feat: implement stat

Author: connerdouglass

memfs.go

@@ -11,6 +11,8 @@ import (
 )
 
 var _ fs.FS = FS(nil)
+var _ fs.StatFS = FS(nil)
+var _ fs.ReadDirFS = FS(nil)
 
 type FS map[string]Entry
 
@@ -21,11 +23,7 @@ func (f FS) Open(name string) (fs.File, error) {
 	}
 
 	// Normalize the path
-	trimmed := path.Clean(name)
-	trimmed = strings.Trim(trimmed, "/")
-	if trimmed == "." {
-		trimmed = ""
-	}
+	trimmed := normalizePath(name)
 
 	// Find the entry with the pathname
 	entry, ok := f[trimmed]
@@ -40,26 +38,46 @@ func (f FS) Open(name string) (fs.File, error) {
 	}
 
 	// Wrap the file in a struct that implements the fs.File interface
-	basename := path.Base(trimmed)
+	basename := path.Base(name)
 	return &inMemFile{
 		reader: io.NopCloser(bytes.NewReader(fileEntry)),
 		entry:  fileEntry.ToEntry(basename),
 	}, nil
 }
 
-func (f FS) ReadDir(name string) ([]fs.DirEntry, error) {
+func (f FS) Stat(name string) (fs.FileInfo, error) {
 	// If the map is nil, return an error
 	if f == nil {
 		return nil, fs.ErrNotExist
 	}
 
 	// Normalize the path
-	trimmed := path.Clean(name)
-	trimmed = strings.Trim(trimmed, "/")
-	if trimmed == "." {
-		trimmed = ""
+	trimmed := normalizePath(name)
+	basename := path.Base(trimmed)
+
+	// Find the entry with the pathname
+	entry, ok := f[trimmed]
+	if ok {
+		return entry.ToEntry(basename).Info()
+	}
+
+	// Check if there are any child entries
+	entries := f.getEntriesInDir(trimmed)
+	if len(entries) > 0 {
+		return Dir{}.ToEntry(basename).Info()
+	}
+	return nil, fs.ErrNotExist
+}
+
+func (f FS) ReadDir(name string) ([]fs.DirEntry, error) {
+	// If the map is nil, return an error
+	if f == nil {
+		return nil, fs.ErrNotExist
 	}
 
+	// Normalize the path
+	trimmed := normalizePath(name)
+
 	// Check if there is an empty directory entry at the path
 	entryAtPath, hasEntry := f[trimmed]
 	if hasEntry {
@@ -69,6 +87,23 @@ func (f FS) ReadDir(name string) ([]fs.DirEntry, error) {
 		}
 	}
 
+	// Get all the child entries of this path
+	entries := f.getEntriesInDir(trimmed)
+
+	// If there are no entries, and also no empty dir nodes, return an error
+	if len(entries) == 0 && !hasEntry && trimmed != "" {
+		return nil, fs.ErrNotExist
+	}
+
+	// Sort the entries by name
+	slices.SortFunc(entries, func(a, b fs.DirEntry) int {
+		return strings.Compare(a.Name(), b.Name())
+	})
+
+	return entries, nil
+}
+
+func (f FS) getEntriesInDir(trimmed string) []fs.DirEntry {
 	// Look for all the entries that are children of the dir path
 	var entries []fs.DirEntry
 	intermediateDirs := make(map[string]struct{})
@@ -93,16 +128,14 @@ func (f FS) ReadDir(name string) ([]fs.DirEntry, error) {
 		// Add the entry to the list of entries
 		entries = append(entries, entry.ToEntry(suffix))
 	}
+	return entries
+}
 
-	// If there are no entries, and also no empty dir nodes, return an error
-	if len(entries) == 0 && !hasEntry && trimmed != "" {
-		return nil, fs.ErrNotExist
+func normalizePath(name string) string {
+	trimmed := path.Clean(name)
+	trimmed = strings.Trim(trimmed, "/")
+	if trimmed == "." {
+		trimmed = ""
 	}
-
-	// Sort the entries by name
-	slices.SortFunc(entries, func(a, b fs.DirEntry) int {
-		return strings.Compare(a.Name(), b.Name())
-	})
-
-	return entries, nil
+	return trimmed
 }

memfs_test.go

@@ -184,6 +184,27 @@ func TestMemFS(t *testing.T) {
 		require.NoError(t, err, "reading dir")
 		require.ElementsMatch(t, []string{"a"}, entryNames(entries), "reading dir")
 	})
+	t.Run("stat files and directories", func(t *testing.T) {
+		fsys := memfs.FS{
+			"hello/foo/a":       memfs.File("helloworld"),
+			"hello/foo/bar/baz": memfs.Dir{},
+		}
+
+		stat, err := fsys.Stat("hello/foo/a")
+		require.NoError(t, err, "stat file")
+		require.Equal(t, "a", stat.Name(), "stat file name")
+		require.Equal(t, false, stat.IsDir(), "stat file is not dir")
+		require.Equal(t, int64(10), stat.Size(), "stat file size")
+
+		stat, err = fsys.Stat("hello/foo/bar/baz")
+		require.NoError(t, err, "stat dir")
+		require.Equal(t, "baz", stat.Name(), "stat dir name")
+		require.Equal(t, true, stat.IsDir(), "stat dir is dir")
+
+		stat, err = fsys.Stat("hello/foo/doesntexist")
+		require.Error(t, err, "stat non-existent file")
+		require.Nil(t, stat, "stat non-existent file")
+	})
 }
 
 func entryNames(entries []fs.DirEntry) []string {