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package validation |
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import ( |
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"encoding/json" |
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"errors" |
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"strings" |
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"golang.org/x/text/language" |
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) |
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// Violation is the abstraction for validator errors. You can use your own implementations on the application |
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// side to use it for your needs. In order for the validator to generate application violations, |
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// it is necessary to implement the ViolationFactory interface and inject it into the validator. |
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// You can do this by using the SetViolationFactory option in the NewValidator constructor. |
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type Violation interface { |
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error |
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// Code is unique, short, and semantic string that can be used to programmatically |
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// test for specific violation. All "code" values are defined in the "github.com/muonsoft/validation/code" package |
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// and are protected by backward compatibility rules. |
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Code() string |
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// Is can be used to check that the violation contains one of the specific codes. |
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// For an empty list, it should always returns false. |
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Is(codes ...string) bool |
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// Message is a translated message with injected values from constraint. It can be used to show |
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// a description of a violation to the end-user. Possible values for build-in constraints |
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// are defined in the "github.com/muonsoft/validation/message" package and can be changed at any time, |
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// even in patch versions. |
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Message() string |
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// MessageTemplate is a template for rendering message. Alongside parameters it can be used to |
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// render the message on the client-side of the library. |
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MessageTemplate() string |
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// Parameters is the map of the template variables and their values provided by the specific constraint. |
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Parameters() []TemplateParameter |
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// PropertyPath is a path that points to the violated property. |
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// See PropertyPath type description for more info. |
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PropertyPath() PropertyPath |
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} |
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// ViolationFactory is the abstraction that can be used to create custom violations on the application side. |
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// Use the SetViolationFactory option on the NewValidator constructor to inject your own factory into the validator. |
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type ViolationFactory interface { |
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// CreateViolation creates a new instance of Violation. |
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CreateViolation( |
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code, |
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messageTemplate string, |
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pluralCount int, |
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parameters []TemplateParameter, |
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propertyPath PropertyPath, |
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lang language.Tag, |
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) Violation |
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} |
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// ViolationList is a slice of violations. It is the usual type of error that is returned from a validator. |
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type ViolationList []Violation |
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// NewViolationFunc is an adapter that allows you to use ordinary functions as a ViolationFactory. |
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type NewViolationFunc func( |
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code, |
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messageTemplate string, |
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pluralCount int, |
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parameters []TemplateParameter, |
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propertyPath PropertyPath, |
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lang language.Tag, |
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) Violation |
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// CreateViolation creates a new instance of a Violation. |
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func (f NewViolationFunc) CreateViolation( |
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code, |
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messageTemplate string, |
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pluralCount int, |
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parameters []TemplateParameter, |
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propertyPath PropertyPath, |
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lang language.Tag, |
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) Violation { |
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return f(code, messageTemplate, pluralCount, parameters, propertyPath, lang) |
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} |
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// Error returns a formatted list of errors as a string. |
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func (violations ViolationList) Error() string { |
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if len(violations) == 0 { |
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return "the list of violations is empty, it looks like you forgot to use the AsError method somewhere" |
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} |
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var s strings.Builder |
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s.Grow(32 * len(violations)) |
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for i, v := range violations { |
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if i > 0 { |
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s.WriteString("; ") |
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} |
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if iv, ok := v.(*internalViolation); ok { |
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iv.writeToBuilder(&s) |
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} else { |
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s.WriteString(v.Error()) |
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} |
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} |
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return s.String() |
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} |
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// AppendFromError appends a single violation or a slice of violations into the end of a given slice. |
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// If an error does not implement the Violation or ViolationList interface, it will return an error itself. |
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// Otherwise nil will be returned. |
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// |
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// Example |
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// violations := make(ViolationList, 0) |
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// err := violations.AppendFromError(previousError) |
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// if err != nil { |
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// // this error is not a violation, processing must fail |
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// return err |
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// } |
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// // violations contain appended violations from the previousError and can be processed further |
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func (violations *ViolationList) AppendFromError(err error) error { |
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if violation, ok := UnwrapViolation(err); ok { |
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*violations = append(*violations, violation) |
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} else if violationList, ok := UnwrapViolationList(err); ok { |
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*violations = append(*violations, violationList...) |
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} else if err != nil { |
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return err |
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} |
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return nil |
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} |
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// Has can be used to check that at least one of the violations contains one of the specific codes. |
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// For an empty list of codes, it should always returns false. |
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func (violations ViolationList) Has(codes ...string) bool { |
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for _, violation := range violations { |
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if violation.Is(codes...) { |
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return true |
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} |
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} |
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return false |
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} |
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// Filter returns a new list of violations with violations of given codes. |
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func (violations ViolationList) Filter(codes ...string) ViolationList { |
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filtered := make(ViolationList, 0, len(violations)) |
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for _, violation := range violations { |
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if violation.Is(codes...) { |
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filtered = append(filtered, violation) |
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} |
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} |
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return filtered |
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} |
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// AsError converts the list of violations to an error. This method correctly handles cases where |
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// the list of violations is empty. It returns nil on an empty list, indicating that the validation was successful. |
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func (violations ViolationList) AsError() error { |
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if len(violations) == 0 { |
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return nil |
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} |
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return violations |
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} |
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// IsViolation can be used to verify that the error implements the Violation interface. |
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func IsViolation(err error) bool { |
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var violation Violation |
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return errors.As(err, &violation) |
