🐞 Bug: HTTP API returns "Internal Server Error" when attempting to encrypt multiple transaction metadata messages.

[jonathanknowles]

Version

a2cac93

Bug description

If:

• the user calls the constructTransaction HTTP API endpoint
• the metadata field is populated with metadata to be encrypted according to CIP-83

And if:

• the included metadata map includes more than one message with a msg key
• the detailed JSON schema option TxMetadataDetailedSchema is used.

Then the HTTP API will return "Internal Server Error".

Reproduction steps

See the following PR that demonstrates the issue:

• Demonstrate that the HTTP API returns "Internal Server Error" when attempting to encrypt multiple transaction metadata messages. #4651

With a fresh checkout of the above PR, run:

$ nix develop
$ just conway-integration-tests-match "encrypt multiple metadata messages"

Example failure links

• https://buildkite.com/cardano-foundation/cardano-wallet/builds/5570#01905814-2e6e-460b-83aa-7cfed4ede245/139-753
• https://buildkite.com/cardano-foundation/cardano-wallet/builds/5570#01905814-2e70-4cc3-b3f8-8f8f3d9eb0f8/139-758

Example failure log extract

only one 'msg' field expected
CallStack (from HasCallStack):
  error, called at src/Cardano/Wallet/Api/Http/Shelley/Server.hs:3207:24 in cardano-wallet-api-2024.5.5-AKdt1G4fjDDEhVlTTGjQVf:Cardano.Wallet.Api.Http.Shelley.Server
From the following response: Left
    ( DecodeFailure "Something went wrong" "Unexpected "Something went wrong", expecting JSON value" )
While verifying value:
  ( Status
      { statusCode = 500
      , statusMessage = "Internal Server Error"
      }
  , Left
      ( DecodeFailure "Something went wrong" "Unexpected "Something went wrong", expecting JSON value" )
  )
expected: Status {statusCode = 202, statusMessage = "Accepted"}
 but got: Status {statusCode = 500, statusMessage = "Internal Server Error"}

Expected behaviour

Either:

• The API returns a dedicated error with a corresponding schema definition, indicating that only one message is allowed to be encrypted.

Or:

• The API accepts more than one message for encryption, and encrypts them all of them.

[jonathanknowles]

The cause of the internal server error is this section of code:

cardano-wallet/lib/api/src/Cardano/Wallet/Api/Http/Shelley/Server.hs

Lines 3202 to 3207 in a2cac93

	parseMessage = \case
	TxMetaMap kvs ->
	case mapMaybe getValue kvs of
	[ ] -> Nothing
	[v] -> Just v
	_vs -> error "only one 'msg' field expected"

The error branch will only be evaluated if the TxMetadataDetailedSchema JSON serialisation option is used in conjunction with a TxMetaMap object that contains multiple msg keys.

If instead the TxMetadataNoSchema JSON serialisation option is used, then only the last msg key-value mapping will be retained, and the error branch will not be evaluated.

See #4647 (comment) for an explanation of why this happens.

[paweljakubas]

addressed and fixed #4651