Make sure replaced pages gets marked as stale

Fixes #12436

3 files changed, 49 insertions, 3 deletions

diff --git a/hugolib/content_map_page.go b/hugolib/content_map_page.go
index 50e1bc35d..5a6b49c55 100644
--- a/hugolib/content_map_page.go
+++ b/hugolib/content_map_page.go
@@ -824,6 +824,9 @@ func (s *contentNodeShifter) Insert(old, new contentNodeI) contentNodeI {
 		if !ok {
 			panic(fmt.Sprintf("unknown type %T", new))
 		}
+		if newp != old {
+			resource.MarkStale(old)
+		}
 		if vv.s.languagei == newp.s.languagei {
 			return new
 		}
@@ -836,7 +839,11 @@ func (s *contentNodeShifter) Insert(old, new contentNodeI) contentNodeI {
 		if !ok {
 			panic(fmt.Sprintf("unknown type %T", new))
 		}
-		resource.MarkStale(vv[newp.s.languagei])
+		oldp := vv[newp.s.languagei]
+		if oldp != newp {
+			resource.MarkStale(oldp)
+		}
+
 		vv[newp.s.languagei] = new
 		return vv
 	case *resourceSource:
@@ -856,7 +863,10 @@ func (s *contentNodeShifter) Insert(old, new contentNodeI) contentNodeI {
 		if !ok {
 			panic(fmt.Sprintf("unknown type %T", new))
 		}
-		resource.MarkStale(vv[newp.LangIndex()])
+		oldp := vv[newp.LangIndex()]
+		if oldp != newp {
+			resource.MarkStale(oldp)
+		}
 		vv[newp.LangIndex()] = newp
 		return vv
 	default:
diff --git a/hugolib/rebuild_test.go b/hugolib/rebuild_test.go
index 4336d8b61..a847af3af 100644
--- a/hugolib/rebuild_test.go
+++ b/hugolib/rebuild_test.go
@@ -1585,3 +1585,39 @@ title: p1
 	b.AddFiles("content/p2.md", "---\ntitle: p2\n---").Build()
 	b.AssertFileContent("public/index.html", "p1|p2|") // this test passes, which doesn't match reality
 }
+
+func TestRebuildHomeThenPageIssue12436(t *testing.T) {
+	t.Parallel()
+
+	files := `
+-- hugo.toml --
+baseURL = "https://example.com"
+disableKinds = ['sitemap','taxonomy','term']
+disableLiveReload = true
+-- layouts/_default/list.html --
+{{ .Content }}
+-- layouts/_default/single.html --
+{{ .Content }}
+-- content/_index.md --
+---
+title: home
+---
+home-content|
+-- content/p1/index.md --
+---
+title: p1
+---
+p1-content|
+`
+
+	b := TestRunning(t, files)
+
+	b.AssertFileContent("public/index.html", "home-content|")
+	b.AssertFileContent("public/p1/index.html", "p1-content|")
+
+	b.EditFileReplaceAll("content/_index.md", "home-content", "home-content-foo").Build()
+	b.AssertFileContent("public/index.html", "home-content-foo")
+
+	b.EditFileReplaceAll("content/p1/index.md", "p1-content", "p1-content-foo").Build()
+	b.AssertFileContent("public/p1/index.html", "p1-content-foo")
+}
diff --git a/hugolib/site_benchmark_new_test.go b/hugolib/site_benchmark_new_test.go
index 023d8e4d5..c028ca526 100644
--- a/hugolib/site_benchmark_new_test.go
+++ b/hugolib/site_benchmark_new_test.go
@@ -487,7 +487,7 @@ Edited!!`, p.Title()))
 
 	// We currently rebuild all the language versions of the same content file.
 	// We could probably optimize that case, but it's not trivial.
-	b.Assert(int(counters.contentRenderCounter.Load()), qt.Equals, 4)
+	b.Assert(int(counters.contentRenderCounter.Load()), qt.Equals, 33)
 	b.AssertFileContent("public"+p.RelPermalink()+"index.html", "Edited!!")
 }