src/utils: add ensureError() function

Typescript v4.4 no longer assumes that the error in catch is an Error
object [1]. This adds a helper function to ensure that caught errors
at least match the Error interface. If not, it creates a new Error
object with the value as the message.

[1]: https://devblogs.microsoft.com/typescript/announcing-typescript-4-4-beta/#using-unknown-in-catch-variables

src/ble-pybricks-service/sagas.ts

@@ -12,7 +12,7 @@ import {
     takeEvery,
 } from 'typed-redux-saga/macro';
 import { Action } from '../actions';
-import { hex } from '../utils';
+import { ensureError, hex } from '../utils';
 import {
     BlePybricksServiceActionType,
     BlePybricksServiceCommandAction,
@@ -101,7 +101,7 @@ function* decodeResponse(action: BlePybricksServiceDidNotifyEventAction): Genera
                 );
         }
     } catch (err) {
-        yield* put(eventProtocolError(err));
+        yield* put(eventProtocolError(ensureError(err)));
     }
 }
 

src/ble-uart/sagas.ts

@@ -48,7 +48,7 @@ import {
 } from '../ble/actions';
 import { BleConnectionState } from '../ble/reducers';
 import { RootState } from '../reducers';
-import { hex } from '../utils';
+import { ensureError, hex } from '../utils';
 import {
     BleUartActionType,
     BleUartWriteAction,
@@ -83,7 +83,7 @@ function* writePybricksCommand(
         yield* call(() => char.writeValueWithoutResponse(action.value.buffer));
         yield* put(didWriteCommand(action.id));
     } catch (err) {
-        yield* put(didFailToWriteCommand(action.id, err));
+        yield* put(didFailToWriteCommand(action.id, ensureError(err)));
     }
 }
 
@@ -99,7 +99,7 @@ function* writeUart(
         yield* call(() => char.writeValueWithoutResponse(action.value.buffer));
         yield* put(didWriteUart(action.id));
     } catch (err) {
-        yield* put(didFailToWriteUart(action.id, err));
+        yield* put(didFailToWriteUart(action.id, ensureError(err)));
     }
 }
 
@@ -132,7 +132,9 @@ function* connect(_action: BleDeviceConnectAction): Generator {
             // this can happen if the use cancels the dialog
             yield* put(didFailToConnect({ reason: Reason.Canceled }));
         } else {
-            yield* put(didFailToConnect({ reason: Reason.Unknown, err }));
+            yield* put(
+                didFailToConnect({ reason: Reason.Unknown, err: ensureError(err) }),
+            );
         }
         return;
     }
@@ -154,7 +156,7 @@ function* connect(_action: BleDeviceConnectAction): Generator {
         server = yield* call([device.gatt, 'connect']);
     } catch (err) {
         disconnectChannel.close();
-        yield* put(didFailToConnect({ reason: Reason.Unknown, err }));
+        yield* put(didFailToConnect({ reason: Reason.Unknown, err: ensureError(err) }));
         return;
     }
 
@@ -172,7 +174,9 @@ function* connect(_action: BleDeviceConnectAction): Generator {
         if (err instanceof DOMException && err.code === DOMException.NOT_FOUND_ERR) {
             yield* put(didFailToConnect({ reason: Reason.NoDeviceInfoService }));
         } else {
-            yield* put(didFailToConnect({ reason: Reason.Unknown, err }));
+            yield* put(
+                didFailToConnect({ reason: Reason.Unknown, err: ensureError(err) }),
+            );
         }
         return;
     }
@@ -186,7 +190,7 @@ function* connect(_action: BleDeviceConnectAction): Generator {
     } catch (err) {
         server.disconnect();
         yield* takeMaybe(disconnectChannel);
-        yield* put(didFailToConnect({ reason: Reason.Unknown, err }));
+        yield* put(didFailToConnect({ reason: Reason.Unknown, err: ensureError(err) }));
         return;
     }
 
