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Better handle content negotiation when accept contains charsets

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Thanks to Philip Witty for help figuring this out.
This commit is contained in:
Loïc Hoguin 2018-11-02 12:36:51 +01:00
parent d4dff21055
commit 399b6a16b4
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GPG key ID: 8A9DF795F6FED764
6 changed files with 231 additions and 19 deletions
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89
src/cowboy_rest.erl
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@ -245,7 +245,7 @@
language_a :: undefined | binary(),
%% Charset.
charsets_p = [] :: [binary()],
charsets_p = undefined :: undefined | [binary()],
charset_a :: undefined | binary(),
%% Whether the resource exists.
@ -503,16 +503,55 @@ match_media_type(Req, State, Accept,
match_media_type(Req, State, Accept, [_Any|Tail], MediaType) ->
match_media_type(Req, State, Accept, Tail, MediaType).
match_media_type_params(Req, State, _Accept,
[Provided = {{TP, STP, '*'}, _Fun}|_Tail],
{{_TA, _STA, Params_A}, _QA, _APA}) ->
PMT = {TP, STP, Params_A},
languages_provided(Req#{media_type => PMT},
State#state{content_type_a=Provided});
match_media_type_params(Req, State, Accept,
[Provided = {PMT = {_TP, _STP, Params_P}, _Fun}|Tail],
[Provided = {{TP, STP, '*'}, _Fun}|Tail],
MediaType = {{TA, _STA, Params_A0}, _QA, _APA}) ->
case lists:keytake(<<"charset">>, 1, Params_A0) of
{value, {_, Charset}, Params_A} when TA =:= <<"text">> ->
%% When we match against a wildcard, the media type is text
%% and has a charset parameter, we call charsets_provided
%% and check that the charset is provided. If the callback
%% is not exported, we accept inconditionally but ignore
%% the given charset so as to not send a wrong value back.
case call(Req, State, charsets_provided) of
no_call ->
languages_provided(Req#{media_type => {TP, STP, Params_A0}},
State#state{content_type_a=Provided});
{stop, Req2, HandlerState} ->
terminate(Req2, State#state{handler_state=HandlerState});
{Switch, Req2, HandlerState} when element(1, Switch) =:= switch_handler ->
switch_handler(Switch, Req2, HandlerState);
{CP, Req2, HandlerState} ->
State2 = State#state{handler_state=HandlerState, charsets_p=CP},
case lists:member(Charset, CP) of
false ->
match_media_type(Req2, State2, Accept, Tail, MediaType);
true ->
languages_provided(Req2#{media_type => {TP, STP, Params_A}},
State2#state{content_type_a=Provided,
charset_a=Charset})
end
end;
_ ->
languages_provided(Req#{media_type => {TP, STP, Params_A0}},
State#state{content_type_a=Provided})
end;
match_media_type_params(Req, State, Accept,
[Provided = {PMT = {TP, STP, Params_P0}, Fun}|Tail],
MediaType = {{_TA, _STA, Params_A}, _QA, _APA}) ->
case lists:sort(Params_P) =:= lists:sort(Params_A) of
case lists:sort(Params_P0) =:= lists:sort(Params_A) of
true when TP =:= <<"text">> ->
%% When a charset was provided explicitly in both the charset header
%% and the media types provided and the negotiation is successful,
%% we keep the charset and don't call charsets_provided. This only
%% applies to text media types, however.
{Charset, Params_P} = case lists:keytake(<<"charset">>, 1, Params_P0) of
false -> {undefined, Params_P0};
{value, {_, Charset0}, Params_P1} -> {Charset0, Params_P1}
end,
languages_provided(Req#{media_type => {TP, STP, Params_P}},
State#state{content_type_a={{TP, STP, Params_P}, Fun},
charset_a=Charset});
true ->
languages_provided(Req#{media_type => PMT},
State#state{content_type_a=Provided});
@ -587,6 +626,26 @@ set_language(Req, State=#state{language_a=Language}) ->
%% charsets_provided should return a list of binary values indicating
%% which charsets are accepted by the resource.
%%
%% A charset may have been selected while negotiating the accept header.
%% There's no need to select one again.
charsets_provided(Req, State=#state{charset_a=Charset})
when Charset =/= undefined ->
set_content_type(Req, State);
%% If charsets_p is defined, use it instead of calling charsets_provided
%% again. We also call this clause during normal execution to avoid
%% duplicating code.
charsets_provided(Req, State=#state{charsets_p=[]}) ->
not_acceptable(Req, State);
charsets_provided(Req, State=#state{charsets_p=CP})
when CP =/= undefined ->
case cowboy_req:parse_header(<<"accept-charset">>, Req) of
undefined ->
set_content_type(Req, State#state{charset_a=hd(CP)});
AcceptCharset0 ->
AcceptCharset = prioritize_charsets(AcceptCharset0),
choose_charset(Req, State, AcceptCharset)
end;
charsets_provided(Req, State) ->
case call(Req, State, charsets_provided) of
no_call ->
@ -595,17 +654,8 @@ charsets_provided(Req, State) ->
terminate(Req2, State#state{handler_state=HandlerState});
{Switch, Req2, HandlerState} when element(1, Switch) =:= switch_handler ->
switch_handler(Switch, Req2, HandlerState);
{[], Req2, HandlerState} ->
not_acceptable(Req2, State#state{handler_state=HandlerState});
{CP, Req2, HandlerState} ->
State2 = State#state{handler_state=HandlerState, charsets_p=CP},
case cowboy_req:parse_header(<<"accept-charset">>, Req2) of
undefined ->
set_content_type(Req2, State2#state{charset_a=hd(CP)});
AcceptCharset ->
AcceptCharset2 = prioritize_charsets(AcceptCharset),
choose_charset(Req2, State2, AcceptCharset2)
end
charsets_provided(Req2, State#state{handler_state=HandlerState, charsets_p=CP})
end.
%% The special value "*", if present in the Accept-Charset field,
@ -690,6 +740,7 @@ variances(Req, State=#state{content_types_p=CTP,
[_|_] -> [<<"accept-language">>|Variances]
end,
Variances3 = case CP of
undefined -> Variances2;
[] -> Variances2;
[_] -> Variances2;
[_|_] -> [<<"accept-charset">>|Variances2]