feat: support virtual contexts (#50)

This adds support for virtual contexts by testing `RegExp` and `Error`
via `toString` instead of an `instanceof` check.

index.js

@@ -1,3 +1,17 @@
+function isErrorInstance(obj) {
+  // eslint-disable-next-line prefer-reflect
+  return obj instanceof Error || Object.prototype.toString.call(obj) === '[object Error]';
+}
+
+function isErrorClass(obj) {
+  return obj === Error || (typeof obj === 'function' && obj.name === 'Error');
+}
+
+function isRegExp(obj) {
+  // eslint-disable-next-line prefer-reflect
+  return Object.prototype.toString.call(obj) === '[object RegExp]';
+}
+
 /**
  * ### .compatibleInstance(thrown, errorLike)
  *
@@ -13,7 +27,7 @@
  */
 
 function compatibleInstance(thrown, errorLike) {
-  return errorLike instanceof Error && thrown === errorLike;
+  return isErrorInstance(errorLike) && thrown === errorLike;
 }
 
 /**
@@ -33,10 +47,10 @@ function compatibleInstance(thrown, errorLike) {
  */
 
 function compatibleConstructor(thrown, errorLike) {
-  if (errorLike instanceof Error) {
+  if (isErrorInstance(errorLike)) {
     // If `errorLike` is an instance of any error we compare their constructors
     return thrown.constructor === errorLike.constructor || thrown instanceof errorLike.constructor;
-  } else if (errorLike.prototype instanceof Error || errorLike === Error) {
+  } else if (isErrorClass(Object.getPrototypeOf(errorLike)) || isErrorClass(errorLike)) {
     // If `errorLike` is a constructor that inherits from Error, we compare `thrown` to `errorLike` directly
     return thrown.constructor === errorLike || thrown instanceof errorLike;
   }
@@ -60,7 +74,7 @@ function compatibleConstructor(thrown, errorLike) {
 
 function compatibleMessage(thrown, errMatcher) {
   const comparisonString = typeof thrown === 'string' ? thrown : thrown.message;
-  if (errMatcher instanceof RegExp) {
+  if (isRegExp(errMatcher)) {
     return errMatcher.test(comparisonString);
   } else if (typeof errMatcher === 'string') {
     return comparisonString.indexOf(errMatcher) !== -1; // eslint-disable-line no-magic-numbers
@@ -82,7 +96,7 @@ function compatibleMessage(thrown, errMatcher) {
 
 function getConstructorName(errorLike) {
   let constructorName = errorLike;
-  if (errorLike instanceof Error) {
+  if (isErrorInstance(errorLike)) {
     constructorName = errorLike.constructor.name;
   } else if (typeof errorLike === 'function') {
     // If `err` is not an instance of Error it is an error constructor itself or another function.

package.json

@@ -32,7 +32,7 @@
     "semantic-release": "semantic-release pre && npm publish && semantic-release post",
     "pretest": "npm run lint && npm run build",
     "test": "npm run test:node && npm run test:browser",
-    "test:browser": "web-test-runner --node-resolve test/",
+    "test:browser": "web-test-runner",
     "test:node": "mocha"
   },
   "config": {
@@ -53,7 +53,8 @@
     "rules": {
       "complexity": "off",
       "max-statements": "off",
-      "prefer-arrow-callback": "off"
+      "prefer-arrow-callback": "off",
+      "prefer-reflect": "off"
     }
   },
   "devDependencies": {

test/virtual-machines.js

@@ -0,0 +1,70 @@
+import { createContext, runInContext } from 'node:vm';
+import { assert } from 'simple-assert';
+import * as checkError from '../index.js';
+
+const vmContext = { checkError };
+createContext(vmContext);
+
+function runCodeInVm(code) {
+  return runInContext(`{${ code }}`, vmContext);
+}
+
+describe('node virtual machines', function () {
+  it('compatibleMessage', function () {
+    assert(runCodeInVm(`
+      const errorInstance = new Error('I am an instance');
+      checkError.compatibleMessage(errorInstance, /instance$/) === true;
+    `) === true);
+  });
+
+  it('constructorName', function () {
+    assert(runCodeInVm(`
+      const errorInstance = new Error('I am an instance');
+      checkError.getConstructorName(errorInstance);
+    `) === 'Error');
+    assert(runCodeInVm(`
+      const derivedInstance = new TypeError('I inherit from Error');
+      checkError.getConstructorName(derivedInstance);
+    `) === 'TypeError');
+  });
+
+  it('compatibleInstance', function () {
+    assert(runCodeInVm(`
+      const errorInstance = new Error('I am an instance');
+      const sameInstance = errorInstance;
+      checkError.compatibleInstance(errorInstance, sameInstance);
+    `) === true);
+    assert(runCodeInVm(`
+      const errorInstance = new Error('I am an instance');
+      const otherInstance = new Error('I am another');
+      checkError.compatibleInstance(errorInstance, otherInstance);
+    `) === false);
+  });
+
+  it('compatibleConstructor', function () {
+    assert(runCodeInVm(`
+      const errorInstance = new Error('I am an instance');
+      const sameInstance = errorInstance;
+      checkError.compatibleConstructor(errorInstance, sameInstance);
+    `) === true);
+    assert(runCodeInVm(`
+      const errorInstance = new Error('I am an instance');
+      const otherInstance = new Error('I an another instance');
+      checkError.compatibleConstructor(errorInstance, otherInstance);
+    `) === true);
+    assert(runCodeInVm(`
+      const errorInstance = new Error('I am an instance');
+      const derivedInstance = new TypeError('I inherit from Error');
+      checkError.compatibleConstructor(derivedInstance, errorInstance);
+    `) === true);
+    assert(runCodeInVm(`
+      const errorInstance = new Error('I am an instance');
+      const derivedInstance = new TypeError('I inherit from Error');
+      checkError.compatibleConstructor(errorInstance, derivedInstance);
+    `) === false);
+    assert(runCodeInVm(`
+      const errorInstance = new TypeError('I am an instance');
+      checkError.compatibleConstructor(errorInstance, TypeError);
+    `) === true);
+  });
+});

web-test-runner.config.js

@@ -0,0 +1,9 @@
+export default {
+  nodeResolve: true,
+  files: [
+    'test/*.js',
+    '!test/virtual-machines.js',
+  ],
+  plugins: [
+  ],
+};