Select macOS runners randomly.

.github/workflows/ci.yml

@@ -33,7 +33,7 @@ jobs:
   test:
     name: ${{ matrix.name }}
     needs: generate-matrix
-    runs-on: macos-11.0
+    runs-on: ${{ matrix.runner }}
     strategy:
       matrix:
         include: ${{ fromJson(needs.generate-matrix.outputs.matrix) }}
@@ -77,11 +77,10 @@ jobs:
             echo '::warning::Removing `conda` symlink is no longer necessary.'
           fi
 
-          if brew tap-info adoptopenjdk/openjdk; then
-            brew untap adoptopenjdk/openjdk
-          else
+          if ! brew untap adoptopenjdk/openjdk; then
             echo '::warning::Untapping adoptopenjdk/openjdk is no longer necessary.'
           fi
+        if: runner.os == 'macOS'
 
       # Workaround until the `cache` action uses the changes from
       # https://github.com/actions/toolkit/pull/580.

cmd/lib/changed_files.rb

@@ -1,23 +1,23 @@
 # frozen_string_literal: true
 
 module ChangedFiles
-  def self.collect(tap)
-    commit_range_start = system_command!("git", args: ["rev-parse", "origin/master"]).stdout.chomp
-    commit_range_end = system_command!("git", args: ["rev-parse", "HEAD"]).stdout.chomp
+  def changed_files
+    commit_range_start = system_command!("git", args: ["rev-parse", "origin"], chdir: path).stdout.chomp
+    commit_range_end = system_command!("git", args: ["rev-parse", "HEAD"], chdir: path).stdout.chomp
     commit_range = "#{commit_range_start}...#{commit_range_end}"
 
     modified_files = system_command!(
-      "git", args: ["diff", "--name-only", "--diff-filter=AMR", commit_range]
+      "git", args: ["diff", "--name-only", "--diff-filter=AMR", commit_range], chdir: path
     ).stdout.split("\n").map { |path| Pathname(path) }
 
     added_files = system_command!(
-      "git", args: ["diff", "--name-only", "--diff-filter=A", commit_range]
+      "git", args: ["diff", "--name-only", "--diff-filter=A", commit_range], chdir: path
     ).stdout.split("\n").map { |path| Pathname(path) }
 
     modified_ruby_files = modified_files.select { |path| path.extname == ".rb" }
     modified_command_files = modified_files.select { |path| path.ascend.to_a.last.to_s == "cmd" }
     modified_github_actions_files = modified_files.select { |path| path.to_s.start_with?(".github/actions/") }
-    modified_cask_files = modified_files.select { |path| tap.cask_file?(path) }
+    modified_cask_files = modified_files.select { |path| cask_file?(path) }
 
     {
       modified_files:                modified_files,

cmd/lib/ci_matrix.rb

@@ -7,10 +7,33 @@ require_relative "changed_files"
 module CiMatrix
   MAX_JOBS = 256
 
+  RUNNERS = {
+    "macos-10.15" => 0.9,
+    "macos-11.0"  => 0.1,
+  }.freeze
+
+  def self.random_runner
+    @random_runner ||= RUNNERS.max_by { |(_, weight)| rand ** (1.0 / weight) }.first
+  end
+
+  def self.runners(path)
+    cask_content = path.read
+
+    if cask_content.match?(/\bMacOS\s*\.version\b/m)
+      # If the cask depends on `MacOS.version`, test it on every possible macOS version.
+      RUNNERS.keys
+    else
+      # Otherwise, select a runner based on weighted random sample.
+      [random_runner]
+    end
+  end
+
   def self.generate(tap, labels: [])
     odie "This command must be run from inside a tap directory." unless tap
 
-    changed_files = ChangedFiles.collect(tap)
+    tap.extend(ChangedFiles)
+
+    changed_files = tap.changed_files
 
     ruby_files_in_wrong_directory =
       changed_files[:modified_ruby_files] - (
@@ -32,8 +55,8 @@ module CiMatrix
     jobs = modified_cask_files.count
     odie "Maximum job matrix size exceeded: #{jobs}/#{MAX_JOBS}" if jobs > MAX_JOBS
 
-    changed_files[:modified_cask_files].map do |path|
-      cask = Cask::CaskLoader.load(path)
+    changed_files[:modified_cask_files].flat_map do |path|
+      cask_token = path.basename(".rb")
 
       appcast_arg = if labels.include?("ci-skip-appcast")
         "--no-appcast"
@@ -45,16 +68,19 @@ module CiMatrix
 
       audit_args << "--new-cask" if changed_files[:added_files].include?(path)
 
-      {
-        name:         "test (#{cask.token})",
-        tap:          tap.name,
-        cask:         {
-          token: cask.token,
-          path:  "./#{path}",
-        },
-        audit_args:   audit_args,
-        skip_install: labels.include?("ci-skip-install"),
-      }
+      runners(path).map do |runner|
+        {
+          name:         "test #{cask_token} (#{runner})",
+          tap:          tap.name,
+          cask:         {
+            token: cask_token,
+            path:  "./#{path}",
+          },
+          audit_args:   audit_args,
+          skip_install: labels.include?("ci-skip-install"),
+          runner:       runner,
+        }
+      end
     end
   end
 end

cmd/lib/generate-matrix.rb

@@ -7,14 +7,20 @@ require_relative "ci_matrix"
 
 pr_url, = ARGV
 
-pr = GitHub.open_api(pr_url)
-labels = pr.fetch("labels").map { |l| l.fetch("name") }
+labels = if pr_url
+  pr = GitHub.open_api(pr_url)
+  pr.fetch("labels").map { |l| l.fetch("name") }
+else
+  []
+end
 
 tap = Tap.from_path(Dir.pwd)
 
+runner = CiMatrix.random_runner
 syntax_job = {
-  name: "syntax",
-  tap:  tap.name,
+  name:   "syntax",
+  tap:    tap.name,
+  runner: runner,
 }
 
 matrix = [syntax_job]
@@ -22,11 +28,18 @@ matrix = [syntax_job]
 unless labels.include?("ci-syntax-only")
   cask_jobs = CiMatrix.generate(tap, labels: labels)
 
-  # If casks were changed, skip `audit` for all others.
-  syntax_job[:skip_audit] = true if cask_jobs.any?
+  if cask_jobs.any?
+    # If casks were changed, skip `audit` for whole tap.
+    syntax_job[:skip_audit] = true
+
+    # The syntax job only runs `style` at this point, which should work on Linux.
+    syntax_job[:runner] = "ubuntu-latest"
+  end
 
   matrix += cask_jobs
 end
 
+syntax_job[:name] += " (#{syntax_job[:runner]})"
+
 puts JSON.pretty_generate(matrix)
 puts "::set-output name=matrix::#{JSON.generate(matrix)}"