From c0795b502908676f1fd62ba0a478c22adec86080 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?fn=20=E2=8C=83=20=E2=8C=A5?=
 <70830482+FnControlOption@users.noreply.github.com>
Date: Sun, 12 Sep 2021 07:56:37 -0700
Subject: [PATCH] upgrade: raise error if developer and there are cyclic
 dependencies

---
 Library/Homebrew/exceptions.rb | 10 ++++++++++
 Library/Homebrew/upgrade.rb    |  3 +--
 2 files changed, 11 insertions(+), 2 deletions(-)

diff --git a/Library/Homebrew/exceptions.rb b/Library/Homebrew/exceptions.rb
index b8c5d4c622..99745cdb8b 100644
--- a/Library/Homebrew/exceptions.rb
+++ b/Library/Homebrew/exceptions.rb
@@ -758,3 +758,13 @@ class ShebangDetectionError < RuntimeError
     super "Cannot detect #{type} shebang: #{reason}."
   end
 end
+
+# Raised when one or more formulae have cyclic dependencies.
+class CyclicDependencyError < RuntimeError
+  def initialize(strongly_connected_components)
+    super <<~EOS
+      The following packages contain cyclic dependencies:
+        #{strongly_connected_components.select { |packages| packages.count > 1 }.map(&:to_sentence).join("\n  ")}
+    EOS
+  end
+end
diff --git a/Library/Homebrew/upgrade.rb b/Library/Homebrew/upgrade.rb
index 8f783f079d..acd654e08e 100644
--- a/Library/Homebrew/upgrade.rb
+++ b/Library/Homebrew/upgrade.rb
@@ -47,8 +47,7 @@ module Homebrew
       begin
         formulae_to_install = dependency_graph.tsort & formulae_to_install
       rescue TSort::Cyclic
-        # Failed to sort formulae topologically because there are cyclic
-        # dependencies. Let FormulaInstaller handle it.
+        raise CyclicDependencyError, dependency_graph.strongly_connected_components if Homebrew::EnvConfig.developer?
       end
 
       formula_installers = formulae_to_install.map do |formula|