Support Basenames (Base .base.eth naming) for EthereumType coins

[cranycrane]

Summary

Blockbook does not support Basenames (Coinbase's ENS-fork naming service on Base, names of the form <label>.base.eth). The existing ENS machinery in bchain/coins/eth/ is deliberately scoped to Ethereum mainnet, so no names are indexed or resolved on Base. This is a feature request to add Basenames support.

Current state

There are two independent name-handling mechanisms for EthereumType coins, both wired to Ethereum mainnet only:

1. Alias indexing (passive, sync-time) — scans NameRegistered logs from trusted registrar contracts and stores address → name aliases. This is what renders a name next to an address in the explorer.

   • getEnsRecord — bchain/coins/eth/dataparser.go:345
   • isTrustedNameRegisteredEvent accepts only the three ENS ETHRegistrarController signatures (5/6/7-arg) — bchain/coins/eth/dataparser.go:336, constants at bchain/coins/eth/contract.go:29-37
   • trusted emitters come from the ens_registrars config; empty ⇒ records nothing (bchain/coins/eth/ethrpc.go:97-99)
   • display suffix appended by FormatAddressAlias = name + EnsSuffix (bchain/coins/eth/ethparser.go:636); default .eth (ethparser.go:68), overridden to .bnb/.trx by BSC/Tron

2. Live forward resolution (search box) — ResolveENS (bchain/coins/eth/ethrpc.go:2546), reachable from explorer search (server/public.go:1266).

   • ensContracts() hard-fails when MainNetChainID != MainNet (bchain/coins/eth/ethrpc.go:2537-2542), disabling resolution on every L2 including Base.

Live reverse resolution (address → name) does not exist in production (only a test stub, tests/dbtestdata/fakechain_ethereumtype.go).

Base config today: configs/coins/base_archive.json has address_aliases: true but no ens_registrars; configs/coins/base.json has neither. A bchain/coins/base/baserpc.go package already exists (chain id 8453) with a ResolveENS passthrough hook — a natural home for Base-specific wiring.

Proposed work

Feature A — Basenames alias indexing (core, recommended first)

• Add the Basenames RegistrarController address to ens_registrars in configs/coins/base.json and configs/coins/base_archive.json, and set address_aliases: true on both.
• Add the Basenames NameRegistered event signature to the constants (bchain/coins/eth/contract.go) and to isTrustedNameRegisteredEvent (dataparser.go:336). Structurally it's already compatible: getEnsRecord needs exactly 3 topics (sig + indexed label + indexed owner, owner in topic[2]) and parseEnsNameFromLogData reads the first dynamic string param by offset.
• Set the display suffix to .base.eth for Base via SetEnsSuffix(".base.eth") in bchain/coins/base/baserpc.go Initialize() (mirrors BSC/Tron). A single flat suffix is correct because the registrar trust-list guarantees every captured alias is a Basename. (Alternative: add a generic ens_suffix config field to eth.Configuration.)
• Backfill historical registrations with blockbook -rebuildensaliases (RebuildEnsAliases, ethrpc.go:1471); give the rescan the Basenames deployment block as a floor to avoid scanning from genesis.
• Tests: real Basenames NameRegistered log fixture → getEnsRecord accepts it and FormatAddressAlias yields <label>.base.eth.

Feature B — live *.eth search resolution (optional)

• Un-gate ensContracts() for Base by overriding it in bchain/coins/base to return the Basenames Registry + BaseRegistrar addresses on chain 8453.
• ResolveENS largely works as-is: .base.eth passes the suffix check and ensNameHash already does full recursive namehash. Caveat: names resolving via CCIP-read/offchain gateways won't resolve through a plain eth_call; on-chain names will.
• Fix or disable expiration: CheckENSExpiration (ethrpc.go:2621) extracts the label as parts[len-1], which for jesse.base.eth yields base (wrong token). Needs Basenames-aware label extraction + Base's BaseRegistrar address, or skip initially.

Out of scope

Live reverse resolution (address → name). The alias index already provides address → name for display.

Facts to confirm before implementing

1. Basenames RegistrarController address on Base.
2. Exact NameRegistered event signature and indexed-param layout.
3. Whether the emitted name is the bare label (jesse) or the full name (decides whether .base.eth suffix is correct or would double-suffix).
4. Registry / L2Resolver / BaseRegistrar addresses (Feature B).
5. Basenames deployment block (backfill floor).