Add method coverage support

[tycooon]

See #782.
Also addresses #801 and #916.
Support for HTML formatter can be found here: simplecov-ruby/simplecov-html#110.

Some notes:

• I had to rework how coverage is parsed/unparsed (see ResultSerialization module).
• Because of that, I had to revert some of ResultMerger optimizations :( Now it's operating Result objects, however it still parses and merges files one be one.
• Coverage is now always stored in memory in symbolized form (lines: [] instead of "lines" => []), just the same way you get it when calling Ruby's Coverage.result. Because of that, a lot of specs were updated.
• Sometimes method owner includes memory address (e.g. when method is called on anonymous class). This makes merging results from different CI jobs problematic, so we replace memory addresses with zero address 0x0000000000000000.
• adapt_pre_simplecov_0_18_result logic was moved to ResultSerialization.deserialize. Also old-style branch info is supported (eval is still used for that).

All this stuff has been battle-tested on a couple of big projects, some of which merge results of multiple CI jobs.

[tycooon]

@PragTob hope you will find some time to review the changes.

[dan-jensen]

EDIT: I think this PR will solve a problem I'm having.

In 0.21.2 I'm encountering an error on this line when executing via rubycritic. Turns out coverage_data is an Array (as documented), and was previously an Integer, so did this line ever work? Related to that, how does coverage_data.fetch(:branches, {}) (below) work?

[tycooon]

coverage_data is a Hash in this PR. So it's strange that you have problems. Maybe you have coverage data in some old format that is breaking the code?

[tycooon]

Update: I see that rubycritic is doing a lot of stuff with simplecov internals. So I guess they will have to update the code if this PR is merged. They already do something similar here for example.

[dan-jensen]

@tycooon just to be clear, I'm not having any problem with this PR. I think this PR will solve my problem 🙂

Also for clarity: the error I encountered was no implicit conversion of String into Integer (TypeError). From my reading of the traceback it looks like this error is internal to simplecov. Yes, it's possible that it's due to some sort of mishandling by rubycritic (which invokes simplecov through find_coverage_percentage). But it seems smart to focus on simplecov first because the existing code doesn't seem to make sense (which is what I was describing above). I'm looking forward to this PR helping to clarify SourceFile, and hopefully also fixing the bug.

Traceback

running simple_cov Traceback (most recent call last): 19: from {PATH}bin/rubycritic:23:in `' 18: from {PATH}bin/rubycritic:23:in `load' 17: from {PATH}lib/ruby/gems/2.7.0/gems/rubycritic-4.6.1/bin/rubycritic:10:in `' 16: from {PATH}lib/ruby/gems/2.7.0/gems/rubycritic-4.6.1/lib/rubycritic/cli/application.rb:21:in `execute' 15: from {PATH}lib/ruby/gems/2.7.0/gems/rubycritic-4.6.1/lib/rubycritic/commands/default.rb:19:in `execute' 14: from {PATH}lib/ruby/gems/2.7.0/gems/rubycritic-4.6.1/lib/rubycritic/commands/default.rb:24:in `critique' 13: from {PATH}lib/ruby/gems/2.7.0/gems/rubycritic-4.6.1/lib/rubycritic/analysers_runner.rb:29:in `run' 12: from {PATH}lib/ruby/gems/2.7.0/gems/rubycritic-4.6.1/lib/rubycritic/analysers_runner.rb:29:in `each' 11: from {PATH}lib/ruby/gems/2.7.0/gems/rubycritic-4.6.1/lib/rubycritic/analysers_runner.rb:32:in `block in run' 10: from {PATH}lib/ruby/gems/2.7.0/gems/rubycritic-4.6.1/lib/rubycritic/analysers/coverage.rb:20:in `run' 9: from {PATH}lib/ruby/gems/2.7.0/gems/rubycritic-4.6.1/lib/rubycritic/core/analysed_modules_collection.rb:32:in `each' 8: from {PATH}lib/ruby/gems/2.7.0/gems/rubycritic-4.6.1/lib/rubycritic/core/analysed_modules_collection.rb:32:in `each' 7: from {PATH}lib/ruby/gems/2.7.0/gems/rubycritic-4.6.1/lib/rubycritic/analysers/coverage.rb:21:in `block in run' 6: from {PATH}lib/ruby/gems/2.7.0/gems/rubycritic-4.6.1/lib/rubycritic/analysers/coverage.rb:38:in `find_coverage_percentage' 5: from {PATH}lib/ruby/gems/2.7.0/gems/simplecov-0.21.2/lib/simplecov/source_file.rb:81:in `covered_percent' 4: from {PATH}lib/ruby/gems/2.7.0/gems/simplecov-0.21.2/lib/simplecov/source_file.rb:35:in `coverage_statistics' 3: from {PATH}lib/ruby/gems/2.7.0/gems/simplecov-0.21.2/lib/simplecov/source_file.rb:333:in `line_coverage_statistics' 2: from {PATH}lib/ruby/gems/2.7.0/gems/simplecov-0.21.2/lib/simplecov/source_file.rb:241:in `lines_strength' 1: from {PATH}lib/ruby/gems/2.7.0/gems/simplecov-0.21.2/lib/simplecov/source_file.rb:43:in `lines' {PATH}lib/ruby/gems/2.7.0/gems/simplecov-0.21.2/lib/simplecov/source_file.rb:224:in `build_lines': no implicit conversion of String into Integer (TypeError)

[tycooon]

Hey @PragTob, maybe you can take a look now?

[pboling]

@PragTob ping!

[0exp]

@PragTob ping!

[gondalez]

Thanks for your work on this PR, it would make a welcome inclusion 🙏

I am curious - would method coverage improve coverage support for ruby 3's endless methods?

I have found that endless methods currently show as covered if they are never executed by tests.
Even if you have branching coverage enabled they report as fully covered.

Example class, spec and coverage report follow.
Note that uncovered_endless_method shows as covered despite not being executed by the test.
Whereas endless_branching_method shows branching coverage failing since it was executed.

I would have expected uncovered_endless_method to show as partially covered.

class CoveragePoc
  # this method is fully covered
  def self.simple_method
    :simple
  end

  # the :b branch for these methods is not covered
  def self.endless_branching_method(arg) = arg ? :a : :b

  def self.branching_method(arg)
    arg ? :a : :b
  end

  # these methods are not covered at all
  def self.uncovered_endless_method = :uncovered_endless

  def self.uncovered_method
    :uncovered
  end
end

RSpec.describe CoveragePoc do
  it 'works' do
    expect(described_class.simple_method).to eq(:simple)
    expect(described_class.branching_method(true)).to eq(:a)
    expect(described_class.endless_branching_method(true)).to eq(:a)
  end
end