No spec compliance test validating hash codes against `multicodec/table.csv`

There is no test that validates the hash function codes in constants.py and funcs.py against the authoritative upstream multicodec table.csv. go-multihash has a TestSpec that does this validation.

Problem

The HASH_CODES dict in constants.py and the Func IntEnum in funcs.py are manually maintained. There is no automated check that:

• Every multihash-tagged entry in the CSV is present
• The codes match the CSV
• The names match the CSV
• No extra entries exist

go-multihash validates against the spec:

func TestSpec(t *testing.T) {
    file, _ := os.Open("spec/multicodec/table.csv")
    // ... reads CSV, filters for tag == "multihash"
    for code, name := range multihash.Codes {
        expectedName, ok := expectedFunctions[code]
        if !ok {
            t.Errorf("multihash %q (%x) not defined in the spec", name, code)
        }
    }
}

Proposed Solution

1. Add the multicodec spec as a git submodule:

   git submodule add https://github.com/multiformats/multicodec spec/multicodec
   

2. Create tests/test_spec.py:

   import csv
   from multihash.constants import HASH_CODES, CODE_HASHES
   
   def test_spec_table_completeness():
       """Every multihash entry in table.csv should be in HASH_CODES."""
       with open("spec/multicodec/table.csv") as f:
           reader = csv.DictReader(f, skipinitialspace=True)
           for row in reader:
               if row["tag"].strip() != "multihash":
                   continue
               name = row["name"].strip()
               code = int(row["code"].strip(), 16)
               assert name in HASH_CODES, f"Missing hash: {name} (0x{code:x})"
               assert HASH_CODES[name] == code, f"Code mismatch for {name}"
   

Related

• Go spec test: go-multihash spec_test.go

Read constants.py and funcs.py, then inspect the proposed tests/test_spec.py approach and the multicodec table at spec/multicodec/table.csv. Run the existing test suite first; done means the test compares every multihash-tagged CSV entry with HASH_CODES and verifies names, codes, missing entries, and extras.