Support SyncGroup error response

SyncGroup could return, for example, an error 27 (rebalance in
progress), which causes a crash in this function, because the response
looks like:
```elixir
<<0, 0, 0, 4, 0, 27, 0, 0, 0, 0>>
```

This handles the case of the empty binary (just the length).

lib/kayrock/member_assignment.ex

@@ -39,6 +39,8 @@ defmodule Kayrock.MemberAssignment do
   @spec deserialize(binary) :: {t, binary}
   def deserialize(<<>>), do: {%__MODULE__{}, <<>>}
 
+  def deserialize(<<0::32-signed>>), do: {%__MODULE__{}, <<>>}
+
   def deserialize(<<0::32-signed, rest>>), do: {%__MODULE__{}, rest}
 
   def deserialize(<<data_size::32-signed, data::size(data_size)-binary, rest::bits>>) do

mix.lock

@@ -1,27 +1,27 @@
 %{
-  "bunt": {:hex, :bunt, "0.2.0", "951c6e801e8b1d2cbe58ebbd3e616a869061ddadcc4863d0a2182541acae9a38", [:mix], [], "hexpm"},
-  "certifi": {:hex, :certifi, "2.5.1", "867ce347f7c7d78563450a18a6a28a8090331e77fa02380b4a21962a65d36ee5", [:rebar3], [{:parse_trans, "~>3.3", [hex: :parse_trans, repo: "hexpm", optional: false]}], "hexpm"},
-  "connection": {:hex, :connection, "1.0.4", "a1cae72211f0eef17705aaededacac3eb30e6625b04a6117c1b2db6ace7d5976", [:mix], [], "hexpm"},
-  "crc32cer": {:hex, :crc32cer, "0.1.3", "8984906c4b4fae6aa292c48f286a1c83b19ad44bd102287acb94d696015967ce", [:make, :rebar, :rebar3], [], "hexpm"},
-  "credo": {:hex, :credo, "1.0.5", "fdea745579f8845315fe6a3b43e2f9f8866839cfbc8562bb72778e9fdaa94214", [:mix], [{:bunt, "~> 0.2.0", [hex: :bunt, repo: "hexpm", optional: false]}, {:jason, "~> 1.0", [hex: :jason, repo: "hexpm", optional: false]}], "hexpm"},
-  "dialyxir": {:hex, :dialyxir, "1.0.0-rc.6", "78e97d9c0ff1b5521dd68041193891aebebce52fc3b93463c0a6806874557d7d", [:mix], [{:erlex, "~> 0.2.1", [hex: :erlex, repo: "hexpm", optional: false]}], "hexpm"},
-  "earmark": {:hex, :earmark, "1.3.2", "b840562ea3d67795ffbb5bd88940b1bed0ed9fa32834915125ea7d02e35888a5", [:mix], [], "hexpm"},
-  "erlex": {:hex, :erlex, "0.2.1", "cee02918660807cbba9a7229cae9b42d1c6143b768c781fa6cee1eaf03ad860b", [:mix], [], "hexpm"},
-  "ex_doc": {:hex, :ex_doc, "0.20.2", "1bd0dfb0304bade58beb77f20f21ee3558cc3c753743ae0ddbb0fd7ba2912331", [:mix], [{:earmark, "~> 1.3", [hex: :earmark, repo: "hexpm", optional: false]}, {:makeup_elixir, "~> 0.10", [hex: :makeup_elixir, repo: "hexpm", optional: false]}], "hexpm"},
-  "excoveralls": {:hex, :excoveralls, "0.11.1", "dd677fbdd49114fdbdbf445540ec735808250d56b011077798316505064edb2c", [:mix], [{:hackney, "~> 1.0", [hex: :hackney, repo: "hexpm", optional: false]}, {:jason, "~> 1.0", [hex: :jason, repo: "hexpm", optional: false]}], "hexpm"},
-  "hackney": {:hex, :hackney, "1.15.1", "9f8f471c844b8ce395f7b6d8398139e26ddca9ebc171a8b91342ee15a19963f4", [:rebar3], [{:certifi, "2.5.1", [hex: :certifi, repo: "hexpm", optional: false]}, {:idna, "6.0.0", [hex: :idna, repo: "hexpm", optional: false]}, {:metrics, "1.0.1", [hex: :metrics, repo: "hexpm", optional: false]}, {:mimerl, "~>1.1", [hex: :mimerl, repo: "hexpm", optional: false]}, {:ssl_verify_fun, "1.1.4", [hex: :ssl_verify_fun, repo: "hexpm", optional: false]}], "hexpm"},
