feta: add globfs

Add a fs.FS impl to allow to filter an existing fs.FS by path patterns.

iox/globfs.go

@@ -0,0 +1,99 @@
+package iox
+
+import (
+	"io/fs"
+	"os"
+	"path"
+)
+
+type GlobFS struct {
+	base     fs.FS
+	patterns []string
+}
+
+// NewGlobFS creates a new GlobFS that exposes only files matching any of the given glob patterns.
+func NewGlobFS(base fs.FS, patterns ...string) *GlobFS {
+	return &GlobFS{base: base, patterns: patterns}
+}
+
+// match reports whether the given path matches any of the configured patterns.
+func (g *GlobFS) match(name string) bool {
+	for _, pat := range g.patterns {
+		if matched, _ := path.Match(pat, name); matched {
+			return true
+		}
+	}
+	return false
+}
+
+func (g *GlobFS) contains(dir string) bool {
+	queue := []string{dir}
+	visited := make(map[string]struct{})
+	for len(queue) > 0 {
+		current := queue[0]
+		queue = queue[1:] // dequeue
+
+		// Prevent visiting same dir multiple times
+		if _, seen := visited[current]; seen {
+			continue
+		}
+		visited[current] = struct{}{}
+
+		entries, err := fs.ReadDir(g.base, current)
+		if err != nil {
+			continue
+		}
+		for _, entry := range entries {
+			rel := path.Join(current, entry.Name())
+			if g.match(rel) {
+				return true
+			}
+			if entry.IsDir() {
+				queue = append(queue, rel)
+			}
+		}
+	}
+	return false
+}
+
+func (g *GlobFS) Open(name string) (fs.File, error) {
+	if g.match(name) {
+		return g.base.Open(name)
+	}
+
+	fi, err := fs.Stat(g.base, name)
+	if err != nil || !fi.IsDir() {
+		return nil, fs.ErrNotExist
+	}
+	if g.contains(name) {
+		return g.base.Open(name)
+	}
+	return nil, fs.ErrNotExist
+}
+
+func (g *GlobFS) ReadDir(name string) ([]fs.DirEntry, error) {
+	if g.match(name) {
+		return fs.ReadDir(g.base, name)
+	}
+
+	entries, err := fs.ReadDir(g.base, name)
+	if err != nil {
+		return nil, err
+	}
+	var children []fs.DirEntry
+	for _, entry := range entries {
+		rel := path.Join(name, entry.Name())
+		if g.match(rel) {
+			children = append(children, entry)
+		}
+		if entry.IsDir() && g.contains(rel) {
+			children = append(children, entry)
+		}
+	}
+
+	if len(children) == 0 {
+		return nil, os.ErrNotExist
+	}
+
+	return children, nil
+}

