fix(sdk): throw a better error for bad chain ID (#3065)

Updates the SDK to throw a better error when the user provides a bad
chain ID. Would've helped an end-user more easily debug an issue where
the chain ID parameter was missing.
Co-authored-by: mergify[bot] <37929162+mergify[bot]@users.noreply.github.com>

.changeset/lovely-mails-cry.md

+---
+'@eth-optimism/sdk': patch
+---
+
+Updates the CCM to throw a better error for missing or invalid chain IDs

packages/sdk/src/cross-chain-messenger.ts

@@ -85,8 +85,18 @@ export class CrossChainMessenger implements ICrossChainMessenger {
   }) {
     this.l1SignerOrProvider = toSignerOrProvider(opts.l1SignerOrProvider)
     this.l2SignerOrProvider = toSignerOrProvider(opts.l2SignerOrProvider)
-    this.l1ChainId = toNumber(opts.l1ChainId)
-    this.l2ChainId = toNumber(opts.l2ChainId)
+
+    try {
+      this.l1ChainId = toNumber(opts.l1ChainId)
+    } catch (err) {
+      throw new Error(`L1 chain ID is missing or invalid: ${opts.l1ChainId}`)
+    }
+
+    try {
+      this.l2ChainId = toNumber(opts.l2ChainId)
+    } catch (err) {
+      throw new Error(`L2 chain ID is missing or invalid: ${opts.l2ChainId}`)
+    }
 
     this.depositConfirmationBlocks =
       opts?.depositConfirmationBlocks !== undefined

packages/sdk/test/cross-chain-messenger.spec.ts

@@ -80,6 +80,32 @@ describe('CrossChainMessenger', () => {
       })
     })
 
+    describe('when given a bad L1 chain ID', () => {
+      it('should throw an error', () => {
+        expect(() => {
+          new CrossChainMessenger({
+            l1SignerOrProvider: ethers.provider,
+            l2SignerOrProvider: ethers.provider,
+            l1ChainId: undefined as any,
+            l2ChainId: L2ChainID.OPTIMISM,
+          })
+        }).to.throw('L1 chain ID is missing or invalid')
+      })
+    })
+
+    describe('when given a bad L2 chain ID', () => {
+      it('should throw an error', () => {
+        expect(() => {
+          new CrossChainMessenger({
+            l1SignerOrProvider: ethers.provider,
+            l2SignerOrProvider: ethers.provider,
+            l1ChainId: L1ChainID.MAINNET,
+            l2ChainId: undefined as any,
+          })
+        }).to.throw('L2 chain ID is missing or invalid')
+      })
+    })
+
     describe('when no custom contract addresses are provided', () => {
       describe('when given a known chain ID', () => {
         it('should use the contract addresses for the known chain ID', () => {