Provide friendly warnings when we can’t access status file.

Author: myronmarston

lib/rspec/core/configuration.rb

@@ -841,9 +841,17 @@ def files_to_run
       def last_run_statuses
         @last_run_statuses ||= Hash.new(UNKNOWN_STATUS).tap do |statuses|
           if (path = example_status_persistence_file_path)
-            ExampleStatusPersister.load_from(path).inject(statuses) do |hash, example|
-              hash[example.fetch(:example_id)] = example.fetch(:status)
-              hash
+            begin
+              ExampleStatusPersister.load_from(path).inject(statuses) do |hash, example|
+                hash[example.fetch(:example_id)] = example.fetch(:status)
+                hash
+              end
+            rescue SystemCallError => e
+              RSpec.warning "Could not read from #{path.inspect} (configured as " \
+                            "`config.example_status_persistence_file_path`) due " \
+                            "to a system error: #{e.inspect}. Please check that " \
+                            "the config option is set to an accessible, valid " \
+                            "file path", :call_site => nil
             end
           end
         end

lib/rspec/core/runner.rb

@@ -117,12 +117,14 @@ def run_specs(example_groups)
     private
 
       def persist_example_statuses
-        return unless @configuration.example_status_persistence_file_path
-
-        ExampleStatusPersister.persist(
-          @world.all_examples,
-          @configuration.example_status_persistence_file_path
-        )
+        return unless (path = @configuration.example_status_persistence_file_path)
+
+        ExampleStatusPersister.persist(@world.all_examples, path)
+      rescue SystemCallError => e
+        RSpec.warning "Could not write example statuses to #{path} (configured as " \
+                      "`config.example_status_persistence_file_path`) due to a " \
+                      "system error: #{e.inspect}. Please check that the config " \
+                      "option is set to an accessible, valid file path", :call_site => nil
       end
 
       # @private

spec/integration/persistence_failures_spec.rb

@@ -0,0 +1,69 @@
+require 'support/aruba_support'
+
+RSpec.describe 'Persistence failures' do
+  include_context "aruba support"
+  before { clean_current_dir }
+
+  context "when `config.example_status_persistence_file_path` is configured" do
+    context "to an invalid file path (e.g. spec/spec_helper.rb/examples.txt)" do
+      before do
+        write_file_formatted "spec/1_spec.rb", "
+          RSpec.configure do |c|
+            c.example_status_persistence_file_path = 'spec/1_spec.rb/examples.txt'
+          end
+          RSpec.describe { example { } }
+        "
+      end
+
+      it 'emits a helpful warning to the user, indicating we cannot write to it, and still runs the spec suite' do
+        run_command "spec/1_spec.rb"
+
+        expect(last_cmd_stderr).to include(
+          "WARNING: Could not write",
+          "spec/1_spec.rb/examples.txt",
+          "config.example_status_persistence_file_path",
+          "Errno:"
+        )
+        expect(last_cmd_stdout).to include("1 example")
+      end
+    end
+
+    context "to a file path for which we lack permissions" do
+      before do
+        write_file_formatted "spec/1_spec.rb", "
+          RSpec.configure do |c|
+            c.example_status_persistence_file_path = 'spec/examples.txt'
+          end
+          RSpec.describe { example { } }
+        "
+
+        write_file_formatted "spec/examples.txt", ""
+        in_current_dir do
+          FileUtils.chmod 0000, "spec/examples.txt"
+        end
+      end
+
+
+      it 'emits a helpful warning to the user, indicating we cannot read from it, and still runs the spec suite' do
+        run_command "spec/1_spec.rb"
+
+        expected_snippets = [
+          "WARNING: Could not read",
+          "spec/examples.txt",
+          "config.example_status_persistence_file_path",
+          "Errno:"
+        ]
+
+        if RSpec::Support::OS.windows?
+          # Not sure why, but on windows it doesn't trigger the read error, it
+          # triggers a write error instead. The important thing is that whatever
+          # system error occurs is reported accurately.
+          expected_snippets[0] = "WARNING: Could not write"
+        end
+
+        expect(last_cmd_stderr).to include(*expected_snippets)
+        expect(last_cmd_stdout).to include("1 example")
+      end
+    end
+  end
+end

spec/support/aruba_support.rb

@@ -17,6 +17,9 @@ def run_command(cmd)
 
     temp_stdout = StringIO.new
     temp_stderr = StringIO.new
+
+    # So that `RSpec.warning` will go to temp_stderr.
+    allow(::Kernel).to receive(:warn) { |msg| temp_stderr.puts(msg) }
     cmd_parts = Shellwords.split(cmd)
 
     handle_current_dir_change do