mirror of
https://github.com/danog/liquid.git
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94 lines
2.6 KiB
Go
94 lines
2.6 KiB
Go
package expressions
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import (
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"fmt"
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"reflect"
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"github.com/osteele/liquid/values"
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)
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// An InterpreterError is an error during expression interpretation.
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// It is used for errors in the input expression, to distinguish them
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// from implementation errors in the interpreter.
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type InterpreterError string
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func (e InterpreterError) Error() string { return string(e) }
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// UndefinedFilter is an error that the named filter is not defined.
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type UndefinedFilter string
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func (e UndefinedFilter) Error() string {
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return fmt.Sprintf("undefined filter %q", string(e))
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}
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// FilterError is the error returned by a filter when it is applied
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type FilterError struct {
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FilterName string
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Err error
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}
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func (e FilterError) Error() string {
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return fmt.Sprintf("error applying filter %q (%q)", e.FilterName, e.Err)
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}
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type valueFn func(Context) values.Value
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// AddFilter adds a filter to the filter dictionary.
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func (c *Config) AddFilter(name string, fn interface{}) {
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rf := reflect.ValueOf(fn)
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switch {
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case rf.Kind() != reflect.Func:
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panic(fmt.Errorf("a filter must be a function"))
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case rf.Type().NumIn() < 1:
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panic(fmt.Errorf("a filter function must have at least one input"))
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case rf.Type().NumOut() < 1 || 2 < rf.Type().NumOut():
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panic(fmt.Errorf("a filter must be have one or two outputs"))
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// case rf.Type().Out(1).Implements(…):
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// panic(typeError("a filter's second output must be type error"))
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}
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if len(c.filters) == 0 {
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c.filters = make(map[string]interface{})
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}
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c.filters[name] = fn
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}
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var closureType = reflect.TypeOf(closure{})
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var interfaceType = reflect.TypeOf([]interface{}{}).Elem()
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func isClosureInterfaceType(t reflect.Type) bool {
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return closureType.ConvertibleTo(t) && !interfaceType.ConvertibleTo(t)
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}
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func (ctx *context) ApplyFilter(name string, receiver valueFn, params []valueFn) (interface{}, error) {
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filter, ok := ctx.filters[name]
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if !ok {
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panic(UndefinedFilter(name))
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}
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fr := reflect.ValueOf(filter)
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args := []interface{}{receiver(ctx).Interface()}
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for i, param := range params {
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if i+1 < fr.Type().NumIn() && isClosureInterfaceType(fr.Type().In(i+1)) {
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expr, err := Parse(param(ctx).Interface().(string))
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if err != nil {
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panic(err)
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}
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args = append(args, closure{expr, ctx})
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} else {
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args = append(args, param(ctx).Interface())
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}
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}
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out, err := values.Call(fr, args)
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if err != nil {
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if e, ok := err.(*values.CallParityError); ok {
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err = &values.CallParityError{NumArgs: e.NumArgs - 1, NumParams: e.NumParams - 1}
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}
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return nil, err
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}
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switch out := out.(type) {
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case []byte:
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return string(out), nil
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default:
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return out, nil
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}
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}
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