-  "idna": {:hex, :idna, "6.0.0", "689c46cbcdf3524c44d5f3dde8001f364cd7608a99556d8fbd8239a5798d4c10", [:rebar3], [{:unicode_util_compat, "0.4.1", [hex: :unicode_util_compat, repo: "hexpm", optional: false]}], "hexpm"},
-  "jason": {:hex, :jason, "1.1.2", "b03dedea67a99223a2eaf9f1264ce37154564de899fd3d8b9a21b1a6fd64afe7", [:mix], [{:decimal, "~> 1.0", [hex: :decimal, repo: "hexpm", optional: true]}], "hexpm"},
-  "kafka_protocol": {:hex, :kafka_protocol, "2.2.7", "a737a5714874ebd4a82f198f79cb438cda5d1054291b0b1c8f241448c332734d", [:rebar, :rebar3], [{:crc32cer, "0.1.3", [hex: :crc32cer, repo: "hexpm", optional: false]}, {:snappyer, "1.2.4", [hex: :snappyer, repo: "hexpm", optional: false]}], "hexpm"},
-  "makeup": {:hex, :makeup, "0.8.0", "9cf32aea71c7fe0a4b2e9246c2c4978f9070257e5c9ce6d4a28ec450a839b55f", [:mix], [{:nimble_parsec, "~> 0.5.0", [hex: :nimble_parsec, repo: "hexpm", optional: false]}], "hexpm"},
-  "makeup_elixir": {:hex, :makeup_elixir, "0.13.0", "be7a477997dcac2e48a9d695ec730b2d22418292675c75aa2d34ba0909dcdeda", [:mix], [{:makeup, "~> 0.8", [hex: :makeup, repo: "hexpm", optional: false]}], "hexpm"},
-  "metrics": {:hex, :metrics, "1.0.1", "25f094dea2cda98213cecc3aeff09e940299d950904393b2a29d191c346a8486", [:rebar3], [], "hexpm"},
-  "mimerl": {:hex, :mimerl, "1.2.0", "67e2d3f571088d5cfd3e550c383094b47159f3eee8ffa08e64106cdf5e981be3", [:rebar3], [], "hexpm"},
-  "nimble_parsec": {:hex, :nimble_parsec, "0.5.0", "90e2eca3d0266e5c53f8fbe0079694740b9c91b6747f2b7e3c5d21966bba8300", [:mix], [], "hexpm"},
-  "parse_trans": {:hex, :parse_trans, "3.3.0", "09765507a3c7590a784615cfd421d101aec25098d50b89d7aa1d66646bc571c1", [:rebar3], [], "hexpm"},
+  "bunt": {:hex, :bunt, "0.2.0", "951c6e801e8b1d2cbe58ebbd3e616a869061ddadcc4863d0a2182541acae9a38", [:mix], [], "hexpm", "7af5c7e09fe1d40f76c8e4f9dd2be7cebd83909f31fee7cd0e9eadc567da8353"},
+  "certifi": {:hex, :certifi, "2.5.1", "867ce347f7c7d78563450a18a6a28a8090331e77fa02380b4a21962a65d36ee5", [:rebar3], [{:parse_trans, "~>3.3", [hex: :parse_trans, repo: "hexpm", optional: false]}], "hexpm", "805abd97539caf89ec6d4732c91e62ba9da0cda51ac462380bbd28ee697a8c42"},
+  "connection": {:hex, :connection, "1.0.4", "a1cae72211f0eef17705aaededacac3eb30e6625b04a6117c1b2db6ace7d5976", [:mix], [], "hexpm", "4a0850c9be22a43af9920a71ab17c051f5f7d45c209e40269a1938832510e4d9"},
+  "crc32cer": {:hex, :crc32cer, "0.1.3", "8984906c4b4fae6aa292c48f286a1c83b19ad44bd102287acb94d696015967ce", [:make, :rebar, :rebar3], [], "hexpm", "e35840bfd312192748bf177e92e85270e2bf0bbc01462da1f7afd4298edae4a7"},
+  "credo": {:hex, :credo, "1.0.5", "fdea745579f8845315fe6a3b43e2f9f8866839cfbc8562bb72778e9fdaa94214", [:mix], [{:bunt, "~> 0.2.0", [hex: :bunt, repo: "hexpm", optional: false]}, {:jason, "~> 1.0", [hex: :jason, repo: "hexpm", optional: false]}], "hexpm", "16105fac37c5c4b3f6e1f70ba0784511fec4275cd8bb979386e3c739cf4e6455"},
+  "dialyxir": {:hex, :dialyxir, "1.0.0-rc.6", "78e97d9c0ff1b5521dd68041193891aebebce52fc3b93463c0a6806874557d7d", [:mix], [{:erlex, "~> 0.2.1", [hex: :erlex, repo: "hexpm", optional: false]}], "hexpm", "49496d63267bc1a4614ffd5f67c45d9fc3ea62701a6797975bc98bc156d2763f"},
