Implement base Exception class that will use the name of the class.

When exception types inherit from `Error`, the *name* property sticks with the
string "Error", making logs less useful.

Issue #259.

␄

lib/base.js

@@ -101,6 +101,59 @@ window.NexusHoratio.base = (function base() {
 
   NH.xunit.testing.testCases.push(EnsureTestCase);
 
+  /** Base exception that uses the name of the class. */
+  class Exception extends Error {
+
+    /** @type {string} */
+    get name() {
+      return this.constructor.name;
+    }
+
+  }
+
+  /* eslint-disable require-jsdoc */
+  class ExceptionTestCase extends NH.xunit.TestCase {
+
+    testBase() {
+      // Assemble/Act
+      const e = new Exception(this.id);
+
+      // Assert
+      this.assertEqual(e.name, 'Exception', 'name');
+      this.assertEqual(
+        e.toString(), 'Exception: ExceptionTestCase.testBase', 'toString'
+      );
+      this.assertTrue(e instanceof Exception, 'is exception');
+      this.assertTrue(e instanceof Error, 'is error');
+      this.assertFalse(e instanceof TypeError, 'is NOT type-error');
+    }
+
+    testInheritance() {
+      // Assemble
+      class TestException extends Exception {}
+      class DifferentException extends Exception {}
+
+      // Act
+      const te = new TestException('silly message');
+
+      // Assert
+      this.assertEqual(te.name, 'TestException', 'name');
+      this.assertEqual(
+        te.toString(), 'TestException: silly message', 'toString'
+      );
+      this.assertTrue(te instanceof TestException, 'is test-exception');
+      this.assertTrue(te instanceof Exception, 'is exception');
+      this.assertTrue(te instanceof Error, 'is error');
+      this.assertFalse(te instanceof TypeError, 'is NOT type-error');
+      this.assertFalse(te instanceof DifferentException,
+        'is NOT different-exception');
+    }
+
+  }
+  /* eslint-enable */
+
+  NH.xunit.testing.testCases.push(ExceptionTestCase);
+
   /**
    * Simple dispatcher (event bus).
    *
@@ -2279,6 +2332,7 @@ window.NexusHoratio.base = (function base() {
     NOT_FOUND: NOT_FOUND,
     ONE_ITEM: ONE_ITEM,
     ensure: ensure,
+    Exception: Exception,
     Dispatcher: Dispatcher,
     MessageQueue: MessageQueue,
     issues: issues,

lib/base.md

@@ -2,11 +2,12 @@
 
 Pure [JavaScript](https://developer.mozilla.org/en-US/docs/Web/JavaScript) stuff.  Nothing here should be [WEB API](https://developer.mozilla.org/en-US/docs/Web/API) aware, except `Logger`'s use of *console*.
 
-## Exported properties (as of version 50)
+## Exported properties (as of version 52)
 * version - Bumped per release.
 * NOT_FOUND - Constant (to make eslint's `no-magic-numbers` setting happy).
 * ONE_ITEM - Constant useful for testing length of an array.
 * ensure - Ensures appropriate versions of NexusHoratio libraries are loaded.
+* Exception - Base exception that uses the name of the class.
 * Dispatcher - Simple dispatcher (event bus).
 * MessageQueue - A simple message system that will queue messages to be delivered.
 * issues - NexusHoratio libraries and apps should log issues here.