Preserve error response bodies before raising

CHANGELOG.md

@@ -1,5 +1,10 @@
 ## [Unreleased]
 
+## [0.3.1] - 2026-08-25
+
+- Preserve error response bodies: replace the http gem's raise_error with
+  flushed_raise_error, which reads the body before raising (fixes #8)
+
 ## [0.3.0] - 2026-08-25
 
 - Require http ~> 6.0
@@ -24,7 +29,8 @@
 - OpenAPI-based code generator
 - RBS type signatures
 
-[Unreleased]: https://github.com/lineofflight/amazon-ads-ruby/compare/v0.3.0...HEAD
+[Unreleased]: https://github.com/lineofflight/amazon-ads-ruby/compare/v0.3.1...HEAD
+[0.3.1]: https://github.com/lineofflight/amazon-ads-ruby/compare/v0.3.0...v0.3.1
 [0.3.0]: https://github.com/lineofflight/amazon-ads-ruby/compare/v0.2.0...v0.3.0
 [0.2.0]: https://github.com/lineofflight/amazon-ads-ruby/compare/v0.1.0...v0.2.0
 [0.1.0]: https://github.com/lineofflight/amazon-ads-ruby/releases/tag/v0.1.0

lib/amazon_ads.rb

@@ -6,7 +6,9 @@
 loader.inflector.inflect("api" => "API", "lwa" => "LWA")
 loader.collapse("#{__dir__}/amazon_ads/apis")
 loader.ignore("#{__dir__}/generator")
+loader.ignore("#{__dir__}/amazon_ads/flushed_raise_error.rb")
 loader.setup
+require_relative "amazon_ads/flushed_raise_error"
 
 # Amazon Ads API client for Ruby
 module AmazonAds

lib/amazon_ads/api.rb

@@ -50,10 +50,10 @@ def http
         .use(:auto_inflate)
 
       if retries.zero?
-        client.use(:raise_error)
+        client.use(:flushed_raise_error)
       else
         client
-          .use(raise_error: { ignore: [429] })
+          .use(flushed_raise_error: { ignore: [429] })
           .retriable(tries: retries + 1, retry_statuses: [429])
       end
     end

lib/amazon_ads/flushed_raise_error.rb

@@ -0,0 +1,32 @@
+# frozen_string_literal: true
+# rbs_inline: enabled
+
+require "http"
+
+module AmazonAds
+  # Drop-in replacement for the http gem's raise_error feature that reads
+  # the response body before raising. HTTP::Client#perform closes the
+  # connection when a feature raises, so with the stock feature the body of
+  # an error response is lost by the time callers rescue HTTP::StatusError.
+  class FlushedRaiseError < HTTP::Feature
+    # Status codes to pass through without raising
+    attr_reader :ignore #: Array[Integer]
+
+    #: (?ignore: Array[Integer]) -> void
+    def initialize(ignore: [])
+      super()
+      @ignore = ignore
+    end
+
+    #: (HTTP::Response) -> HTTP::Response
+    def wrap_response(response)
+      return response if response.code < 400
+      return response if ignore.include?(response.code)
+
+      response.flush # memoize the body before Client#perform closes the connection
+      raise HTTP::StatusError, response
+    end
+
+    HTTP::Options.register_feature(:flushed_raise_error, self)
+  end
+end

lib/amazon_ads/lwa.rb

@@ -33,7 +33,7 @@ def request
 
     #: () -> HTTP::Client
     def http
-      @http.use(:raise_error)
+      @http.use(:flushed_raise_error)
     end
 
     #: () -> Hash[Symbol, String]

lib/amazon_ads/version.rb

@@ -1,5 +1,5 @@
 # frozen_string_literal: true
 
 module AmazonAds
-  VERSION = "0.3.0"
+  VERSION = "0.3.1"
 end

test/.env.example

@@ -3,3 +3,4 @@ AMAZON_ADS_CLIENT_SECRET=CLIENT_SECRET
 AMAZON_ADS_TEST_REFRESH_TOKEN=REFRESH_TOKEN
 AMAZON_ADS_TEST_REGION=NA
 AMAZON_ADS_TEST_PROFILE_ID=PROFILE_ID
+AMAZON_ADS_TEST_EU_PROFILE_ID=PROFILE_ID

test/amazon_ads/apis/test_campaigns.rb

@@ -12,4 +12,18 @@ def test_query_campaign
 
     assert_predicate(res.status, :success?)
   end
+
+  def test_query_campaign_rejects_bare_string_filter
+    api = AmazonAds::Campaigns.new(
+      region: "EU",
+      profile_id: ENV.fetch("AMAZON_ADS_TEST_EU_PROFILE_ID", "0"),
+      access_token:,
+    )
+    error = assert_raises(HTTP::StatusError) do
+      api.query_campaign(ad_product_filter: "SPONSORED_PRODUCTS")
+    end
+
+    assert_equal(400, error.response.status.code)
+    assert(error.response.body.to_s.length.positive?)
+  end
 end

test/amazon_ads/test_flushed_raise_error.rb

@@ -0,0 +1,54 @@
+# frozen_string_literal: true
+
+require "test_helper"
+require "socket"
+
+class TestFlushedRaiseError < Minitest::Test
+  BODY = '{"message":"BAD_REQUEST: adProductFilter must be an object"}'
+
+  def setup
+    # test_helper hooks VCR into WebMock for every test, which intercepts
+    # HTTP::Client#perform before it ever opens a socket. This test exists
+    # specifically to exercise that real socket path, so bypass both for
+    # its duration.
+    VCR.turn_off!
+    WebMock.allow_net_connect!
+
+    @server = TCPServer.new("127.0.0.1", 0)
+    @port = @server.addr[1]
+    @thread = Thread.new do
+      socket = @server.accept
+      socket.readpartial(4096)
+      socket.write(
+        "HTTP/1.1 400 Bad Request\r\n" \
+          "Content-Type: application/json\r\n" \
+          "Content-Length: #{BODY.bytesize}\r\n" \
+          "Connection: close\r\n" \
+          "\r\n#{BODY}",
+      )
+      socket.close
+    end
+  end
+
+  def teardown
+    @thread.kill
+    @server.close
+
+    WebMock.disable_net_connect!
+    VCR.turn_on!
+  end
+
+  def test_status_error_retains_body
+    error = assert_raises(HTTP::StatusError) do
+      HTTP.use(:flushed_raise_error).get("http://127.0.0.1:#{@port}/")
+    end
+
+    assert_equal(BODY, error.response.body.to_s)
+  end
+
+  def test_ignored_codes_pass_through
+    response = HTTP.use(flushed_raise_error: { ignore: [400] }).get("http://127.0.0.1:#{@port}/")
+
+    assert_equal(400, response.status.code)
+  end
+end