formula*: add source download support for download queue.

This should allow downloading the formula files from GitHub in
parallel too.

Author: MikeMcQuaid

Library/Homebrew/api/formula.rb

@@ -28,8 +28,8 @@ def self.fetch(name)
         Homebrew::API.fetch "formula/#{name}.json"
       end
 
-      sig { params(formula: ::Formula).returns(::Formula) }
-      def self.source_download(formula)
+      sig { params(formula: ::Formula, download_queue: T.nilable(Homebrew::DownloadQueue)).returns(Homebrew::API::SourceDownload) }
+      def self.source_download(formula, download_queue: nil)
         path = formula.ruby_source_path || "Formula/#{formula.name}.rb"
         git_head = formula.tap_git_head || "HEAD"
         tap = formula.tap&.full_name || "Homebrew/homebrew-core"
@@ -39,7 +39,19 @@ def self.source_download(formula)
           formula.ruby_source_checksum,
           cache: HOMEBREW_CACHE_API_SOURCE/"#{tap}/#{git_head}/Formula",
         )
-        download.fetch
+
+        if download_queue
+          download_queue.enqueue(download)
+        elsif !download.cache.exist?
+          download.fetch
+        end
+
+        download
+      end
+
+      sig { params(formula: ::Formula).returns(::Formula) }
+      def self.source_download_formula(formula)
+        download = source_download(formula)
 
         with_env(HOMEBREW_FORBID_PACKAGES_FROM_PATHS: nil) do
           Formulary.factory(download.symlink_location,

Library/Homebrew/formula_installer.rb

@@ -317,8 +317,12 @@ def prelude_fetch
       end
     end
 
-    # Needs to be done before expand_dependencies for compute_dependencies
-    fetch_bottle_tab if pour_bottle?
+    if pour_bottle?
+      # Needs to be done before expand_dependencies for compute_dependencies
+      fetch_bottle_tab
+    elsif formula.loaded_from_api?
+      Homebrew::API::Formula.source_download(formula, download_queue:)
+    end
 
     fetch_fetch_deps unless ignore_deps?
 
@@ -1446,7 +1450,7 @@ def fetch
 
       !downloadable_object.cached_download.exist?
     else
-      @formula = Homebrew::API::Formula.source_download(formula) if formula.loaded_from_api?
+      @formula = Homebrew::API::Formula.source_download_formula(formula) if formula.loaded_from_api?
 
       if (download_queue = self.download_queue)
         formula.enqueue_resources_and_patches(download_queue:)