Fix assets vs data issue

And possibly some other related file mount issues.

Fixes #12133

hugofs/rootmapping_fs.go

@@ -43,7 +43,6 @@ var _ ReverseLookupProvder = (*RootMappingFs)(nil)
 func NewRootMappingFs(fs afero.Fs, rms ...RootMapping) (*RootMappingFs, error) {
 	rootMapToReal := radix.New()
 	realMapToRoot := radix.New()
-	var virtualRoots []RootMapping
 
 	addMapping := func(key string, rm RootMapping, to *radix.Tree) {
 		var mappings []RootMapping
@@ -154,11 +153,8 @@ func NewRootMappingFs(fs afero.Fs, rms ...RootMapping) (*RootMappingFs, error) {
 
 		addMapping(rev, rm, realMapToRoot)
 
-		virtualRoots = append(virtualRoots, rm)
 	}
 
-	rootMapToReal.Insert(filepathSeparator, virtualRoots)
-
 	rfs := &RootMappingFs{
 		Fs:            fs,
 		rootMapToReal: rootMapToReal,
@@ -414,6 +410,7 @@ func (fs *RootMappingFs) getRoots(key string) (string, []RootMapping) {
 	for {
 		var found bool
 		ss, vv, found := tree.LongestPrefix(key)
+
 		if !found || (levels < 2 && ss == key) {
 			break
 		}

hugolib/datafiles_test.go

@@ -64,3 +64,21 @@ v1: {{  site.Data.MyFolder.MyData.v1 }}|
 
 	b.AssertFileContent("public/index.html", "v1: my_v1|")
 }
+
+// Issue #12133
+func TestDataNoAssets(t *testing.T) {
+	t.Parallel()
+
+	files := `
+-- hugo.toml --
+disableKinds = ['page','rss','section','sitemap','taxonomy','term']
+-- assets/data/foo.toml --
+content = "I am assets/data/foo.toml"
+-- layouts/index.html --
+|{{ site.Data.foo.content }}|
+	`
+
+	b := Test(t, files)
+
+	b.AssertFileContent("public/index.html", "||")
+}