tools: add assert-no-message-literals lint rule

.eslintrc.yaml

@@ -169,6 +169,7 @@ rules:
 
   # Custom rules in tools/eslint-rules
   assert-throws-arguments: [error, { requireTwo: true }]
+  assert-no-message-literals: error
   no-unescaped-regexp-dot: error
 
 # Global scoped method and vars

tools/eslint-rules/assert-no-message-literals.js

@@ -0,0 +1,72 @@
+/**
+ * @fileoverview Check that calls to assert methods never have a simple
+ * string literal as the `message` argument.
+ * @author Anna Henningsen
+ */
+'use strict';
+
+//------------------------------------------------------------------------------
+// Rule Definition
+//------------------------------------------------------------------------------
+
+function checkThrowsArguments(context, node) {
+  if (node.callee.type === 'MemberExpression' &&
+      node.callee.object.name === 'assert') {
+    const args = node.arguments;
+    let messageArg = null;
+    switch (node.callee.property.name) {
+      case 'deepEqual':
+      case 'deepStrictEqual':
+      case 'equal':
+      case 'notDeepEqual':
+      case 'notDeepStrictEqual':
+      case 'notEqual':
+      case 'notStrictEqual':
+      case 'strictEqual':
+        if (args.length > 2)
+          messageArg = args[2];
+        break;
+      case 'ok':
+        if (args.length > 1)
+          messageArg = args[1];
+        break;
+      case 'doesNotThrow':
+      case 'throws':
+        if (args.length > 2) {
+          messageArg = args[2];
+        } else if (args.length > 1 && args[1].type === 'Literal' &&
+                   !args[1].regex) {
+          messageArg = args[1];
+        }
+        break;
+      case 'ifError':
+      case 'fail':
+        return;
+    }
+
+    if (messageArg === null)
+      return;
+
+    if (messageArg.type === 'Literal') {
+      context.report({
+        message: 'Unexpected literal assertion message',
+        node: messageArg
+      });
+    }
+  }
+}
+
+module.exports = {
+  meta: {
+    schema: [
+      {
+        type: 'object',
+      }
+    ]
+  },
+  create: function(context) {
+    return {
+      CallExpression: (node) => checkThrowsArguments(context, node)
+    };
+  }
+};