feat(dynamic-resharding): allow dynamic shard layout in genesis

[jancionear]

Currently the code expects genesis to have a static shard layout. This causes trouble on forknets which start from the latest mainnet state, which has a dynamic shard layout. Let's allow having a genesis with dynamic shard layout.

[codecov]

Codecov Report

❌ Patch coverage is 85.71429% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 73.45%. Comparing base (7ac98ed) to head (c36c870).
⚠️ Report is 2 commits behind head on master.

Files with missing lines	Patch %	Lines
core/primitives/src/epoch_manager.rs	87.50%	0 Missing and 1 partial ⚠️
core/store/src/genesis/initialization.rs	0.00%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master   #16148      +/-   ##
==========================================
- Coverage   73.46%   73.45%   -0.02%     
==========================================
  Files         861      861              
  Lines      190324   190453     +129     
  Branches   190324   190453     +129     
==========================================
+ Hits       139820   139893      +73     
- Misses      46059    46107      +48     
- Partials     4445     4453       +8     

Flag	Coverage Δ
pytests-nightly	1.21% <0.00%> (-0.01%)	⬇️
unittests	70.08% <85.71%> (-0.01%)	⬇️
unittests-nightly	70.14% <85.71%> (-0.01%)	⬇️
unittests-spice	65.75% <85.71%> (-0.02%)	⬇️

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[greptile-apps]

Greptile Summary

This PR allows genesis initialization to use the shard layout declared in genesis when the epoch configuration uses dynamic resharding.

• Stores the genesis shard layout in AllEpochConfig and exposes static-first fallback selection.
• Uses the effective genesis layout when constructing genesis epoch information and sharded genesis state.
• Updates constructors and tests to supply the genesis layout explicitly.

Confidence Score: 5/5

The PR appears safe to merge, with no concrete correctness or security failures identified in the changed paths.

The epoch manager and genesis-state initializer consistently prefer an authoritative static epoch layout and fall back to the same concrete genesis-declared layout only when dynamic configuration omits one; all updated constructors supply matching layouts.

Flowchart

%%{init: {'theme': 'neutral'}}%%
flowchart TD
    A[Load genesis epoch config] --> B{Static shard layout available?}
    B -->|Yes| C[Use epoch-config shard layout]
    B -->|No| D[Use genesis-config shard layout]
    C --> E[Construct genesis EpochInfo]
    D --> E
    C --> F[Initialize sharded genesis state]
    D --> F

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_{Reviews (1): Last reviewed commit: "essentials" | Re-trigger Greptile}

[Copilot]

Pull request overview

Enables genesis initialization and genesis epoch creation to work when the genesis protocol version uses dynamic resharding (i.e., the epoch config no longer defines a static shard layout), by falling back to the shard layout declared in the genesis config.

Changes:

• Use genesis.config.shard_layout as a fallback when the genesis epoch config has no static shard layout during store genesis initialization.
• Extend AllEpochConfig to carry the genesis-declared shard layout and expose a helper to obtain the correct genesis shard layout (static-from-epoch-config vs fallback-from-genesis-config).
• Update epoch-manager genesis logic and unit tests to use the new AllEpochConfig constructor signature and genesis shard layout accessor.

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
core/store/src/genesis/initialization.rs	Falls back to genesis-declared shard layout when epoch config has no static layout.
core/primitives/src/epoch_manager.rs	Stores genesis shard layout in AllEpochConfig and adds genesis_shard_layout() accessor.
chain/epoch-manager/src/tests/mod.rs	Updates tests to provide genesis_shard_layout to AllEpochConfig.
chain/epoch-manager/src/test_utils.rs	Threads a test shard layout into AllEpochConfig::from_epoch_config_store.
chain/epoch-manager/src/lib.rs	Passes genesis_config.shard_layout into AllEpochConfig during construction.
chain/epoch-manager/src/genesis.rs	Uses self.config.genesis_shard_layout() for genesis epoch creation instead of requiring a static layout.

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[VanBarbascu]

LGTM but I'd ask @Wiezzel to review on this too.

[Wiezzel]

A couple of comments:

1. We should clean up the fork tool as well. override_epoch_configs should stop forcing Static for versions where the base config is dynamic (tools/fork-network/src/cli.rs:955-962), and make_and_write_genesis should take the target layout as a parameter instead of extracting it from the epoch config (cli.rs:1596-1598). Tt already has target_shard_layout at both call sites and already writes it into genesis.config.shard_layout.
2. GenesisConfig::shard_layout is tagged with #[serde(default = "default_shard_layout")] which results in a single-shard layout and it's never validated. That could lead to some silent unwanted fallback – can we improve it?
3. proposals_to_epoch info silently drops the layout if DynamicResharding protocol feature is not enabled. I'd add a check in make_genesis_epoch_info – if dynamic resharding is not enabled on genesis protocol version, require that epoch config contains static shard layout.