Captures proc output instead of calling it

[swaathi]

A specific bug occurs with TodoList specs where the proc that is captured by the exception refers to a portion of the code which returns an array but outputs a string.

This array causes issues when showing the HTML diff:

To solve this, I capture the output of the proc instead of calling it.

Testing

Test this using the following script (add it to the root of this repository):

# bundle exec rspec stdout_demo.rb --format RSpec::EnrichedJson::Formatters::EnrichedJsonFormatter -r ./lib/rspec/enriched_json

RSpec.describe "stdout" do
  it "captures actual when spec fails" do
    expect { puts "Hello" }.to output("Bye\n").to_stdout
  end

  it "captures actual when spec passes" do
    expect { puts "Hello" }.to output("Hello\n").to_stdout
  end
end

Both cases should return an actual that is a string — not an array.

Learn Output

The specs on Learn now look like this:

When the spec fails:

When the spec passes:

Important

Capture Proc output to stdout in serialize_value and add tests for output matchers.

• Behavior:
  • Modify serialize_value in ExpectationHelperWrapper to capture Proc output to stdout instead of calling it directly.
  • Add "Output Matchers" category in demo.rb.
• Tests:
  • Remove Proc serialization test in oj_serialization_spec.rb.
  • Add stdout_matcher_spec.rb to test capturing of stdout output for passing and failing cases.
• Version:
  • Increment version to 0.8.3 in version.rb.

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[ellipsis-dev]

Caution

Changes requested ❌

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1. lib/rspec/enriched_json/expectation_helper_wrapper.rb:50

• Draft comment:
  Using global $stdout reassignment may lead to issues in concurrent environments. Consider a thread-safe approach if needed.
• Reason this comment was not posted:
  Decided after close inspection that this draft comment was likely wrong and/or not actionable: usefulness confidence = 30% vs. threshold = 50% This is a legitimate concern - modifying global state like $stdout can cause issues if multiple threads try to capture output simultaneously. However, this is in a test helper for RSpec, which typically runs tests sequentially. The code does properly restore the original stdout. The risk is real but may be acceptable for the testing context. I may be underestimating the likelihood of concurrent test execution. Some teams do run RSpec in parallel. While parallel test execution exists, RSpec's parallelization happens at the process level, not thread level, so each test process would have its own $stdout. The comment raises a valid concern but is likely overly cautious for this specific RSpec testing context where process-level parallelization is more common than thread-level.

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[ellipsis-dev]

Important

Looks good to me! 👍

Reviewed 28c7483 in 34 seconds. Click for details.

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1. demo.rb:414

• Draft comment:
  New 'Output Matchers' category added. Verify that the category name and ordering match your intended grouping for failing tests. The trailing comma is acceptable in Ruby.
• Reason this comment was not posted:
  Confidence changes required: 0% <= threshold 50% None

2. spec/oj_serialization_spec.rb:42

• Draft comment:
  Removed Proc serialization tests. Ensure that capturing proc output (instead of calling it) is documented and that tests reflect the new intended behavior.
• Reason this comment was not posted:
  Confidence changes required: 0% <= threshold 50% None

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