fix: answer the page when a background handler throws (closes #280)

src/background/index.js

@@ -170,6 +170,16 @@ function approvedNonce(approvedTx) {
     }
 }
 
+// What the page is told when a request failed in a way the wallet has no
+// specific answer for. -32603 is the JSON-RPC internal error EIP-1474 defines
+// and EIP-1193 defers to for RPC-layer failures; no EIP-1193 4xxx code
+// describes "the wallet broke", and one is not invented here. The cause is
+// logged rather than put in the message: the page gets a stable sentence, the
+// background console gets the throw.
+const INTERNAL_ERROR_CODE = -32603;
+const INTERNAL_ERROR_MESSAGE =
+    "AutistMask could not complete this request because of an internal error.";
+
 async function getState() {
     const result = await storageGet("autistmask");
     return (
@@ -1093,9 +1103,26 @@ runtime.onMessage.addListener((msg, sender, sendResponse) => {
                 // keep fallback
             }
         }
-        handleRpc(msg.method, msg.params, trustedOrigin).then((response) => {
-            sendResponse(response);
-        });
+        handleRpc(msg.method, msg.params, trustedOrigin)
+            .then((response) => {
+                sendResponse(response);
+            })
+            .catch((err) => {
+                // Without this the page's window.ethereum.request() promise
+                // stays pending forever: no response is sent, the content
+                // script posts nothing back, and the dApp cannot tell the
+                // failure from a slow wallet. handleRpc does real work —
+                // state loads, provider calls, transaction population — so
+                // "it does not throw today" is not a property anyone is
+                // maintaining.
+                log.errorf("RPC request failed:", msg.method, err);
+                sendResponse({
+                    error: {
+                        code: INTERNAL_ERROR_CODE,
+                        message: INTERNAL_ERROR_MESSAGE,
+                    },
+                });
+            });
         return true;
     }
 
@@ -1202,6 +1229,10 @@ runtime.onMessage.addListener((msg, sender, sendResponse) => {
             return false;
         }
 
+        // Which phase the last-resort .catch() below reports. Everything up to
+        // the broadcastTransaction() call provably never reached the network,
+        // so an escape from there must not tell the user it might have.
+        let lastResortStage = TX_STAGE_VERIFY;
         (async () => {
             // The chain this attempt is on, read once. Verification below
             // refuses an artifact signed for any other chain, and the nonce
@@ -1285,6 +1316,7 @@ runtime.onMessage.addListener((msg, sender, sendResponse) => {
 
             try {
                 const provider = getProvider(state.rpcUrl);
+                lastResortStage = TX_STAGE_BROADCAST;
                 const tx = await provider.broadcastTransaction(msg.rawSignedTx);
                 if (nonce !== null) spent.add(nonce);
                 settleApproval(
@@ -1316,7 +1348,28 @@ runtime.onMessage.addListener((msg, sender, sendResponse) => {
                     stage: outcome.stage,
                 });
             }
-        })();
+        })().catch((e) => {
+            // Every statement above is inside a try, but a throw from one of
+            // the catch blocks escapes as an unhandled rejection and neither
+            // the popup nor the page is ever answered. Settle both, through
+            // the same chokepoint as every other retirement.
+            log.errorf("transaction approval response failed:", e);
+            settleApproval(
+                msg.id,
+                {
+                    error: {
+                        code: INTERNAL_ERROR_CODE,
+                        message: INTERNAL_ERROR_MESSAGE,
+                    },
+                },
+                { holdsClaim: true },
+            );
+            sendResponse({
+                error: INTERNAL_ERROR_MESSAGE,
+                retryable: false,
+                stage: lastResortStage,
+            });
+        });
         return true;
     }
 
@@ -1400,7 +1453,25 @@ runtime.onMessage.addListener((msg, sender, sendResponse) => {
                 }
                 sendResponse({ error: errMsg, retryable });
             }
-        })();
+        })().catch((e) => {
+            // Same shape as the transaction path: a throw out of the catch
+            // block above would leave the popup and the page both waiting.
+            log.errorf("sign approval response failed:", e);
+            settleApproval(
+                msg.id,
+                {
+                    error: {
+                        code: INTERNAL_ERROR_CODE,
+                        message: INTERNAL_ERROR_MESSAGE,
+                    },
+                },
+                { holdsClaim: true },
+            );
+            sendResponse({
+                error: INTERNAL_ERROR_MESSAGE,
+                retryable: false,
+            });
+        });
         return true;
     }