chore: import upstream snapshot with attribution

internal/skillcontent/reader.go

@@ -0,0 +1,209 @@
+// Copyright (c) 2026 Lark Technologies Pte. Ltd.
+// SPDX-License-Identifier: MIT
+
+// Package skillcontent reads embedded skill content from an injected fs.FS
+// rooted at the skill list (entries like "lark-calendar/SKILL.md").
+package skillcontent
+
+import (
+	"io/fs"
+	"path"
+	"sort"
+	"strings"
+
+	"github.com/larksuite/cli/errs"
+	"gopkg.in/yaml.v3"
+)
+
+type Reader struct {
+	fsys fs.FS
+}
+
+func New(fsys fs.FS) *Reader { return &Reader{fsys: fsys} }
+
+type SkillInfo struct {
+	Name        string         `json:"name"`
+	Description string         `json:"description"`
+	Version     string         `json:"version,omitempty"`
+	Metadata    map[string]any `json:"metadata,omitempty"`
+}
+
+// DirEntry.Path is skill-prefixed (e.g. "lark-doc/references/x.md") so it can be
+// fed straight back into `read`.
+type DirEntry struct {
+	Path  string `json:"path"`
+	IsDir bool   `json:"is_dir"`
+}
+
+func (r *Reader) List() ([]SkillInfo, error) {
+	entries, err := fs.ReadDir(r.fsys, ".")
+	if err != nil {
+		return nil, errs.NewInternalError(errs.SubtypeFileIO, "failed to read embedded skills: %v", err)
+	}
+	out := make([]SkillInfo, 0, len(entries))
+	for _, e := range entries {
+		if !e.IsDir() {
+			continue
+		}
+		// Skip dirs that aren't real skills (no SKILL.md).
+		if info, ok := r.skillInfo(e.Name()); ok {
+			out = append(out, info)
+		}
+	}
+	sort.Slice(out, func(i, j int) bool { return out[i].Name < out[j].Name })
+	return out, nil
+}
+
+func (r *Reader) skillInfo(name string) (SkillInfo, bool) {
+	data, err := fs.ReadFile(r.fsys, name+"/SKILL.md")
+	if err != nil {
+		return SkillInfo{}, false
+	}
+	desc, version, metadata := parseFrontmatter(data)
+	return SkillInfo{Name: name, Description: desc, Version: version, Metadata: metadata}, true
+}
+
+// ListPath lists one directory layer (no recursion) under "<name>" or
+// "<name>/<sub>", returning the entries and the cleaned path listed.
+func (r *Reader) ListPath(arg string) ([]DirEntry, string, error) {
+	name, sub := SplitArg(arg)
+	if err := r.ensureSkill(name); err != nil {
+		return nil, "", err
+	}
+	dir := name
+	if sub != "" {
+		cleaned, err := cleanSubPath(sub)
+		if err != nil {
+			return nil, "", err
+		}
+		dir = name + "/" + cleaned
+		info, err := fs.Stat(r.fsys, dir)
+		if err != nil {
+			return nil, "", errs.NewValidationError(errs.SubtypeInvalidArgument,
+				"path %q not found in skill %q", sub, name).
+				WithHint("run 'lark-cli skills list " + name + "' to see files in this skill")
+		}
+		if !info.IsDir() {
+			return nil, "", errs.NewValidationError(errs.SubtypeInvalidArgument,
+				"path %q is a file, not a directory; use 'lark-cli skills read %s/%s' to read it", sub, name, cleaned)
+		}
+	}
+	entries, err := fs.ReadDir(r.fsys, dir)
+	if err != nil {
+		return nil, "", errs.NewInternalError(errs.SubtypeFileIO,
+			"failed to read embedded skill content: %v", err)
+	}
+	out := make([]DirEntry, 0, len(entries))
+	for _, e := range entries {
+		out = append(out, DirEntry{Path: dir + "/" + e.Name(), IsDir: e.IsDir()})
+	}
+	sort.Slice(out, func(i, j int) bool { return out[i].Path < out[j].Path })
+	return out, dir, nil
+}
+
+// SplitArg splits "<name>/<rest>" at the first separator; an argument with no
+// separator is a bare skill name (rest "").
