tpl: adds truth and bool template functions

The behavior of `truth` and `bool` is described in the corresponding
test cases and examples. The decision-making around the behavior is a
based on combination of the existing behavior of strconv.ParseBool in go
and the MDN definition of "truthy" as JavaScript has the most interop
with the Hugo ecosystem.

Addresses #9160 and (indirectly) #5792
This commit is contained in:
Khayyam Saleem 2023-01-28 12:21:22 -05:00 committed by ksaleem
parent f650e4d751
commit 5a72de2600
5 changed files with 230 additions and 0 deletions

View file

@ -0,0 +1,48 @@
---
title: bool
linktitle: bool
description: Creates a `bool` from the argument passed into the function.
date: 2023-01-28
publishdate: 2023-01-28
lastmod: 2023-01-28
categories: [functions]
menu:
docs:
parent: "functions"
keywords: [strings,boolean,bool]
signature: ["bool INPUT"]
workson: []
hugoversion:
relatedfuncs: [truth]
deprecated: false
aliases: []
---
Useful for turning ints, strings, and nil into booleans.
```
{{ bool "true" }} → true
{{ bool "false" }} → false
{{ bool "TRUE" }} → true
{{ bool "FALSE" }} → false
{{ truth "t" }} → true
{{ truth "f" }} → false
{{ truth "T" }} → true
{{ truth "F" }} → false
{{ bool "1" }} → true
{{ bool "0" }} → false
{{ bool 1 }} → true
{{ bool 0 }} → false
{{ bool true }} → true
{{ bool false }} → false
{{ bool nil }} → false
```
This function will throw a type-casting error for most other types or strings. For less strict behavior, see [`truth`](/functions/truth).

View file

@ -0,0 +1,53 @@
---
title: truth
linktitle: truth
description: Creates a `bool` from the truthyness of the argument passed into the function
date: 2023-01-28
publishdate: 2023-01-28
lastmod: 2023-01-28
categories: [functions]
menu:
docs:
parent: "functions"
keywords: [strings,boolean,bool,truthy,falsey]
signature: ["truth INPUT"]
workson: []
hugoversion:
relatedfuncs: [bool]
deprecated: false
aliases: []
---
Useful for turning different types into booleans based on their [truthy-ness](https://developer.mozilla.org/en-US/docs/Glossary/Truthy).
It follows the same rules as [`bool`](/functions/bool), but with increased flexibility.
```
{{ truth "true" }} → true
{{ truth "false" }} → false
{{ truth "TRUE" }} → true
{{ truth "FALSE" }} → false
{{ truth "t" }} → true
{{ truth "f" }} → false
{{ truth "T" }} → true
{{ truth "F" }} → false
{{ truth "1" }} → true
{{ truth "0" }} → false
{{ truth 1 }} → true
{{ truth 0 }} → false
{{ truth true }} → true
{{ truth false }} → false
{{ truth nil }} → false
{{ truth "cheese" }} → true
{{ truth 1.67 }} → true
```
This function will not throw an error. For more strict behavior, see [`bool`](/functions/bool).

View file

@ -46,6 +46,28 @@ func (ns *Namespace) ToFloat(v any) (float64, error) {
return _cast.ToFloat64E(v)
}
// ToBool converts v to a boolean.
func (ns *Namespace) ToBool(v any) (bool, error) {
v = convertTemplateToString(v)
return _cast.ToBoolE(v)
}
// ToTruth yields the same behavior as ToBool when possible.
// If the cast is unsuccessful, ToTruth converts v to a boolean using the JavaScript [definition of truthy](https://developer.mozilla.org/en-US/docs/Glossary/Truthy).
// Accordingly, it never yields an error, but maintains the signature of other cast methods for consistency.
func (ns *Namespace) ToTruth(v any) (bool, error) {
result, err := ns.ToBool(v)
if err != nil {
switch v {
case "", "nil", "null", "undefined", "NaN":
return false, nil
default:
return true, nil
}
}
return result, nil
}
func convertTemplateToString(v any) any {
switch vv := v.(type) {
case template.HTML:

View file

@ -117,3 +117,92 @@ func TestToFloat(t *testing.T) {
c.Assert(result, qt.Equals, test.expect, errMsg)
}
}
func TestToBool(t *testing.T) {
t.Parallel()
c := qt.New(t)
ns := New()
for i, test := range []struct {
v any
expect any
error any
}{
{"true", true, nil},
{"false", false, nil},
{"TRUE", true, nil},
{"FALSE", false, nil},
{"t", true, nil},
{"f", false, nil},
{"T", true, nil},
{"F", false, nil},
{"1", true, nil},
{"0", false, nil},
{1, true, nil},
{0, false, nil},
{true, true, nil},
{false, false, nil},
{nil, false, nil},
// error cases
{"cheese", nil, false},
{"", nil, false},
{1.67, nil, false},
} {
errMsg := qt.Commentf("[%d] %v", i, test.v)
result, err := ns.ToBool(test.v)
if b, ok := test.error.(bool); ok && !b {
c.Assert(err, qt.Not(qt.IsNil), errMsg)
continue
}
c.Assert(err, qt.IsNil, errMsg)
c.Assert(result, qt.Equals, test.expect, errMsg)
}
}
func TestToTruth(t *testing.T) {
t.Parallel()
c := qt.New(t)
ns := New()
for i, test := range []struct {
v any
expect any
}{
{"true", true},
{"false", false},
{"TRUE", true},
{"FALSE", false},
{"t", true},
{"f", false},
{"T", true},
{"F", false},
{"1", true},
{"0", false},
{1, true},
{0, false},
{"cheese", true},
{"", false},
{1.67, true},
{template.HTML("2"), true},
{template.CSS("3"), true},
{template.HTMLAttr("4"), true},
{template.JS("-5.67"), true},
{template.JSStr("6"), true},
{t, true},
{nil, false},
{"null", false},
{"undefined", false},
{"NaN", false},
} {
errMsg := qt.Commentf("[%d] %v", i, test.v)
result, err := ns.ToTruth(test.v)
c.Assert(err, qt.IsNil, errMsg)
c.Assert(result, qt.Equals, test.expect, errMsg)
}
}

View file

@ -52,6 +52,24 @@ func init() {
},
)
ns.AddMethodMapping(ctx.ToBool,
[]string{"bool"},
[][2]string{
{`{{ "0" | bool | printf "%T" }}`, `bool`},
{`{{ "true" | bool }}`, `true`},
{`{{ "false" | bool }}`, `false`},
},
)
ns.AddMethodMapping(ctx.ToTruth,
[]string{"truth"},
[][2]string{
{`{{ "1234" | truth | printf "%T" }}`, `bool`},
{`{{ "1234" | truth }}`, `true`},
{`{{ "" | truth }}`, `false`},
},
)
return ns
}