api: use formulae.brew.sh for cask-source API again.

GitHub's raw endpoint is proving hilariously unreliable for us here.

Library/Homebrew/api.rb

@@ -94,17 +94,29 @@ def self.fetch_json_api_file(endpoint, target:)
       end
     end
 
-    sig { params(filepath: String, repo: String, git_head: T.nilable(String)).returns(String) }
-    def self.fetch_file_source(filepath, repo:, git_head: nil)
-      git_head ||= "master"
-      endpoint = "#{git_head}/#{filepath}"
-      return cache[endpoint] if cache.present? && cache.key?(endpoint)
-
-      raw_url = "https://raw.githubusercontent.com/#{repo}/#{endpoint}"
-      output = Utils::Curl.curl_output("--fail", raw_url)
-      raise ArgumentError, "No file found at #{Tty.underline}#{raw_url}#{Tty.reset}" unless output.success?
+    sig { params(name: String, git_head: T.nilable(String)).returns(String) }
+    def self.fetch_homebrew_cask_source(name, git_head: nil)
+      git_head = "master" if git_head.blank?
+      raw_endpoint = "#{git_head}/Casks/#{name}.rb"
+      return cache[raw_endpoint] if cache.present? && cache.key?(raw_endpoint)
+
+      # This API sometimes returns random 404s so needs a fallback at formulae.brew.sh.
+      raw_source_url = "https://raw.githubusercontent.com/Homebrew/homebrew-cask/#{raw_endpoint}"
+      api_source_url = "#{HOMEBREW_API_DEFAULT_DOMAIN}/cask-source/#{name}.rb"
+      output = Utils::Curl.curl_output("--fail", raw_source_url)
+
+      if !output.success? || output.blank?
+        output = Utils::Curl.curl_output("--fail", api_source_url)
+        if !output.success? || output.blank?
+          raise ArgumentError, <<~EOS
+            No valid file found at either of:
+            #{Tty.underline}#{raw_source_url}#{Tty.reset}
+            #{Tty.underline}#{api_source_url}#{Tty.reset}
+          EOS
+        end
+      end
 
-      cache[endpoint] = output.stdout
+      cache[raw_endpoint] = output.stdout
     end
 
     sig { params(json: Hash).returns(Hash) }

Library/Homebrew/api/cask.rb

@@ -17,7 +17,7 @@ def fetch(token)
 
         sig { params(token: String, git_head: T.nilable(String)).returns(String) }
         def fetch_source(token, git_head: nil)
-          Homebrew::API.fetch_file_source "Casks/#{token}.rb", repo: "Homebrew/homebrew-cask", git_head: git_head
+          Homebrew::API.fetch_homebrew_cask_source token, git_head: git_head
         end
 
         sig { returns(Hash) }

Library/Homebrew/test/api/cask_spec.rb

@@ -8,6 +8,7 @@
 
   before do
     stub_const("Homebrew::API::HOMEBREW_CACHE_API", cache_dir)
+    Homebrew::API.clear_cache
   end
 
   def mock_curl_download(stdout:)

Library/Homebrew/test/api_spec.rb

@@ -9,6 +9,10 @@
   let(:json_hash) { JSON.parse(json) }
   let(:json_invalid) { '{"foo":"bar"' }
 
+  before do
+    described_class.clear_cache
+  end
+
   def mock_curl_output(stdout: "", success: true)
     curl_output = OpenStruct.new(stdout: stdout, success?: success)
     allow(Utils::Curl).to receive(:curl_output).and_return curl_output
@@ -68,15 +72,15 @@ def mock_curl_download(stdout:)
   describe "::fetch_file_source" do
     it "fetches a file" do
       mock_curl_output stdout: json
-      fetched_json = described_class.fetch_file_source("foo.json", repo: "Homebrew/homebrew-core", git_head: "master")
+      fetched_json = described_class.fetch_homebrew_cask_source("foo", git_head: "master")
       expect(fetched_json).to eq json
     end
 
     it "raises an error if the file does not exist" do
       mock_curl_output success: false
       expect {
-        described_class.fetch_file_source("bar.txt", repo: "Homebrew/homebrew-core", git_head: "master")
-      }.to raise_error(ArgumentError, /No file found/)
+        described_class.fetch_homebrew_cask_source("bar", git_head: "master")
+      }.to raise_error(ArgumentError, /No valid file found/)
     end
   end
 end