iox/globfs_test.go

@@ -0,0 +1,234 @@
+package iox
+
+import (
+	"io/fs"
+	"reflect"
+	"sort"
+	"testing"
+	"testing/fstest"
+)
+
+func setupFS() fs.ReadDirFS {
+	// Create an in-memory FS with a mix of files and directories
+	return fstest.MapFS{
+		"main.go":           &fstest.MapFile{Data: []byte("package main")},
+		"main_test.go":      &fstest.MapFile{Data: []byte("package main_test")},
+		"README.md":         &fstest.MapFile{Data: []byte("# readme")},
+		"LICENSE":           &fstest.MapFile{Data: []byte("MIT")},
+		"docs/guide.md":     &fstest.MapFile{Data: []byte("Docs")},
+		"docs/other.txt":    &fstest.MapFile{Data: []byte("Other")},
+		"docs/hidden/.keep": &fstest.MapFile{Data: []byte("")},
+		"assets/img.png":    &fstest.MapFile{Data: []byte("PNG")},
+		"assets/style.css":  &fstest.MapFile{Data: []byte("CSS")},
+		".gitignore":        &fstest.MapFile{Data: []byte("*.log")},
+		".hiddenfile":       &fstest.MapFile{Data: []byte("")},
+		"emptydir/":         &fstest.MapFile{Mode: fs.ModeDir},
+	}
+}
+
+// helper to get base names for easier comparison
+func basenames(entries []fs.DirEntry) []string {
+	names := []string{}
+	for _, e := range entries {
+		names = append(names, e.Name())
+	}
+	sort.Strings(names)
+	return names
+}
+
+func TestGlobFSMultiplePatterns(t *testing.T) {
+	memfs := setupFS()
+	gfs := NewGlobFS(memfs, "*.go", "*.md", "assets/*", "docs/guide.md", ".gitignore")
+
+	tests := []struct {
+		path    string
+		want    []string
+		wantErr bool
+	}{
+		{path: ".", want: []string{"README.md", "assets", "docs", "main.go", "main_test.go", ".gitignore"}},
+		{path: "assets", want: []string{"img.png", "style.css"}},
+		{path: "docs", want: []string{"guide.md"}},
+		{path: "docs/hidden", want: []string{}, wantErr: true},
+		{path: "emptydir", want: []string{}, wantErr: true},
+	}
+
+	for _, tc := range tests {
+		tc := tc // capture range variable
+		t.Run(tc.path, func(t *testing.T) {
+			entries, err := fs.ReadDir(gfs, tc.path)
+			if tc.wantErr && err == nil {
+				t.Errorf("expected error, got nil")
+				return
+			}
+			if !tc.wantErr && err != nil {
+				t.Errorf("unexpected error: %v", err)
+				return
+			}
+			got := basenames(entries)
+			sort.Strings(tc.want)
+			if !reflect.DeepEqual(got, tc.want) {
+				t.Errorf("got %v; want %v", got, tc.want)
+			}
+		})
+	}
+}
+
+func TestGlobFSOpen(t *testing.T) {
+	memfs := setupFS()
+	gfs := NewGlobFS(memfs, "*.go", "*.md", "assets/*", "docs/guide.md", ".gitignore")
+
+	type test struct {
+		path    string
+		wantErr bool
+	}
+	tests := []test{
+		{path: "main.go"},
+		{path: "README.md"},
+		{path: "LICENSE", wantErr: true},
+		{path: "assets/img.png"},
+		{path: "assets/style.css"},
+		{path: "assets/nonexistent.png", wantErr: true},
+		{path: "docs/guide.md"},
+		{path: "docs/other.txt", wantErr: true},
+		{path: ".gitignore"},
+		{path: ".hiddenfile", wantErr: true},
+		{path: "docs/hidden/.keep", wantErr: true},
+		{path: "emptydir", wantErr: true},
+		{path: "docs"},   // allowed because it contains matching file(s)
+		{path: "assets"}, // allowed because it contains matching file(s)
+	}
+	for _, tc := range tests {
+		tc := tc
+		t.Run(tc.path, func(t *testing.T) {
+			f, err := gfs.Open(tc.path)
+			if tc.wantErr && err == nil {
+				t.Errorf("expected error, got file")
+				if f != nil {
+					f.Close()
+				}
+			} else if !tc.wantErr && err != nil {
+				t.Errorf("unexpected error: %v", err)
+			} else if !tc.wantErr && err == nil {
+				info, _ := f.Stat()
+				if info.IsDir() {
+					_, derr := fs.ReadDir(gfs, tc.path)
+					if derr != nil && !tc.wantErr {
+						t.Errorf("unexpected error: %v", derr)
+					}
+				}
+				f.Close()
+			}
+		})
+	}
+}
+
+func TestGlobFSReadFile(t *testing.T) {
+	memfs := setupFS()
+	gfs := NewGlobFS(memfs, "*.go", "*.md", "assets/*", ".gitignore")
+
+	tests := []struct {
+		name    string
+		want    []byte
+		wantErr bool
+	}{
+		{name: "main.go", want: []byte("package main")},
+		{name: "main_test.go", want: []byte("package main_test")},
+		{name: "README.md", want: []byte("# readme")},
+		{name: "assets/img.png", want: []byte("PNG")},
+		{name: "assets/style.css", want: []byte("CSS")},
+		{name: ".gitignore", want: []byte("*.log")},
+		{name: "LICENSE", wantErr: true},           // not allowed by filter
+		{name: "docs/guide.md", wantErr: true},     // not allowed by filter
+		{name: "docs/hidden/.keep", wantErr: true}, // not allowed by filter
+		{name: "doesnotexist.txt", wantErr: true},  // does not exist
+	}
+
+	for _, tc := range tests {
+		tc := tc
+		t.Run(tc.name, func(t *testing.T) {
+			got, err := fs.ReadFile(gfs, tc.name)
+			if tc.wantErr {
+				if err == nil {
+					t.Errorf("expected error, got nil (got=%q)", got)
+				}
+			} else {
+				if err != nil {
+					t.Errorf("unexpected error: %v", err)
+				}
+				if string(got) != string(tc.want) {
+					t.Errorf("got %q; want %q", got, tc.want)
+				}
+			}
+		})
+	}
+}
+
+func TestGlobFSRelativePaths(t *testing.T) {
+	memfs := setupFS()
+	gfs := NewGlobFS(memfs, "docs/*.md")
+	entries, err := fs.ReadDir(gfs, "docs")
+	if err != nil {
+		t.Fatal(err)
+	}
+	got := basenames(entries)
+	want := []string{"guide.md"}
+	if !reflect.DeepEqual(got, want) {
+		t.Errorf("docs/*.md: got %v, want %v", got, want)
+	}
+}
+
+func TestGlobFSNoMatchesOpen(t *testing.T) {
+	gfs := NewGlobFS(setupFS(), "*.xyz")
+	_, err := gfs.Open("main.go")
+	if err == nil {
+		t.Fatal("expected error when opening file with no matches")
+	}
+}
+
+func TestGlobFSNoMatchesStat(t *testing.T) {
+	gfs := NewGlobFS(setupFS(), "*.xyz")
+	_, err := fs.Stat(gfs, "main.go")
+	if err == nil {
+		t.Fatal("expected error with no matches: stat")
+	}
+}
+
+func TestGlobFSNoMatchesReadDir(t *testing.T) {
+	gfs := NewGlobFS(setupFS(), "*.xyz")
+	_, err := fs.ReadDir(gfs, "main.go")
+	if err == nil {
+		t.Fatal("expected error with no matches: readdir")
+	}
+}
+
+func TestGlobFSNoMatchesReadFile(t *testing.T) {
+	gfs := NewGlobFS(setupFS(), "*.xyz")
+	_, err := fs.ReadFile(gfs, "main.go")
+	if err == nil {
+		t.Fatal("expected error with no matches: readfile")
+	}
+}
+
+func TestGlobFS_IntegrationWithStdlib(t *testing.T) {
+	memfs := setupFS()
+	gfs := NewGlobFS(memfs, "*.go", "docs/guide.md")
+	// Use fs.WalkDir with our filtered FS
+	var walked []string
+	err := fs.WalkDir(gfs, ".", func(path string, d fs.DirEntry, err error) error {
+		if err != nil {
+			return err
+		}
+		walked = append(walked, path)
+		return nil
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+	// Only files and dirs matching or containing matches should appear
+	for _, p := range walked {
+		if p == "." || p == "main.go" || p == "main_test.go" || p == "docs" || p == "docs/guide.md" {
+			continue
+		}
+		t.Errorf("WalkDir: unexpected path %q", p)
+	}
+}