Fix timeout error on xread w/ block 0 option and resolve #836

Author: supercaracal

lib/redis.rb

@@ -3470,6 +3470,8 @@ def _xread(args, keys, ids, blocking_timeout_msec)
     synchronize do |client|
       if blocking_timeout_msec.nil?
         client.call(args, &HashifyStreams)
+      elsif blocking_timeout_msec.to_f.zero?
+        client.call_without_timeout(args, &HashifyStreams)
       else
         timeout = client.timeout.to_f + blocking_timeout_msec.to_f / 1000.0
         client.call_with_timeout(args, timeout, &HashifyStreams)

test/lint/streams.rb

@@ -346,6 +346,20 @@ def test_xread_with_block_option
       assert_equal({}, actual)
     end
 
+    def test_xread_does_not_raise_timeout_error_when_the_block_option_is_zero_msec
+      prepared = false
+      actual = nil
+      wire = Wire.new do
+        prepared = true
+        actual = redis.xread('s1', 0, block: 0)
+      end
+      Wire.pass until prepared
+      redis.dup.xadd('s1', { f: 'v1' }, id: '0-1')
+      wire.join
+
+      assert_equal ['v1'], actual.fetch('s1').map { |i| i.last['f'] }
+    end
+
     def test_xread_with_invalid_arguments
       assert_raise(Redis::CommandError) { redis.xread(nil, nil) }
       assert_raise(Redis::CommandError) { redis.xread('', '') }