Throw a "data too large" error in ListMapper when parsing data bigger than a certain size like 100MB

Modules/Sources/Networking/Mapper/ListMapper.swift

@@ -1,5 +1,22 @@
 import Foundation
 
+/// Shared error types for mappers.
+///
+public enum MapperError: LocalizedError {
+    case dataTooLarge
+
+    public var errorDescription: String? {
+        switch self {
+        case .dataTooLarge:
+            return NSLocalizedString(
+                "mapper.error.data.too.large",
+                value: "The response data is too large to process.",
+                comment: "Error message when API response data exceeds the maximum allowed size."
+            )
+        }
+    }
+}
+
 /// ListMapper: Maps generic WooCommerce REST API Lists
 ///
 struct ListMapper<Output: Decodable>: Mapper {
@@ -9,9 +26,23 @@ struct ListMapper<Output: Decodable>: Mapper {
     ///
     let siteID: Int64
 
+    let maxSizeInBytes: Int64?
+
+    /// - Parameters:
+    ///   - siteID: The site identifier associated with the items that will be parsed.
+    ///   - maxSizeInBytes: Optional maximum size of the response data in bytes. Defaults to 100MB.
+    init(siteID: Int64, maxSizeInBytes: Int64? = 100 * 1024 * 1024) {
+        self.siteID = siteID
+        self.maxSizeInBytes = maxSizeInBytes
+    }
+
     /// (Attempts) to convert a dictionary into [Output].
     ///
     func map(response: Data) throws -> [Output] {
+        if let maxSizeInBytes, Int64(response.count) > maxSizeInBytes {
+            throw MapperError.dataTooLarge
+        }
+
         let decoder = JSONDecoder()
         decoder.dateDecodingStrategy = .formatted(DateFormatter.Defaults.dateTimeFormatter)
         decoder.userInfo = [

Networking/NetworkingTests/Mapper/ListMapperTests.swift

@@ -137,4 +137,60 @@ struct ListMapperTests {
         // Then we map to an empty array
         #expect(posProducts == [])
     }
+
+    @Test func it_throws_error_when_exceeding_default_size_limit() throws {
+        // Given a large response that exceeds the size limit
+        let largeData = Data(repeating: 0, count: 101 * 1024 * 1024) // 101MB, exceeding 100MB limit
+
+        // When we map with default size limit
+        // Then it throws MapperError.dataTooLarge
+        #expect(throws: MapperError.dataTooLarge) {
+            _ = try ListMapper<Order>(siteID: 123).map(response: largeData)
+        }
+    }
+
+    @Test func it_throws_error_when_exceeding_custom_size_limit() throws {
+        // Given a response that's larger than a custom limit but smaller than default
+        let mediumData = Data(repeating: 0, count: 2 * 1024 * 1024) // 2MB
+        let customLimit: Int64 = 1 * 1024 * 1024 // 1MB limit
+
+        // When we map with custom size limit
+        // Then it throws MapperError.dataTooLarge
+        #expect(throws: MapperError.dataTooLarge) {
+            _ = try ListMapper<Order>(siteID: 123, maxSizeInBytes: customLimit).map(response: mediumData)
+        }
+    }
+
+    @Test func it_skips_size_check_when_maxSizeInBytes_is_nil() throws {
+        // Given a large response
+        let largeData = Data(repeating: 0, count: 101 * 1024 * 1024) // 101MB
+
+        // When we map with nil size limit (should skip size check)
+        // Then it should attempt to decode (will fail due to invalid JSON, but not due to size)
+        do {
+            _ = try ListMapper<Order>(siteID: 123, maxSizeInBytes: nil).map(response: largeData)
+            Issue.record("Expected decoding to fail due to invalid JSON")
+        } catch MapperError.dataTooLarge {
+            Issue.record("Expected decoding error, not size error")
+        } catch {
+            // Expected decoding error due to invalid JSON data
+        }
+    }
+
+    @Test func it_succeeds_when_data_exactly_at_maxSizeInBytes() throws {
+        // Given data that's exactly at the size limit
+        let exactSizeData = Data(repeating: 0, count: 100 * 1024) // Exactly 100KB
+        let limit: Int64 = 100 * 1024 // 100KB limit
+
+        // When we map with exact size limit
+        // Then it should attempt to decode (will fail due to invalid JSON, but not due to size)
+        do {
+            _ = try ListMapper<Order>(siteID: 123, maxSizeInBytes: limit).map(response: exactSizeData)
+            Issue.record("Expected decoding to fail due to invalid JSON")
+        } catch MapperError.dataTooLarge {
+            Issue.record("Expected decoding error, not size error")
+        } catch {
+            // Expected decoding error due to invalid JSON data
+        }
+    }
 }