Hash include with composable matcher gives misleading diff

[owst]

Expecting a hash to include another when using composable matchers gives a misleading diff for the subset of the hash that did match:

  1) includes should include {:a => /2/, :b => "bar"}
     Failure/Error:
       expect(
         {
           a: '123',
           b: 'foo',
         }
       ).to include(a: /2/, b: 'bar')
     
       expected {:a => "123", :b => "foo"} to include {:b => "bar"}
       Diff:
       @@ -1,3 +1,3 @@
       -:a => /2/,
       -:b => "bar",
       +:a => "123",
       +:b => "foo",

Notice that

-:a => /2/,
+:a => "123",

is in the diff, despite "123" being matched by /2/ - this can make it harder to determine what the problem is, with a larger hash.

N.b. that the expected {:a => "123", :b => "foo"} to include {:b => "bar"} part of the failure message is good, and does indicate the problem - this issue is only about the "Diff:" part.

Your environment

Resolving dependencies...
Using bundler 1.17.3
Using diff-lcs 1.3
Using rspec-support 3.7.1
Using rspec-core 3.7.1
Using rspec-expectations 3.7.0
Using rspec-mocks 3.7.0
Using rspec 3.7.0
Ruby version is: 2.5.3

Steps to reproduce

# frozen_string_literal: true

begin
  require "bundler/inline"
rescue LoadError => e
  $stderr.puts "Bundler version 1.10 or later is required. Please update your Bundler"
  raise e
end

gemfile(true) do
  source "https://rubygems.org"

  gem "rspec", "3.7.0" # Activate the gem and version you are reporting the issue against.
end

puts "Ruby version is: #{RUBY_VERSION}"
require 'rspec/autorun'

RSpec.describe 'includes' do
  it do
    expect(
      {
        a: '123',
        b: 'foo',
      }
    ).to include(a: /2/, b: 'bar')
  end
end

Expected behavior

The diff does not highlight matched entries as different:

@@ -1,3 +1,3 @@
 :a => "123",
-:b => "bar",
+:b => "foo",

Actual behavior

The diff does highlight matched entries as different:

@@ -1,3 +1,3 @@
-:a => /2/,
-:b => "bar",
+:a => "123",
+:b => "foo",

[benoittgt]

Hello

match should work.

You can try:

# frozen_string_literal: true

begin
  require "bundler/inline"
rescue LoadError => e
  raise e
end

gemfile(true) do
  source "https://rubygems.org"

  gem "rspec"
end

require 'rspec/autorun'

RSpec.describe 'includes' do
  it do
    expect(
      {
        a: '123',
        b: 'foo',
      }
    ).to match(a: /2/, b: 'foo')
  end
end

[benoittgt]

Sorry to close the issue. My answer is not the one you expect. Let me have a further look.

[JonRowe]

The issue here is that the differ diff-lcs diffs objects as strings, and the strings are different, thus this is the output we get. Improving this is something we'd very much like but theres no immediate bug fix here.