elvish/pkg/eval/vals/has_key.go

package vals

import (
	"reflect"

	"src.elv.sh/pkg/persistent/hashmap"
)

// HasKeyer wraps the HasKey method.
type HasKeyer interface {
	// HasKey returns whether the receiver has the given argument as a valid
	// key.
	HasKey(any) bool
}

// HasKey returns whether a container has a key. It is implemented for the Map
// type, StructMap types, and types satisfying the HasKeyer interface. It falls
// back to iterating keys using IterateKeys, and if that fails, it falls back to
// calling Len and checking if key is a valid numeric or slice index. Otherwise
// it returns false.
func HasKey(container, key any) bool {
	switch container := container.(type) {
	case HasKeyer:
		return container.HasKey(key)
	case Map:
		return hashmap.HasKey(container, key)
	case StructMap:
		return hasKeyStructMap(container, key)
	case PseudoStructMap:
		return hasKeyStructMap(container.Fields(), key)
	default:
		var found bool
		err := IterateKeys(container, func(k any) bool {
			if key == k {
				found = true
			}
			return !found
		})
		if err == nil {
			return found
		}
		if len := Len(container); len >= 0 {
			// TODO(xiaq): Not all types that implement Lener have numerical
			// indices
			_, err := ConvertListIndex(key, len)
			return err == nil
		}
		return false
	}
}

func hasKeyStructMap(m StructMap, k any) bool {
	kstring, ok := k.(string)
	if !ok || kstring == "" {
		return false
	}
	for _, fieldName := range getStructMapInfo(reflect.TypeOf(m)).fieldNames {
		if fieldName == kstring {
			return true
		}
	}
	return false
}