refactor!(eth-json-rpc-middleware): Migrate to JsonRpcEngineV2
#6976
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4 tasks
…hten v2 types
- InternalProvider
- replace rpcHandler with server
- wrap legacy engine via asV2Middleware + JsonRpcServer
- update tests
- asV2Middleware: fix middleware signature
- providerFromMiddleware
- Use providerFromMiddlewareV2 and asV2Middleware to wrap legacy
middleware
- json-rpc-engine:
- add MiddlewareConstraint
- update JsonRpcServer/asV2Middleware generics
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Nov 5, 2025
## Explanation Per #6327, migrates `@metamask/eth-json-rpc-provider` to `JsonRpcEngineV2` following its recent introduction. Intended to be closely followed by #6976 and subsequently released. The `InternalProvider` is updated to use `JsonRpcServer` under the hood. It can be constructed with a `JsonRpcServer` or legacy engine, but the latter will be wrapped by a `JsonRpcServer` in order to ensure consistent behavior across all internal providers. Meanwhile, `providerFromEngine()` is removed, it being a useless wrapper over the `InternalProvider` constructor. Elsewhere in the monorepo, these changes revealed a discrepancy in behavior between the error handling of the legacy engine and `asV2Middleware()`, which the latter is amended to resolve. In addition, the changes to the `InternalProvider` revealed that the legacy engine tolerates responses with `{ result: undefined }`. This is impossible to express using the V2 engine, which caused some `NetworkController` tests reliant on the legacy behavior to fail. Further investigation proved that these `undefined` results would error elsewhere in our JSON-RPC pipelines, so we simply remove these test cases. The upshot is that we no longer retry `undefined` results for "child requests" in the `retryOnEmpty` middleware. It is unclear if this was occurring in practice, and it ought to be treated as a breach of contract by the RPC endpoint if it does. ## References - Progresses: #6327 ## Checklist - [x] I've updated the test suite for new or updated code as appropriate - [x] I've updated documentation (JSDoc, Markdown, etc.) for new or updated code as appropriate - [x] I've communicated my changes to consumers by [updating changelogs for packages I've changed](https://github.com/MetaMask/core/tree/main/docs/contributing.md#updating-changelogs), highlighting breaking changes as necessary - [x] I've prepared draft pull requests for clients and consumer packages to resolve any breaking changes - Not intended to be shipped without #6976, but it appears we could if we wanted to: - MetaMask/metamask-extension#37521 - MetaMask/metamask-mobile#22154 <!-- CURSOR_SUMMARY --> --- > [!NOTE] > Migrates provider to JsonRpcEngineV2 with updated InternalProvider and helpers, adjusts error/empty-result handling, and updates dependent packages/tests. > > - **eth-json-rpc-provider**: > - Migrate to `JsonRpcEngineV2`; `InternalProvider` now wraps legacy engines via `asV2Middleware`/`JsonRpcEngineV2` and returns results directly. > - Add `providerFromMiddlewareV2`; deprecate `providerFromMiddleware`; remove `providerFromEngine`. > - Switch ID generation from `uuid` to `nanoid`; update exports/tests accordingly. > - **json-rpc-engine (v2)**: > - Add/expand V2 types and exports (`MiddlewareConstraint`, `MergedContextOf`, etc.). > - Update `asV2Middleware` to deserialize errors and ignore `{ error: undefined }` while forwarding results; add tests. > - Rename `unserializeError` to `deserializeError` and adjust usage/tests. > - **eth-json-rpc-middleware**: > - Change `retryOnEmpty` to treat only `null` and `"<nil>"` as empty (stop retrying `undefined`). > - **network-controller**: > - Replace `providerFromEngine` usage with `new InternalProvider({ engine })`. > - Align tests with new empty-result behavior and provider construction. > - **eth-block-tracker tests**: > - Construct providers via `InternalProvider` instead of `providerFromEngine`. > - **Tooling/Config**: > - Add TS/Jest path mapping for `@metamask/json-rpc-engine/v2`. > > <sup>Written by [Cursor Bugbot](https://cursor.com/dashboard?tab=bugbot) for commit 4a63eea. This will update automatically on new commits. Configure [here](https://cursor.com/dashboard?tab=bugbot).</sup> <!-- /CURSOR_SUMMARY -->
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Going to reopen this on top of #7061. |
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