Implement keg relocation fix for Homebrew-created files

- Add homebrew_created_file? method to identify service files
- Add prepare_relocation_to_placeholders_for_homebrew_files method
- Modify replace_text_in_files to handle Homebrew files separately
- Homebrew-created files now get full path relocation instead of selective relocation

Co-authored-by: MikeMcQuaid <125011+MikeMcQuaid@users.noreply.github.com>

Library/Homebrew/keg_relocate.rb

@@ -157,6 +157,39 @@ class Keg
     relocation
   end
 
+  sig { params(file: Pathname).returns(T::Boolean) }
+  def homebrew_created_file?(file)
+    # Service files created by Homebrew
+    return true if file.extname == ".plist" && file.basename.to_s.start_with?("homebrew.")
+    return true if file.extname == ".service" && file.basename.to_s.start_with?("homebrew.")
+    return true if file.extname == ".timer" && file.basename.to_s.start_with?("homebrew.")
+
+    false
+  end
+
+  sig { returns(Relocation) }
+  def prepare_relocation_to_placeholders_for_homebrew_files
+    relocation = Relocation.new
+
+    # For Homebrew-created files, always use full prefix replacement
+    # These files are generated by Homebrew so they should always be relocatable
+    relocation.add_replacement_pair(:prefix, HOMEBREW_PREFIX.to_s, PREFIX_PLACEHOLDER, path: true)
+    relocation.add_replacement_pair(:cellar, HOMEBREW_CELLAR.to_s, CELLAR_PLACEHOLDER, path: true)
+
+    # when HOMEBREW_PREFIX == HOMEBREW_REPOSITORY we should use HOMEBREW_PREFIX for all relocations to avoid
+    # being unable to differentiate between them.
+    if HOMEBREW_PREFIX != HOMEBREW_REPOSITORY
+      relocation.add_replacement_pair(:repository, HOMEBREW_REPOSITORY.to_s, REPOSITORY_PLACEHOLDER, path: true)
+    end
+    relocation.add_replacement_pair(:library, HOMEBREW_LIBRARY.to_s, LIBRARY_PLACEHOLDER, path: true)
+    relocation.add_replacement_pair(:perl,
+                                    %r{\A#![ \t]*(?:/usr/bin/perl\d\.\d+|#{HOMEBREW_PREFIX}/opt/perl/bin/perl)( |$)}o,
+                                    "#!#{PERL_PLACEHOLDER}\\1")
+    relocation.add_replacement_pair(:java, JAVA_REGEX, JAVA_PLACEHOLDER)
+
+    relocation
+  end
+
   sig { returns(T::Array[Pathname]) }
   def replace_locations_with_placeholders
     relocation = prepare_relocation_to_placeholders.freeze
@@ -200,7 +233,22 @@ class Keg
     files ||= text_files | libtool_files
 
     changed_files = T.let([], T::Array[Pathname])
+
+    # Separate Homebrew-created files from regular files
+    homebrew_files = []
+    regular_files = []
+
     files.map { path.join(_1) }.group_by { |f| f.stat.ino }.each_value do |first, *rest|
+      file_group = [first, *rest]
+      if homebrew_created_file?(first)
+        homebrew_files << file_group
+      else
+        regular_files << file_group
+      end
+    end
+
+    # Process regular files with normal relocation
+    regular_files.each do |first, *rest|
       s = first.open("rb", &:read)
 
       next unless relocation.replace_text!(s)
@@ -217,6 +265,29 @@ class Keg
         rest.each { |file| FileUtils.ln(first, file, force: true) }
       end
     end
+
+    # Process Homebrew-created files with full relocation
+    unless homebrew_files.empty?
+      homebrew_relocation = prepare_relocation_to_placeholders_for_homebrew_files.freeze
+      homebrew_files.each do |first, *rest|
+        s = first.open("rb", &:read)
+
+        next unless homebrew_relocation.replace_text!(s)
+
+        changed_files += [first, *rest].map { |file| file.relative_path_from(path) }
+
+        begin
+          first.atomic_write(s)
+        rescue SystemCallError
+          first.ensure_writable do
+            first.open("wb") { |f| f.write(s) }
+          end
+        else
+          rest.each { |file| FileUtils.ln(first, file, force: true) }
+        end
+      end
+    end
+
     changed_files
   end
 

