Output chained matchers description

[inkstak]

Subject of the issue

I've created a custom matcher which allows to chain other matchers against a computed value :

matcher :have_html_body do
  chain :to, :other_matcher

  match do |actual|
    @actual = actual.parsed_body

    html_body_valid?(@actual) && other_matcher_matches?(@actual)
  end

  def other_matcher_matches?(actual)
    other_matcher.nil? || other_matcher.matches?(actual)
  end
end

I can then chain any matchers to match the parsed body :

expect(response).to have_html_body.to include("Hello World")
expect(response).to have_html_body.to match(/hello/)
expect(response).to have_html_body.to have_selector("#test", text: "Hello World")

It works fine, but descriptions are cumbersome :

is expected to have html body to #<RSpec::Matchers::BuiltIn::Include:0x0000000108887c10 [...long output...]>
is expected to have html body to #<RSpec::Matchers::BuiltIn::Match:0x000000010f476228 [...long output...]>
is expected to have html body to #<Capybara::RSpecMatchers::Matchers::HaveText:0x0000000140b35fd8 [...long output...]>

Expected behavior

It should generate a readable description :

is expected to have html body to include "Hello World"
is expected to have html body to match /hello/
is expected to have html body to have visible css "#test" with text "Hello World"

Your environment

• Ruby 3.2.2
• rspec 3.12.0
• rspec-expectations 3.12.3
• rspec-support 3.12.1

config.include_chain_clauses_in_custom_matcher_descriptions is already set to true

Investigation

There are 3 methods involved to generate chained description :

• RSpec::Matchers::DSL#chained_method_clause_sentences
• RSpec::Matchers::EnglishPhrasing#list
• RSpec::Support::ObjectFormatter.format

I'm not sure which one is the most relevant to fix the issue but my guess is EnglishPhrasing. Something like :

   def self.list(obj)
     return " #{RSpec::Support::ObjectFormatter.format(obj)}" if !obj || Struct === obj || Hash === obj
-    items = Array(obj).map { |w| RSpec::Support::ObjectFormatter.format(w) }
+    items = Array(obj).map { |w| w.is_a?(RSpec::Matchers::Composable) ? w.description : RSpec::Support::ObjectFormatter.format(w) }

[pirj]

This is not how you chain matchers. There’s the and/or mechanism built-in http://rspec.info/features/3-12/rspec-expectations/compound-expectations/

[inkstak]

Thanks, but I dont want to chain matcher with the same subject. Matchers chained to have_html_body.to receive a transformed subject.

[pirj]

~Your example is not indicative of that: you pass @actual to the other matcher.~ Sorry, my bad, I’ve missed the parse_body part.

I understand what you are trying to work around. This will be solved in this pr https://github.com/rspec/rspec-expectations/pull/1319, but it’s a breaking change, so only in RSpec 4.

[inkstak]

Sounds nice but it seems to me that the PR you've linked will only change the output diff on test failures. Am I wrong ? Maybe this is part of larger changes for RSpec 4 ?

In the matcher above, I have no problem to output a good failure message of chained matchers ... except for the description part.

matcher :have_html_body do
  chain :to,     :other_matcher
  chain :not_to, :other_negative_matcher

  failure_message do
    message  = "expected to #{description}"
    message += "\n#{other_matcher&.failure_message}" if other_matcher
    message += "\n#{other_negative_matcher&.failure_message_when_negated}" if other_negative_matcher
    message
  end
end

[pirj]

Do you have any issue with printed example descriptions of chained matchers built using the built-in compound mechanism?

[pirj]

Confusingly, chain is not to chain matchers, but rather to add qualifiers to the same matcher. Think be_within/of. See http://rspec.info/documentation/3.12/rspec-expectations/RSpec/Matchers/DSL/Macros.html#chain-instance_method

i can’t tell if dsl-defined matchers are compoundable by default.