+func SplitArg(arg string) (name, rest string) {
+	name, rest, _ = strings.Cut(arg, "/")
+	return name, rest
+}
+
+// parseFrontmatter best-effort-extracts the frontmatter fields; missing or
+// unparseable frontmatter yields ("", "", nil), never an error.
+func parseFrontmatter(skillMD []byte) (description, version string, metadata map[string]any) {
+	lines := strings.Split(string(skillMD), "\n")
+	if strings.TrimRight(lines[0], "\r") != "---" {
+		return "", "", nil
+	}
+	block := make([]string, 0, len(lines))
+	closed := false
+	for _, ln := range lines[1:] {
+		if strings.TrimRight(ln, "\r") == "---" {
+			closed = true
+			break
+		}
+		block = append(block, ln)
+	}
+	if !closed {
+		return "", "", nil
+	}
+	var fm struct {
+		Description string         `yaml:"description"`
+		Version     string         `yaml:"version"`
+		Metadata    map[string]any `yaml:"metadata"`
+	}
+	if err := yaml.Unmarshal([]byte(strings.Join(block, "\n")), &fm); err != nil {
+		return "", "", nil
+	}
+	return fm.Description, fm.Version, fm.Metadata
+}
+
+func (r *Reader) ReadSkill(name string) ([]byte, error) {
+	if err := r.ensureSkill(name); err != nil {
+		return nil, err
+	}
+	data, err := fs.ReadFile(r.fsys, name+"/SKILL.md")
+	if err != nil {
+		return nil, errs.NewInternalError(errs.SubtypeFileIO,
+			"failed to read embedded skill content: %v", err)
+	}
+	return data, nil
+}
+
+func (r *Reader) ensureSkill(name string) error {
+	if name == "" || strings.ContainsAny(name, `/\`) || name == "." || name == ".." {
+		return unknownSkill(name)
+	}
+	info, err := fs.Stat(r.fsys, name)
+	if err != nil || !info.IsDir() {
+		return unknownSkill(name)
+	}
+	return nil
+}
+
+func unknownSkill(name string) error {
+	return errs.NewValidationError(errs.SubtypeInvalidArgument, "unknown skill %q", name).
+		WithHint("run 'lark-cli skills list' to see available skills")
+}
+
+// cleanSubPath returns the cleaned form of relpath, rejecting absolute paths and
+// ".." escapes. relpath must be non-empty (callers handle the skill-root case).
+func cleanSubPath(relpath string) (string, error) {
+	cleaned := path.Clean(relpath)
+	// path.Clean only treats '/' as a separator, so a Windows-style "..\" prefix
+	// survives; reject it explicitly alongside "../".
+	if relpath == "" || path.IsAbs(relpath) || cleaned == "." ||
+		cleaned == ".." || strings.HasPrefix(cleaned, "../") || strings.HasPrefix(cleaned, `..\`) {
+		return "", errs.NewValidationError(errs.SubtypeInvalidArgument,
+			"invalid path %q: must be a relative path without '..'", relpath)
+	}
+	return cleaned, nil
+}
+
+// ReadReference returns the bytes of <name>/<relpath> and the cleaned path.
+func (r *Reader) ReadReference(name, relpath string) ([]byte, string, error) {
+	if err := r.ensureSkill(name); err != nil {
+		return nil, "", err
+	}
+	cleaned, err := cleanSubPath(relpath)
+	if err != nil {
+		return nil, "", err
+	}
+	full := name + "/" + cleaned
+	info, err := fs.Stat(r.fsys, full)
+	if err != nil {
+		return nil, "", errs.NewValidationError(errs.SubtypeInvalidArgument,
+			"reference %q not found in skill %q", relpath, name).
