for i := range constraints { |
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err := violations.AppendFromError(constraints[i].ValidateProperty(ctx, validator, property)) |
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if err != nil { |
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return nil, err |
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} |
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} |
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return violations, nil |
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}) |
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} |
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type recursionKey string |
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const nestingLevelKey recursionKey = "nestingLevel" |
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func (p Property) Validate(ctx context.Context, validator *validation.Validator) error { |
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return validator.Validate( |
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// Incrementing nesting level in context with special function. |
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contextWithNextNestingLevel(ctx), |
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// Executing validation for maximum nesting level of properties. |
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ValidProperty(&p, ItIsNotDeeperThan(3)), |
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validation.StringProperty("name", p.Name, it.IsNotBlank()), |
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// This should run recursive validation for properties. |
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validation.ValidSliceProperty("properties", p.Properties), |
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) |
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} |
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// This function increments current nesting level. |
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func contextWithNextNestingLevel(ctx context.Context) context.Context { |
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level, ok := ctx.Value(nestingLevelKey).(int) |
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if !ok { |
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level = -1 |
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} |
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return context.WithValue(ctx, nestingLevelKey, level+1) |
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} |
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func ExampleValidator_Validate_usingContextWithRecursion() { |
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properties := []Property{ |
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{ |
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Name: "top", |
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Properties: []Property{ |
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{ |
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Name: "middle", |
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Properties: []Property{ |
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{ |
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Name: "low", |
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Properties: []Property{ |
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// This property should cause a violation. |
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{Name: "limited"}, |
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}, |
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}, |
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}, |
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}, |
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}, |
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}, |
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} |
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err := validator.Validate(context.Background(), validation.ValidSlice(properties)) |
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fmt.Println(err) |
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fmt.Println("errors.Is(err, ErrNestingLimitReached) =", errors.Is(err, ErrNestingLimitReached)) |
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// Output: |
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// violation at "[0].properties[0].properties[0].properties[0]": "Maximum nesting level reached." |
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// errors.Is(err, ErrNestingLimitReached) = true |
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} |
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muonsoft /
validation
