formula_creator: fetch missing version from latest GitHub release

Library/Homebrew/formula_creator.rb

@@ -24,15 +24,48 @@ module Homebrew
     def initialize(url:, name: nil, version: nil, tap: nil, mode: nil, license: nil, fetch: false, head: false)
       @url = url
 
-      if name.blank?
+      version = if version.present?
+        odebug "version from user: #{version}"
+        Version.new(version)
+      else
+        odebug "version from url: #{version}"
+        Version.detect(url)
+      end
+
+      if (match_github = url.match %r{github\.com/(?<user>[^/]+)/(?<repo>[^/]+).*})
+        user = match_github[:user]
+        repository = T.must(match_github[:repo])
+        if repository.end_with?(".git")
+          repository = repository.delete_suffix(".git")
+          head = true
+        end
+        odebug "github: #{user} #{repository} head:#{head}"
+        if name.blank?
+          name = repository
+          odebug "name from github: #{name}"
+        end
+
+        github = GitHub.repository(user, repository) if fetch
+
+        latest_release = if version.null? && fetch && !head
+          begin
+            GitHub.get_latest_release(user, repository)
+          rescue GitHub::API::HTTPNotFoundError
+            odebug "github: latest_release lookup failed: #{url}"
+            nil
+          end
+        end
+        if latest_release
+          version = Version.new(latest_release["tag_name"])
+          odebug "github: version from latest_release: #{@version}"
+        end
+
+      elsif name.blank?
         stem = Pathname.new(url).stem
         name = if stem.start_with?("index.cgi") && stem.include?("=")
           # special cases first
           # gitweb URLs e.g. http://www.codesrc.com/gitweb/index.cgi?p=libzipper.git;a=summary
           stem.rpartition("=").last
-        elsif url =~ %r{github\.com/\S+/(\S+)/(archive|releases)/}
-          # e.g. https://github.com/stella-emu/stella/releases/download/6.7/stella-6.7-src.tar.xz
-          T.must(Regexp.last_match(1))
         else
           # e.g. http://digit-labs.org/files/tools/synscan/releases/synscan-5.02.tar.gz
           pathver = Version.parse(stem).to_s
@@ -41,12 +74,7 @@ module Homebrew
         odebug "name from url: #{name}"
       end
       @name = T.let(name, String)
-
+      @github = T.let(github, T.untyped)
-      version = if version.present?
-        Version.new(version)
-      else
-        Version.detect(url)
-      end
       @version = T.let(version, Version)
 
       tap = if tap.blank?
@@ -60,19 +88,7 @@ module Homebrew
       @license = T.let(license.presence, T.nilable(String))
       @fetch = fetch
 
-      case url
-      when %r{github\.com/(\S+)/(\S+)\.git}
-        head = true
-        user = Regexp.last_match(1)
-        repository = Regexp.last_match(2)
-        github = GitHub.repository(user, repository) if fetch
-      when %r{github\.com/(\S+)/(\S+)/(archive|releases)/}
-        user = Regexp.last_match(1)
-        repository = Regexp.last_match(2)
-        github = GitHub.repository(user, repository) if fetch
-      end
       @head = head
-      @github = T.let(github, T.untyped)
 
       @sha256 = T.let(nil, T.nilable(String))
       @desc = T.let(nil, T.nilable(String))

Library/Homebrew/test/formula_creator_spec.rb

@@ -38,12 +38,29 @@ RSpec.describe Homebrew::FormulaCreator do
         github_user: "stella-emu",
         github_repo: "stella",
       },
+      "GitHub latest release":     {
+        url:            "https://github.com/buildpacks/pack",
+        name:           "pack",
+        version:        "v0.37.0",
+        fetch:          true,
+        github_user:    "buildpacks",
+        github_repo:    "pack",
+        latest_release: { "tag_name" => "v0.37.0" },
+      },
     }
 
     tests.each do |description, test|
       it "parses #{description}" do
         fetch = test.fetch(:fetch, false)
-        allow(GitHub).to receive(:repository).with(test.fetch(:github_user), test.fetch(:github_repo)) if fetch
+        allow(GitHub).to receive(:repository).with(test.fetch(:github_user), test.fetch(:github_repo)).once if fetch
+
+        latest_release = test.fetch(:latest_release, nil) if fetch
+        if latest_release
+          expect(GitHub).to receive(:get_latest_release)
+            .with(test.fetch(:github_user), test.fetch(:github_repo))
+            .and_return(test.fetch(:latest_release))
+            .once
+        end
 
         formula_creator = described_class.new(url: test.fetch(:url), fetch:)