fix(rpc): error handling

[bar-bera]

Not sure here on what we should consider transient as an error, beside -32000. Also added -32603 for now but maybe should be considered fatal.

[Copilot]

Pull request overview

This PR improves RPC error handling in the execution client by properly distinguishing between transient and fatal JSON-RPC errors. The changes ensure that transient errors like server errors (-32000) and internal errors (-32603) trigger infinite retries, while fatal errors like parse errors (-32700) cause immediate failure without retrying.

Changes:

• Added comprehensive test coverage for both transient and fatal RPC error scenarios using an HTTP proxy pattern
• Introduced isTransientError helper function to classify transient errors (ErrServer, ErrInternal) that should be retried
• Updated IsFatalError and IsNonFatalError logic to properly exclude transient errors from fatal classification
• Added ErrorCode() method to RPC Error type to support error code inspection

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 3 comments.

File	Description
testing/simulated/rpc_errors_test.go	New test suite with HTTP proxy to inject JSON-RPC errors and verify recovery behavior for transient errors and immediate failure for fatal errors
execution/client/errors.go	Added isTransientError helper and updated error classification logic to properly handle transient vs fatal errors
execution/client/ethclient/rpc/types.go	Added ErrorCode() method to satisfy jsonrpc.Error interface

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 62.69%. Comparing base (01e5e7b) to head (59bc955).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3029      +/-   ##
==========================================
+ Coverage   62.63%   62.69%   +0.05%     
==========================================
  Files         357      357              
  Lines       17224    17226       +2     
==========================================
+ Hits        10788    10799      +11     
+ Misses       5580     5572       -8     
+ Partials      856      855       -1     

Files with missing lines	Coverage Δ
execution/client/ethclient/rpc/types.go	50.00% <100.00%> (+50.00%)	⬆️

... and 3 files with indirect coverage changes

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[calbera]

I'm not sure we need to update behavior for the jsonrpc.ErrServer, jsonrpc.ErrInternal errors. Can you confirm from the EL (or maybe even CL spec) in which case these are returned and how they should be handled. I'm more inclined to file a ticket for this (to investigate further) and leave this change out of this bug fix PR @bar-bera

[fridrik01]

Agree, lets keep the IsFatalError/IsNonFatalError logic the same in this PR and look at them separately

[bar-bera]

ok agree to not touch the logic, just keep the test structure in case we want to test different behavior for different errors

[fridrik01]

LGTM