Add HTTP::Server#bind_unix (#5959)

* Add HTTP::Server#bind_unix

* fixup! Add HTTP::Server#bind_unix

spec/std/http/server/server_spec.cr

@@ -1,5 +1,7 @@
 require "spec"
 require "http/server"
+require "http/client/response"
+require "tempfile"
 
 private class RaiseErrno < IO
   def initialize(@value : Int32)
@@ -40,6 +42,16 @@ private class ReverseResponseOutput < IO
   end
 end
 
+# TODO: replace with `HTTP::Client` once it supports connecting to Unix socket (#2735)
+private def unix_request(path)
+  UNIXSocket.open(path) do |io|
+    request = HTTP::Request.new("GET", "/", HTTP::Headers{"X-Unix-Socket" => path})
+    request.to_io(io)
+
+    HTTP::Client::Response.from_io(io).body
+  end
+end
+
 module HTTP
   class Server
     describe Response do
@@ -310,6 +322,42 @@ module HTTP
         end
       end
     end
+
+    {% if flag?(:unix) %}
+      describe "#bind_unix" do
+        it "binds to different unix sockets" do
+          path1 = Tempfile.tempname
+          path2 = Tempfile.tempname
+
+          begin
+            server = Server.new do |context|
+              # TODO: Replace custom header with local_address (#5784)
+              context.response.print "Test Server (#{context.request.headers["X-Unix-Socket"]?})"
+              context.response.close
+            end
+
+            socket1 = UNIXServer.new(path1)
+            server.bind socket1
+            socket2 = server.bind_unix path2
+
+            spawn server.listen
+
+            Fiber.yield
+
+            unix_request(path1).should eq "Test Server (#{path1})"
+            unix_request(path2).should eq "Test Server (#{path2})"
+
+            server.close
+
+            File.exists?(path1).should be_false
+            File.exists?(path2).should be_false
+          ensure
+            File.delete(path1) if File.exists?(path1)
+            File.delete(path2) if File.exists?(path2)
+          end
+        end
+      end
+    {% end %}
   end
 
   describe HTTP::Server::RequestProcessor do

src/http/server.cr

@@ -162,6 +162,20 @@ class HTTP::Server
     bind_tcp host, 0, reuse_port
   end
 
+  # Creates a `UNIXServer` bound to *path* and adds it as a socket.
+  #
+  # ```
+  # server = HTTP::Server.new { }
+  # server.bind_unix "/tmp/my-socket.sock"
+  # ```
+  def bind_unix(path : String) : Socket::UNIXAddress
+    server = UNIXServer.new(path)
+
+    bind(server)
+
+    server.local_address
+  end
+
   # Adds a `Socket::Server` *socket* to this server.
   def bind(socket : Socket::Server) : Nil
     raise "Can't add socket to running server" if listening?