refactor: replace ! assertions in factories with LazyProviderMap.getOrThrow

The factory closures all used providerMap.get(chainId)! to coerce the
optional return into a non-null provider. That's safe today because every
validator map's isSupported predicate is a subset of LazyProviderMap's
supported set, but it's a brittle invariant — narrowing the supported set
in a future change would silently produce undefined providers wrapped
inside validator instances.

Add LazyProviderMap.getOrThrow(chainId): StaticJsonRpcProvider that throws
a clear error if the chainId isn't supported, and use it from the four
factory closures. The structural ProviderMap interface (Map-compatible
.get returning T | undefined) is unchanged.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: codyborn

lib/handlers/check-order-status/index.ts

@@ -24,7 +24,7 @@ const providerMap = new LazyProviderMap()
 
 const relayOrderValidator = new OffChainRelayOrderValidator(() => new Date().getTime() / 1000)
 const relayOrderValidatorMap = new OnChainValidatorMap<OnChainRelayOrderValidator>([], {
-  factory: (chainId) => new OnChainRelayOrderValidator(providerMap.get(chainId)!, chainId),
+  factory: (chainId) => new OnChainRelayOrderValidator(providerMap.getOrThrow(chainId), chainId),
   isSupported: (chainId) => supportedChainSet.has(chainId),
 })
 

lib/handlers/post-limit-order/index.ts

@@ -30,12 +30,12 @@ const isSupportedChain = (chainId: ChainId) => supportedChainSet.has(chainId)
 const providerMap = new LazyProviderMap()
 
 const onChainValidatorMap = new OnChainValidatorMap<OnChainOrderValidator>([], {
-  factory: (chainId) => new OnChainOrderValidator(providerMap.get(chainId)!, chainId),
+  factory: (chainId) => new OnChainOrderValidator(providerMap.getOrThrow(chainId), chainId),
   isSupported: isSupportedChain,
 })
 
 const relayOrderValidatorMap = new OnChainValidatorMap<OnChainRelayOrderValidator>([], {
-  factory: (chainId) => new OnChainRelayOrderValidator(providerMap.get(chainId)!, chainId),
+  factory: (chainId) => new OnChainRelayOrderValidator(providerMap.getOrThrow(chainId), chainId),
   isSupported: isSupportedChain,
 })
 

lib/handlers/post-order/index.ts

@@ -37,17 +37,17 @@ const isSupportedChain = (chainId: ChainId) => supportedChainSet.has(chainId)
 const providerMap = new LazyProviderMap()
 
 const onChainValidatorMap = new OnChainValidatorMap<OnChainOrderValidator>([], {
-  factory: (chainId) => new OnChainOrderValidator(providerMap.get(chainId)!, chainId),
+  factory: (chainId) => new OnChainOrderValidator(providerMap.getOrThrow(chainId), chainId),
   isSupported: isSupportedChain,
 })
 
 const onChainV4ValidatorMap = new OnChainValidatorMap<OnChainV4OrderValidator>([], {
-  factory: (chainId) => new OnChainV4OrderValidator(providerMap.get(chainId)!, chainId),
+  factory: (chainId) => new OnChainV4OrderValidator(providerMap.getOrThrow(chainId), chainId),
   isSupported: (chainId) => isSupportedChain(chainId) && !!OnChainV4QuoterMapping[chainId],
 })
 
 const relayOrderValidatorMap = new OnChainValidatorMap<OnChainRelayOrderValidator>([], {
-  factory: (chainId) => new OnChainRelayOrderValidator(providerMap.get(chainId)!, chainId),
+  factory: (chainId) => new OnChainRelayOrderValidator(providerMap.getOrThrow(chainId), chainId),
   isSupported: isSupportedChain,
 })
 

lib/handlers/shared/index.ts

@@ -28,4 +28,15 @@ export class LazyProviderMap implements ProviderMap {
     }
     return provider
   }
+
+  // Strict variant for callers (e.g. validator factories) that must receive a
+  // provider. Throws if the chainId is outside this map's supported set
+  // instead of returning undefined.
+  getOrThrow(chainId: ChainId): StaticJsonRpcProvider {
+    const provider = this.get(chainId)
+    if (!provider) {
+      throw new Error(`No RPC provider configured for chain ${chainId}`)
+    }
+    return provider
+  }
 }