Allow cascade _target to work with non toml fm

The TOML lib unmarshals slices of string maps to []map[string]interface{}
whereas YAML and JSON decode to []interface{}

The existing tests only check for TOML working correctly, and _target
with cascade did not work at all for frontmatter defined in other formats.

Add a function to normalize those slices

Fixes #7874

2 files changed, 57 insertions, 4 deletions

diff --git a/hugolib/cascade_test.go b/hugolib/cascade_test.go
index 336acdcf3..a112fe10c 100644
--- a/hugolib/cascade_test.go
+++ b/hugolib/cascade_test.go
@@ -459,4 +459,58 @@ S1|p1:|p2:p2|
 
 	})
 
+	c.Run("slice with yaml _target", func(c *qt.C) {
+		b := newBuilder(c)
+
+		b.WithContent("_index.md", `---
+title: "Home"
+cascade:
+- p1: p1
+  _target:
+    path: "**p1**"
+- p2: p2
+  _target:
+    kind: "section"
+---
+`)
+
+		b.Build(BuildCfg{})
+
+		b.AssertFileContent("public/index.html", `
+P1|p1:p1|p2:|
+S1|p1:|p2:p2|
+`)
+
+	})
+
+	c.Run("slice with json _target", func(c *qt.C) {
+		b := newBuilder(c)
+
+		b.WithContent("_index.md", `{
+"title": "Home",
+"cascade": [
+  {
+    "p1": "p1",
+	"_target": {
+	  "path": "**p1**"
+    }
+  },{
+    "p2": "p2",
+	"_target": {
+      "kind": "section"
+    }
+  }
+]
+}
+`)
+
+		b.Build(BuildCfg{})
+
+		b.AssertFileContent("public/index.html", `
+		P1|p1:p1|p2:|
+		S1|p1:|p2:p2|
+		`)
+
+	})
+
 }
diff --git a/hugolib/page__meta.go b/hugolib/page__meta.go
index 52ffbb880..d23718315 100644
--- a/hugolib/page__meta.go
+++ b/hugolib/page__meta.go
@@ -342,8 +342,7 @@ func (pm *pageMeta) setMetadata(parentBucket *pagesMapBucket, p *pageState, fron
 		if p.bucket != nil {
 			// Check for any cascade define on itself.
 			if cv, found := frontmatter["cascade"]; found {
-				switch v := cv.(type) {
-				case []map[string]interface{}:
+				if v, err := maps.ToSliceStringMap(cv); err == nil {
 					p.bucket.cascade = make(map[page.PageMatcher]maps.Params)
 
 					for _, vv := range v {
@@ -367,12 +366,12 @@ func (pm *pageMeta) setMetadata(parentBucket *pagesMapBucket, p *pageState, fron
 						}
 
 					}
-				default:
+				} else {
 					p.bucket.cascade = map[page.PageMatcher]maps.Params{
 						page.PageMatcher{}: maps.ToStringMap(cv),
 					}
-				}
 
+				}
 			}
 		}
 	} else {