fix(chainspec): make --chain required on stage/db subcommands

[camembera]

Summary

Removes all supported built-in chains from bera-reth, and makes the --chain <path> option work.

Details

The --chain parameter advertises ethereum chains, but not Bera's. This is not useful. It's not possible to bake in bera-mainnet because the spec is 48mb. And only bepolia would be silly. So that's the reason why there should be no --chain builtins.

The bug regarding --chain <path> manifested in rewinds. For various reasons, I have to sometimes rewind state (see paradigmxyz/reth#23234).

So to "unwind", I have to provide a --chain parameter. Because of a flaw in this function, passing "--chain /path/to/genesis.json" does not work. The workaround to accomplish an unwind was: make a hardlink or symlink ./mainnet (in the directory where bera-reth is being invoked) pointing to genesis.json

n.b. reth node does not use this path to evaluate --chain

Fix

Two changes to BerachainChainSpecParser:

1. Override default_value() to return None — makes --chain a required argument on all EnvironmentArgs-based subcommands (stage unwind, stage run, db, prune, …). Omitting it now fails with a clear "required argument missing" rather than a file-not-found on "mainnet".

2. Replace the borrowed SUPPORTED_CHAINS from reth_ethereum_cli with &[] — stops advertising mainnet, sepolia, etc. as valid --chain values when they cannot be resolved.

The node subcommand is unaffected — it uses NodeCommand's own chain argument wiring, not EnvironmentArgs.

Testing

• cargo check clean
• 48 existing chainspec unit tests pass (cargo test -p bera-reth -- chainspec)
• No existing tests invoke stage/db subcommands without --chain

Summary by CodeRabbit

• Bug Fixes
  • The --chain CLI parameter is now required for subcommands instead of being optional with a default fallback.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: b192ce9c-bf1a-49ec-aaa7-658bbdeaf8b5

📥 Commits

Reviewing files that changed from the base of the PR and between 23b13a2 and e69caaf.

📒 Files selected for processing (1)

• src/chainspec/mod.rs

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📝 Walkthrough

Walkthrough

The pull request removes Ethereum's supported chains list delegation from Berachain's chainspec parser and replaces it with an empty list, while making the --chain CLI argument required by returning None from the default_value() method instead of allowing implicit defaults.

Changes

Cohort / File(s)	Summary
Berachain Chainspec Configuration src/chainspec/mod.rs	Removed Ethereum SUPPORTED_CHAINS import. Updated BerachainChainSpecParser to use empty SUPPORTED_CHAINS list and added default_value() method returning None, making --chain a required parameter.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~8 minutes

Poem

🐰 No more borrowing chains from the east,
Berachain stands independent, at least!
The --chain flag now demands to be seen,
No defaults allowed—requirements are keen.
A simpler directive, explicit and clean! 🌿

🚥 Pre-merge checks | ✅ 2 | ❌ 1

❌ 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%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ 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 accurately describes the main change: making --chain required on stage/db subcommands by removing default values and unsupported chains.

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✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch fix/chain-spec-parser-default

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[Copilot]

Pull request overview

This PR makes the --chain parameter required on Berachain's EnvironmentArgs-based subcommands (like stage, db, prune) by fixing two bugs in the BerachainChainSpecParser implementation. The changes address issues where:

1. Berachain doesn't have built-in named chain specs to advertise (genesis allocation is too large to embed)
2. Omitting --chain would incorrectly fall back to "mainnet" and fail with file-not-found errors

Changes:

• Removed the import of SUPPORTED_CHAINS from reth_ethereum_cli::chainspec and replaced it with an empty slice &[] to prevent advertising Ethereum chain names that cannot actually be resolved
• Added a default_value() method override returning None to make --chain a required argument on EnvironmentArgs-based subcommands, eliminating the previous broken fallback behavior
• Added comprehensive comments explaining the changes and their rationale

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[calbera]

I'm okay with this, but would ideally prefer the default be bera-mainnet, as was done in bera-geth. This would require embedding the genesis into the code/binary however. And obv update tooling docs accordingly

[camembera]

@calbera I'd be cool with that too, but was cautious about embedding such a colossal genesis. I'll rework. bepolia too?

[calbera]

@camembera yes worth doing bepolia too

[fridrik01]

LGTM, fine with bundling beramainnet/bepolia genesis in a separate commit

[calbera]

lgtm lets merge this, just filed a ticket for the future work @camembera, we should try to get this in sooner than later