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Diffstat (limited to 'common/hreflect/helpers.go')
-rw-r--r-- | common/hreflect/helpers.go | 91 |
1 files changed, 91 insertions, 0 deletions
diff --git a/common/hreflect/helpers.go b/common/hreflect/helpers.go new file mode 100644 index 000000000..db7b208b5 --- /dev/null +++ b/common/hreflect/helpers.go @@ -0,0 +1,91 @@ +// Copyright 2019 The Hugo Authors. All rights reserved. +// Some functions in this file (see comments) is based on the Go source code, +// copyright The Go Authors and governed by a BSD-style license. +// +// Licensed under the Apache License, Version 2.0 (the "License"); +// you may not use this file except in compliance with the License. +// You may obtain a copy of the License at +// http://www.apache.org/licenses/LICENSE-2.0 +// +// Unless required by applicable law or agreed to in writing, software +// distributed under the License is distributed on an "AS IS" BASIS, +// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. +// See the License for the specific language governing permissions and +// limitations under the License. + +// Package hreflect contains reflect helpers. +package hreflect + +import ( + "reflect" + + "github.com/gohugoio/hugo/common/types" +) + +// IsTruthful returns whether in represents a truthful value. +// See IsTruthfulValue +func IsTruthful(in interface{}) bool { + switch v := in.(type) { + case reflect.Value: + return IsTruthfulValue(v) + default: + return IsTruthfulValue(reflect.ValueOf(in)) + } + +} + +var zeroType = reflect.TypeOf((*types.Zeroer)(nil)).Elem() + +// IsTruthfulValue returns whether the given value has a meaningful truth value. +// This is based on template.IsTrue in Go's stdlib, but also considers +// IsZero and any interface value will be unwrapped before it's considered +// for truthfulness. +// +// Based on: +// https://github.com/golang/go/blob/178a2c42254166cffed1b25fb1d3c7a5727cada6/src/text/template/exec.go#L306 +func IsTruthfulValue(val reflect.Value) (truth bool) { + val = indirectInterface(val) + + if !val.IsValid() { + // Something like var x interface{}, never set. It's a form of nil. + return + } + + if val.Type().Implements(zeroType) { + return !val.Interface().(types.Zeroer).IsZero() + } + + switch val.Kind() { + case reflect.Array, reflect.Map, reflect.Slice, reflect.String: + truth = val.Len() > 0 + case reflect.Bool: + truth = val.Bool() + case reflect.Complex64, reflect.Complex128: + truth = val.Complex() != 0 + case reflect.Chan, reflect.Func, reflect.Ptr, reflect.Interface: + truth = !val.IsNil() + case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64: + truth = val.Int() != 0 + case reflect.Float32, reflect.Float64: + truth = val.Float() != 0 + case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr: + truth = val.Uint() != 0 + case reflect.Struct: + truth = true // Struct values are always true. + default: + return + } + + return +} + +// Based on: https://github.com/golang/go/blob/178a2c42254166cffed1b25fb1d3c7a5727cada6/src/text/template/exec.go#L931 +func indirectInterface(v reflect.Value) reflect.Value { + if v.Kind() != reflect.Interface { + return v + } + if v.IsNil() { + return reflect.Value{} + } + return v.Elem() +} |