mfer/builder.go

@@ -335,7 +335,7 @@ func (b *Builder) Build(ctx context.Context, w io.Writer) error {
 	}
 
 	// Create a temporary manifest to use existing serialization
-	m := &manifest{
+	m := &Manifest{
 		pbInner:        inner,
 		signingOptions: b.signingOptions,
 		fixedUUID:      b.fixedUUID,

mfer/checker.go

@@ -123,7 +123,7 @@ func NewChecker(opts *CheckerOptions) (*Checker, error) {
 	}
 
 	var (
-		m            *manifest
+		m            *Manifest
 		manifestInfo os.FileInfo
 		err          error
 	)

mfer/deserialize.go

@@ -48,7 +48,7 @@ func validateUUID(data []byte) error {
 
 // validateOuterHeader checks the outer message's version, compression
 // type, and UUID.
-func (m *manifest) validateOuterHeader() error {
+func (m *Manifest) validateOuterHeader() error {
 	if m.pbOuter.GetVersion() != MFFileOuter_VERSION_ONE {
 		return errUnknownVersion
 	}
@@ -70,7 +70,7 @@ func (m *manifest) validateOuterHeader() error {
 // signature is present, verifies it against the embedded public key, which
 // must be one key, and checks that the signer field is that key's
 // fingerprint.
-func (m *manifest) verifyOuterIntegrity() error {
+func (m *Manifest) verifyOuterIntegrity() error {
 	h := sha256.New()
 
 	_, err := h.Write(m.pbOuter.GetInnerMessage())
@@ -117,7 +117,7 @@ func (m *manifest) verifyOuterIntegrity() error {
 
 // decompressInner decompresses the inner payload, enforcing size limits
 // to prevent decompression bombs.
-func (m *manifest) decompressInner() ([]byte, error) {
+func (m *Manifest) decompressInner() ([]byte, error) {
 	bb := bytes.NewBuffer(m.pbOuter.GetInnerMessage())
 
 	// By default the decoder decodes a payload under 128 KiB in full,
@@ -259,7 +259,7 @@ func validateEntryHashes(entry *MFFilePath) error {
 	}
 }
 
-func (m *manifest) deserializeInner() error {
+func (m *Manifest) deserializeInner() error {
 	err := m.validateOuterHeader()
 	if err != nil {
 		return err
@@ -364,10 +364,8 @@ func validateMagic(dat []byte) bool {
 
 // NewManifestFromReader reads a manifest from an io.Reader. It refuses a
 // manifest larger than MaxManifestSize, reading at most one byte past it.
-//
-//nolint:revive // unexported-return: exporting manifest is owner question 13
-func NewManifestFromReader(input io.Reader) (*manifest, error) {
-	m := &manifest{}
+func NewManifestFromReader(input io.Reader) (*Manifest, error) {
+	m := &Manifest{}
 
 	dat, err := readAtMost(input, MaxManifestSize)
 	if err != nil {
@@ -426,9 +424,7 @@ type ManifestFromFileOptions struct {
 
 // NewManifestFromFile reads a manifest from a file. It returns an error if
 // opts is nil or its path is empty.
-//
-//nolint:revive // unexported-return: exporting manifest is owner question 13
-func NewManifestFromFile(opts *ManifestFromFileOptions) (*manifest, error) {
+func NewManifestFromFile(opts *ManifestFromFileOptions) (*Manifest, error) {
 	if opts == nil || opts.Path == "" {
 		return nil, errManifestPathEmpty
 	}

mfer/errmsg_test.go

@@ -85,7 +85,7 @@ func TestValidatePathMessagesVerbatim(t *testing.T) {
 func TestSerializeInnerNotSetMessagesVerbatim(t *testing.T) {
 	t.Parallel()
 
-	m := &manifest{}
+	m := &Manifest{}
 
 	err := m.generate(context.Background())
 	require.ErrorIs(t, err, errInnerNotSet)

mfer/manifest.go

@@ -15,13 +15,10 @@ var (
 	errSHA256NotSet = errors.New("SHA256 hash not set")
 )
 
-// manifest holds the internal representation of a manifest file.
-// Use NewManifestFromFile or NewManifestFromReader to load an existing
-// manifest, or use Builder to create a new one.
-//
-// Whether this type should be exported is an open design question owned by
-// the repository owner; see README design question 13.
-type manifest struct {
+// Manifest is a manifest loaded by NewManifestFromFile or
+// NewManifestFromReader. Its fields are private; only its methods are the
+// library's API.
+type Manifest struct {
 	pbInner        *MFFile
 	pbOuter        *MFFileOuter
 	output         *bytes.Buffer
@@ -29,7 +26,9 @@ type manifest struct {
 	fixedUUID      []byte // if set, use this UUID instead of generating one
 }
 
