Fix regression on handling of overlapping file mounts

But note that the overlay file system is set up horizontally (project -> module1 -> module2), so I would not recommend too complex overlapping mount setups within the same module.

But this worked in v0.122.0, so we should fix it.

Fixes #12103

helpers/general.go

@@ -328,7 +328,14 @@ func PrintFs(fs afero.Fs, path string, w io.Writer) {
 	}
 
 	afero.Walk(fs, path, func(path string, info os.FileInfo, err error) error {
-		fmt.Fprintln(w, filepath.ToSlash(path))
+		if err != nil {
+			panic(fmt.Sprintf("error: path %q: %s", path, err))
+		}
+		path = filepath.ToSlash(path)
+		if path == "" {
+			path = "."
+		}
+		fmt.Fprintln(w, path, info.IsDir())
 		return nil
 	})
 }

hugofs/rootmapping_fs.go

@@ -323,7 +323,6 @@ func (fs *RootMappingFs) Stat(name string) (os.FileInfo, error) {
 	if err != nil {
 		return nil, err
 	}
-
 	return fis[0], nil
 }
 
@@ -403,16 +402,42 @@ func (fs *RootMappingFs) getRoot(key string) []RootMapping {
 }
 
 func (fs *RootMappingFs) getRoots(key string) (string, []RootMapping) {
-	return fs.getRootsIn(key, fs.rootMapToReal)
+	tree := fs.rootMapToReal
+	levels := strings.Count(key, filepathSeparator)
+	seen := make(map[RootMapping]bool)
+
+	var roots []RootMapping
+	var s string
+
+	for {
+		var found bool
+		ss, vv, found := tree.LongestPrefix(key)
+		if !found || (levels < 2 && ss == key) {
+			break
+		}
+
+		for _, rm := range vv.([]RootMapping) {
+			if !seen[rm] {
+				seen[rm] = true
+				roots = append(roots, rm)
+			}
+		}
+		s = ss
+
+		// We may have more than one root for this key, so walk up.
+		oldKey := key
+		key = filepath.Dir(key)
+		if key == oldKey {
+			break
+		}
+	}
+
+	return s, roots
 }
 
 func (fs *RootMappingFs) getRootsReverse(key string) (string, []RootMapping) {
-	return fs.getRootsIn(key, fs.realMapToRoot)
-}
-
-func (fs *RootMappingFs) getRootsIn(key string, tree *radix.Tree) (string, []RootMapping) {
+	tree := fs.realMapToRoot
 	s, v, found := tree.LongestPrefix(key)
-
 	if !found {
 		return "", nil
 	}

hugolib/filesystems/basefs_test.go

@@ -478,11 +478,47 @@ Home.
 	_ = stat("blog/b1.md")
 }
 
+func TestStaticComposite(t *testing.T) {
+	files := `
+-- hugo.toml --
+disableKinds = ["taxonomy", "term"]
+[module]
+[[module.mounts]]
+source = "myfiles/f1.txt"
+target = "static/files/f1.txt"
+[[module.mounts]]
+source = "f3.txt"
+target = "static/f3.txt"
+[[module.mounts]]
+source = "static"
+target = "static"
+-- static/files/f2.txt --
+f2
+-- myfiles/f1.txt --
+f1
+-- f3.txt --
+f3
+-- layouts/home.html --
+Home.
+
+`
+	b := hugolib.Test(t, files)
+
+	b.AssertFs(b.H.BaseFs.StaticFs(""), `
+. true
+f3.txt false
+files true
+files/f1.txt false
+files/f2.txt false
+`)
+}
+
 func checkFileCount(fs afero.Fs, dirname string, c *qt.C, expected int) {
 	c.Helper()
-	count, _, err := countFilesAndGetFilenames(fs, dirname)
-	c.Assert(err, qt.IsNil)
-	c.Assert(count, qt.Equals, expected)
+	count, names, err := countFilesAndGetFilenames(fs, dirname)
+	namesComment := qt.Commentf("filenames: %v", names)
+	c.Assert(err, qt.IsNil, namesComment)
+	c.Assert(count, qt.Equals, expected, namesComment)
 }
 
 func checkFileContent(fs afero.Fs, filename string, c *qt.C, expected ...string) {

hugolib/integrationtest_builder.go

@@ -275,9 +275,13 @@ func (s *IntegrationTestBuilder) AssertFileContentExact(filename string, matches
 }
 
 func (s *IntegrationTestBuilder) AssertPublishDir(matches ...string) {
+	s.AssertFs(s.fs.PublishDir, matches...)
+}
+
+func (s *IntegrationTestBuilder) AssertFs(fs afero.Fs, matches ...string) {
 	s.Helper()
 	var buff bytes.Buffer
-	helpers.PrintFs(s.H.Fs.PublishDir, "", &buff)
+	helpers.PrintFs(fs, "", &buff)
 	printFsLines := strings.Split(buff.String(), "\n")
 	sort.Strings(printFsLines)
 	content := strings.TrimSpace((strings.Join(printFsLines, "\n")))

testscripts/commands/hugo__static_composite.txt

@@ -0,0 +1,27 @@
+hugo
+ls public/files
+checkfile public/files/f1.txt
+checkfile public/files/f2.txt
+checkfile public/f3.txt
+
+-- hugo.toml --
+disableKinds = ["taxonomy", "term"]
+[module]
+[[module.mounts]]
+source = "myfiles/f1.txt"
+target = "static/files/f1.txt"
+[[module.mounts]]
+source = "f3.txt"
+target = "static/f3.txt"
+[[module.mounts]]
+source = "static"
+target = "static"
+-- static/files/f2.txt --
+f2
+-- myfiles/f1.txt --
+f1
+-- f3.txt --
+f3
+-- layouts/home.html --
+Home.
+