brew update-license-data: checks if it is outdated. If so, save new ver

Library/Homebrew/dev-cmd/update-license-data.rb

+# frozen_string_literal: true
+
+require "commands"
+require "cli/parser"
+require "open-uri"
+require "json"
+
+module Homebrew
+  module_function
+  SPDX_FOLDER_PATH = (HOMEBREW_LIBRARY_PATH/"data").freeze
+  FILE_NAME = "spdx.json".freeze
+  NEW_FILE_NAME = "spdx_new.json".freeze
+  SPDX_DATA_URL = "https://raw.githubusercontent.com/spdx/license-list-data/master/json/licenses.json"
+
+  def update_license_data_args
+    Homebrew::CLI::Parser.new do
+      usage_banner <<~EOS
+        `update_license_data` <cmd>
+
+        Update SPDX license data in the Homebrew repository.
+      EOS
+      switch "--fail-if-outdated",
+             description: "Return a failing status code if current license data's version is different from the upstream. This "\
+                          "can be used to notify CI when the SPDX license data is out of date."
+    end
+  end
+
+  def update_license_data
+    update_license_data_args.parse
+    p args
+    curr_spdx_hash = File.open(SPDX_FOLDER_PATH/FILE_NAME, 'r') do |f|
+      JSON.parse(f.read)
+    end
+    puts "Fetching newest version of SPDX License data..."
+    updated_spdx_string = open(SPDX_DATA_URL) do |json|
+       json.read
+    end
+
+    updated_spdx_hash = JSON.parse(updated_spdx_string)
+    if curr_spdx_hash["licenseListVersion"] != updated_spdx_hash["licenseListVersion"]
+
+      puts "Current version is #{curr_spdx_hash["licenseListVersion"]} but newest version is #{updated_spdx_hash["licenseListVersion"]}\n"\
+      "Updating existing licences data file..."
+      File.open(SPDX_FOLDER_PATH/FILE_NAME, "wb") do |file|
+          file.write(updated_spdx_string)
+      end
+      if args.fail_if_outdated
+        Homebrew.failed = true
+      end
+      end
+    else
+      puts "Current version of license data is updated. No change required"
+    end
+  end