Publishing pubsub with multibase encoded topic name not working as expected

[Arlodotexe]

Checklist

• This is a bug report, not a question. Ask questions on discuss.ipfs.io.
• I have searched on the issue tracker for my bug.
• I am running the latest go-ipfs version or have an issue updating.

Installation method

ipfs-desktop

Version

go-ipfs version: 0.8.0
Repo version: 11
System version: amd64/windows
Golang version: go1.15.8

Config

{
  "API": {
    "HTTPHeaders": {
      "Access-Control-Allow-Methods": [
        "PUT",
        "POST"
      ],
      "Access-Control-Allow-Origin": [
        "webui://-",
        "http://localhost:3000",
        "http://0.0.0.0:5001",
        "https://webui.ipfs.io"
      ]
    }
  },
  "Addresses": {
    "API": "/ip4/0.0.0.0/tcp/5001",
    "Announce": [],
    "AppendAnnounce": null,
    "Gateway": "/ip4/0.0.0.0/tcp/8080",
    "NoAnnounce": [],
    "Swarm": [
      "/ip4/0.0.0.0/tcp/4001",
      "/ip6/::/tcp/4001",
      "/ip4/0.0.0.0/udp/4001/quic",
      "/ip6/::/udp/4001/quic"
    ]
  },
  "AutoNAT": {},
  "Bootstrap": [
    "/dnsaddr/bootstrap.libp2p.io/p2p/QmNnooDu7bfjPFoTZYxMNLWUQJyrVwtbZg5gBMjTezGAJN",
    "/dnsaddr/bootstrap.libp2p.io/p2p/QmQCU2EcMqAqQPR2i9bChDtGNJchTbq5TbXJJ16u19uLTa",
    "/dnsaddr/bootstrap.libp2p.io/p2p/QmbLHAnMoJPWSCR5Zhtx6BHJX9KiKNN6tpvbUcqanj75Nb",
    "/dnsaddr/bootstrap.libp2p.io/p2p/QmcZf59bWwK5XFi76CZX8cbJ4BhTzzA3gU1ZjYZcYW3dwt",
    "/ip4/104.131.131.82/tcp/4001/p2p/QmaCpDMGvV2BGHeYERUEnRQAwe3N8SzbUtfsmvsqQLuvuJ",
    "/ip4/104.131.131.82/udp/4001/quic/p2p/QmaCpDMGvV2BGHeYERUEnRQAwe3N8SzbUtfsmvsqQLuvuJ"
  ],
  "DNS": {
    "Resolvers": null
  },
  "Datastore": {
    "BloomFilterSize": 0,
    "GCPeriod": "1h",
    "HashOnRead": false,
    "Spec": {
      "mounts": [
        {
          "child": {
            "path": "blocks",
            "shardFunc": "/repo/flatfs/shard/v1/next-to-last/2",
            "sync": true,
            "type": "flatfs"
          },
          "mountpoint": "/blocks",
          "prefix": "flatfs.datastore",
          "type": "measure"
        },
        {
          "child": {
            "compression": "none",
            "path": "datastore",
            "type": "levelds"
          },
          "mountpoint": "/",
          "prefix": "leveldb.datastore",
          "type": "measure"
        }
      ],
      "type": "mount"
    },
    "StorageGCWatermark": 90,
    "StorageMax": "10GB"
  },
  "Discovery": {
    "MDNS": {
      "Enabled": true,
      "Interval": 10
    }
  },
  "Experimental": {
    "AcceleratedDHTClient": false,
    "FilestoreEnabled": false,
    "GraphsyncEnabled": false,
    "Libp2pStreamMounting": false,
    "P2pHttpProxy": false,
    "StrategicProviding": false,
    "UrlstoreEnabled": false
  },
  "Gateway": {
    "APICommands": [],
    "HTTPHeaders": {
      "Access-Control-Allow-Headers": [
        "X-Requested-With",
        "Range",
        "User-Agent"
      ],
      "Access-Control-Allow-Methods": [
        "GET"
      ],
      "Access-Control-Allow-Origin": [
        "*"
      ]
    },
    "NoDNSLink": false,
    "NoFetch": false,
    "PathPrefixes": [],
    "PublicGateways": null,
    "RootRedirect": "",
    "Writable": false
  },
  "Identity": {
    "PeerID": "12D3KooWPV5RH3Avim5hyMVsmcfTkY9hg56u5G7NHaBCWoPUrarT"
  },
  "Internal": {},
  "Ipns": {
    "RecordLifetime": "",
    "RepublishPeriod": "",
    "ResolveCacheSize": 128
  },
  "Migration": {
    "DownloadSources": null,
    "Keep": ""
  },
  "Mounts": {
    "FuseAllowOther": false,
    "IPFS": "/home/arlog/ipfs",
    "IPNS": "/home/arlog/ipns"
  },
  "Peering": {
    "Peers": null
  },
  "Pinning": {
    "RemoteServices": {}
  },
  "Plugins": {
    "Plugins": null
  },
  "Provider": {
    "Strategy": ""
  },
  "Pubsub": {
    "DisableSigning": false,
    "Router": ""
  },
  "Reprovider": {
    "Interval": "12h",
    "Strategy": "all"
  },
  "Routing": {
    "Type": "dht"
  },
  "Swarm": {
    "AddrFilters": null,
    "ConnMgr": {
      "GracePeriod": "300s",
      "HighWater": 300,
      "LowWater": 50,
      "Type": "basic"
    },
    "DisableBandwidthMetrics": false,
    "DisableNatPortMap": false,
    "RelayClient": {},
    "RelayService": {},
    "Transports": {
      "Multiplexers": {},
      "Network": {
        "QUIC": true
      },
      "Security": {}
    }
  }
}

Description

Following the directions at #8343

1. Manually create a Base64Url encoded topic name using https://base64.guru/standards/base64url/encode. In this sample, I encoded the word test.
2. Set up a REST client (Postman or Nightingale) to POST to a local node with http://127.0.0.1:5001/api/v0/pubsub/pub?arg=dGVzdA. Form-data field data can be anything, encoded or not.
3. Send the request. You should get this error back with a 500:

{
  "Message": "URL arg must be multibase encoded: selected encoding not supported",
  "Code": 0,
  "Type": "error"
}

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[Arlodotexe]

Finally got the ipfs multibase working on a fresh Ubuntu WSL install.

Looks like the data needs to be prefixed with u for some reason. So test encoded to dGVzdA needs to be udGVzdA instead. This should probably be documented in some form.