-func (m *manifest) String() string {
+// String returns a short description giving the number of files the
+// manifest lists, such as "<Manifest count=3>".
+func (m *Manifest) String() string {
 	count := 0
 	if m.pbInner != nil {
 		count = len(m.pbInner.GetFiles())
@@ -39,7 +38,7 @@ func (m *manifest) String() string {
 }
 
 // Files returns all file entries from a loaded manifest.
-func (m *manifest) Files() []*MFFilePath {
+func (m *Manifest) Files() []*MFFilePath {
 	if m.pbInner == nil {
 		return nil
 	}
@@ -50,7 +49,7 @@ func (m *manifest) Files() []*MFFilePath {
 // Signer returns the fingerprint of the key that made a loaded manifest's
 // signature, which loading the manifest checked, or nil if the manifest is
 // not signed.
-func (m *manifest) Signer() []byte {
+func (m *Manifest) Signer() []byte {
 	if len(m.pbOuter.GetSignature()) == 0 {
 		return nil
 	}
@@ -60,14 +59,14 @@ func (m *manifest) Signer() []byte {
 
 // CreatedAt returns the createdAt timestamp of a loaded manifest, or nil
 // if the manifest has none.
-func (m *manifest) CreatedAt() *Timestamp {
+func (m *Manifest) CreatedAt() *Timestamp {
 	return m.pbInner.GetCreatedAt()
 }
 
 // signatureString generates the canonical string used for signing/verification.
 // Format: MAGIC-UUID-MULTIHASH where UUID and multihash are hex-encoded.
 // Requires pbOuter to be set with Uuid and Sha256 fields.
-func (m *manifest) signatureString() (string, error) {
+func (m *Manifest) signatureString() (string, error) {
 	if m.pbOuter == nil {
 		return "", errOuterNotSet
 	}

mfer/manifest_external_test.go

@@ -0,0 +1,49 @@
+package mfer_test
+
+import (
+	"bytes"
+	"context"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+	"sneak.berlin/go/mfer/mfer"
+)
+
+// archive keeps a loaded manifest in a field, as a type in a program that
+// imports mfer would.
+type archive struct {
+	manifest *mfer.Manifest
+}
+
+// fileCount takes a loaded manifest, as a function in such a program would.
+func fileCount(m *mfer.Manifest) int {
+	return len(m.Files())
+}
+
+// A program that imports mfer can name the type of a loaded manifest, keep
+// one in a struct field, pass it to its own functions, and read it through
+// its methods.
+func TestManifestIsUsableOutsideThePackage(t *testing.T) {
+	t.Parallel()
+
+	content := []byte("hello\n")
+	builder := mfer.NewBuilder()
+
+	_, err := builder.AddFile("hello.txt", mfer.FileSize(len(content)),
+		mfer.ModTime{}, 0, bytes.NewReader(content), nil)
+	require.NoError(t, err)
+
+	var written bytes.Buffer
+	require.NoError(t, builder.Build(context.Background(), &written))
+
+	loaded, err := mfer.NewManifestFromReader(&written)
+	require.NoError(t, err)
+
+	a := archive{manifest: loaded}
+
+	require.Equal(t, 1, fileCount(a.manifest))
+	require.Equal(t, "hello.txt", a.manifest.Files()[0].GetPath())
+	require.Nil(t, a.manifest.Signer())
+	require.Nil(t, a.manifest.CreatedAt())
+	require.Equal(t, "<Manifest count=1>", a.manifest.String())
+}

mfer/manifest_test.go

@@ -21,7 +21,7 @@ func TestSignatureString(t *testing.T) {
 		"e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855")
 	require.NoError(t, err)
 
-	m := &manifest{pbOuter: &MFFileOuter{Uuid: manifestUUID[:], Sha256: sha256Hash}}
+	m := &Manifest{pbOuter: &MFFileOuter{Uuid: manifestUUID[:], Sha256: sha256Hash}}
 
 	got, err := m.signatureString()
 	require.NoError(t, err)

mfer/serialize.go

@@ -51,7 +51,7 @@ func newTimestampFromTime(t time.Time) *Timestamp {
 	}
 }
 
-func (m *manifest) generate(ctx context.Context) error {
+func (m *Manifest) generate(ctx context.Context) error {
 	if m.pbInner == nil {
 		return errInnerNotSet
 	}
@@ -78,7 +78,7 @@ func (m *manifest) generate(ctx context.Context) error {
 	return nil
 }
 
-func (m *manifest) generateOuter(ctx context.Context) error {
+func (m *Manifest) generateOuter(ctx context.Context) error {
 	if m.pbInner == nil {
 		return errInternal
 	}
@@ -145,7 +145,7 @@ func (m *manifest) generateOuter(ctx context.Context) error {
 // signOuter signs the outer message with the secret key in the signing
 // options and embeds the signature, the key's fingerprint and its public
 // key.
-func (m *manifest) signOuter(ctx context.Context) error {
+func (m *Manifest) signOuter(ctx context.Context) error {
 	// Unlocking a protected key can take a while; do not start once ctx
 	// has ended.
 	err := ctx.Err()