Prevent users from uninstalling casks with dependents

Library/Homebrew/cask/uninstall.rb

@@ -1,6 +1,8 @@
 # typed: strict
 # frozen_string_literal: true
 
+require "cask_dependent"
+require "dependents_message"
 require "utils/output"
 
 module Cask
@@ -19,5 +21,24 @@ def self.uninstall_casks(*casks, binaries: false, force: false, verbose: false)
         Installer.new(cask, binaries:, force:, verbose:).uninstall
       end
     end
+
+    sig { params(casks: ::Cask::Cask, named_args: T::Array[String]).void }
+    def self.check_dependent_casks(*casks, named_args: [])
+      dependents = []
+      requireds = casks.map(&:token)
+      caskroom = ::Cask::Caskroom.casks
+
+      caskroom.each do |dependent|
+        d = CaskDependent.new(dependent)
+        dependencies = d.recursive_requirements.filter_map { |r| r.cask if r.is_a?(CaskDependent::Requirement) }
+        next unless dependencies.intersect?(requireds)
+
+        dependents << dependent.token
+      end
+
+      return if dependents.empty?
+
+      DependentsMessage.new(requireds, dependents, named_args:).output
+    end
   end
 end

Library/Homebrew/cmd/uninstall.rb

@@ -61,6 +61,9 @@ def run
           named_args:          args.named,
         )
 
+        Cask::Uninstall.check_dependent_casks(*casks, named_args: args.named) unless args.ignore_dependencies?
+        return if Homebrew.failed?
+
         if args.zap?
           casks.each do |cask|
             odebug "Zapping Cask #{cask}"

Library/Homebrew/dependents_message.rb

@@ -0,0 +1,44 @@
+# typed: strict
+# frozen_string_literal: true
+
+require "utils/output"
+
+class DependentsMessage
+  include ::Utils::Output::Mixin
+
+  sig { returns(T::Array[T.any(String, Keg)]) }
+  attr_reader :reqs
+
+  sig { returns(T::Array[String]) }
+  attr_reader :deps, :named_args
+
+  sig { params(requireds: T::Array[T.any(String, Keg)], dependents: T::Array[String], named_args: T::Array[String]).void }
+  def initialize(requireds, dependents, named_args: [])
+    @reqs = requireds
+    @deps = dependents
+    @named_args = named_args
+  end
+
+  sig { void }
+  def output
+    ofail <<~EOS
+      Refusing to uninstall #{reqs.to_sentence}
+      because #{reqs.one? ? "it" : "they"} #{are_required_by_deps}.
+      You can override this and force removal with:
+        #{sample_command}
+    EOS
+  end
+
+  protected
+
+  sig { returns(String) }
+  def sample_command
+    "brew uninstall --ignore-dependencies #{named_args.join(" ")}"
+  end
+
+  sig { returns(String) }
+  def are_required_by_deps
+    "#{reqs.one? ? "is" : "are"} required by #{deps.to_sentence}, " \
+      "which #{deps.one? ? "is" : "are"} currently installed"
+  end
+end