Clarify data type returned by partial and partialCached

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Joe Mooring 2023-11-14 15:38:04 -08:00 committed by GitHub
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@ -1,7 +1,7 @@
---
title: Go template functions
title: Go template functions, operators, and statements
linkTitle: go template
description: Template functions and statements provided by Go's text/template package.
description: Template functions, operators, and statements provided by Go's text/template package.
categories: []
keywords: []
menu:
@ -9,6 +9,6 @@ menu:
parent: functions
---
These are the statements, operators, and functions provided by Go's [text/template] package.
These are the functions, operators, and statements provided by Go's [text/template] package.
[text/template]: https://pkg.go.dev/text/template

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@ -0,0 +1,110 @@
---
title: return
description: Used within partial templates, terminates template execution and returns the given value, if any.
categories: []
keywords: []
action:
aliases: []
related:
- functions/partials/Include
- functions/partials/IncludeCached
returnType: any
signatures: ['return [VALUE]']
toc: true
---
The `return` statement is a custom addition to Go's [text/template] package. Used within partial templates, the `return` statement terminates template execution and returns the given value, if any.
The returned value may be of any data type including, but not limited to, [`bool`], [`float`], [`int`], [`map`], [`resource`], [`slice`], and [`string`].
A `return` statement without a value returns an empty string of type `template.HTML`.
[`bool`]: /getting-started/glossary/#bool
[`float`]: /getting-started/glossary/#float
[`int`]: /getting-started/glossary/#int
[`map`]: /getting-started/glossary/#map
[`resource`]: /getting-started/glossary/#resource
[`slice`]: /getting-started/glossary/#slice
[`string`]: /getting-started/glossary/#string
[text/template]: https://pkg.go.dev/text/template
{{% note %}}
Unlike `return` statements in other languages, Hugo executes the first occurence of the `return` statement regardless of its position within logical blocks. See [usage](#usage) notes below.
{{% /note %}}
## Example
By way of example, let's create a partial template that _renders_ HTML, describing whether the given number is odd or even:
{{< code file="layouts/partials/odd-or-even.html" >}}
{{ if math.ModBool . 2 }}
<p>{{ . }} is even</p>
{{ else }}
<p>{{ . }} is odd</p>
{{ end }}
{{< /code >}}
When called, the partial renders HTML:
```go-html-template
{{ partial "odd-or-even.html" 42 }} → <p>42 is even</p>
```
Instead of rendering HTML, let's create a partial that _returns_ a boolean value, reporting whether the given number is even:
{{< code file="layouts/partials/is-even.html" >}}
{{ return math.ModBool . 2 }}
{{< /code >}}
With this template:
```go-html-template
{{ $number := 42 }}
{{ if partial "is-even.html" $number }}
<p>{{ $number }} is even</p>
{{ else }}
<p>{{ $number }} is odd</p>
{{ end }}
```
Hugo renders:
```html
<p>42 is even</p>
```
See additional examples in the [partial templates] section.
[partial templates]: /templates/partials/#returning-a-value-from-a-partial
## Usage
{{% note %}}
Unlike `return` statements in other languages, Hugo executes the first occurence of the `return` statement regardless of its position within logical blocks
{{% /note %}}
A partial that returns a value must contain only one `return` statement, placed at the end of the template.
For example:
{{< code file="layouts/partials/is-even.html" >}}
{{ $result := false }}
{{ if math.ModBool . 2 }}
{{ $result = "even" }}
{{ else }}
{{ $result = "odd" }}
{{ end }}
{{ return $result }}
{{< /code >}}
{{% note %}}
The construct below is incorrect; it contains more than one `return` statement.
{{% /note %}}
{{< code file="layouts/partials/do-not-do-this.html" >}}
{{ if math.ModBool . 2 }}
{{ return "even" }}
{{ else }}
{{ return "odd" }}
{{ end }}
{{< /code >}}

