Keep unlocker list working when unlocker metadata is corrupt (closes #42)

PGPUnlocker.GetID() panicked when its metadata could not be read or
parsed, which took down `secret unlocker list` for every unlocker. It
now warns with the unlocker's directory and returns `pgp-unknown`;
metadata with an empty GPG key ID counts as corrupt too.
ListUnlockers now skips, with a warning, an unlocker whose metadata
file is unreadable or not JSON, as it already did for a missing one.
The listing's ID lookup skips such a directory without warning again.

This is the first half of the issue only. Passing the mnemonic in
memory moved to #60.

Model: opus-5-5

internal/cli/unlockers_list_test.go

@@ -1,13 +1,18 @@
 // Unlocker List Tests
 //
-// Tests for `secret unlocker list` behavior when the unlockers.d directory
-// cannot be read while the listing is being rendered:
+// Tests for `secret unlocker list` behavior when the unlockers.d directory,
+// or an unlocker's metadata in it, cannot be read while the listing is
+// being rendered:
 //
 //   - TestUnlockersListSkipsUnreadableUnlockersDir: an unreadable
 //     unlockers.d yields no rows rather than rows bearing synthesized IDs.
 //   - TestUnlockersListSkipsOnlyUnreadableEntries: a readable entry is
 //     still listed, with its real ID and its current-unlocker marker,
 //     when a later entry's scan fails.
+//   - TestUnlockersListToleratesCorruptMetadata: one unlocker's corrupt
+//     metadata does not stop the others from being listed.
+//   - TestUnlockersListSkipsUnreadableMetadata: an unlocker whose metadata
+//     file cannot be read is left out, and the other is still listed.
 //
 // The listing resolves each unlocker's real ID by rescanning unlockers.d
 // after the vault has already enumerated it. If that rescan fails the ID
@@ -92,6 +97,28 @@ func (f *unlockersDirFailFs) Open(name string) (afero.File, error) {
 	return f.Fs.Open(name)
 }
 
+// errMetadataUnreadable is returned by the test filesystem in place of a
+// successful open of one unlocker's metadata file.
+var errMetadataUnreadable = errors.New("input/output error")
+
+// metadataReadFailFs fails every open of the file at unreadablePath. The
+// file still exists, so checking for it succeeds and only reading it fails.
+type metadataReadFailFs struct {
+	afero.Fs
+
+	unreadablePath string
+}
+
+//nolint:ireturn // afero.File is the interface required by afero.Fs
+func (f *metadataReadFailFs) Open(name string) (afero.File, error) {
+	if name == f.unreadablePath {
+		return nil, errMetadataUnreadable
+	}
+
+	//nolint:wrapcheck // test double must return the wrapped Fs error as-is
+	return f.Fs.Open(name)
+}
+
 // writePGPUnlocker writes a PGP unlocker directory with metadata that
 // yields the real ID "pgp-<keyID>".
 func writePGPUnlocker(
@@ -227,3 +254,79 @@ func TestUnlockersListReadableEntriesAreListed(t *testing.T) {
 	assert.True(t, unlockers[0].IsCurrent)
 	assert.False(t, unlockers[1].IsCurrent)
 }
+
+// TestUnlockersListToleratesCorruptMetadata asserts that one unlocker with
+// corrupt metadata does not stop the listing. Metadata that is not JSON
+// leaves that unlocker out; PGP metadata without a usable GPG key ID lists
+// it as "pgp-unknown". The healthy unlocker is listed with its real ID.
+func TestUnlockersListToleratesCorruptMetadata(t *testing.T) {
+	t.Parallel()
+
+	healthyID := "pgp-" + listTestGPGKeyID + "A"
+
+	tests := []struct {
+		name     string
+		metadata string
+		wantIDs  []string
+	}{
+		{
+			name:     "not JSON",
+			metadata: "not json",
+			wantIDs:  []string{healthyID},
+		},
+		{
+			name:     "GPG key ID of the wrong type",
+			metadata: `{"type": "pgp", "gpgKeyId": 42}`,
+			wantIDs:  []string{healthyID, "pgp-unknown"},
+		},
+		{
+			name:     "GPG key ID missing",
+			metadata: `{"type": "pgp"}`,
+			wantIDs:  []string{healthyID, "pgp-unknown"},
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			t.Parallel()
+
+			fs := newListTestVault(t, 2)
+			metadataPath := filepath.Join(listTestStateDir, "vaults.d",
+				listTestVaultName, listTestUnlockersDirName,
+				listTestUnlockerDirTwo, listTestMetadataFileName)
+			require.NoError(t, afero.WriteFile(
+				fs, metadataPath, []byte(tt.metadata), listTestFilePerm,
+			))
+
+			unlockers := listUnlockersJSON(t, fs)
+			require.Len(t, unlockers, len(tt.wantIDs))
+
+			for i, wantID := range tt.wantIDs {
+				assert.Equal(t, wantID, unlockers[i].ID)
+			}
+		})
+	}
+}
+
+// TestUnlockersListSkipsUnreadableMetadata asserts that an unlocker whose
+// metadata file exists but cannot be read is left out of the listing, and
+// the other unlocker is still listed with its real ID. The unreadable one
+// sorts first, so finding the other's ID has to step past it as well.
+func TestUnlockersListSkipsUnreadableMetadata(t *testing.T) {
+	t.Parallel()
+
+	base := newListTestVault(t, 2)
+	fs := &metadataReadFailFs{
+		Fs: base,
+		unreadablePath: filepath.Join(listTestStateDir, "vaults.d",
+			listTestVaultName, listTestUnlockersDirName,
+			listTestUnlockerDirOne, listTestMetadataFileName),
+	}
+
+	unlockers := listUnlockersJSON(t, fs)
+
+	require.Len(t, unlockers, 1,
+		"only the unlocker with readable metadata may be listed")
+	assert.Equal(t, "pgp-"+listTestGPGKeyID+"B", unlockers[0].ID,
+		"the listed row must carry the real unlocker ID")
+}