Improve error reporting on run control evaluation

features/run_control/evaluation.feature

@@ -7,3 +7,12 @@ Feature: run control file evaluation
       """
     When I start uhwm
     Then the output must contain "run control evaluation"
+
+  Scenario: reports run control code in backtrace on errors
+    Given a run control file with:
+      """
+      'no error on first line'
+      fail 'fails on second line'
+      """
+    When I start uhwm
+    Then the output must match /\.uhwmrc\.rb:2:.+fails on second line/

lib/uh/wm/run_control.rb

@@ -12,7 +12,7 @@ module Uh
         def evaluate env
           rc_path = File.expand_path(env.rc_path)
           rc = new env
-          rc.evaluate File.read(rc_path) if File.exist?(rc_path)
+          rc.evaluate File.read(rc_path), rc_path if File.exist?(rc_path)
         end
       end
 
@@ -20,8 +20,8 @@ module Uh
         @env = env
       end
 
-      def evaluate code
+      def evaluate code, path
-        instance_eval code
+        instance_eval code, path
       end
 
       def key keysym, &block

spec/uh/wm/run_control_spec.rb

@@ -23,7 +23,8 @@ module Uh
         end
 
         it 'tells the new instance to evaluate run control file content' do
-          expect(rc).to receive(:evaluate).with ':run_control_code'
+          expect(rc)
+            .to receive(:evaluate).with(':run_control_code', env.rc_path)
           allow(described_class).to receive(:new) { rc }
           described_class.evaluate env
         end
@@ -39,12 +40,12 @@ module Uh
 
       describe '#evaluate' do
         it 'evaluates given code' do
-          expect { rc.evaluate 'throw :run_control_code' }
+          expect { rc.evaluate 'throw :run_control_code', 'some_path' }
             .to throw_symbol :run_control_code
         end
 
         it 'provides access to assigned env' do
-          expect { rc.evaluate 'fail @env.object_id.to_s' }
+          expect { rc.evaluate 'fail @env.object_id.to_s', 'some_path' }
             .to raise_error env.object_id.to_s
         end
       end