From fb0268da7eeb298a1f13c1809855eedee975200b Mon Sep 17 00:00:00 2001
From: Mike McQuaid <mike@mikemcquaid.com>
Date: Tue, 4 Aug 2020 10:47:41 +0100
Subject: [PATCH] license: handle "Public Domain".

Allow `:public_domain` to be used as a `license` value and ensure that
it's handled correctly by `brew info`, `brew audit` and `brew install`.
---
 Library/Homebrew/cmd/info.rb          | 8 +++++++-
 Library/Homebrew/dev-cmd/audit.rb     | 8 ++++----
 Library/Homebrew/formula.rb           | 2 ++
 Library/Homebrew/formula_installer.rb | 9 ++++++---
 docs/Formula-Cookbook.md              | 2 +-
 5 files changed, 20 insertions(+), 9 deletions(-)

diff --git a/Library/Homebrew/cmd/info.rb b/Library/Homebrew/cmd/info.rb
index d975d131f9..42089d4d87 100644
--- a/Library/Homebrew/cmd/info.rb
+++ b/Library/Homebrew/cmd/info.rb
@@ -211,7 +211,13 @@ module Homebrew
 
     puts "From: #{Formatter.url(github_info(f))}"
 
-    puts "License: #{f.license.join(", ")}" if f.license
+    if f.license.present?
+      licenses = f.license
+                  .map(&:to_s)
+                  .join(", ")
+                  .sub("public_domain", "Public Domain")
+      puts "License: #{licenses}"
+    end
 
     unless f.deps.empty?
       ohai "Dependencies"
diff --git a/Library/Homebrew/dev-cmd/audit.rb b/Library/Homebrew/dev-cmd/audit.rb
index ba44997d7e..3ca72994b1 100644
--- a/Library/Homebrew/dev-cmd/audit.rb
+++ b/Library/Homebrew/dev-cmd/audit.rb
@@ -337,12 +337,12 @@ module Homebrew
 
     def audit_license
       if formula.license.present?
-        non_standard_licenses = []
-        formula.license.each do |license|
+        non_standard_licenses = formula.license.map do |license|
+          next if license == :public_domain
           next if @spdx_data["licenses"].any? { |spdx| spdx["licenseId"] == license }
 
-          non_standard_licenses << license
-        end
+          license
+        end.compact
 
         if non_standard_licenses.present?
           problem "Formula #{formula.name} contains non-standard SPDX licenses: #{non_standard_licenses}."
diff --git a/Library/Homebrew/formula.rb b/Library/Homebrew/formula.rb
index 735f333424..10ab763470 100644
--- a/Library/Homebrew/formula.rb
+++ b/Library/Homebrew/formula.rb
@@ -2221,6 +2221,8 @@ class Formula
     # Multiple licenses means that the software is licensed under multiple licenses.
     # Do not use multiple licenses if e.g. different parts are under different licenses.
     # <pre>license "BSD-2-Clause"</pre>
+    # <pre>license ["MIT", "GPL-2.0"]</pre>
+    # <pre>license :public_domain</pre>
     def license(args = nil)
       if args.nil?
         @licenses
diff --git a/Library/Homebrew/formula_installer.rb b/Library/Homebrew/formula_installer.rb
index d9b5e6d1c3..e70d60089e 100644
--- a/Library/Homebrew/formula_installer.rb
+++ b/Library/Homebrew/formula_installer.rb
@@ -1129,14 +1129,17 @@ class FormulaInstaller
   end
 
   def forbidden_license_check
-    forbidden_licenses = Homebrew::EnvConfig.forbidden_licenses.to_s.split(" ")
+    forbidden_licenses = Homebrew::EnvConfig.forbidden_licenses
+                                            .to_s
+                                            .sub("Public Domain", "public_domain")
+                                            .split(" ")
     return if forbidden_licenses.blank?
 
     compute_dependencies.each do |dep, _|
       next if @ignore_deps
 
       dep_f = dep.to_formula
-      next unless dep_f.license.all? { |license| forbidden_licenses.include? license }
+      next unless dep_f.license.all? { |license| forbidden_licenses.include?(license.to_s) }
 
       raise CannotInstallFormulaError, <<~EOS
         The installation of #{formula.name} has a dependency on #{dep.name} where all its licenses are forbidden: #{dep_f.license}.
@@ -1144,7 +1147,7 @@ class FormulaInstaller
     end
     return if @only_deps
 
-    return unless formula.license.all? { |license| forbidden_licenses.include? license }
+    return unless formula.license.all? { |license| forbidden_licenses.include?(license.to_s) }
 
     raise CannotInstallFormulaError, <<~EOS
       #{formula.name}'s licenses are all forbidden: #{formula.license}.
diff --git a/docs/Formula-Cookbook.md b/docs/Formula-Cookbook.md
index f3fad76169..30b373e6e1 100644
--- a/docs/Formula-Cookbook.md
+++ b/docs/Formula-Cookbook.md
@@ -91,7 +91,7 @@ Try to summarise from the [`homepage`](https://rubydoc.brew.sh/Formula#homepage%
 
 **We don’t accept new formulae into Homebrew/homebrew-core without a [`license`](https://rubydoc.brew.sh/Formula#license-class_method)!**
 
-Find the license identifier from the [SPDX License List](https://spdx.org/licenses/). We only accept licenses from this list that are a [Debian Free Software Guidelines license](https://wiki.debian.org/DFSGLicenses).
+Find the license identifier from the [SPDX License List](https://spdx.org/licenses/) (or `:public_domain` for software in the public domain). We only accept licenses from this list that are a [Debian Free Software Guidelines license](https://wiki.debian.org/DFSGLicenses) (or public domain based on [the Debian Free Software Guidelines on Public Domain software](https://wiki.debian.org/DFSGLicenses#Public_Domain)).
 
 If the software is available under multiple licenses, you should list them all in an array: