Fix HasMenuCurrent and IsDescendant/IsAncestor when comparing to itself

There may be sites in the wild that depends on the faulty behaviour of IsDescendant/IsAncestor when comparing to itself, but

* The documentation and common sense says that a thing cannot be descendant or ancestor to itself.
* The bug introduced in `HasMenuCurrent` comes directly from that confusion.

Fixes #9846

3 files changed, 74 insertions, 12 deletions

diff --git a/hugolib/content_map_test.go b/hugolib/content_map_test.go
index 014ef9c7d..883587a01 100644
--- a/hugolib/content_map_test.go
+++ b/hugolib/content_map_test.go
@@ -383,8 +383,8 @@ Blog Section: {{ template "print-page" $blog }}
 Blog Sub Section: {{ template "print-page" $blogSub }}
 Page: {{ template "print-page" $page }}
 Bundle: {{ template "print-page" $bundle }}
-IsDescendant: true: {{ $page.IsDescendant $blog }} true: {{ $blogSub.IsDescendant $blog }} true: {{ $bundle.IsDescendant $blog }} true: {{ $page4.IsDescendant $blog }} true: {{ $blog.IsDescendant $home }} true: {{ $blog.IsDescendant $blog }} false: {{ $home.IsDescendant $blog }}
-IsAncestor: true: {{ $blog.IsAncestor $page }} true: {{ $home.IsAncestor $blog }} true: {{ $blog.IsAncestor $blogSub }} true: {{ $blog.IsAncestor $bundle }} true: {{ $blog.IsAncestor $page4 }} true: {{ $home.IsAncestor $page }} true: {{ $blog.IsAncestor $blog }} false: {{ $page.IsAncestor $blog }} false: {{ $blog.IsAncestor $home }}  false: {{ $blogSub.IsAncestor $blog }}
+IsDescendant: true: {{ $page.IsDescendant $blog }} true: {{ $blogSub.IsDescendant $blog }} true: {{ $bundle.IsDescendant $blog }} true: {{ $page4.IsDescendant $blog }} true: {{ $blog.IsDescendant $home }} false: {{ $blog.IsDescendant $blog }} false: {{ $home.IsDescendant $blog }}
+IsAncestor: true: {{ $blog.IsAncestor $page }} true: {{ $home.IsAncestor $blog }} true: {{ $blog.IsAncestor $blogSub }} true: {{ $blog.IsAncestor $bundle }} true: {{ $blog.IsAncestor $page4 }} true: {{ $home.IsAncestor $page }} false: {{ $blog.IsAncestor $blog }} false: {{ $page.IsAncestor $blog }} false: {{ $blog.IsAncestor $home }}  false: {{ $blogSub.IsAncestor $blog }}
 IsDescendant overlap1: false: {{ $overlap1.IsDescendant $overlap2 }}
 IsDescendant overlap2: false: {{ $overlap2.IsDescendant $overlap1 }}
 IsAncestor overlap1: false: {{ $overlap1.IsAncestor $overlap2 }}
@@ -426,8 +426,8 @@ Draft5: {{ if (.Site.GetPage "blog/draftsection/sub/page") }}FOUND{{ end }}|
         Blog Sub Section: Page 3|/blog/subsection/|2019-06-03|Current Section: blog/subsection|Resources: application: /blog/subsection/subdata.json|
         Page: Page 1|/blog/page1/|2019-06-01|Current Section: blog|Resources: 
         Bundle: Page 12|/blog/bundle/|0001-01-01|Current Section: blog|Resources: application: /blog/bundle/data.json|page: |
-        IsDescendant: true: true true: true true: true true: true true: true true: true false: false
-        IsAncestor: true: true true: true true: true true: true true: true true: true true: true false: false false: false  false: false
+        IsDescendant: true: true true: true true: true true: true true: true false: false false: false
+        IsAncestor: true: true true: true true: true true: true true: true true: true false: false false: false false: false  false: false
         IsDescendant overlap1: false: false
         IsDescendant overlap2: false: false
         IsAncestor overlap1: false: false
diff --git a/hugolib/menu_test.go b/hugolib/menu_test.go
index 796ac3beb..4237082af 100644
--- a/hugolib/menu_test.go
+++ b/hugolib/menu_test.go
@@ -524,3 +524,67 @@ Blog|HasMenuCurrent: false|Page: Page(/blog/_index.md)
 Blog|IsMenuCurrent: false|Page: Page(/blog/_index.md)
 `)
 }
+
+// Issue 9846
+func TestMenuHasMenuCurrentSection(t *testing.T) {
+	t.Parallel()
+
+	files := `
+-- config.toml --
+disableKinds = ['RSS','sitemap','taxonomy','term']
+[[menu.main]]
+name = 'Home'
+pageRef = '/'
+weight = 1
+
+[[menu.main]]
+name = 'Tests'
+pageRef = '/tests'
+weight = 2
+[[menu.main]]
+name = 'Test 1'
+pageRef = '/tests/test-1'
+parent = 'Tests'
+weight = 1
+
+-- content/tests/test-1.md --
+---
+title: "Test 1"
+---
+-- layouts/_default/list.html --
+{{ range site.Menus.main }}
+{{ .Name }}|{{ .URL }}|IsMenuCurrent = {{ $.IsMenuCurrent "main" . }}|HasMenuCurrent = {{ $.HasMenuCurrent "main" . }}|
+{{ range .Children }}
+{{ .Name }}|{{ .URL }}|IsMenuCurrent = {{ $.IsMenuCurrent "main" . }}|HasMenuCurrent = {{ $.HasMenuCurrent "main" . }}|
+{{ end }}
+{{ end }}
+
+{{/* Some tests for issue 9925 */}}
+{{ $page := .Site.GetPage "tests/test-1" }}
+{{ $section := site.GetPage "tests" }}
+
+Home IsAncestor Self: {{ site.Home.IsAncestor site.Home }}
+Home IsDescendant Self: {{ site.Home.IsDescendant site.Home }}
+Section IsAncestor Self: {{ $section.IsAncestor $section }}
+Section IsDescendant Self: {{ $section.IsDescendant $section}}
+Page IsAncestor Self: {{ $page.IsAncestor $page }}
+Page IsDescendant Self: {{ $page.IsDescendant $page}}
+`
+
+	b := NewIntegrationTestBuilder(
+		IntegrationTestConfig{
+			T:           t,
+			TxtarString: files,
+		},
+	).Build()
+
+	b.AssertFileContent("public/tests/index.html", `
+Tests|/tests/|IsMenuCurrent = true|HasMenuCurrent = false
+Home IsAncestor Self: false
+Home IsDescendant Self: false
+Section IsAncestor Self: false
+Section IsDescendant Self: false
+Page IsAncestor Self: false
+Page IsDescendant Self: false
+`)
+}
diff --git a/hugolib/page__tree.go b/hugolib/page__tree.go
index d2b1f684a..828500e62 100644
--- a/hugolib/page__tree.go
+++ b/hugolib/page__tree.go
@@ -36,6 +36,9 @@ func (pt pageTree) IsAncestor(other any) (bool, error) {
 	}
 
 	ref1, ref2 := pt.p.getTreeRef(), tp.getTreeRef()
+	if ref1 != nil && ref2 != nil && ref1.key == ref2.key {
+		return false, nil
+	}
 
 	if ref1 != nil && ref1.key == "/" {
 		return true, nil
@@ -50,10 +53,6 @@ func (pt pageTree) IsAncestor(other any) (bool, error) {
 		return ref1.n.p.IsHome(), nil
 	}
 
-	if ref1.key == ref2.key {
-		return true, nil
-	}
-
 	if strings.HasPrefix(ref2.key, ref1.key) {
 		return true, nil
 	}
@@ -82,6 +81,9 @@ func (pt pageTree) IsDescendant(other any) (bool, error) {
 	}
 
 	ref1, ref2 := pt.p.getTreeRef(), tp.getTreeRef()
+	if ref1 != nil && ref2 != nil && ref1.key == ref2.key {
+		return false, nil
+	}
 
 	if ref2 != nil && ref2.key == "/" {
 		return true, nil
@@ -96,10 +98,6 @@ func (pt pageTree) IsDescendant(other any) (bool, error) {
 		return ref2.n.p.IsHome(), nil
 	}
 
-	if ref1.key == ref2.key {
-		return true, nil
-	}
-
 	if strings.HasPrefix(ref1.key, ref2.key) {
 		return true, nil
 	}