(feat) Add PreCodec modifier

[justinkaseman]

No description provided.

[pablolagreca]

@ilija42 I think this is the first use case we have for passing a function as part of the config right?. I think we need to review the implications of allowing this since it would mean that the configuration cannot be serialized/deserialized and force the config to be a go binary.

[ilija42]

We have an address modifier which gets injected at runtime, but maintains the ability to serialize/deserialize because the CR injects the functionality automatically based on the config. I wonder if we can do something similar here.
CC @justinkaseman what are the different codec factories that would be injected here? Can we have a constant in the modifier config which injects different things inside of the chain Relayers in a switch case?

[justinkaseman]

Here is an example of what one would look like for the current Capability Encoder, which currently only supports EVM.

Usage through the OCR3 Capability looks like passing it config as so:

consensus := ocr3cap.ReduceConsensusConfig[computeOutput]{
		Encoder: ocr3cap.EncoderEVM,
		EncoderConfig: map[string]any{
		    "subabi": map[string]any{"Reports.Bundle": "uint256 Ask, uint256 Bid"},
		    "abi": "(bytes32 FeedID, bytes Bundle, uint32 Timestamp)[] Reports",
		},

--

I'm not sure that I see a use case for passing more than one factory at once into the modifier. The codec gets injected one level up in the Encoder. Imagining a different chain Relayer (e.g. a non-EVM chain), the switch case would live in the Encoder and pick which factory to use in the modifier based on the chain family.

One fringe use case may be mixed encodings, such as wanting part of the report encoded for EVM and one part for non-EVM. For this we could just use multiple chained modifiers, one per chain family. So the user would pass something more like:

		    "subabi": map[string]any{
                           "evm": map[string]any{"Reports.BundleEVM": "uint256 Ask, uint256 Bid"},
                           "nonevm": map[string]any{"Reports.BundleNonEVM": "uint256 Ask, uint256 Bid"},
                     }

[ilija42]

I was thinking of this https://github.com/smartcontractkit/chainlink/blob/9d8d9f48b92cab72de51e4484cc7b0833b1ccf6b/core/services/relay/evm/chain_reader.go#L145

[ilija42]

If we can make this modifier more static then we wouldn't break the serialization

[justinkaseman]

Pushed a change similar to AddressModifier!

[pablolagreca]

Can we add more detailed documentation and probably examples in the doc?. Currently codec and codec modifiers are complex from an usability standpoint and it would be great to have more docs/examples for this new codec.

[justinkaseman]

Added an example! Let me know what else you think is missing and I can add more words

[ilija42]

Looks better now, just need the accompanying EVM PR, and maybe adding a function in other repos(at least Solana) that says that this modifier is not supported

[ilija42]

looks good now

Requested changes made. Moving forward with Ilija's approval.