warn about nil being passed

Author: skatkov

lib/rspec/rails/matchers/have_reported_error.rb

@@ -37,9 +37,10 @@ class HaveReportedError < RSpec::Rails::Matchers::BaseMatcher
         #   Expected message when first param is a class
         def initialize(expected_error_or_message = UndefinedValue, expected_message = nil)
           @attributes = {}
+          @warn_about_nil_error = expected_error_or_message.nil?
 
           case expected_error_or_message
-          when nil, UndefinedValue
+          when UndefinedValue
             @expected_error = nil
             @expected_message = expected_message
           when String, Regexp
@@ -65,6 +66,8 @@ def matches?(block)
             raise ArgumentError, "this matcher doesn't work with value expectations"
           end
 
+          warn_about_nil_error! if @warn_about_nil_error
+
           @error_subscriber = ErrorSubscriber.new
           ::Rails.error.subscribe(@error_subscriber)
 
@@ -213,6 +216,18 @@ def unmatched_attributes(actual)
             end
           end
         end
+
+        def warn_about_nil_error!
+          RSpec.warn_with("Using the `have_reported_error` matcher with a `nil` error is probably " \
+                         "unintentional, it risks false positives, since `have_reported_error` " \
+                         "will match when any error is reported to Rails.error, potentially " \
+                         "allowing the expectation to pass without the specific error you are " \
+                         "intending to test for being reported. " \
+                         "Instead consider providing a specific error class or message. " \
+                         "This message can be suppressed by setting: " \
+                         "`RSpec::Expectations.configuration.on_potential_false" \
+                         "_positives = :nothing`")
+        end
       end
 
       # @api public

spec/rspec/rails/matchers/have_reported_error_spec.rb

@@ -17,8 +17,10 @@ class AnotherTestError < StandardError; end
       expect {Rails.error.report(StandardError.new("test error"))}.to have_reported_error
     end
 
-    it "passes when an error is reported with explicit nil argument" do
-      expect {Rails.error.report(StandardError.new("test error"))}.to have_reported_error(nil)
+    it "fails when an error is reported with explicit nil argument" do
+      expect {
+        expect {Rails.error.report(StandardError.new("test error"))}.to have_reported_error(nil)
+      }.to raise_error(RuntimeError, /Using the `have_reported_error` matcher with a `nil` error is probably unintentional/)
     end
 
     it "fails when no errors are reported" do
@@ -29,7 +31,7 @@ class AnotherTestError < StandardError; end
 
     it "fails when no errors are reported with explicit nil argument" do
       expect {
-        expect { "no error" }.to have_reported_error(nil)
+        expect { "no error" }.to have_reported_error
       }.to fail_with(/Expected the block to report an error, but none was reported./)
     end