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} |
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// IsViolationList can be used to verify that the error implements the ViolationList. |
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func IsViolationList(err error) bool { |
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var violations ViolationList |
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return errors.As(err, &violations) |
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} |
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// UnwrapViolation is a short function to unwrap Violation from the error. |
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func UnwrapViolation(err error) (Violation, bool) { |
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var violation Violation |
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as := errors.As(err, &violation) |
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return violation, as |
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} |
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// UnwrapViolationList is a short function to unwrap ViolationList from the error. |
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func UnwrapViolationList(err error) (ViolationList, bool) { |
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var violations ViolationList |
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as := errors.As(err, &violations) |
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return violations, as |
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} |
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type internalViolation struct { |
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code string |
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message string |
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messageTemplate string |
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parameters []TemplateParameter |
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propertyPath PropertyPath |
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} |
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func (v internalViolation) Is(codes ...string) bool { |
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for _, code := range codes { |
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if v.code == code { |
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return true |
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} |
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} |
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return false |
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} |
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func (v internalViolation) Error() string { |
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var s strings.Builder |
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s.Grow(32) |
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v.writeToBuilder(&s) |
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return s.String() |
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} |
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func (v internalViolation) writeToBuilder(s *strings.Builder) { |
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s.WriteString("violation") |
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if len(v.propertyPath) > 0 { |
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s.WriteString(" at '" + v.propertyPath.String() + "'") |
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} |
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s.WriteString(": " + v.message) |
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} |
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func (v internalViolation) Code() string { |
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return v.code |
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} |
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func (v internalViolation) Message() string { |
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return v.message |
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} |
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func (v internalViolation) MessageTemplate() string { |
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return v.messageTemplate |
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} |
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func (v internalViolation) Parameters() []TemplateParameter { |
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return v.parameters |
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} |
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func (v internalViolation) PropertyPath() PropertyPath { |
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return v.propertyPath |
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} |
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func (v internalViolation) MarshalJSON() ([]byte, error) { |
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return json.Marshal(struct { |
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Code string `json:"code"` |
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Message string `json:"message"` |
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PropertyPath PropertyPath `json:"propertyPath,omitempty"` |
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}{ |
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Code: v.code, |
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Message: v.message, |
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PropertyPath: v.propertyPath, |
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}) |
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} |
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type internalViolationFactory struct { |
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translator *Translator |
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} |
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func newViolationFactory(translator *Translator) *internalViolationFactory { |
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return &internalViolationFactory{translator: translator} |
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} |
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func (factory *internalViolationFactory) CreateViolation( |
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code, |
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messageTemplate string, |
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pluralCount int, |
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parameters []TemplateParameter, |
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propertyPath PropertyPath, |
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lang language.Tag, |
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) Violation { |
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message := factory.translator.translate(lang, messageTemplate, pluralCount) |
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return &internalViolation{ |
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code: code, |
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message: renderMessage(message, parameters), |
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messageTemplate: messageTemplate, |
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parameters: parameters, |
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propertyPath: propertyPath, |
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} |
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} |
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// ViolationBuilder used to build an instance of a Violation. |
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type ViolationBuilder struct { |
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code string |
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messageTemplate string |
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pluralCount int |
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parameters []TemplateParameter |
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propertyPath PropertyPath |
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language language.Tag |
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violationFactory ViolationFactory |
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} |
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// NewViolationBuilder creates a new ViolationBuilder. |
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func NewViolationBuilder(factory ViolationFactory) *ViolationBuilder { |
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return &ViolationBuilder{violationFactory: factory} |
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} |
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// BuildViolation creates a new ViolationBuilder for composing Violation object fluently. |
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func (b *ViolationBuilder) BuildViolation(code, message string) *ViolationBuilder { |
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return &ViolationBuilder{ |
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code: code, |
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messageTemplate: message, |
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violationFactory: b.violationFactory, |
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} |
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} |
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// SetParameters sets parameters that can be injected into the violation message. |
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func (b *ViolationBuilder) SetParameters(parameters []TemplateParameter) *ViolationBuilder { |
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b.parameters = parameters |
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return b |
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} |
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// AddParameter adds one parameter into a slice of parameters. |
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func (b *ViolationBuilder) AddParameter(name, value string) *ViolationBuilder { |
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b.parameters = append(b.parameters, TemplateParameter{Key: name, Value: value}) |
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return b |
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} |
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// SetPropertyPath sets a property path of violated attribute. |
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func (b *ViolationBuilder) SetPropertyPath(path PropertyPath) *ViolationBuilder { |
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b.propertyPath = path |
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return b |
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} |
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// SetPluralCount sets a plural number that will be used for message pluralization during translations. |
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func (b *ViolationBuilder) SetPluralCount(pluralCount int) *ViolationBuilder { |
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b.pluralCount = pluralCount |
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return b |
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} |
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// SetLanguage sets language that will be used to translate the violation message. |
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func (b *ViolationBuilder) SetLanguage(tag language.Tag) *ViolationBuilder { |
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b.language = tag |
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return b |
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} |
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// CreateViolation creates a new violation with given parameters and returns it. |
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// Violation is created by calling the CreateViolation method of the ViolationFactory. |
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func (b *ViolationBuilder) CreateViolation() Violation { |
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return b.violationFactory.CreateViolation( |
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b.code, |
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b.messageTemplate, |
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b.pluralCount, |
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b.parameters, |
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b.propertyPath, |
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b.language, |
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) |
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} |
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