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package form
import (
"errors"
"fmt"
"html/template"
"strings"
)
type builder struct {
tpl *template.Template
}
// Inputs will parse the provided struct into fields and then execute the
// template with each field. The returned HTML is simply all of these results
// appended one after another.
//
// Inputs' second argument - errs - will be used to render errors for
// individual fields.
func (b *builder) Inputs(v interface{}, errs ...error) (template.HTML, error) {
tpl, err := b.tpl.Clone()
if err != nil {
return "", err
}
fields := fields(v)
errors := fieldErrors(errs)
var html template.HTML
for _, field := range fields {
var sb strings.Builder
tpl.Funcs(template.FuncMap{
"errors": func() []string {
if errs, ok := errors[field.Name]; ok {
return errs
}
return nil
},
})
err := tpl.Execute(&sb, field)
if err != nil {
return "", err
}
html = html + template.HTML(sb.String())
}
return html, nil
}
// FuncMap returns a template.FuncMap that defines both the inputs_for and
// inputs_and_errors_for functions for usage in the template package. The
// latter is provided via a closure because variadic parameters and the
// template package don't play very nicely and this just simplifies things
// a lot for end users of the form package.
func FuncMap(formTpl *template.Template) template.FuncMap {
b := builder{tpl: formTpl}
return template.FuncMap{
"inputs_for": b.Inputs,
"inputs_and_errors_for": func(v interface{}, errs []error) (template.HTML, error) {
return b.Inputs(v, errs...)
},
}
}
// ParsingFuncMap is present to make it a little easier to build the input template.
// In order to parse a template that uses the `errors` function, you need to have
// that template defined when the template is parsed. We clearly don't know whether
// a field has an error or not until it is parsed.
func ParsingFuncMap() template.FuncMap {
return template.FuncMap{
"errors": func() []string {
return nil
},
}
}
type FieldError struct {
Field string
Issue string
}
func (fe FieldError) Error() string {
return fmt.Sprintf("%s: %v", fe.Field, fe.Issue)
}
// errors will build a map where each key is the field name, and each
// value is a slice of strings representing errors with that field.
func fieldErrors(errs []error) map[string][]string {
ret := make(map[string][]string)
for _, err := range errs {
var fe FieldError
if !errors.As(err, &fe) {
fmt.Println(err, "isnt field error")
continue
}
ret[fe.Field] = append(ret[fe.Field], fe.Issue)
}
return ret
}
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