Fix URLCache query parameter differentiation on Linux

URLCache in swift-corelibs-foundation does not differentiate cache
entries by URL query parameters. Work around this by creating synthetic
cache key URLs that encode the full URL (including query string) into
the path component, ensuring unique cache entries on all platforms.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: BrentMifsud

Sources/Simplicity/Implementation/CacheMiddleware.swift

@@ -67,7 +67,7 @@ public actor CacheMiddleware: Middleware {
         next: nonisolated(nonsending) @Sendable (MiddlewareRequest) async throws -> MiddlewareResponse
     ) async throws -> MiddlewareResponse {
         let url = request.url
-        let urlRequest = URLRequest(url: url)
+        let urlRequest = cacheKeyRequest(for: url)
 
         // Handle cache policy
         switch request.cachePolicy {
@@ -120,7 +120,7 @@ public actor CacheMiddleware: Middleware {
         status: HTTPResponse.Status = .ok,
         headerFields: HTTPFields = HTTPFields()
     ) {
-        let urlRequest = URLRequest(url: url)
+        let urlRequest = cacheKeyRequest(for: url)
 
         var headerDict: [String: String] = [:]
         for field in headerFields {
@@ -145,7 +145,7 @@ public actor CacheMiddleware: Middleware {
     ///
     /// - Parameter url: The URL whose cached response should be removed.
     public func removeCached(for url: URL) {
-        let urlRequest = URLRequest(url: url)
+        let urlRequest = cacheKeyRequest(for: url)
         urlCache.removeCachedResponse(for: urlRequest)
     }
 
@@ -159,7 +159,7 @@ public actor CacheMiddleware: Middleware {
     /// - Parameter url: The URL to check.
     /// - Returns: `true` if a cached response exists, `false` otherwise.
     public func hasCachedResponse(for url: URL) -> Bool {
-        let urlRequest = URLRequest(url: url)
+        let urlRequest = cacheKeyRequest(for: url)
         return urlCache.cachedResponse(for: urlRequest) != nil
     }
 

Sources/Simplicity/Implementation/URLCacheCompat.swift

@@ -0,0 +1,30 @@
+//
+//  URLCacheCompat.swift
+//  Simplicity
+//
+
+import Foundation
+#if canImport(FoundationNetworking)
+import FoundationNetworking
+#endif
+
+/// Creates a `URLRequest` to use as a `URLCache` key for the given URL.
+///
+/// On Linux, `URLCache` in swift-corelibs-foundation does not differentiate cache entries
+/// by URL query parameters. This function works around the limitation by encoding the full
+/// URL (including query string) into a synthetic path component, ensuring unique cache keys.
+///
+/// On Apple platforms, this simply returns `URLRequest(url:)`.
+func cacheKeyRequest(for url: URL) -> URLRequest {
+    #if canImport(FoundationNetworking)
+    // Encode the entire URL (scheme, host, path, query, fragment) into a single
+    // percent-encoded path segment. The resulting synthetic URL has no query component,
+    // so URLCache cannot collapse entries that differ only by query parameters.
+    let encoded = url.absoluteString.addingPercentEncoding(
+        withAllowedCharacters: .alphanumerics
+    ) ?? url.absoluteString
+    return URLRequest(url: URL(string: "simplicity-cache://entry/\(encoded)")!)
+    #else
+    return URLRequest(url: url)
+    #endif
+}

Sources/Simplicity/Implementation/URLSessionClient.swift

@@ -349,7 +349,7 @@ public actor URLSessionClient: Client {
     ) async throws(ClientError) where R.SuccessResponseBody: Encodable {
         let cache = urlCache ?? .shared
         let url = request.requestURL(baseURL: baseURL)
-        let urlRequest = URLRequest(url: url)
+        let urlRequest = cacheKeyRequest(for: url)
 
         let data: Data
         do {
@@ -386,7 +386,7 @@ public actor URLSessionClient: Client {
     ) async throws(ClientError) -> Response<R.SuccessResponseBody, R.FailureResponseBody> {
         let cache = urlCache ?? .shared
         let url = request.requestURL(baseURL: baseURL)
-        let urlRequest = URLRequest(url: url)
+        let urlRequest = cacheKeyRequest(for: url)
 
         guard let cachedResponse = cache.cachedResponse(for: urlRequest),
               let httpURLResponse = cachedResponse.response as? HTTPURLResponse,
@@ -407,7 +407,7 @@ public actor URLSessionClient: Client {
     ) async {
         let cache = urlCache ?? .shared
         let url = request.requestURL(baseURL: baseURL)
-        let urlRequest = URLRequest(url: url)
+        let urlRequest = cacheKeyRequest(for: url)
         cache.removeCachedResponse(for: urlRequest)
     }
 }

Tests/SimplicityTests/CacheMiddlewareTests.swift

@@ -261,8 +261,6 @@ struct CacheMiddlewareTests {
         #expect(hasCached)
     }
 
-    // URLCache in swift-corelibs-foundation does not differentiate cache entries by query parameters.
-    #if !canImport(FoundationNetworking)
     @Test
     func testDifferentQueryParams_differentCacheEntries() async throws {
         // Arrange
@@ -330,7 +328,6 @@ struct CacheMiddlewareTests {
         #expect(cached1.body == data1)
         #expect(cached2.body == data2)
     }
-    #endif
 
     @Test
     func testRemoveCached_invalidatesEntry() async throws {

Tests/SimplicityTests/URLSessionHTTPClientTests.swift

@@ -535,8 +535,6 @@ struct URLSessionClientCacheTests {
         #expect(cached.headerFields[HTTPField.Name("X-Custom")!] == "value")
     }
 
-    // URLCache in swift-corelibs-foundation does not differentiate cache entries by query parameters.
-    #if !canImport(FoundationNetworking)
     @Test
     func testCachedResponse_differentQueryParams_differentCacheEntries() async throws {
         // Arrange
@@ -555,7 +553,6 @@ struct URLSessionClientCacheTests {
         #expect(try cached1.decodeSuccessBody() == model1)
         #expect(try cached2.decodeSuccessBody() == model2)
     }
-    #endif
 
     @Test
     func testClearNetworkCache_clearsAllCachedResponses() async throws {