@@ -198,7 +202,7 @@ function* connect(_action: BleDeviceConnectAction): Generator {
     } catch (err) {
         server.disconnect();
         yield* takeMaybe(disconnectChannel);
-        yield* put(didFailToConnect({ reason: Reason.Unknown, err }));
+        yield* put(didFailToConnect({ reason: Reason.Unknown, err: ensureError(err) }));
         return;
     }
 
@@ -214,7 +218,7 @@ function* connect(_action: BleDeviceConnectAction): Generator {
     } catch (err) {
         server.disconnect();
         yield* takeMaybe(disconnectChannel);
-        yield* put(didFailToConnect({ reason: Reason.Unknown, err }));
+        yield* put(didFailToConnect({ reason: Reason.Unknown, err: ensureError(err) }));
         return;
     }
 
@@ -226,7 +230,7 @@ function* connect(_action: BleDeviceConnectAction): Generator {
     } catch (err) {
         server.disconnect();
         yield* takeMaybe(disconnectChannel);
-        yield* put(didFailToConnect({ reason: Reason.Unknown, err }));
+        yield* put(didFailToConnect({ reason: Reason.Unknown, err: ensureError(err) }));
         return;
     }
 
@@ -249,7 +253,9 @@ function* connect(_action: BleDeviceConnectAction): Generator {
         } catch (err) {
             server.disconnect();
             yield* takeMaybe(disconnectChannel);
-            yield* put(didFailToConnect({ reason: Reason.Unknown, err }));
+            yield* put(
+                didFailToConnect({ reason: Reason.Unknown, err: ensureError(err) }),
+            );
             return;
         }
 
@@ -273,7 +279,9 @@ function* connect(_action: BleDeviceConnectAction): Generator {
         if (err instanceof DOMException && err.code === DOMException.NOT_FOUND_ERR) {
             yield* put(didFailToConnect({ reason: Reason.NoPybricksService }));
         } else {
-            yield* put(didFailToConnect({ reason: Reason.Unknown, err }));
+            yield* put(
+                didFailToConnect({ reason: Reason.Unknown, err: ensureError(err) }),
+            );
         }
         return;
     }
@@ -287,7 +295,7 @@ function* connect(_action: BleDeviceConnectAction): Generator {
     } catch (err) {
         server.disconnect();
         yield* takeMaybe(disconnectChannel);
-        yield* put(didFailToConnect({ reason: Reason.Unknown, err }));
+        yield* put(didFailToConnect({ reason: Reason.Unknown, err: ensureError(err) }));
         return;
     }
 
@@ -326,7 +334,7 @@ function* connect(_action: BleDeviceConnectAction): Generator {
         pybricksControlChannel.close();
         server.disconnect();
         yield* takeMaybe(disconnectChannel);
-        yield* put(didFailToConnect({ reason: Reason.Unknown, err }));
+        yield* put(didFailToConnect({ reason: Reason.Unknown, err: ensureError(err) }));
         return;
     }
 
@@ -349,7 +357,9 @@ function* connect(_action: BleDeviceConnectAction): Generator {
         if (err instanceof DOMException && err.code === DOMException.NOT_FOUND_ERR) {
             yield* put(didFailToConnect({ reason: Reason.NoPybricksService }));
         } else {
-            yield* put(didFailToConnect({ reason: Reason.Unknown, err }));
+            yield* put(
+                didFailToConnect({ reason: Reason.Unknown, err: ensureError(err) }),
+            );
         }
         return;
     }
@@ -362,7 +372,7 @@ function* connect(_action: BleDeviceConnectAction): Generator {
         pybricksControlChannel.close();
         server.disconnect();
         yield* takeMaybe(disconnectChannel);
-        yield* put(didFailToConnect({ reason: Reason.Unknown, err }));
+        yield* put(didFailToConnect({ reason: Reason.Unknown, err: ensureError(err) }));
         return;
     }
 