+			WithHint("run 'lark-cli skills list " + name + "' to see files in this skill")
+	}
+	if info.IsDir() {
+		return nil, "", errs.NewValidationError(errs.SubtypeInvalidArgument,
+			"reference %q is a directory, not a file", relpath)
+	}
+	data, err := fs.ReadFile(r.fsys, full)
+	if err != nil {
+		return nil, "", errs.NewInternalError(errs.SubtypeFileIO,
+			"failed to read embedded skill content: %v", err)
+	}
+	return data, cleaned, nil
+}

internal/skillcontent/reader_test.go

@@ -0,0 +1,290 @@
+// Copyright (c) 2026 Lark Technologies Pte. Ltd.
+// SPDX-License-Identifier: MIT
+
+package skillcontent
+
+import (
+	"errors"
+	"strings"
+	"testing"
+	"testing/fstest"
+
+	"github.com/larksuite/cli/errs"
+)
+
+func testFS() fstest.MapFS {
+	return fstest.MapFS{
+		"lark-calendar/SKILL.md":             {Data: []byte("---\nname: lark-calendar\nversion: 1.0.0\ndescription: \"Calendar skill\"\nmetadata:\n  requires:\n    bins: [\"lark-cli\"]\n  cliHelp: \"lark-cli calendar --help\"\n---\nbody\n")},
+		"lark-calendar/references/agenda.md": {Data: []byte("# Agenda")},
+		"lark-calendar/references/create.md": {Data: []byte("# Create")},
+		"lark-calendar/assets/tpl.html":      {Data: []byte("<html></html>")},
+		"lark-im/SKILL.md":                   {Data: []byte("no frontmatter here\n")},
+		"lark-im/references/send.md":         {Data: []byte("# Send")},
+	}
+}
+
+func TestList(t *testing.T) {
+	r := New(testFS())
+	skills, err := r.List()
+	if err != nil {
+		t.Fatalf("List() error: %v", err)
+	}
+	if len(skills) != 2 {
+		t.Fatalf("got %d skills, want 2", len(skills))
+	}
+	if skills[0].Name != "lark-calendar" || skills[1].Name != "lark-im" {
+		t.Fatalf("skills not sorted by name: %v", skills)
+	}
+	if skills[0].Description != "Calendar skill" {
+		t.Errorf("description: got %q, want %q", skills[0].Description, "Calendar skill")
+	}
+	// version is the frontmatter `version:` field, passed through for drift checks.
+	if skills[0].Version != "1.0.0" {
+		t.Errorf("version: got %q, want %q", skills[0].Version, "1.0.0")
+	}
+	// metadata is the frontmatter `metadata:` block, passed through verbatim.
+	if skills[0].Metadata == nil {
+		t.Fatal("expected metadata for lark-calendar")
+	}
+	if skills[0].Metadata["cliHelp"] != "lark-cli calendar --help" {
+		t.Errorf("metadata.cliHelp: got %v", skills[0].Metadata["cliHelp"])
+	}
+	// No frontmatter → empty description and nil metadata (omitted from JSON).
+	if skills[1].Description != "" {
+		t.Errorf("lark-im description: got %q, want empty", skills[1].Description)
+	}
+	if skills[1].Metadata != nil {
+		t.Errorf("lark-im metadata: got %v, want nil", skills[1].Metadata)
+	}
+	if skills[1].Version != "" {
+		t.Errorf("lark-im version: got %q, want empty", skills[1].Version)
+	}
+}
+
+func TestListPath(t *testing.T) {
+	r := New(testFS())
+
+	// Skill root: direct children only (one layer), each path skill-prefixed.
