[FVM] Add chain as a parameter to the runtime pool by janezpodhostnik · Pull Request #8302 · onflow/flow-go

janezpodhostnik · Jan 6, 2026

Chain in the ReusableCadenceRuntimePool is currently unused and will be used for injecting EVM definitions in upcoming PRs.

Summary by CodeRabbit

Refactor
- Enhanced runtime pool initialization to support chain-aware configuration across the system.
- Reorganized runtime pool infrastructure to improve chain parameter propagation through execution contexts.
- Updated internal method signatures to accept chain information during runtime setup.

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coderabbitai · Jan 6, 2026

📝 Walkthrough

Walkthrough

The pull request refactors the Cadence runtime pool initialization across the FVM and execution layers to accept a chain parameter. Pool constructors and runtime parameter initialization functions are updated to include the chain argument, with all call sites modified accordingly. The implementation is reorganized into a dedicated pool file.

Changes

Cohort / File(s)	Summary
Runtime Pool Refactoring `fvm/runtime/reusable_cadence_runtime.go`, `fvm/runtime/reusable_cadence_runtime_pool.go`	Extracted pool-based runtime reuse infrastructure from `reusable_cadence_runtime.go` into new dedicated file. Added `chain` parameter to `ReusableCadenceRuntimePool` struct and constructors (`NewReusableCadenceRuntimePool`, `NewCustomReusableCadenceRuntimePool`). Pool now retains chain information for runtime creation.
Environment Layer Updates `fvm/environment/env.go`, `fvm/environment/runtime.go`	Updated `DefaultRuntimeParams()` signature to accept `flow.Chain` parameter. `DefaultEnvironmentParams()` now passes `chainID.Chain()` when calling `DefaultRuntimeParams()`. Chain flows into pool initialization.
Test & Benchmark Updates `fvm/runtime/reusable_cadence_runtime_test.go`, `fvm/fvm_test.go`, `fvm/fvm_bench_test.go`, `engine/execution/computation/computer_test.go`, `engine/execution/computation/manager_benchmark_test.go`, `fvm/environment/system_contracts_test.go`	Updated all pool constructor calls to include `chain` argument (e.g., `flow.Testnet.Chain()`, `chainID.Chain()`, `b.conf.GetChainID().Chain()`). Introduced `vmTestDefaultChain` variable in FVM tests for consistency.
Execution & Manager Updates `engine/execution/computation/manager.go`, `integration/internal/emulator/blockchain.go`	Added `chainID.Chain()` to `NewReusableCadenceRuntimePool()` calls within manager and emulator initialization.
EVM Parameter Rename `fvm/evm/evm.go`	Renamed `SetupEnvironment` parameter from `runtimeEnv` to `cadenceEnv` for clarity (type unchanged).

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~22 minutes

Poem

🐰 A chain runs through the pools we weave,
From FVM to runtime, we now believe—
Each pool now knows its home so true,
Testnet or Mainnet, the chain shines through!
Threading parameters with care and grace,
Our reusable runtimes find their place. ✨

Pre-merge checks and finishing touches

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	You can run `@coderabbitai generate docstrings` to improve docstring coverage.

✅ Passed checks (2 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title '[FVM] Add chain as a parameter to the runtime pool' directly and concisely describes the main change across the pull request: adding a chain parameter to ReusableCadenceRuntimePool and propagating it through all call sites.

✨ Finishing touches

📝 Generate docstrings

📜 Recent review details

Configuration used: defaults

Review profile: CHILL

Plan: Pro

📥 Commits

Reviewing files that changed from the base of the PR and between 216a53f and 5c7a93c.

📒 Files selected for processing (13)

engine/execution/computation/computer/computer_test.go
engine/execution/computation/manager.go
engine/execution/computation/manager_benchmark_test.go
fvm/environment/env.go
fvm/environment/runtime.go
fvm/environment/system_contracts_test.go
fvm/evm/evm.go
fvm/fvm_bench_test.go
fvm/fvm_test.go
fvm/runtime/reusable_cadence_runtime.go
fvm/runtime/reusable_cadence_runtime_pool.go
fvm/runtime/reusable_cadence_runtime_test.go
integration/internal/emulator/blockchain.go

🧰 Additional context used

📓 Path-based instructions (7)

**/*.go

📄 CodeRabbit inference engine (.cursor/rules/coding_conventions.mdc)

Follow Go coding conventions as documented in @docs/agents/CodingConventions.md

Follow Go coding standards and conventions as documented in @docs/agents/GoDocs.md

**/*.go: Follow the existing module structure in /module/, /engine/, /model/ and use dependency injection patterns for component composition
Implement proper interfaces before concrete types
Follow Go naming conventions and the project's coding style defined in /docs/CodingConventions.md
Use mock generators: run make generate-mocks after interface changes
All inputs must be considered potentially byzantine; error classification is context-dependent and no code path is safe unless explicitly proven and documented
Use comprehensive error wrapping for debugging; avoid fmt.Errorf, use irrecoverable package for exceptions
NEVER log and continue on best effort basis; ALWAYS explicitly handle errors
Uses golangci-lint with custom configurations (.golangci.yml) and custom linters for Flow-specific conventions (struct write checking)

Files:

fvm/fvm_bench_test.go
engine/execution/computation/manager_benchmark_test.go
engine/execution/computation/manager.go
fvm/runtime/reusable_cadence_runtime_test.go
fvm/environment/system_contracts_test.go
fvm/environment/runtime.go
fvm/fvm_test.go
fvm/environment/env.go
fvm/runtime/reusable_cadence_runtime.go
engine/execution/computation/computer/computer_test.go
integration/internal/emulator/blockchain.go
fvm/evm/evm.go
fvm/runtime/reusable_cadence_runtime_pool.go

**/*_test.go