How can a plugin author lookup an Interaction in the Pact struct during PrepareInteractionForVerification?

[mefellows]

This request was spawned from pact-foundation/pact-reference#278

Background
I'm trying to understand how a Plugin can look up the interaction in the pact file during verification.

In PrepareInteractionForVerification and VerifyInteraction the plugin will receive an InteractionKey that has a unique reference for the plugin to (presumably) label and find an interaction.

In the case of PrepareInteractionForVerification if no key is set on the interaction in the consumer DSL, the Pact struct if parsed, will not have any interactions with a key on them, and thus the interaction can't be found this way. There is no other identifying information at this step that can be used to look up the correct interaction from the pact.

This is why had the previous query about the keys above. I'm confused as to how the gRPC plugin is able to lookup by the interaction's key, despite not setting keys explicitly from the client. The Pact struct serialised over the protobuf definition does not have any keys in it:

For example, here is a Golang log message for the incoming message for VerifyInteraction:

2023/06/05 22:03:42 [INFO] received VerifyInteraction request: interactionData:{body:{contentType:"application/matt"  content:{value:"MATTMATT"}}}  config:{fields:{key:"host"  value:{string_value:"localhost"}}  fields:{key:"port"  value:{number_value:50160}}}  pact:"{\"consumer\":{\"name\":\"matttcpconsumer\"},\"interactions\":[{\"description\":\"Matt message\",\"pending\":false,\"providerStates\":[{\"name\":\"the world exists\"}],\"request\":{\"contents\":{\"content\":\"MATThellotcpMATT\",\"contentType\":\"application/matt\",\"contentTypeHint\":\"DEFAULT\",\"encoded\":false}},\"response\":[{\"contents\":{\"content\":\"MATTtcpworldMATT\",\"contentType\":\"application/matt\",\"contentTypeHint\":\"DEFAULT\",\"encoded\":false}}],\"transport\":\"matt\",\"type\":\"Synchronous/Messages\"}],\"metadata\":{\"pactRust\":{\"ffi\":\"0.4.5\",\"mockserver\":\"1.1.1\",\"models\":\"1.1.2\"},\"pactSpecification\":{\"version\":\"4.0\"},\"plugins\":[{\"configuration\":{},\"name\":\"matt\",\"version\":\"0.0.7\"}]},\"provider\":{\"name\":\"matttcpprovider\"}}"  interactionKey:"928c6a4275c7cafd"

Note how the interactionKey is present on the struct, but there is no matching key in the Pact struct.

This leads me to think that unique_key is an internal method only available to the Rust library, and not something that can be relied upon over the wire, and is why I thought removing the key generation could be a breaking change as far as behaviour is concerned.

(UPDATE: I thought perhaps I could work around it by setting a key on the interaction but I don't think there is an FFI for it)

Response from Ron:

Unfortunately, we can't remove InteractionKey from PrepareInteractionForVerification, because that will change the interface to existing plugins. We will have to create a V2 of the plugin interface.
At the moment it works by magic.

Ask

How can a plugin author lookup an Interaction in the Pact struct during PrepareInteractionForVerification?

[github-actions]

👋 Hi! The 'smartbear-supported' label has just been added to this issue, which will create an internal tracking ticket in PactFlow's Jira (PACT-1066). We will use this to prioritise and assign a team member to this task. All activity will be public on this ticket. For now, sit tight and we'll update this ticket once we have more information on the next steps.

See our documentation for more information.

[mefellows]

(moving to plugins repo)