github_runner_matrix: filter incompatible testing formulae

`brew test-bot` can occasionally spend a long time doing nothing when
testing dependents.[^1] This is because it takes a long time to work out
that there is nothing to do.

To fix this, let's adjust `brew determine-test-runners` to pass on only
the list of formulae for which there is work to be done so that
`brew test-bot` doesn't need to waste time working this out.

[^1]: For example, it spends about 15 minutes doing nothing at https://github.com/Homebrew/homebrew-core/actions/runs/10500178069/job/29133091332?pr=180185

Library/Homebrew/github_runner_matrix.rb

@@ -10,7 +10,15 @@ class GitHubRunnerMatrix
   RunnerSpec = T.type_alias { T.any(LinuxRunnerSpec, MacOSRunnerSpec) }
   private_constant :RunnerSpec
 
-  MacOSRunnerSpecHash = T.type_alias { { name: String, runner: String, timeout: Integer, cleanup: T::Boolean } }
+  MacOSRunnerSpecHash = T.type_alias do
+    {
+      name:             String,
+      runner:           String,
+      timeout:          Integer,
+      cleanup:          T::Boolean,
+      testing_formulae: String,
+    }
+  end
   private_constant :MacOSRunnerSpecHash
 
   LinuxRunnerSpecHash = T.type_alias do
@@ -21,6 +29,7 @@ class GitHubRunnerMatrix
       workdir:          String,
       timeout:          Integer,
       cleanup:          T::Boolean,
+      testing_formulae: String,
     }
   end
   private_constant :LinuxRunnerSpecHash
@@ -49,6 +58,8 @@ class GitHubRunnerMatrix
     @deleted_formulae = T.let(deleted_formulae, T::Array[String])
     @all_supported = T.let(all_supported, T::Boolean)
     @dependent_matrix = T.let(dependent_matrix, T::Boolean)
+    @compatible_testing_formulae = T.let({}, T::Hash[GitHubRunner, T::Array[TestRunnerFormula]])
+    @formulae_with_untested_dependents = T.let({}, T::Hash[GitHubRunner, T::Array[TestRunnerFormula]])
 
     @runners = T.let([], T::Array[GitHubRunner])
     generate_runners!
@@ -102,6 +113,7 @@ class GitHubRunnerMatrix
     raise "Unexpected arch: #{arch}" if VALID_ARCHES.exclude?(arch)
 
     runner = GitHubRunner.new(platform:, arch:, spec:, macos_version:)
+    runner.spec.testing_formulae += testable_formulae(runner)
     runner.active = active_runner?(runner)
     runner.freeze
   end
@@ -185,47 +197,50 @@ class GitHubRunnerMatrix
     @runners.freeze
   end
 
+  sig { params(runner: GitHubRunner).returns(T::Array[String]) }
+  def testable_formulae(runner)
+    formulae = if @dependent_matrix
+      formulae_with_untested_dependents(runner)
+    else
+      compatible_testing_formulae(runner)
+    end
+
+    formulae.map(&:name)
+  end
+
   sig { params(runner: GitHubRunner).returns(T::Boolean) }
   def active_runner?(runner)
-    if @dependent_matrix
+    return true if @all_supported || @deleted_formulae.present?
-      formulae_have_untested_dependents?(runner)
-    elsif !@all_supported && @deleted_formulae.empty?
-      compatible_formulae = @testing_formulae.dup
 
+    testable_formulae(runner).present?
+  end
+
+  sig { params(runner: GitHubRunner).returns(T::Array[TestRunnerFormula]) }
+  def compatible_testing_formulae(runner)
+    @compatible_testing_formulae[runner] ||= begin
       platform = runner.platform
       arch = runner.arch
       macos_version = runner.macos_version
 
-      compatible_formulae.select! do |formula|
+      @testing_formulae.select do |formula|
         next false if macos_version && !formula.compatible_with?(macos_version)
 
         formula.public_send(:"#{platform}_compatible?") &&
           formula.public_send(:"#{arch}_compatible?")
       end
-
-      compatible_formulae.present?
-    else
-      true
     end
   end
 
-  sig { params(runner: GitHubRunner).returns(T::Boolean) }
+  sig { params(runner: GitHubRunner).returns(T::Array[TestRunnerFormula]) }
-  def formulae_have_untested_dependents?(runner)
+  def formulae_with_untested_dependents(runner)
+    @formulae_with_untested_dependents[runner] ||= begin
       platform = runner.platform
       arch = runner.arch
       macos_version = runner.macos_version
 
-    @testing_formulae.any? do |formula|
+      compatible_testing_formulae(runner).select do |formula|
-      # If the formula has a platform/arch/macOS version requirement, then its
-      # dependents don't need to be tested if these requirements are not satisfied.
-      next false unless formula.public_send(:"#{platform}_compatible?")
-      next false unless formula.public_send(:"#{arch}_compatible?")
-      next false if macos_version.present? && !formula.compatible_with?(macos_version)
-
         compatible_dependents = formula.dependents(platform:, arch:, macos_version: macos_version&.to_sym)
-                                     .dup
+                                       .select do |dependent_f|
-
-      compatible_dependents.select! do |dependent_f|
           next false if macos_version && !dependent_f.compatible_with?(macos_version)
 
           dependent_f.public_send(:"#{platform}_compatible?") &&
@@ -238,3 +253,4 @@ class GitHubRunnerMatrix
       end
     end
   end
+end

Library/Homebrew/linux_runner_spec.rb

@@ -8,6 +8,7 @@ class LinuxRunnerSpec < T::Struct
   const :workdir, String
   const :timeout, Integer
   const :cleanup, T::Boolean
+  prop  :testing_formulae, T::Array[String], default: []
 
   sig {
     returns({
@@ -17,6 +18,7 @@ class LinuxRunnerSpec < T::Struct
       workdir:          String,
       timeout:          Integer,
       cleanup:          T::Boolean,
+      testing_formulae: String,
     })
   }
   def to_h
@@ -27,6 +29,7 @@ class LinuxRunnerSpec < T::Struct
       workdir:,
       timeout:,
       cleanup:,
+      testing_formulae: testing_formulae.join(","),
     }
   end
 end

Library/Homebrew/macos_runner_spec.rb

@@ -6,14 +6,24 @@ class MacOSRunnerSpec < T::Struct
   const :runner, String
   const :timeout, Integer
   const :cleanup, T::Boolean
+  prop  :testing_formulae, T::Array[String], default: []
 
-  sig { returns({ name: String, runner: String, timeout: Integer, cleanup: T::Boolean }) }
+  sig {
+    returns({
+      name:             String,
+      runner:           String,
+      timeout:          Integer,
+      cleanup:          T::Boolean,
+      testing_formulae: String,
+    })
+  }
   def to_h
     {
       name:,
       runner:,
       timeout:,
       cleanup:,
+      testing_formulae: testing_formulae.join(","),
     }
   end
 end