fix(synapse-core): throw UnsupportedChainError from getChain and getTransport

Normalize unsupported-chain failures onto one error type, and give devnet a default local HTTP transport so all asChain-supported networks have a getTransport path.

Author: hugomrdias

packages/synapse-core/src/chains.ts

@@ -322,10 +322,15 @@ export const devnet: FilecoinChain = {
   genesisTimestamp: 0,
 }
 
+export namespace getChain {
+  export type ErrorType = UnsupportedChainError
+}
+
 /**
  * Get a chain by id
  *
  * @param [id] - The chain id. Defaults to mainnet.
+ * @throws Errors {@link getChain.ErrorType}
  */
 export function getChain(id?: number): FilecoinChain {
   if (id == null) {
@@ -340,7 +345,7 @@ export function getChain(id?: number): FilecoinChain {
     case 31415926:
       return devnet
     default:
-      throw new Error(`Chain with id ${id} not found`)
+      throw new UnsupportedChainError(id)
   }
 }
 

packages/synapse-core/src/client.ts

@@ -1,7 +1,8 @@
 import { type Client, fallback, http, type RpcSchema, type Transport, type Chain as ViemChain } from 'viem'
 import type { Account } from 'viem/accounts'
 import type { FilecoinChain } from './chains.ts'
-import { asChain, calibration, mainnet } from './chains.ts'
+import { asChain, calibration, devnet, mainnet } from './chains.ts'
+import { UnsupportedChainError } from './errors/chains.ts'
 import type { Extended } from './types.ts'
 
 /**
@@ -29,11 +30,25 @@ export const calibrationTransport = fallback(
 )
 
 /**
- * Get the default ranked fallback transport for a Filecoin chain.
+ * Local HTTP transport for Filecoin Devnet.
+ *
+ * Uses the chain's default RPC; there is no public fallback set.
+ */
+export const devnetTransport = http(devnet.rpcUrls.default.http[0])
+
+export namespace getTransport {
+  export type ErrorType = UnsupportedChainError
+}
+
+/**
+ * Get the default HTTP transport for a Filecoin chain.
+ *
+ * Mainnet and Calibration use fallbacks across public RPC endpoints. Devnet
+ * uses the local default RPC.
  *
  * @param chain - The viem chain to resolve a transport for.
- * @returns The ranked fallback transport for mainnet or Calibration.
- * @throws Error if the chain is not supported.
+ * @returns The default transport for the chain.
+ * @throws Errors {@link getTransport.ErrorType}
  */
 export function getTransport(chain: ViemChain): Transport {
   if (chain.id === mainnet.id) {
@@ -44,7 +59,11 @@ export function getTransport(chain: ViemChain): Transport {
     return calibrationTransport
   }
 
-  throw new Error(`Unsupported chain: ${chain.id}`)
+  if (chain.id === devnet.id) {
+    return devnetTransport
+  }
+
+  throw new UnsupportedChainError(chain.id)
 }
 
 /**

packages/synapse-core/test/chains.test.ts

@@ -21,8 +21,11 @@ describe('chains', () => {
       assert.strictEqual(getChain(31_415_926), devnet)
     })
 
-    it('should throw for unknown chain id', () => {
-      assert.throws(() => getChain(999), /Chain with id 999 not found/)
+    it('should throw UnsupportedChainError for unknown chain id', () => {
+      assert.throws(
+        () => getChain(999),
+        (err: unknown) => UnsupportedChainError.is(err)
+      )
     })
   })
 

packages/synapse-core/test/client.test.ts

@@ -0,0 +1,29 @@
+import assert from 'assert'
+import type { Chain as ViemChain } from 'viem'
+import { calibration, devnet, mainnet } from '../src/chains.ts'
+import { calibrationTransport, devnetTransport, getTransport, mainnetTransport } from '../src/client.ts'
+import { UnsupportedChainError } from '../src/errors/chains.ts'
+
+describe('client', () => {
+  describe('getTransport', () => {
+    it('should return the mainnet fallback transport', () => {
+      assert.strictEqual(getTransport(mainnet), mainnetTransport)
+    })
+
+    it('should return the calibration fallback transport', () => {
+      assert.strictEqual(getTransport(calibration), calibrationTransport)
+    })
+
+    it('should return the devnet HTTP transport', () => {
+      assert.strictEqual(getTransport(devnet), devnetTransport)
+    })
+
+    it('should throw UnsupportedChainError for an unknown chain', () => {
+      const unknownChain = { id: 1 } as ViemChain
+      assert.throws(
+        () => getTransport(unknownChain),
+        (err: unknown) => UnsupportedChainError.is(err)
+      )
+    })
+  })
+})