📈 Add benchmark rake task to compare gem versions

To compare against the latest release:
```console
$ rake benchmarks:compare
```

To compare against several different versions:
```console
$ rake benchmarks:compare[0.1.1,0.2.2,0.3.7,0.4.2]
```

To filter or apply any other `benchmark-driver` arguments:
```console
$ rake benchmarks:compare BENCHMARK_ARGS="--filter 'fetch|search'"
```

Author: nevans

.gitignore

@@ -8,3 +8,4 @@
 /spec/reports/
 /tmp/
 /Gemfile.lock
+benchmarks/Gemfile*

Gemfile

@@ -8,3 +8,5 @@ gem "rake"
 gem "rdoc"
 gem "test-unit"
 gem "test-unit-ruby-core", git: "https://github.com/ruby/test-unit-ruby-core"
+
+gem "benchmark-driver"

benchmarks/.gitignore

@@ -0,0 +1 @@
+Gemfile-*.lock

benchmarks/generate_parser_benchmarks

@@ -81,6 +81,11 @@ benchmark:
       response = load_response("../test/net/imap/fixtures/response_parser/body_structure_responses.yml",
                                "test_bodystructure_bug8167_delivery_status_with_extra_data")
   script: parser.parse(response)
+- name: bodystructure_extension_fields
+  prelude: |2
+      response = load_response("../test/net/imap/fixtures/response_parser/body_structure_responses.yml",
+                               "test_bodystructure_extension_fields")
+  script: parser.parse(response)
 - name: bodystructure_mixed_boundary
   prelude: |2
       response = load_response("../test/net/imap/fixtures/response_parser/body_structure_responses.yml",
@@ -156,6 +161,16 @@ benchmark:
       response = load_response("../test/net/imap/fixtures/response_parser/quirky_behaviors.yml",
                                "test_invalid_noop_response_is_ignored")
   script: parser.parse(response)
+- name: invalid_noop_response_with_numeric_prefix
+  prelude: |2
+      response = load_response("../test/net/imap/fixtures/response_parser/quirky_behaviors.yml",
+                               "test_invalid_noop_response_with_numeric_prefix")
+  script: parser.parse(response)
+- name: invalid_noop_response_with_unparseable_data
+  prelude: |2
+      response = load_response("../test/net/imap/fixtures/response_parser/quirky_behaviors.yml",
+                               "test_invalid_noop_response_with_unparseable_data")
+  script: parser.parse(response)
 - name: invalid_search_response_multiple_result_with_trailing_space
   prelude: |2
       response = load_response("../test/net/imap/fixtures/response_parser/search_responses.yml",

benchmarks/parser.yml

@@ -25,7 +25,8 @@ Gem::Specification.new do |spec|
   # Specify which files should be added to the gem when it is released.
   # The `git ls-files -z` loads the files in the RubyGem that have been added into git.
   spec.files         = Dir.chdir(File.expand_path('..', __FILE__)) do
-    `git ls-files -z 2>/dev/null`.split("\x0").reject { |f| f.match(%r{^(bin|test|spec|features|rfcs)/}) }
+    `git ls-files -z 2>/dev/null`.split("\x0")
+      .reject {|f| f.match(%r{^(bin|test|spec|benchmarks|features|rfcs)/}) }
   end
   spec.bindir        = "exe"
   spec.executables   = spec.files.grep(%r{^exe/}) { |f| File.basename(f) }

net-imap.gemspec

@@ -0,0 +1,98 @@
+# frozen_string_literal: true
+
+PARSER_TEST_FIXTURES = FileList.new "test/net/imap/fixtures/response_parser/*.yml"
+CLOBBER.include "benchmarks/parser.yml"
+CLEAN.include   "benchmarks/Gemfile-*"
+
+BENCHMARK_INIT = <<RUBY
+  require "yaml"
+  require "net/imap"
+
+  def load_response(file, name)
+    YAML.unsafe_load_file(file).dig(:tests, name, :response)
+      .force_encoding "ASCII-8BIT" \\
+      or abort "ERRORO: missing %p fixture data in %p" % [name, file]
+  end
+
+  parser   = Net::IMAP::ResponseParser.new
+RUBY
+
+PER_BENCHMARK_PRELUDE = <<RUBY
+  response = load_response(%p,
+                           %p)
+RUBY
+
+file "benchmarks/parser.yml" => PARSER_TEST_FIXTURES do |t|
+  require "yaml"
+  require "pathname"
+  require "net/imap"
+
+  path = Pathname.new(__dir__) / "../test/net/imap/fixtures/response_parser"
+  files = path.glob("*.yml")
+  tests = files.flat_map {|file|
+    file.read
+      .gsub(%r{([-:]) !ruby/struct:\S+}) { $1 }
+      .then {
+        YAML.safe_load(_1, filename: file,
+                       permitted_classes: [Symbol, Regexp], aliases: true)
+      }
+      .fetch(:tests)
+      .select {|test_name, test|
+        :parser_assert_equal == test.fetch(:test_type) {
+          test.key?(:expected) ? :parser_assert_equal : :parser_pending
+        }
+      }
+      .map {|test_name, _|
+        [file.relative_path_from(__dir__).to_s, test_name.to_s]
+      }
+  }
+
+  benchmarks = tests.map {|file, fixture_name|
+    {"name"    => fixture_name.delete_prefix("test_"),
+     "prelude" => PER_BENCHMARK_PRELUDE % [file, fixture_name],
+     "script"  => "parser.parse(response)"}
+  }
+    .sort_by { _1["name"] }
+
+  YAML.dump({"prelude" => BENCHMARK_INIT, "benchmark" => benchmarks})
+    .then { File.write t.name, _1 }
+end
+
+namespace :benchmarks do
+  desc "Generate benchmarks from fixture data"
+  task :generate => "benchmarks/parser.yml"
+
+  desc "run the parser benchmarks comparing multiple gem versions"
+  task :compare => :generate do |task, args|
+    cd Pathname.new(__dir__) + ".."
+    current = `git describe --tags --dirty`.chomp
+    current = "dev" if current.empty?
+    versions = args.to_a
+    if versions.empty?
+      latest = %x{git describe --tags --abbrev=0 --match 'v*.*.*'}.chomp
+      versions = latest.empty? ? [] : [latest.delete_prefix("v")]
+    end
+    versions = versions.to_h { [_1, "Gemfile-v#{_1}"] }
+    cd "benchmarks" do
+      versions.each do |version, gemfile|
+        File.write gemfile, <<~RUBY
+          # frozen_string_literal: true
+          source "https://rubygems.org"
+          gem "net-imap", #{version.dump}
+        RUBY
+      end
+      versions = {current => "../Gemfile" , **versions}.map {
+        "%s::/usr/bin/env BUNDLE_GEMFILE=%s ruby" % _1
+      }.join(";")
+
+      extra = ENV.fetch("BENCHMARK_ARGS", "").shellsplit
+
+      sh("benchmark-driver",
+         "--bundler",
+         "-e", versions,
+         "parser.yml",
+         *extra)
+    end
+  end
+
+end