+  "earmark": {:hex, :earmark, "1.3.2", "b840562ea3d67795ffbb5bd88940b1bed0ed9fa32834915125ea7d02e35888a5", [:mix], [], "hexpm", "e3be2bc3ae67781db529b80aa7e7c49904a988596e2dbff897425b48b3581161"},
+  "erlex": {:hex, :erlex, "0.2.1", "cee02918660807cbba9a7229cae9b42d1c6143b768c781fa6cee1eaf03ad860b", [:mix], [], "hexpm", "df65aa8e1e926941982b208f5957158a52b21fbba06ba8141fff2b8c5ce87574"},
+  "ex_doc": {:hex, :ex_doc, "0.20.2", "1bd0dfb0304bade58beb77f20f21ee3558cc3c753743ae0ddbb0fd7ba2912331", [:mix], [{:earmark, "~> 1.3", [hex: :earmark, repo: "hexpm", optional: false]}, {:makeup_elixir, "~> 0.10", [hex: :makeup_elixir, repo: "hexpm", optional: false]}], "hexpm", "8e24fc8ff9a50b9f557ff020d6c91a03cded7e59ac3e0eec8a27e771430c7d27"},
+  "excoveralls": {:hex, :excoveralls, "0.11.1", "dd677fbdd49114fdbdbf445540ec735808250d56b011077798316505064edb2c", [:mix], [{:hackney, "~> 1.0", [hex: :hackney, repo: "hexpm", optional: false]}, {:jason, "~> 1.0", [hex: :jason, repo: "hexpm", optional: false]}], "hexpm", "493daf5a2dd92d022a1c29e7edcc30f1bce1ffe10fb3690fac63889346d3af2f"},
+  "hackney": {:hex, :hackney, "1.15.1", "9f8f471c844b8ce395f7b6d8398139e26ddca9ebc171a8b91342ee15a19963f4", [:rebar3], [{:certifi, "2.5.1", [hex: :certifi, repo: "hexpm", optional: false]}, {:idna, "6.0.0", [hex: :idna, repo: "hexpm", optional: false]}, {:metrics, "1.0.1", [hex: :metrics, repo: "hexpm", optional: false]}, {:mimerl, "~>1.1", [hex: :mimerl, repo: "hexpm", optional: false]}, {:ssl_verify_fun, "1.1.4", [hex: :ssl_verify_fun, repo: "hexpm", optional: false]}], "hexpm", "c2790c9f0f7205f4a362512192dee8179097394400e745e4d20bab7226a8eaad"},
+  "idna": {:hex, :idna, "6.0.0", "689c46cbcdf3524c44d5f3dde8001f364cd7608a99556d8fbd8239a5798d4c10", [:rebar3], [{:unicode_util_compat, "0.4.1", [hex: :unicode_util_compat, repo: "hexpm", optional: false]}], "hexpm", "4bdd305eb64e18b0273864920695cb18d7a2021f31a11b9c5fbcd9a253f936e2"},
+  "jason": {:hex, :jason, "1.1.2", "b03dedea67a99223a2eaf9f1264ce37154564de899fd3d8b9a21b1a6fd64afe7", [:mix], [{:decimal, "~> 1.0", [hex: :decimal, repo: "hexpm", optional: true]}], "hexpm", "fdf843bca858203ae1de16da2ee206f53416bbda5dc8c9e78f43243de4bc3afe"},
+  "kafka_protocol": {:hex, :kafka_protocol, "2.2.7", "a737a5714874ebd4a82f198f79cb438cda5d1054291b0b1c8f241448c332734d", [:rebar, :rebar3], [{:crc32cer, "0.1.3", [hex: :crc32cer, repo: "hexpm", optional: false]}, {:snappyer, "1.2.4", [hex: :snappyer, repo: "hexpm", optional: false]}], "hexpm", "8e0ffba5c9a1214a7e27a961e345eaa3b500c5fa435be66f9fb95a8f7c2f8ded"},
+  "makeup": {:hex, :makeup, "0.8.0", "9cf32aea71c7fe0a4b2e9246c2c4978f9070257e5c9ce6d4a28ec450a839b55f", [:mix], [{:nimble_parsec, "~> 0.5.0", [hex: :nimble_parsec, repo: "hexpm", optional: false]}], "hexpm", "5fbc8e549aa9afeea2847c0769e3970537ed302f93a23ac612602e805d9d1e7f"},
+  "makeup_elixir": {:hex, :makeup_elixir, "0.13.0", "be7a477997dcac2e48a9d695ec730b2d22418292675c75aa2d34ba0909dcdeda", [:mix], [{:makeup, "~> 0.8", [hex: :makeup, repo: "hexpm", optional: false]}], "hexpm", "adf0218695e22caeda2820eaba703fa46c91820d53813a2223413da3ef4ba515"},
