errors: factor out "of type" text generation

Also slightly revise the grammar of two-expected value scenario.
nodejs · Apr 25, 2017 · c02820a · c02820a
1 parent 061c5da
commit c02820a
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Showing 2 changed files with 18 additions and 11 deletions.
diff --git a/lib/internal/errors.js b/lib/internal/errors.js
@@ -91,22 +91,29 @@ E('ERR_UNKNOWN_BUILTIN_MODULE', (id) => `No such built-in module: ${id}`);
 
 function invalidArgType(name, expected, actual) {
   assert(name, 'name is required');
+  var msg = `The "${name}" argument must be ${oneOf(expected, 'type')}`;
+  if (arguments.length >= 3) {
+    msg += `. Received type ${actual !== null ? typeof actual : 'null'}`;
+  }
+  return msg;
+}
+
+function oneOf(expected, thing) {
   assert(expected, 'expected is required');
-  var msg = `The "${name}" argument must be `;
+  assert(typeof thing === 'string', 'thing is required');
   if (Array.isArray(expected)) {
-    var len = expected.length;
+    const len = expected.length;
+    assert(len > 0, 'At least one expected value needs to be specified');
     expected = expected.map((i) => String(i));
-    if (len > 1) {
-      msg += `one of type ${expected.slice(0, len - 1).join(', ')}, or ` +
+    if (len > 2) {
+      return `one of ${thing} ${expected.slice(0, len - 1).join(', ')}, or ` +
              expected[len - 1];
+    } else if (len === 2) {
+      return `one of ${thing} ${expected[0]} or ${expected[1]}`;
     } else {
-      msg += `of type ${expected[0]}`;
+      return `of ${thing} ${expected[0]}`;
     }
   } else {
-    msg += `of type ${String(expected)}`;
+    return `of ${thing} ${String(expected)}`;
   }
-  if (arguments.length >= 3) {
-    msg += `. Received type ${actual !== null ? typeof actual : 'null'}`;
-  }
-  return msg;
 }
diff --git a/test/parallel/test-internal-errors.js b/test/parallel/test-internal-errors.js
@@ -137,7 +137,7 @@ assert.strictEqual(errors.message('ERR_INVALID_ARG_TYPE', ['a', 'b']),
 assert.strictEqual(errors.message('ERR_INVALID_ARG_TYPE', ['a', ['b']]),
                    'The "a" argument must be of type b');
 assert.strictEqual(errors.message('ERR_INVALID_ARG_TYPE', ['a', ['b', 'c']]),
-                   'The "a" argument must be one of type b, or c');
+                   'The "a" argument must be one of type b or c');
 assert.strictEqual(errors.message('ERR_INVALID_ARG_TYPE',
                                   ['a', ['b', 'c', 'd']]),
                    'The "a" argument must be one of type b, c, or d');