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@ -1,19 +1,24 @@
---
title: partials.Include
description: Executes the given partial template, optionally passing context. If the partial contains a return statement, returns that value, else returns the rendered output.
description: Executes the given partial template, optionally passing context. If the partial template contains a return statement, returns the given value, else returns the rendered output.
categories: []
keywords: []
action:
aliases: [partial]
related:
- functions/go-template/template
- functions/go-template/return
- functions/partials/IncludeCached
- functions/go-template/template
- methods/page/Render
returnType: any
signatures: ['partials.Include NAME [CONTEXT]']
aliases: [/functions/partial]
---
Without a [`return`] statement, the `partial` function returns a string of type `template.HTML`. With a `return` statement, the `partial` function can return any data type.
[`return`]: /functions/go-template/return
In this example we have three partial templates:
```text
@ -60,4 +65,21 @@ Then, within the partial template:
<p>{{ .name }} is majoring in {{ .major }}. Their grade point average is {{ .gpa }}.</p>
```
To return a value from a partial template, it must contain only one `return` statement, placed at the end of the template:
```go-html-template
{{ $result := false }}
{{ if math.ModBool . 2 }}
{{ $result = "even" }}
{{ else }}
{{ $result = "odd" }}
{{ end }}
{{ return $result }}
```
See&nbsp;[details][`return`].
[`return`]: /functions/go-template/return
[breadcrumb navigation]: /content-management/sections/#ancestors-and-descendants
[details]: /functions/go-template/return

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@ -1,13 +1,14 @@
---
title: partials.IncludeCached
description: Executes the given template and caches the result, optionally passing context. If the partial contains a return statement, returns that value, else returns the rendered output.
description: Executes the given template and caches the result, optionally passing context. If the partial template contains a return statement, returns teh given value, else returns the rendered output.
categories: []
keywords: []
action:
aliases: [partialCached]
related:
- functions/go-template/template
- functions/go-template/return
- functions/partials/Include
- functions/go-template/template
- methods/page/Render
returnType: any
signatures: ['partials.IncludeCached LAYOUT CONTEXT [VARIANT...]']
@ -17,7 +18,11 @@ signatures:
aliases: [/functions/partialcached]
---
The `partialCached` template function can offer significant performance gains for complex templates that don't need to be re-rendered on every invocation.
Without a [`return`] statement, the `partialCached` function returns a string of type `template.HTML`. With a `return` statement, the `partialCached` function can return any data type.
The `partialCached` function can offer significant performance gains for complex templates that don't need to be re-rendered on every invocation.
{{% note %}}
Each Site (or language) has its own `partialCached` cache, so each site will execute a partial once.
@ -31,18 +36,32 @@ Here is the simplest usage:
{{ partialCached "footer.html" . }}
```
You can also pass additional arguments to `partialCached` to create *variants* of the cached partial. For example, if you have a complex partial that should be identical when rendered for pages within the same section, you could use a variant based upon section so that the partial is only rendered once per section:
Pass additional arguments to `partialCached` to create variants of the cached partial. For example, if you have a complex partial that should be identical when rendered for pages within the same section, use a variant based on section so that the partial is only rendered once per section:
{{< code file=partial-cached-example.html >}}
{{ partialCached "footer.html" . .Section }}
{{< /code >}}
If you need to pass additional arguments to create unique variants, you can pass as many variant arguments as you need:
Pass additional arguments, of any data type, as needed to create unique variants:
```go-html-template
{{ partialCached "footer.html" . .Params.country .Params.province }}
```
Note that the variant arguments are not made available to the underlying partial template. They are only use to create a unique cache key. Since Hugo `0.61.0` you can use any object as cache key(s), not just strings.
The variant arguments are not available to the underlying partial template; they are only used to create unique cache keys.
See also [The Full Partial Series Part 1: Caching!](https://regisphilibert.com/blog/2019/12/hugo-partial-series-part-1-caching-with-partialcached/).
To return a value from a partial template, it must contain only one `return` statement, placed at the end of the template:
```go-html-template
{{ $result := false }}
{{ if math.ModBool . 2 }}
{{ $result = "even" }}
{{ else }}
{{ $result = "odd" }}
{{ end }}
{{ return $result }}
```
See&nbsp;[details][`return`].
[`return`]: /functions/go-template/return