+  "metrics": {:hex, :metrics, "1.0.1", "25f094dea2cda98213cecc3aeff09e940299d950904393b2a29d191c346a8486", [:rebar3], [], "hexpm", "69b09adddc4f74a40716ae54d140f93beb0fb8978d8636eaded0c31b6f099f16"},
+  "mimerl": {:hex, :mimerl, "1.2.0", "67e2d3f571088d5cfd3e550c383094b47159f3eee8ffa08e64106cdf5e981be3", [:rebar3], [], "hexpm", "f278585650aa581986264638ebf698f8bb19df297f66ad91b18910dfc6e19323"},
+  "nimble_parsec": {:hex, :nimble_parsec, "0.5.0", "90e2eca3d0266e5c53f8fbe0079694740b9c91b6747f2b7e3c5d21966bba8300", [:mix], [], "hexpm", "5c040b8469c1ff1b10093d3186e2e10dbe483cd73d79ec017993fb3985b8a9b3"},
+  "parse_trans": {:hex, :parse_trans, "3.3.0", "09765507a3c7590a784615cfd421d101aec25098d50b89d7aa1d66646bc571c1", [:rebar3], [], "hexpm", "17ef63abde837ad30680ea7f857dd9e7ced9476cdd7b0394432af4bfc241b960"},
   "snappy": {:git, "https://github.com/fdmanana/snappy-erlang-nif", "e8907ee8e37cfa07d933a070669a88798082c3d7", []},
-  "snappyer": {:hex, :snappyer, "1.2.4", "6d739c534cd2339633127a2b40279be71f149e5842c5363a4d88e66efb7c1fec", [:make, :rebar, :rebar3], [], "hexpm"},
-  "ssl_verify_fun": {:hex, :ssl_verify_fun, "1.1.4", "f0eafff810d2041e93f915ef59899c923f4568f4585904d010387ed74988e77b", [:make, :mix, :rebar3], [], "hexpm"},
-  "unicode_util_compat": {:hex, :unicode_util_compat, "0.4.1", "d869e4c68901dd9531385bb0c8c40444ebf624e60b6962d95952775cac5e90cd", [:rebar3], [], "hexpm"},
-  "varint": {:hex, :varint, "1.2.0", "61bffd9dcc2d5242d59f75694506b4d4013bb103f6a23e34b94f89cebb0c1ab3", [:mix], [], "hexpm"},
+  "snappyer": {:hex, :snappyer, "1.2.4", "6d739c534cd2339633127a2b40279be71f149e5842c5363a4d88e66efb7c1fec", [:make, :rebar, :rebar3], [], "hexpm", "76abb8ed503722e10ee0f587956662881af9009067efdec87798a03db3527184"},
+  "ssl_verify_fun": {:hex, :ssl_verify_fun, "1.1.4", "f0eafff810d2041e93f915ef59899c923f4568f4585904d010387ed74988e77b", [:make, :mix, :rebar3], [], "hexpm", "603561dc0fd62f4f2ea9b890f4e20e1a0d388746d6e20557cafb1b16950de88c"},
+  "unicode_util_compat": {:hex, :unicode_util_compat, "0.4.1", "d869e4c68901dd9531385bb0c8c40444ebf624e60b6962d95952775cac5e90cd", [:rebar3], [], "hexpm", "1d1848c40487cdb0b30e8ed975e34e025860c02e419cb615d255849f3427439d"},
+  "varint": {:hex, :varint, "1.2.0", "61bffd9dcc2d5242d59f75694506b4d4013bb103f6a23e34b94f89cebb0c1ab3", [:mix], [], "hexpm", "d94941ed8b9d1a5fdede9103a5e52035bd0aaf35081d44e67713a36799927e47"},
 }

test/kayrock/member_assignment_test.exs

@@ -7,6 +7,13 @@ defmodule Kayrock.MemberAssignmentTest do
     assert MemberAssignment.deserialize(<<>>) == {%MemberAssignment{}, <<>>}
   end
 
+  # This matches the response from an error response to SyncGroup, for example
+  test "deserialize no assignements" do
+    member_assignment = <<0, 0, 0, 0>>
+    {got, ""} = MemberAssignment.deserialize(member_assignment)
+    assert got == %MemberAssignment{version: 0}
+  end
+
   test "deserialize member assignments" do
     member_assignment = <<0::16, 1::32, 6::16, "topic1", 3::32, 1::32, 3::32, 5::32>>
     member_assignment = <<byte_size(member_assignment)::32-signed, member_assignment::bytes>>