fix(api): read an ArcGIS error code 503 as RateLimited

CHANGELOG.md

@@ -6,6 +6,12 @@ uses [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
 ## [Unreleased]
 
+### Fixed
+
+- An ArcGIS error object with code 503 was `ServerError`. It is now
+  `RateLimited`, the same as an HTTP 503 and as the README and `error.hpp`
+  say.
+
 ## [0.4.2] - 2026-09-25
 
 ### Changed
@@ -24,9 +30,9 @@ uses [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 - Builds without floating-point `std::from_chars` (libc++ before 20, and
   macOS targets before 26) parsed numeric strings such as probability labels
   with a string stream, which disagreed with every other build. It read
-  `0x10` as 16 and rejected `12abc`, `inf`, `nan`, subnormals such as
-  `1e-310`, and a bare trailing exponent such as `5e`, so those fields became
-  0 on those builds. Every platform now uses the fast_float code that Glaze
+  `0x10` as 16 and rejected `12abc`, subnormals such as `1e-310`, and a
+  bare trailing exponent such as `5e`, so those fields became 0 on those
+  builds. Every platform now uses the fast_float code that Glaze
   already bundles, which also parses a number in about a tenth of the
   stream's instructions.
 - The `parse_*` functions could read past the end of the `std::string_view`

src/api/client.cpp

@@ -429,8 +429,8 @@ struct ArcGISClient::Impl {
 	}
 
 	/// Page through `query`, build each page's payload from its tree with
-	/// `build`, and move the page's `items` into `payload`. The body is freed
-	/// first, so peak memory is one page's tree plus the result.
+	/// `build`, and move the page's `items` into `payload`. Each page's body is
+	/// freed before its payload is built, so the two are never alive together.
 	template <typename Payload, typename Item, typename Build>
 	[[nodiscard]] Result<Payload> paged_into(const LayerQuery& query, Payload payload,
 											 std::vector<Item> Payload::*items,

src/core/error.cpp

@@ -77,7 +77,8 @@ Error Error::from_arcgis(int arcgis_code, const std::string& body) {
 	if (arcgis_code == 404) {
 		// A retired service path. An empty product is HTTP 200 with no features.
 		err.code = ErrorCode::NotFound;
-	} else if (arcgis_code == 429) {
+	} else if (arcgis_code == 429 || arcgis_code == 503) {
+		// The same codes as from_response.
 		err.code = ErrorCode::RateLimited;
 	} else if (arcgis_code >= 500 && arcgis_code <= 599) {
 		err.code = ErrorCode::ServerError;

tests/test_client.cpp

@@ -8,6 +8,7 @@
 #include "support/fixtures.hpp"
 
 #include <cstdint>
+#include <format>
 #include <gtest/gtest.h>
 #include <memory>
 #include <string>
@@ -260,6 +261,8 @@ TEST(ArcGISClientPaging, EncodesParametersAndFetchesEveryPage) {
 
 	ASSERT_TRUE(result);
 	ASSERT_EQ(result->size(), 2u);
+	EXPECT_EQ((*result)[0], truncated_page(2000));
+	EXPECT_EQ((*result)[1], R"({"features":[],"exceededTransferLimit":false})");
 	ASSERT_EQ(transport->requests.size(), 2u);
 	EXPECT_NE(transport->requests[0].find("where=LABEL%20%3D%20%27SLGT%27"), std::string::npos);
 	EXPECT_NE(transport->requests[0].find("outFields=LABEL%2Cvalid"), std::string::npos);
@@ -371,6 +374,27 @@ TEST(ArcGISClientPaging, KeepsTheArcGISErrorDetails) {
 	EXPECT_EQ(result.error().detail, "'where' parameter is invalid.; Check field names.");
 }
 
+TEST(ArcGISClientPaging, ClassifiesArcGIS5xxCodesLikeHttpStatuses) {
+	// HTTP 503 is RateLimited and other 5xx are ServerError, so the same codes
+	// in an ArcGIS error object mean the same.
+	for (const auto& [code, expected] :
+		 {std::pair{503, ErrorCode::RateLimited}, std::pair{500, ErrorCode::ServerError}}) {
+		std::shared_ptr<RecordingTransport> transport = std::make_shared<RecordingTransport>();
+		transport->responses = {
+			{200,
+			 std::format(R"({{"error":{{"code":{},"message":"Busy","details":[]}}}})", code),
+			 {}},
+		};
+		const ArcGISClient client{transport};
+
+		const Result<CategoricalOutlookPayload> result = client.query_categorical(1);
+
+		ASSERT_FALSE(result) << code;
+		EXPECT_EQ(result.error().code, expected) << code;
+		EXPECT_EQ(result.error().http_status, code);
+	}
+}
+
 // ===== What a 404 means =====
 //
 // SPC's static products answer 404 when nothing is issued. Any other 404 is a

tools/verify_fixture_checksums.py

@@ -25,7 +25,10 @@ def main() -> int:
     actual = {
         path
         for path in FIXTURES.iterdir()
-        if path.is_file() and path.name not in {"README.md", "SHA256SUMS"}
+        # Dotfiles such as a Finder .DS_Store are not fixtures.
+        if path.is_file()
+        and not path.name.startswith(".")
+        and path.name not in {"README.md", "SHA256SUMS"}
     }
     if actual != set(expected):
         missing = sorted(str(path.relative_to(ROOT)) for path in actual - set(expected))