@@ -374,7 +384,7 @@ function* connect(_action: BleDeviceConnectAction): Generator {
         pybricksControlChannel.close();
         server.disconnect();
         yield* takeMaybe(disconnectChannel);
-        yield* put(didFailToConnect({ reason: Reason.Unknown, err }));
+        yield* put(didFailToConnect({ reason: Reason.Unknown, err: ensureError(err) }));
         return;
     }
 
@@ -406,7 +416,7 @@ function* connect(_action: BleDeviceConnectAction): Generator {
         pybricksControlChannel.close();
         server.disconnect();
         yield* takeMaybe(disconnectChannel);
-        yield* put(didFailToConnect({ reason: Reason.Unknown, err }));
+        yield* put(didFailToConnect({ reason: Reason.Unknown, err: ensureError(err) }));
         return;
     }
 

src/firmware/sagas.ts

@@ -53,7 +53,7 @@ import {
     compile,
 } from '../mpy/actions';
 import { RootState } from '../reducers';
-import { defined, hex, maybe } from '../utils';
+import { defined, ensureError, hex, maybe } from '../utils';
 import { fmod, sumComplement32 } from '../utils/math';
 import { isAndroid } from '../utils/os';
 import {
@@ -487,7 +487,7 @@ function* flashFirmware(action: FlashFirmwareFlashAction): Generator {
 
         yield* put(didFinish());
     } catch (err) {
-        yield* put(didFailToFinish(FailToFinishReasonType.Unknown, err));
+        yield* put(didFailToFinish(FailToFinishReasonType.Unknown, ensureError(err)));
         yield* disconnectAndCancel();
     }
 }

src/lwp3-bootloader/sagas-ble.ts

@@ -5,6 +5,7 @@
 
 import { END, eventChannel } from 'redux-saga';
 import { call, cancel, put, spawn, takeEvery, takeMaybe } from 'typed-redux-saga/macro';
+import { ensureError } from '../utils';
 import {
     BootloaderConnectionAction,
     BootloaderConnectionActionType,
@@ -35,7 +36,7 @@ function* write(
         }
         yield* put(didSend());
     } catch (err) {
-        yield* put(didFailToSend(err));
+        yield* put(didFailToSend(ensureError(err)));
     }
 }
 
@@ -64,7 +65,7 @@ function* connect(_action: BootloaderConnectionAction): Generator {
             // this can happen if the use cancels the dialog
             yield* put(didFailToConnect(Reason.Canceled));
         } else {
-            yield* put(didFailToConnect(Reason.Unknown, err));
+            yield* put(didFailToConnect(Reason.Unknown, ensureError(err)));
         }
         return;
     }
@@ -88,7 +89,7 @@ function* connect(_action: BootloaderConnectionAction): Generator {
         server = yield* call([device.gatt, 'connect']);
     } catch (err) {
         disconnectChannel.close();
-        yield* put(didFailToConnect(Reason.Unknown, err));
+        yield* put(didFailToConnect(Reason.Unknown, ensureError(err)));
         return;
     }
 
@@ -103,7 +104,7 @@ function* connect(_action: BootloaderConnectionAction): Generator {
             // https://chromium-review.googlesource.com/c/chromium/src/+/2214098
             yield* put(didFailToConnect(Reason.GattServiceNotFound));
         } else {
-            yield* put(didFailToConnect(Reason.Unknown, err));
+            yield* put(didFailToConnect(Reason.Unknown, ensureError(err)));
         }
         return;
     }
@@ -117,7 +118,7 @@ function* connect(_action: BootloaderConnectionAction): Generator {
     } catch (err) {
         server.disconnect();
         yield* takeMaybe(disconnectChannel);
-        yield* put(didFailToConnect(Reason.Unknown, err));
+        yield* put(didFailToConnect(Reason.Unknown, ensureError(err)));
         return;
     }
 