+	entries, listed, err := r.ListPath("lark-calendar")
+	if err != nil {
+		t.Fatalf("ListPath root error: %v", err)
+	}
+	if listed != "lark-calendar" {
+		t.Errorf("listed path: got %q", listed)
+	}
+	want := map[string]bool{ // path → isDir
+		"lark-calendar/SKILL.md":   false,
+		"lark-calendar/references": true,
+		"lark-calendar/assets":     true,
+	}
+	if len(entries) != len(want) {
+		t.Fatalf("root entries: got %v, want %d entries", entries, len(want))
+	}
+	for _, e := range entries {
+		isDir, ok := want[e.Path]
+		if !ok {
+			t.Errorf("unexpected entry %q", e.Path)
+			continue
+		}
+		if e.IsDir != isDir {
+			t.Errorf("%q is_dir: got %v, want %v", e.Path, e.IsDir, isDir)
+		}
+	}
+	// Entries are sorted by path.
+	if entries[0].Path != "lark-calendar/SKILL.md" {
+		t.Errorf("entries not sorted: %v", entries)
+	}
+
+	// Subdirectory: one layer under <name>/<subpath>.
+	subEntries, subListed, err := r.ListPath("lark-calendar/references")
+	if err != nil {
+		t.Fatalf("ListPath subdir error: %v", err)
+	}
+	if subListed != "lark-calendar/references" {
+		t.Errorf("listed subpath: got %q", subListed)
+	}
+	if len(subEntries) != 2 ||
+		subEntries[0].Path != "lark-calendar/references/agenda.md" ||
+		subEntries[1].Path != "lark-calendar/references/create.md" {
+		t.Errorf("subdir entries: got %v", subEntries)
+	}
+
+	// Unknown skill → typed validation error.
+	if _, _, err := r.ListPath("no-such-skill"); err == nil {
+		t.Error("expected error for unknown skill")
+	} else {
+		var verr *errs.ValidationError
+		if !errors.As(err, &verr) {
+			t.Errorf("expected *errs.ValidationError, got %T", err)
+		}
+	}
+
+	// Path that points at a file (not a dir) → validation error.
+	if _, _, err := r.ListPath("lark-calendar/SKILL.md"); err == nil {
+		t.Error("expected error listing a file")
+	} else if !strings.Contains(err.Error(), "is a file") {
+		t.Errorf("message: got %q", err.Error())
+	}
+
+	// Nonexistent subpath → validation error.
+	if _, _, err := r.ListPath("lark-calendar/nope"); err == nil {
+		t.Error("expected not-found error")
+	} else if !strings.Contains(err.Error(), "not found") {
+		t.Errorf("message: got %q", err.Error())
+	}
+
+	// Traversal in the subpath is rejected, no listing leaked.
+	for _, bad := range []string{"lark-calendar/../lark-im", "lark-calendar/../../etc", `lark-calendar/..\x`} {
+		entries, _, err := r.ListPath(bad)
+		if err == nil {
+			t.Errorf("expected rejection for %q", bad)
+		}
+		if entries != nil {
+			t.Errorf("entries leaked for %q: %v", bad, entries)
+		}
+	}
+}
+
+func TestReadSkill(t *testing.T) {
+	r := New(testFS())
+
+	data, err := r.ReadSkill("lark-calendar")
+	if err != nil {
+		t.Fatalf("ReadSkill error: %v", err)
+	}
+	if !strings.HasPrefix(string(data), "---\nname: lark-calendar") {
+		t.Errorf("unexpected content: %q", string(data))
+	}
+
+	_, err = r.ReadSkill("no-such-skill")
+	if err == nil {
+		t.Fatal("expected error for unknown skill")
+	}
+	var verr *errs.ValidationError
+	if !errors.As(err, &verr) {
+		t.Fatalf("expected *errs.ValidationError, got %T", err)
+	}
+	if !strings.Contains(verr.Message, `unknown skill "no-such-skill"`) {
+		t.Errorf("message: got %q", verr.Message)
+	}
+
+	if _, err := r.ReadSkill("../etc"); err == nil {
+		t.Error("expected error for name with separator")
+	}
+}
+
