feat: support native Error causes

Author: legobeat

jest.config.js

@@ -45,10 +45,10 @@ module.exports = {
   // An object that configures minimum threshold enforcement for coverage results
   coverageThreshold: {
     global: {
-      branches: 93.05,
+      branches: 92.64,
       functions: 94.44,
-      lines: 92.96,
-      statements: 92.96,
+      lines: 92.85,
+      statements: 92.85,
     },
   },
 

src/classes.ts

@@ -6,7 +6,7 @@ import { hasProperty, isObject, isPlainObject } from '@metamask/utils';
 import safeStringify from 'fast-safe-stringify';
 
 import type { OptionalDataWithOptionalCause } from './utils';
-import { serializeCause } from './utils';
+import { dataHasCause, serializeCause } from './utils';
 
 export type { SerializedJsonRpcError };
 
@@ -19,9 +19,6 @@ export type { SerializedJsonRpcError };
 export class JsonRpcError<
   Data extends OptionalDataWithOptionalCause,
 > extends Error {
-  // This can be removed when tsconfig lib and/or target have changed to >=es2022
-  public cause: OptionalDataWithOptionalCause;
-
   public code: number;
 
   public data?: Data;
@@ -35,18 +32,21 @@ export class JsonRpcError<
       throw new Error('"message" must be a non-empty string.');
     }
 
-    super(message);
-    this.code = code;
-    if (data !== undefined) {
-      this.data = data;
-      if (
-        isObject(data) &&
-        hasProperty(data, 'cause') &&
-        isObject(data.cause)
-      ) {
+    if (dataHasCause(data)) {
+      super(message, { cause: data.cause });
+      // Browser backwards-compatibility
+      if (!this.cause) {
         this.cause = data.cause;
       }
+    } else {
+      super(message);
+    }
+
+    if (data !== undefined) {
+      this.data = data;
     }
+
+    this.code = code;
   }
 
   /**

src/utils.test.ts

@@ -16,7 +16,7 @@ import {
   dummyMessage,
   dummyData,
 } from './__fixtures__';
-import { getMessageFromCode, serializeError } from './utils';
+import { dataHasCause, getMessageFromCode, serializeError } from './utils';
 
 const rpcCodes = errorCodes.rpc;
 
@@ -310,3 +310,23 @@ describe('serializeError', () => {
     });
   });
 });
+
+describe('dataHasCause', () => {
+  it('returns false for invalid data types', () => {
+    [undefined, null, 'hello', 1234].forEach(data => {
+      const result = dataHasCause(data);
+      expect(result).toBe(false);
+    });
+  });
+  it('returns false for invalid cause types', () => {
+    [undefined, null, 'hello', 1234].forEach(cause => {
+      const result = dataHasCause({cause});
+      expect(result).toBe(false);
+    });
+  });
+  it('returns true when cause is object', () => {
+    const data = {cause: {}};
+    const result = dataHasCause(data);
+    expect(result).toBe(true);
+  });
+});

src/utils.ts

@@ -211,3 +211,17 @@ function serializeObject(object: RuntimeObject): Json {
     {},
   );
 }
+
+/**
+ * Returns true if supplied error data has a usable `cause` property; false otherwise.
+ *
+ * @param data - Optional data to validate.
+ * @returns Whether cause property is present and an object.
+ */
+export function dataHasCause(
+  data: OptionalDataWithOptionalCause,
+): data is { cause: object } {
+  return isObject(data)
+    && hasProperty(data, 'cause')
+    && isObject(data.cause);
+}

tsconfig.json

@@ -4,7 +4,7 @@
     "exactOptionalPropertyTypes": true,
     "forceConsistentCasingInFileNames": true,
     // Remove custom `cause` field from JsonRpcError when updating
-    "lib": ["ES2020"],
+    "lib": ["ES2022"],
     "module": "CommonJS",
     "moduleResolution": "node",
     "noEmit": true,