provide hooks for custom backends

src/utilities/request.jl

@@ -1,3 +1,21 @@
+# this is used to allow custom dispatches to `_http_request`
+abstract type AbstractBackend end
+
+"""
+    AWS.HTTPBackend <: AWS.AbstractBackend
+
+An `HTTPBackend` can hold default `http_options::AbstractDict{Symbol,<:Any}`
+to pass to HTTP.jl, which can be overwritten per-request by any `http_options`
+supplied there.
+"""
+struct HTTPBackend{T<:AbstractDict{Symbol,<:Any}} <: AbstractBackend
+    http_options::T
+end
+
+HTTPBackend() = HTTPBackend(LittleDict{Symbol,String}())
+
+const DEFAULT_BACKEND = Ref{Union{Nothing, AbstractBackend}}(HTTPBackend())
+
 Base.@kwdef mutable struct Request
     service::String
     api_version::String
@@ -13,6 +31,7 @@ Base.@kwdef mutable struct Request
     http_options::AbstractDict{Symbol,<:Any}=LittleDict{Symbol,String}()
     return_raw::Bool=false
     response_dict_type::Type{<:AbstractDict}=LittleDict
+    backend::AbstractBackend=DEFAULT_BACKEND[]
 end
 
 
@@ -54,7 +73,7 @@ function submit_request(aws::AbstractAWSConfig, request::Request; return_headers
     @repeat 3 try
         credentials(aws) === nothing || sign!(aws, request)
 
-        response = @mock _http_request(request)
+        response = @mock _http_request(request.backend, request)
 
         if response.status in REDIRECT_ERROR_CODES
             if HTTP.header(response, "Location") != ""
@@ -141,7 +160,9 @@ function submit_request(aws::AbstractAWSConfig, request::Request; return_headers
 end
 
 
-function _http_request(request::Request)
+function _http_request(http_backend::HTTPBackend, request::Request)
+    http_options = merge(http_backend.http_options, request.http_options)
+
     @repeat 4 try
         http_stack = HTTP.stack(redirect=false, retry=false, aws_authorization=false)
 
@@ -157,7 +178,7 @@ function _http_request(request::Request)
             request.content;
             require_ssl_verification=false,
             response_stream=request.response_stream,
-            request.http_options...
+            http_options...
         )
     catch e
         # Base.IOError is needed because HTTP.jl can often have errors that aren't

src/utilities/utilities.jl

@@ -68,6 +68,7 @@ function _extract_common_kw_args(service, args)
         headers=LittleDict{String, String}(_pop!(args, "headers", [])),
         http_options=_pop!(args, "http_options", LittleDict{Symbol, String}()),
         response_dict_type=_pop!(args, "response_dict_type", LittleDict),
+        backend=_pop!(args, "backend", DEFAULT_BACKEND[]),
     )
 end
 

test/patch.jl

@@ -56,7 +56,7 @@ end
 
 
 function _aws_http_request_patch(response::HTTP.Messages.Response=_response())
-    return @patch AWS._http_request(request::Request) = response
+    return @patch AWS._http_request(::Any, request::Request) = response
 end
 
 _cred_file_patch = @patch function dot_aws_credentials_file()
@@ -73,7 +73,7 @@ _web_identity_patch = function (;
     session_token="web_session_token",
     role_arn="arn:aws:sts:::assumed-role/role-name",
 )
-    @patch function AWS._http_request(request)
+    @patch function AWS._http_request(::AWS.HTTPBackend, request)
         params = Dict(split.(split(request.content, '&'), '='))
         creds = Dict(
             "AccessKeyId" => access_key,