execution/chain: emit chain.Config ChainID and TTD as unquoted JSON numbers#21282
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execution/chain: emit chain.Config ChainID and TTD as unquoted JSON numbers#21282yperbasis wants to merge 2 commits into
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…umbers #21119 migrated chain.Config.ChainID and chain.Config.TerminalTotalDifficulty from *big.Int to *uint256.Int. uint256.Int.UnmarshalJSON accepts both quoted and unquoted decimals, so Erigon reads either form. But its MarshalJSON emits a quoted string ("1"), and math/big.Int.UnmarshalJSON rejects that form. Release/3.4 (still on *big.Int for these fields) therefore panics at startup on any chaindata written by 3.5+: panic: math/big: cannot unmarshal "\"1\"" into a *big.Int Add a Config.MarshalJSON that emits ChainID and TerminalTotalDifficulty as unquoted JSON numbers via a small wrapper type, restoring the 3.4-compatible wire format. Read paths are unchanged. Limitation: chaindata already written by 3.5+ before this fix is not retroactively healed — it still contains the quoted-string form. Downgrades to 3.4 are only viable after a future 3.5+ run that rewrites the config.
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Pull request overview
Restores Erigon 3.4 wire compatibility for the chain.Config JSON encoding by adding a custom MarshalJSON that emits ChainID and TerminalTotalDifficulty as unquoted JSON numbers (matching big.Int's encoding) rather than uint256.Int's default quoted-decimal string form. Without this, chaindata written by 3.5+ panics when read back by 3.4's *big.Int-typed parser.
Changes:
- Introduce
legacyJSONUint256wrapper that marshals a*uint256.Intas an unquoted decimal (ornullwhen nil). - Add
Config.MarshalJSONthat re-emitschainId/terminalTotalDifficultythrough the wrapper via an anonymous-struct-with-embedded-alias pattern (field shadowing on JSON tags) so all other fields continue to be encoded by the default encoder. - Add tests pinning the unquoted-number wire format, verifying
*big.Intdecoding compatibility, the uint256 round-trip, and nil-field behavior.
Reviewed changes
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| File | Description |
|---|---|
| execution/chain/chain_config.go | Adds legacyJSONUint256 and Config.MarshalJSON to emit ChainID/TTD as unquoted decimals for 3.4 read compatibility. |
| execution/chain/chain_config_test.go | New tests TestConfigJSONLegacyCompat and TestConfigJSONNilUint256Fields covering wire format, legacy *big.Int decode, round-trip, and nil/omitempty. |
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…fNotExist The chain.Config MarshalJSON fix only takes effect when something rewrites the config. WriteChainConfig runs unconditionally on every startup, so the genesis-hash-keyed ConfigTable entry is healed automatically. But the kv.GenesisKey-keyed Genesis blob is only ever written once (on first init), so on existing chaindata it stays in the legacy quoted-string form and the next 3.4 read still panics at ReadGenesis. Detect the legacy form (chainId/terminalTotalDifficulty as quoted strings) inside WriteGenesisIfNotExist and re-marshal in place. The rewrite is one-shot: once the unquoted form is on disk, subsequent calls short-circuit. Tested by hand-crafting a legacy blob, running WriteGenesisIfNotExist, and asserting the stored bytes are now in big.Int-compatible form.
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Follow-up: extended the fix to also migrate the kv.GenesisKey blob in WriteGenesisIfNotExist. Without this, MarshalJSON only heals the genesis-hash-keyed ConfigTable entry (rewritten on every startup), but the kv.GenesisKey-keyed Genesis JSON stays in the legacy uint256-quoted form forever and the next 3.4 read still panics at ReadGenesis. Verified by reproducing the panic against a main-written datadir, applying the patch, and confirming 3.4 then boots cleanly. |
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| if len(existing) > 0 { | ||
| // If the stored blob predates the chain.Config JSON-compat fix, the | ||
| // ChainID / TerminalTotalDifficulty fields are quoted strings, which | ||
| // older binaries (still on *big.Int for those fields) reject. Detect | ||
| // and re-marshal in place so subsequent downgrades can read the DB. | ||
| if needsLegacyGenesisRewrite(existing) { | ||
| var stored types.Genesis | ||
| if err := json.Unmarshal(existing, &stored); err != nil { | ||
| return fmt.Errorf("rewrite legacy genesis JSON: unmarshal: %w", err) | ||
| } | ||
| val, err := json.Marshal(&stored) | ||
| if err != nil { | ||
| return fmt.Errorf("rewrite legacy genesis JSON: marshal: %w", err) | ||
| } | ||
| return db.Put(kv.ConfigTable, kv.GenesisKey, val) | ||
| } |
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| return bytes.Contains(blob, []byte(`"chainId":"`)) || | ||
| bytes.Contains(blob, []byte(`"terminalTotalDifficulty":"`)) | ||
| } | ||
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Summary
Config.MarshalJSONthat emitsChainIDandTerminalTotalDifficultyas unquoted JSON numbers via a smalllegacyJSONUint256wrapper, restoring the 3.4-compatible wire format.uint256.Int.UnmarshalJSONalready accepts both quoted and unquoted decimals.Why
#21119 migrated
chain.Config.ChainIDandchain.Config.TerminalTotalDifficultyfrom*big.Intto*uint256.Int.uint256.Int.MarshalJSONemits a quoted decimal (\"1\"), andmath/big.Int.UnmarshalJSONrejects that form. Release/3.4, which still stores these as*big.Int, therefore panics at startup on any chaindata written by 3.5+:(Reproduced locally: pointing a fresh
release/3.4binary at a datadir last touched bymainaborts inWriteChainConfig's read-back path before the node starts.)Limitation
Chaindata already written by 3.5+ before this fix is not retroactively healed — it still contains the quoted-string form. Downgrades to 3.4 are only viable after a 3.5+ run with this fix re-writes the chain config.
Test plan
TestConfigJSONLegacyCompatpins the unquoted-number wire format and verifies the bytes decode into a*big.Int-typed struct (the 3.4 shape).TestConfigJSONNilUint256Fieldscovers nil/omitempty.make lintclean.make erigon integrationbuilds.go test -short ./execution/chain/... ./db/rawdb/... ./execution/state/genesiswrite/...passes.🤖 Generated with Claude Code