From 1d1c8fe4ad10872bbbed29699fdda4106ca3be51 Mon Sep 17 00:00:00 2001
From: Alessandro Rodi <coorasse@gmail.com>
Date: Wed, 6 Jul 2022 14:19:43 +0200
Subject: [PATCH] Disable negated matcher for rspec

---
 CHANGELOG.md                 |  2 ++
 lib/cancan/matchers.rb       | 11 +++++++++++
 spec/cancan/matchers_spec.rb |  6 ++----
 3 files changed, 15 insertions(+), 4 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 98fb2e7d..e320fe3f 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,7 @@
 ## Unreleased
 
+* Disable `expect(...).not_to be_able_to(:action_a, :action_b)` for multiple actions because it leads to ambiguity. ([@coorasse][])
+
 ## 3.4.0
 
 * [#691](https://github.com/CanCanCommunity/cancancan/pull/691): Add two new subquery strategies: `joined_alias_exists_subquery`, `joined_alias_each_rule_as_exists_subquery`. ([@kaspernj][])
diff --git a/lib/cancan/matchers.rb b/lib/cancan/matchers.rb
index ccc8e0b5..34c6cb39 100644
--- a/lib/cancan/matchers.rb
+++ b/lib/cancan/matchers.rb
@@ -23,6 +23,17 @@
     end
   end
 
+  match_when_negated do |ability|
+    actions = args.first
+    if actions.is_a? Array
+      raise NotImplementedError, "`expect(...).not_to be_able_to(:action_a, :action_b)` is no longer supported.\n" \
+                                 "This syntax leads to ambiguity and it has therefore been disabled.\n" \
+                                 'Please split into separate expectations.'
+    else
+      !ability.can?(*args)
+    end
+  end
+
   # Check that RSpec is < 2.99
   if !respond_to?(:failure_message) && respond_to?(:failure_message_for_should)
     alias_method :failure_message, :failure_message_for_should
diff --git a/spec/cancan/matchers_spec.rb b/spec/cancan/matchers_spec.rb
index 5990e1a4..fe0b1e14 100644
--- a/spec/cancan/matchers_spec.rb
+++ b/spec/cancan/matchers_spec.rb
@@ -46,13 +46,11 @@
     end
 
     it 'delegates to can? with array of abilities with empty array' do
-      is_expected.not_to be_able_to([], 123)
+      expect { is_expected.not_to be_able_to([], 123) }.to raise_error(NotImplementedError)
     end
 
     it 'delegates to can? with array of abilities with only one eligible ability' do
-      is_expected.to receive(:can?).with(:read, 123) { true }
-      is_expected.to receive(:can?).with(:update, 123) { false }
-      is_expected.not_to be_able_to(%i[read update], 123)
+      expect { is_expected.not_to be_able_to(%i[read update], 123) }.to raise_error(NotImplementedError)
     end
   end
 end