+func TestReadReference(t *testing.T) {
+	r := New(testFS())
+
+	data, cleaned, err := r.ReadReference("lark-calendar", "references/agenda.md")
+	if err != nil {
+		t.Fatalf("ReadReference error: %v", err)
+	}
+	if string(data) != "# Agenda" {
+		t.Errorf("content: got %q", string(data))
+	}
+	if cleaned != "references/agenda.md" {
+		t.Errorf("cleaned path: got %q", cleaned)
+	}
+
+	if _, _, err := r.ReadReference("lark-calendar", "references/nope.md"); err == nil {
+		t.Error("expected not-found error")
+	} else if !strings.Contains(err.Error(), "not found") {
+		t.Errorf("message: got %q", err.Error())
+	}
+
+	if _, _, err := r.ReadReference("lark-calendar", "references"); err == nil {
+		t.Error("expected directory error")
+	} else if !strings.Contains(err.Error(), "is a directory") {
+		t.Errorf("message: got %q", err.Error())
+	}
+
+	for _, bad := range []string{"../../etc/passwd", "/etc/passwd", "..", "", "references/../../im/SKILL.md", `..\..\x`} {
+		data, _, err := r.ReadReference("lark-calendar", bad)
+		if err == nil {
+			t.Errorf("expected rejection for %q", bad)
+		}
+		if data != nil {
+			t.Errorf("content leaked for %q: %q", bad, string(data))
+		}
+		var verr *errs.ValidationError
+		if !errors.As(err, &verr) {
+			t.Errorf("expected validation error for %q, got %T", bad, err)
+		}
+	}
+}
+
+func TestParseFrontmatter(t *testing.T) {
+	cases := []struct {
+		name        string
+		input       string
+		wantDesc    string
+		wantVer     string
+		wantHasMeta bool
+	}{
+		{
+			name:        "description, version and metadata",
+			input:       "---\ndescription: My skill\nversion: 2.1.0\nmetadata:\n  cliHelp: \"x\"\n---\nbody\n",
+			wantDesc:    "My skill",
+			wantVer:     "2.1.0",
+			wantHasMeta: true,
+		},
+		{
+			name:     "description only, no metadata",
+			input:    "---\ndescription: Plain\n---\nbody\n",
+			wantDesc: "Plain",
+		},
+		{
+			name:  "no frontmatter",
+			input: "no frontmatter here\n",
+		},
+		{
+			name:  "unclosed frontmatter",
+			input: "---\ndescription: Never closed\n",
+		},
+		{
+			name:  "malformed YAML inside frontmatter",
+			input: "---\n: bad: yaml: [\n---\nbody\n",
+		},
+		{
+			name:        "CRLF line endings",
+			input:       "---\r\ndescription: CRLF skill\r\nmetadata:\r\n  cliHelp: \"y\"\r\n---\r\nbody\r\n",
+			wantDesc:    "CRLF skill",
+			wantHasMeta: true,
+		},
+		{
+			name:  "empty input",
+			input: "",
+		},
+	}
+	for _, tc := range cases {
+		t.Run(tc.name, func(t *testing.T) {
+			desc, ver, meta := parseFrontmatter([]byte(tc.input))
+			if desc != tc.wantDesc {
+				t.Errorf("description = %q, want %q", desc, tc.wantDesc)
+			}
+			if ver != tc.wantVer {
+				t.Errorf("version = %q, want %q", ver, tc.wantVer)
+			}
+			if (meta != nil) != tc.wantHasMeta {
+				t.Errorf("metadata = %v, wantHasMeta %v", meta, tc.wantHasMeta)
+			}
+		})
+	}
+}
+
+func TestReadSkillMissingFile(t *testing.T) {
+	// Use a separate MapFS so testFS() (and TestList) are unaffected.
+	emptyFS := fstest.MapFS{
+		"lark-empty/references/x.md": {Data: []byte("# X")},
+	}
+	r := New(emptyFS)
+	_, err := r.ReadSkill("lark-empty")
+	if err == nil {
+		t.Fatal("expected error when SKILL.md is absent")
+	}
+	var ierr *errs.InternalError
+	if !errors.As(err, &ierr) {
+		t.Fatalf("expected *errs.InternalError, got %T: %v", err, err)
+	}
+}