1 files changed, 48 insertions, 0 deletions
diff --git a/tools/lint/eslint/eslint-plugin-mozilla/lib/rules/reject-addtask-only.js b/tools/lint/eslint/eslint-plugin-mozilla/lib/rules/reject-addtask-only.js
new file mode 100644
index 0000000000..fa6de2f8b9
--- /dev/null
+++ b/tools/lint/eslint/eslint-plugin-mozilla/lib/rules/reject-addtask-only.js
@@ -0,0 +1,48 @@
+/**
+ * @fileoverview Don't allow only() in tests
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/.
+ */
+
+"use strict";
+
+module.exports = {
+  meta: {
+    docs: {
+      url: "https://firefox-source-docs.mozilla.org/code-quality/lint/linters/eslint-plugin-mozilla/reject-addtask-only.html",
+    },
+    hasSuggestions: true,
+    schema: [],
+    type: "suggestion",
+  },
+
+  create(context) {
+    return {
+      CallExpression(node) {
+        if (
+          ["add_task", "decorate_task"].includes(
+            node.callee.object?.callee?.name
+          ) &&
+          node.callee.property?.name == "only"
+        ) {
+          context.report({
+            node,
+            message: `add_task(...).only() not allowed - add an exception if this is intentional`,
+            suggest: [
+              {
+                desc: "Remove only() call from task",
+                fix: fixer =>
+                  fixer.replaceTextRange(
+                    [node.callee.object.range[1], node.range[1]],
+                    ""
+                  ),
+              },
+            ],
+          });
+        }
+      },
+    };
+  },
+};