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Use pattern matching to serialize bool values #104

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merged 3 commits into from
Dec 30, 2016
Merged

Use pattern matching to serialize bool values #104

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605a90e
Use a case statement to serialize bool values
jparise Dec 30, 2016
c6ed05c
Match directly in serialize/2 function clause
jparise Dec 30, 2016
4b0503a
Strictly match just true and false for :bool
jparise Dec 30, 2016
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11 changes: 3 additions & 8 deletions lib/thrift/protocols/binary.ex
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Original file line number Diff line number Diff line change
Expand Up @@ -36,10 +36,6 @@ defmodule Thrift.Protocols.Binary do
def int_type({:set, _}), do: 14
def int_type({:list, _}), do: 15

defp bool_to_int(false), do: 0
defp bool_to_int(nil), do: 0
defp bool_to_int(_), do: 1

defp to_message_type(:call), do: 1
defp to_message_type(:reply), do: 2
defp to_message_type(:exception), do: 3
Expand All @@ -53,10 +49,9 @@ defmodule Thrift.Protocols.Binary do
def serialize(_, nil) do
[]
end
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This clause should not exist. The way we serialize nil depends on its context.

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That sounds right to me. I'll remove it in its own PR so we can track the specific motivation.

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This clause is removed in #105.

def serialize(:bool, value) do
value = bool_to_int(value)
<<value::8-signed>>
end
def serialize(:bool, nil), do: <<0::8-signed>>
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Now that I think about it - should this clause ever get called? If a value is nil then it's not set and should be skipped.

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If a boolean field in a struct is nil, that field would be omitted. That logic isn't represented in this generic serialization because it doesn't handle structs. It passes them off to presumably-generated struct serializers. (See serialize(:struct, _) further down.)

If you serialize a list of bools, we would treat a nil in that list as falsey.

serialize({:list, :bool}, [nil, false, true]) |> :erlang.iolist_to_binary
# <<2, 0, 0, 0, 3, 0, 0, 1>>
#   |  \--------/  |  |  \- true
#   |      |       |  \---- false
#   |      |       \------- nil
#   |      \--------------- length = 3
#   \---------------------- element type = bool

Note that this doesn't currently work because of the serialize(_, nil) clause further up.

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I think implicit here is whether we want to watch to support "truthy" / "falsey" inputs or if we should explicitly require true or false atoms (where all other inputs result in an :error).

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@pguillory's comment makes sense to me. @jparise raises a good point, too.

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Yeah good point. If we're not sure, it might be better to start strict, true/false only. We can become less strict later without breaking applications.

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Good point @pguillory.

Related - some thrift clients (I know the Ruby client does this) provide validation functionality - e.g., are required fields set, is a string field actually a string, etc. It's slow but it's usually optional. I typically enable it for testing but disable it in production. This might be something to add a TODO for later?

def serialize(:bool, false), do: <<0::8-signed>>
def serialize(:bool, _), do: <<1::8-signed>>
def serialize(:i8, value) do
<<value::8-signed>>
end
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