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Allow for return partials with falsy arguments #9298

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Dec 17, 2021
Merged

Allow for return partials with falsy arguments #9298

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449d1dd
Allow for return partials with falsy arguments
ptgott Dec 4, 2021
4708b1e
Address PR feedback
ptgott Dec 17, 2021
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38 changes: 25 additions & 13 deletions hugolib/template_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -456,22 +456,34 @@ complex: 80: 80
`,
)
})
}

c.Run("Zero argument", func(c *qt.C) {
b := newBuilder(c)

b.WithTemplatesAdded(
"index.html", `
Test Partials With Return Values:

add42: fail: {{ partial "add42.tpl" 0 }}
// Issue 7528
func TestPartialWithZeroedArgs(t *testing.T) {

`,
)
b := newTestSitesBuilder(t)
b.WithTemplatesAdded("index.html",
`
X{{ partial "retval" dict }}X
X{{ partial "retval" slice }}X
X{{ partial "retval" "" }}X
X{{ partial "retval" false }}X
X{{ partial "retval" 0 }}X
{{ define "partials/retval" }}
{{ return 123 }}
{{ end }}`)

b.WithContentAdded("p.md", ``)
b.Build(BuildCfg{})
b.AssertFileContent("public/index.html",
`
X123X
X123X
X123X
X123X
X123X
`)

e := b.CreateSites().BuildE(BuildCfg{})
b.Assert(e, qt.Not(qt.IsNil))
})
}

func TestPartialCached(t *testing.T) {
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5 changes: 0 additions & 5 deletions tpl/partials/partials.go
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Expand Up @@ -25,7 +25,6 @@ import (
"strings"
"sync"

"github.com/gohugoio/hugo/common/hreflect"
texttemplate "github.com/gohugoio/hugo/tpl/internal/go_templates/texttemplate"

"github.com/gohugoio/hugo/helpers"
Expand Down Expand Up @@ -121,10 +120,6 @@ func (ns *Namespace) Include(name string, contextList ...interface{}) (interface
var w io.Writer

if info.HasReturn {
if !hreflect.IsTruthful(context) {
// TODO(bep) we need to fix this, but it is non-trivial.
return nil, errors.New("partial that returns a value needs a non-zero argument.")
}
// Wrap the context sent to the template to capture the return value.
// Note that the template is rewritten to make sure that the dot (".")
// and the $ variable points to Arg.
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14 changes: 10 additions & 4 deletions tpl/tplimpl/template_ast_transformers.go
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Expand Up @@ -112,7 +112,11 @@ func getParseTree(templ tpl.Template) *parse.Tree {
}

const (
partialReturnWrapperTempl = `{{ $_hugo_dot := $ }}{{ $ := .Arg }}{{ with .Arg }}{{ $_hugo_dot.Set ("PLACEHOLDER") }}{{ end }}`
// We parse this template and modify the nodes in order to assign
// the return value of a partial to a contextWrapper via Set. We use
// "range" over a one-element slice so we can shift dot to the
// partial's argument, Arg, while allowing Arg to be falsy.
partialReturnWrapperTempl = `{{ $_hugo_dot := $ }}{{ $ := .Arg }}{{ range (slice .Arg) }}{{ $_hugo_dot.Set ("PLACEHOLDER") }}{{ end }}`
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I suspect it would be easier to understand if you make contextWrapper.Arg a []interface{} -- and just add a comment there explaining why it's a slice with a single value.

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I gave this a go, though my attempt at a comment depended on explaining what we were doing with the partialReturnWrapperTempl. In the end, I found it simpler to add a comment above partialReturnWrapperTempl while leaving contextWrapper.Arg as it was. How does that sound?

)

var partialReturnWrapper *parse.ListNode
Expand All @@ -125,16 +129,18 @@ func init() {
partialReturnWrapper = templ.Tree.Root
}

// wrapInPartialReturnWrapper copies and modifies the parsed nodes of a
// predefined partial return wrapper to insert those of a user-defined partial.
func (c *templateContext) wrapInPartialReturnWrapper(n *parse.ListNode) *parse.ListNode {
wrapper := partialReturnWrapper.CopyList()
withNode := wrapper.Nodes[2].(*parse.WithNode)
retn := withNode.List.Nodes[0]
rangeNode := wrapper.Nodes[2].(*parse.RangeNode)
retn := rangeNode.List.Nodes[0]
setCmd := retn.(*parse.ActionNode).Pipe.Cmds[0]
setPipe := setCmd.Args[1].(*parse.PipeNode)
// Replace PLACEHOLDER with the real return value.
// Note that this is a PipeNode, so it will be wrapped in parens.
setPipe.Cmds = []*parse.CommandNode{c.returnNode}
withNode.List.Nodes = append(n.Nodes, retn)
rangeNode.List.Nodes = append(n.Nodes, retn)

return wrapper
}
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