Introduce Placer interface (#18)

When implemented, the `Place` method of the `Placer` interface tells `Render` in `El` where to put a Node. This is relevant for helpers that want to be rendered like attributes, inside the parent element.

Fixes the bug where `attr.Classes` was rendered outside the element.

2 files changed, 10 insertions, 0 deletions

diff --git a/attr/attributes.go b/attr/attributes.go
index 56fcd74..415e6f1 100644
--- a/attr/attributes.go
+++ b/attr/attributes.go
@@ -35,6 +35,10 @@ func (c Classes) Render() string {
 	return g.Attr("class", strings.Join(included, " ")).Render()
 }
 
+func (c Classes) Place() g.Placement {
+	return g.Inside
+}
+
 // String satisfies fmt.Stringer.
 func (c Classes) String() string {
 	return c.Render()
diff --git a/attr/attributes_test.go b/attr/attributes_test.go
index 9c7ece7..4da28e3 100644
--- a/attr/attributes_test.go
+++ b/attr/attributes_test.go
@@ -3,6 +3,7 @@ package attr_test
 import (
 	"testing"
 
+	g "github.com/maragudk/gomponents"
 	"github.com/maragudk/gomponents/assert"
 	"github.com/maragudk/gomponents/attr"
 )
@@ -29,6 +30,11 @@ func TestClasses(t *testing.T) {
 		})
 	})
 
+	t.Run("renders as attribute in an element", func(t *testing.T) {
+		e := g.El("div", attr.Classes{"hat": true})
+		assert.Equal(t, `<div class="hat"/>`, e)
+	})
+
 	t.Run("also works with fmt", func(t *testing.T) {
 		a := attr.Classes{"hat": true}
 		if a.String() != ` class="hat"` {