@@ -147,7 +148,7 @@ function* connect(_action: BootloaderConnectionAction): Generator {
         notificationChannel.close();
         server.disconnect();
         yield* takeMaybe(disconnectChannel);
-        yield* put(didFailToConnect(Reason.Unknown, err));
+        yield* put(didFailToConnect(Reason.Unknown, ensureError(err)));
         return;
     }
 

src/lwp3-bootloader/sagas.ts

@@ -12,7 +12,7 @@ import {
     takeEvery,
 } from 'typed-redux-saga/macro';
 import { Action } from '../actions';
-import { hex } from '../utils';
+import { ensureError, hex } from '../utils';
 import { isWindows } from '../utils/os';
 import {
     BootloaderConnectionActionType,
@@ -172,7 +172,7 @@ function* decodeResponse(action: BootloaderConnectionDidReceiveAction): Generato
                 );
         }
     } catch (err) {
-        yield* put(didError(err));
+        yield* put(didError(ensureError(err)));
     }
 }
 

src/settings/sagas.ts

@@ -9,6 +9,7 @@ import { EventChannel, eventChannel } from 'redux-saga';
 import { call, fork, put, select, take, takeEvery } from 'typed-redux-saga/macro';
 import { AppActionType } from '../app/actions';
 import { RootState } from '../reducers';
+import { ensureError } from '../utils';
 import {
     SettingsActionType,
     SettingsSetBooleanAction,
@@ -80,7 +81,7 @@ function* storeSetting(action: SettingsSetBooleanAction): Generator {
     try {
         localStorage.setItem(key, newValue);
     } catch (err) {
-        yield* put(didFailToSetBoolean(action.id, err));
+        yield* put(didFailToSetBoolean(action.id, ensureError(err)));
     }
 
     // storage event is only raised when a value is changed externally, so we

src/utils/index.test.ts

@@ -1,7 +1,7 @@
 // SPDX-License-Identifier: MIT
 // Copyright (c) 2020 The Pybricks Authors
 
-import { assert, defined, hex, maybe } from '.';
+import { assert, defined, ensureError, hex, maybe } from '.';
 
 test('assert', () => {
     const assertTrue = jest.fn(() => assert(true, 'should not throw'));
@@ -34,3 +34,13 @@ test('hex', () => {
     expect(hex(1, 4)).toBe('0x0001');
     expect(hex(2, 8)).toBe('0x00000002');
 });
+
+test('ensureError', () => {
+    const err = new Error('test error');
+    expect(ensureError(err)).toBe(err);
+
+    const stringToErrorMessage = 'not an Error';
+    const stringToError = expect(ensureError(stringToErrorMessage));
+    stringToError.toHaveProperty('name', 'Error');
+    stringToError.toHaveProperty('message', stringToErrorMessage);
+});

src/utils/index.ts

@@ -1,5 +1,5 @@
 // SPDX-License-Identifier: MIT
-// Copyright (c) 2020 The Pybricks Authors
+// Copyright (c) 2020-2021 The Pybricks Authors
 
 /**
  * Asserts that an assumption is true. This is used to detect programmer errors
@@ -29,7 +29,7 @@ export async function maybe<T>(promise: Promise<T>): Promise<Maybe<T>> {
     try {
         return [await promise];
     } catch (err) {
-        return [undefined, err];
+        return [undefined, ensureError(err)];
     }
 }
 
@@ -41,3 +41,25 @@ export async function maybe<T>(promise: Promise<T>): Promise<Maybe<T>> {
 export function hex(n: number, pad: number): string {
     return `0x${n.toString(16).padStart(pad, '0')}`;
 }
+
+function isError(err: unknown): err is Error {
+    const maybeError = err as Error;
+
+    return (
+        maybeError !== undefined &&
+        typeof maybeError.name === 'string' &&
+        typeof maybeError.message === 'string'
+    );
+}
+
+export function ensureError(err: unknown): Error {
+    if (isError(err)) {
+        return err;
+    }
+
+    if (typeof err === 'string') {
+        return new Error(err);
+    }
+
+    return Error(String(err));
+}