refactor: replace hardcoded _get_tag with generated TAG_TABLE

multicodec/code.py

@@ -9,7 +9,7 @@
 
 from __future__ import annotations
 
-from .constants import CODE_TABLE, CODECS, NAME_TABLE
+from .constants import CODE_TABLE, CODECS, NAME_TABLE, TAG_TABLE
 
 # ReservedStart is the (inclusive) start of the reserved range of codes that
 # are safe to use for internal purposes.
@@ -188,260 +188,8 @@ def tag(self) -> str:
 
 
 def _get_tag(code: int) -> str:
-    """Get the tag for a codec code (mirrors go-multicodec's Tag() method)."""
-    name = CODE_TABLE.get(code, "")
-
-    # CID
-    if name in ("cidv1", "cidv2", "cidv3"):
-        return "cid"
-
-    # Encryption
-    if name in ("aes-gcm-256",):
-        return "encryption"
-
-    # Filecoin
-    if name in ("fil-commitment-unsealed", "fil-commitment-sealed"):
-        return "filecoin"
-
-    # Hash (non-multihash)
-    if name in (
-        "murmur3-x64-64",
-        "murmur3-32",
-        "murmur3-128",
-        "crc32",
-        "crc64-ecma",
-        "crc64-nvme",
-        "murmur3-x64-128",
-        "sha256a",
-        "xxh-32",
-        "xxh-64",
-        "xxh3-64",
-        "xxh3-128",
-    ):
-        return "hash"
-
-    # Holochain
-    if "holochain" in name:
-        return "holochain"
-
-    # IPLD
-    if name in (
-        "cbor",
-        "raw",
-        "dag-pb",
-        "dag-cbor",
-        "libp2p-key",
-        "git-raw",
-        "torrent-info",
-        "torrent-file",
-        "blake3-hashseq",
-        "leofcoin-block",
-        "leofcoin-tx",
-        "leofcoin-pr",
-        "dag-jose",
-        "dag-cose",
-        "eth-block",
-        "eth-block-list",
-        "eth-tx-trie",
-        "eth-tx",
-        "eth-tx-receipt-trie",
-        "eth-tx-receipt",
-        "eth-state-trie",
-        "eth-account-snapshot",
-        "eth-storage-trie",
-        "eth-receipt-log-trie",
-        "eth-receipt-log",
-        "bitcoin-block",
-        "bitcoin-tx",
-        "bitcoin-witness-commitment",
-        "zcash-block",
-        "zcash-tx",
-        "stellar-block",
-        "stellar-tx",
-        "decred-block",
-        "decred-tx",
-        "dash-block",
-        "dash-tx",
-        "swarm-manifest",
-        "swarm-feed",
-        "beeson",
-        "dag-json",
-        "swhid-1-snp",
-        "json",
-        "rdfc-1",
-        "json-jcs",
-    ):
-        return "ipld"
-
-    # Key
-    if any(
-        k in name
-        for k in (
-            "-pub",
-            "-priv",
-            "secp256k1",
-            "bls12_381",
-            "x25519",
-            "ed25519",
-            "p256",
-            "p384",
-            "p521",
-            "ed448",
-            "x448",
-            "sr25519",
-            "rsa",
-            "sm2",
-            "mlkem",
-            "jwk",
-        )
-    ):
-        return "key"
-
-    # Libp2p
-    if name in ("libp2p-peer-record", "libp2p-relay-rsvp"):
-        return "libp2p"
-
-    # Multiaddr
-    if name in (
-        "ip4",
-        "tcp",
-        "dccp",
-        "ip6",
-        "ip6zone",
-        "ipcidr",
-        "dns",
-        "dns4",
-        "dns6",
-        "dnsaddr",
-        "sctp",
-        "udp",
-        "p2p-webrtc-star",
-        "p2p-webrtc-direct",
-        "p2p-stardust",
-        "p2p-circuit",
-        "udt",
-        "utp",
-        "unix",
-        "thread",
-        "p2p",
-        "https",
-        "onion",
-        "onion3",
-        "garlic64",
-        "garlic32",
-        "tls",
-        "sni",
-        "noise",
-        "shs",
-        "quic",
-        "quic-v1",
-        "webtransport",
-        "certhash",
-        "ws",
-        "wss",
-        "p2p-websocket-star",
-        "http",
-        "http-path",
-        "webrtc-direct",
-        "webrtc",
-        "plaintextv2",
-        "scion",
-        "memory",
-    ):
-        return "multiaddr"
-
-    # Multiformat
-    if name in ("multicodec", "multihash", "multiaddr", "multibase", "varsig"):
-        return "multiformat"
-
-    # Multihash
-    if any(
-        h in name
-        for h in (
-            "identity",
-            "sha1",
-            "sha2-",
-            "sha3-",
-            "shake-",
-            "keccak-",
-            "blake2b-",
-            "blake2s-",
-            "blake3",
-            "dbl-sha2-",
-            "md4",
-            "md5",
-            "bmt",
-            "ripemd-",
-            "x11",
-            "kangarootwelve",
-            "sm3-",
-            "poseidon-",
-            "skein",
-        )
-    ):
-        return "multihash"
-
-    # Namespace
-    if name in (
-        "path",
-        "lbry",
-        "streamid",
-        "ipld-ns",
-        "ipfs-ns",
-        "swarm-ns",
-        "ipns-ns",
-        "zeronet",
-        "dnslink",
-        "skynet-ns",
-        "arweave-ns",
-        "subspace-ns",
-        "kumandra-ns",
-    ):
-        return "namespace"
-
-    # Serialization
-    if name in (
-        "protobuf",
-        "rlp",
-        "bencode",
-        "messagepack",
-        "car",
-        "car-index-sorted",
-        "car-multihash-index-sorted",
-        "ipns-record",
-        "x509-certificate",
-        "ssz",
-    ):
-        return "serialization"
-
-    # Transport
-    if name in (
-        "transport-bitswap",
-        "transport-graphsync-filecoinv1",
-        "transport-ipfs-gateway-http",
-    ):
-        return "transport"
-
-    # Varsig
-    if name in (
-        "nonstandard-sig",
-        "es256k",
-        "bls12_381-g1-sig",
-        "bls12_381-g2-sig",
-        "eddsa",
-        "eip-191",
-        "es256",
-        "es384",
-        "es512",
-        "rs256",
-    ):
-        return "varsig"
-
-    # Zeroxcert
-    if name in ("zeroxcert-imprint-256",):
-        return "zeroxcert"
-
-    return "<unknown>"
+    """Get the tag for a codec code from the generated TAG_TABLE."""
+    return TAG_TABLE.get(code, "<unknown>")
 
 
 # Cache for known codes list

multicodec/constants.py

@@ -3938,3 +3938,4 @@
 
 NAME_TABLE: dict[str, int] = {name: cast(int, value["prefix"]) for name, value in CODECS.items()}
 CODE_TABLE: dict[int, str] = {cast(int, value["prefix"]): name for name, value in CODECS.items()}
+TAG_TABLE: dict[int, str] = {cast(int, value["prefix"]): cast(str, value["tag"]) for name, value in CODECS.items()}

newsfragments/37.bugfix.rst

@@ -0,0 +1 @@
+Return the correct ``multikey``, ``multisig``, ``nonce``, ``shelter``, ``softhash``, and ``vlad`` tags from ``Code.tag()``.

newsfragments/40.bugfix.rst

@@ -0,0 +1 @@
+Derive ``Code.tag()`` from the multicodec table so every codec returns its CSV tag.

newsfragments/42.misc.rst

@@ -0,0 +1 @@
+Add tests verifying ``Code.tag()`` matches the multicodec table for every registered codec.

tests/test_code.py

@@ -117,6 +117,25 @@ def test_code_tag(self):
         code = Code(0x55)  # raw
         assert code.tag() == "ipld"
 
+        # Previously missing categories (issue #37)
+        assert Code(0xA000).tag() == "multikey"  # chacha20-poly1305
+        assert Code(0xD01300).tag() == "multisig"  # es256k-msig
+        assert Code(0xD01301).tag() == "multisig"  # bls12_381-g1-msig
+        assert Code(0x123B).tag() == "nonce"
+        assert Code(0x511E00).tag() == "shelter"  # shelter-contract-manifest
+        assert Code(0xCC01).tag() == "softhash"  # iscc
+        assert Code(0x1207).tag() == "vlad"
+
+        # Unknown code
+        assert Code(0x999999).tag() == "<unknown>"
+
+    def test_code_tag_matches_codecs_for_all(self):
+        """Every registered codec's tag() matches CODECS metadata (issue #42)."""
+        from multicodec.constants import CODECS
+
+        for name, info in CODECS.items():
+            assert Code(info["prefix"]).tag() == info["tag"], name
+
     def test_code_status(self):
         """Test Code.status property."""
         # Permanent codec

tests/test_constants_metadata.py

@@ -1,6 +1,6 @@
 """Smoke tests for enriched CODECS metadata from update-table.py."""
 
-from multicodec.constants import CODE_TABLE, CODECS, NAME_TABLE
+from multicodec.constants import CODE_TABLE, CODECS, NAME_TABLE, TAG_TABLE
 
 
 def test_codecs_include_csv_metadata_keys():
@@ -22,3 +22,10 @@ def test_identity_preserves_description():
 def test_name_and_code_tables_still_use_prefix():
     assert NAME_TABLE["sha2-256"] == 0x12
     assert CODE_TABLE[0x12] == "sha2-256"
+
+
+def test_tag_table_matches_codecs():
+    assert TAG_TABLE[0x12] == "multihash"
+    assert len(TAG_TABLE) == len(CODECS)
+    for name, info in CODECS.items():
+        assert TAG_TABLE[info["prefix"]] == info["tag"], name

tools/update-table.py

@@ -29,6 +29,9 @@
 CODE_TABLE: dict[int, str] = {
     cast(int, value["prefix"]): name for name, value in CODECS.items()
 }
+TAG_TABLE: dict[int, str] = {
+    cast(int, value["prefix"]): cast(str, value["tag"]) for name, value in CODECS.items()
+}
 """