Library/Homebrew/test/keg_relocate/homebrew_files_spec.rb

@@ -0,0 +1,127 @@
+# frozen_string_literal: true
+
+require "keg_relocate"
+require "keg"
+
+RSpec.describe Keg, "#homebrew_created_file?" do
+  let(:keg) { instance_double(described_class) }
+  let(:path) { Pathname.new("/tmp/test") }
+
+  before do
+    allow(keg).to receive(:path).and_return(path)
+    allow(keg).to receive(:homebrew_created_file?).and_call_original
+  end
+
+  it "identifies Homebrew service files correctly" do
+    plist_file = instance_double(Pathname, extname: ".plist", basename: Pathname.new("homebrew.foo.plist"))
+    service_file = instance_double(Pathname, extname: ".service", basename: Pathname.new("homebrew.foo.service"))
+    timer_file = instance_double(Pathname, extname: ".timer", basename: Pathname.new("homebrew.foo.timer"))
+    regular_file = instance_double(Pathname, extname: ".txt", basename: Pathname.new("readme.txt"))
+    non_homebrew_plist = instance_double(Pathname, extname: ".plist", basename: Pathname.new("com.example.foo.plist"))
+
+    allow(plist_file.basename).to receive(:to_s).and_return("homebrew.foo.plist")
+    allow(service_file.basename).to receive(:to_s).and_return("homebrew.foo.service")
+    allow(timer_file.basename).to receive(:to_s).and_return("homebrew.foo.timer")
+    allow(regular_file.basename).to receive(:to_s).and_return("readme.txt")
+    allow(non_homebrew_plist.basename).to receive(:to_s).and_return("com.example.foo.plist")
+
+    expect(keg.homebrew_created_file?(plist_file)).to be true
+    expect(keg.homebrew_created_file?(service_file)).to be true
+    expect(keg.homebrew_created_file?(timer_file)).to be true
+    expect(keg.homebrew_created_file?(regular_file)).to be false
+    expect(keg.homebrew_created_file?(non_homebrew_plist)).to be false
+  end
+end
+
+RSpec.describe Keg, "#prepare_relocation_to_placeholders_for_homebrew_files" do
+  include FileUtils
+
+  let(:keg_path) { Pathname.new(Dir.mktmpdir) }
+  let(:keg) { described_class.new(keg_path) }
+
+  after do
+    rmtree keg_path
+  end
+
+  it "creates relocation with full prefix replacement for Homebrew files" do
+    relocation = keg.prepare_relocation_to_placeholders_for_homebrew_files
+
+    # Verify that the relocation includes full prefix replacement
+    prefix_old, prefix_new = relocation.replacement_pair_for(:prefix)
+    
+    expect(prefix_new).to eq("@@HOMEBREW_PREFIX@@")
+    expect(prefix_old).to be_a(Regexp)
+    expect("#{HOMEBREW_PREFIX}/bin/foo").to match(prefix_old)
+  end
+end
+
+RSpec.describe Keg, "#replace_text_in_files with Homebrew-created files" do
+  include FileUtils
+
+  let(:keg_path) { Pathname.new(Dir.mktmpdir) }
+  let(:keg) { described_class.new(keg_path) }
+
+  before do
+    allow(keg).to receive(:name).and_return("test-formula")
+    allow(keg).to receive(:new_usr_local_relocation?).and_return(true)
+  end
+
+  after do
+    rmtree keg_path
+  end
+
+  it "applies full relocation to Homebrew-created files" do
+    # Create a mock service file
+    service_file = keg_path/"homebrew.test-formula.service"
+    service_content = <<~SERVICE
+      [Unit]
+      Description=Test Service
+
+      [Service]
+      ExecStart=#{HOMEBREW_PREFIX}/bin/test-command
+      Environment="PATH=#{HOMEBREW_PREFIX}/bin:#{HOMEBREW_PREFIX}/sbin:/usr/bin"
+      WorkingDirectory=#{HOMEBREW_PREFIX}/var/test
+
+      [Install]
+      WantedBy=multi-user.target
+    SERVICE
+    
+    service_file.write(service_content)
+    
+    # Create a regular file that should get selective relocation
+    regular_file = keg_path/"test.txt"
+    regular_content = <<~CONTENT
+      This is a test file.
+      It references #{HOMEBREW_PREFIX}/opt/something
+      And also #{HOMEBREW_PREFIX}/bin/something
+    CONTENT
+    
+    regular_file.write(regular_content)
+    
+    # Mock the text_files method to return our test files
+    allow(keg).to receive(:text_files).and_return([service_file.basename, regular_file.basename])
+    allow(keg).to receive(:libtool_files).and_return([])
+    
+    # Create a regular relocation that would only replace specific paths
+    relocation = keg.prepare_relocation_to_placeholders
+    
+    # Call replace_text_in_files
+    changed_files = keg.replace_text_in_files(relocation)
+    
+    # Check results
+    expect(changed_files).to include(service_file.basename)
+    expect(changed_files).to include(regular_file.basename)
+    
+    # Service file should have full relocation (including /bin path)
+    service_result = service_file.read
+    expect(service_result).to include("@@HOMEBREW_PREFIX@@/bin/test-command")
+    expect(service_result).to include("PATH=@@HOMEBREW_PREFIX@@/bin:@@HOMEBREW_PREFIX@@/sbin:/usr/bin")
+    expect(service_result).to include("WorkingDirectory=@@HOMEBREW_PREFIX@@/var/test")
+    
+    # Regular file should have selective relocation (only /opt path replaced)
+    regular_result = regular_file.read
+    expect(regular_result).to include("@@HOMEBREW_PREFIX@@/opt/something")
+    # bin path should NOT be replaced in regular files when using new usr local relocation
+    expect(regular_result).to include("#{HOMEBREW_PREFIX}/bin/something")
+  end
+end