Add parsed errors to default OutputError message (#36)

Author: msx2

CHANGELOG.md

@@ -1,5 +1,8 @@
 # Opera Changelog
 
+### 0.4.1 - Feb 18, 2026
+- Add parsed errors to default `output!` exception message
+
 ### 0.4.0 - May 22, 2025
 
 - Stop handling exceptions

Gemfile.lock

@@ -1,7 +1,7 @@
 PATH
   remote: .
   specs:
-    opera (0.4.0)
+    opera (0.4.1)
 
 GEM
   remote: https://rubygems.org/

lib/opera/operation/result.rb

@@ -38,7 +38,13 @@ def failures
       end
 
       def output!
-        raise OutputError.new('Cannot retrieve output from a Failure.', errors) if failure?
+        if failure?
+          errors_combined = errors.map do |key, messages|
+            "- #{key}: #{messages.join('; ')}"
+          end.join("\n")
+
+          raise OutputError.new("Operation failed — output cannot be retrieved.\n#{errors_combined}", errors)
+        end
 
         output
       end

lib/opera/version.rb

@@ -1,5 +1,5 @@
 # frozen_string_literal: true
 
 module Opera
-  VERSION = '0.4.0'
+  VERSION = '0.4.1'
 end

spec/opera/operation/result_spec.rb

@@ -39,13 +39,38 @@ module Opera
         it { expect(subject.output!).to eq(:example) }
       end
 
-      context 'with Failure' do
-        before { subject.add_error(:example, 'Example') }
+      context 'with a single error' do
+        before { subject.add_error(:example, 'Example error') }
 
         it 'raises exception' do
           expect { subject.output! }.to raise_error(Opera::Operation::Result::OutputError) do |error|
-            expect(error.message).to eq('Cannot retrieve output from a Failure.')
-            expect(error.errors).to eq(example: ['Example'])
+            expect(error.message).to eq(
+              "Operation failed — output cannot be retrieved.\n- example: Example error"
+            )
+            expect(error.errors).to eq(example: ['Example error'])
+          end
+        end
+      end
+
+      context 'with multiple errors' do
+        before do
+          subject.add_errors(
+            example: ['Example error', 'Unexpected behavior'],
+            other_example: ['Hello darkness, my old friend']
+          )
+        end
+
+        it 'raises exception' do
+          expect { subject.output! }.to raise_error(Opera::Operation::Result::OutputError) do |error|
+            expect(error.message).to eq(
+              "Operation failed — output cannot be retrieved.\n" \
+              "- example: Example error; Unexpected behavior\n" \
+              "- other_example: Hello darkness, my old friend"
+            )
+            expect(error.errors).to eq(
+              example: ['Example error', 'Unexpected behavior'],
+              other_example: ['Hello darkness, my old friend']
+            )
           end
         end
       end