Fix encoding of plain text bodies (#9)

Fix encoding of plain text bodies

### Motivation

When the content type `text/plain` is used, we had a bug where we were encoding the text using `Codable` into a JSON fragment, i.e. `hello` -> `"hello"` (note the added quotes), which is incorrect. We should be using `LosslessStringConvertible` for primitive types, so that `hello` is sent as `hello` (without the quotes).

### Modifications

Fixed the body conversion methods to use the string conversion if possible, and only use the `Codable` implementation for complex types.

### Result

When content type is `text/plain` (and other plain text variants), `hello` is sent as `hello`, not `"hello"`.

### Test Plan

Updated unit tests and added new ones to cover these cases.


Reviewed by: simonjbeaumont

Builds:
     ✔︎ pull request validation (5.8) - Build finished. 
     ✔︎ pull request validation (5.9) - Build finished. 
     ✔︎ pull request validation (nightly) - Build finished. 
     ✔︎ pull request validation (soundness) - Build finished. 

#9

Author: czechboy0

Sources/OpenAPIRuntime/Conversion/Converter+Client.swift

@@ -90,7 +90,18 @@ extension Converter {
         from data: Data,
         transforming transform: (T) -> C
     ) throws -> C {
-        let decoded = try decoder.decode(type, from: data)
+        let decoded: T
+        if let myType = T.self as? _StringParameterConvertible.Type {
+            guard
+                let stringValue = String(data: data, encoding: .utf8),
+                let decodedValue = myType.init(stringValue)
+            else {
+                throw RuntimeError.failedToDecodePrimitiveBodyFromData
+            }
+            decoded = decodedValue as! T
+        } else {
+            decoded = try decoder.decode(type, from: data)
+        }
         return transform(decoded)
     }
 
@@ -128,6 +139,12 @@ extension Converter {
     ) throws -> Data {
         let body = transform(value)
         headerFields.add(name: "content-type", value: body.contentType)
+        if let value = value as? _StringParameterConvertible {
+            guard let data = value.description.data(using: .utf8) else {
+                throw RuntimeError.failedToEncodePrimitiveBodyIntoData
+            }
+            return data
+        }
         return try encoder.encode(body.value)
     }
 

Sources/OpenAPIRuntime/Conversion/Converter+Server.swift

@@ -262,7 +262,18 @@ public extension Converter {
         guard let data else {
             return nil
         }
-        let decoded = try decoder.decode(type, from: data)
+        let decoded: T
+        if let myType = T.self as? _StringParameterConvertible.Type {
+            guard
+                let stringValue = String(data: data, encoding: .utf8),
+                let decodedValue = myType.init(stringValue)
+            else {
+                throw RuntimeError.failedToDecodePrimitiveBodyFromData
+            }
+            decoded = decodedValue as! T
+        } else {
+            decoded = try decoder.decode(type, from: data)
+        }
         return transform(decoded)
     }
 
@@ -297,7 +308,14 @@ public extension Converter {
     ) throws -> Data {
         let body = transform(value)
         headerFields.add(name: "content-type", value: body.contentType)
-        return try encoder.encode(body.value)
+        let bodyValue = body.value
+        if let value = bodyValue as? _StringParameterConvertible {
+            guard let data = value.description.data(using: .utf8) else {
+                throw RuntimeError.failedToEncodePrimitiveBodyIntoData
+            }
+            return data
+        }
+        return try encoder.encode(bodyValue)
     }
 
     // MARK: Body - Data

Sources/OpenAPIRuntime/Errors/RuntimeError.swift

@@ -36,6 +36,8 @@ internal enum RuntimeError: Error, CustomStringConvertible, LocalizedError, Pret
 
     // Body
     case missingRequiredRequestBody
+    case failedToEncodePrimitiveBodyIntoData
+    case failedToDecodePrimitiveBodyFromData
 
     // Transport/Handler
     case transportFailed(Error)
@@ -69,6 +71,10 @@ internal enum RuntimeError: Error, CustomStringConvertible, LocalizedError, Pret
             return "Failed to decode query parameter named '\(name)' to type \(type)."
         case .missingRequiredRequestBody:
             return "Missing required request body"
+        case .failedToEncodePrimitiveBodyIntoData:
+            return "Failed to encode a primitive body into data"
+        case .failedToDecodePrimitiveBodyFromData:
+            return "Failed to decode a primitive body from data"
         case .transportFailed(let underlyingError):
             return "Transport failed with error: \(underlyingError.localizedDescription)"
         case .handlerFailed(let underlyingError):

Tests/OpenAPIRuntimeTests/Conversion/Test_Converter+Client.swift

@@ -73,6 +73,24 @@ final class Test_ClientConverterExtensions: Test_Runtime {
         XCTAssertEqual(body, testStruct)
     }
 
+    func testBodyGetData_success() throws {
+        let body = try converter.bodyGet(
+            Data.self,
+            from: testStructData,
+            transforming: { $0 }
+        )
+        XCTAssertEqual(body, testStructData)
+    }
+
+    func testBodyGetString_success() throws {
+        let body = try converter.bodyGet(
+            String.self,
+            from: testStringData,
+            transforming: { $0 }
+        )
+        XCTAssertEqual(body, testString)
+    }
+
     func testBodyAddComplexOptional_success() throws {
         var headerFields: [HeaderField] = []
         let data = try converter.bodyAddOptional(
@@ -116,4 +134,68 @@ final class Test_ClientConverterExtensions: Test_Runtime {
             ]
         )
     }
+
+    func testBodyAddDataOptional_success() throws {
+        var headerFields: [HeaderField] = []
+        let data = try converter.bodyAddOptional(
+            testStructPrettyData,
+            headerFields: &headerFields,
+            transforming: { .init(value: $0, contentType: "application/octet-stream") }
+        )
+        XCTAssertEqual(data, testStructPrettyData)
+        XCTAssertEqual(
+            headerFields,
+            [
+                .init(name: "content-type", value: "application/octet-stream")
+            ]
+        )
+    }
+
+    func testBodyAddDataRequired_success() throws {
+        var headerFields: [HeaderField] = []
+        let data = try converter.bodyAddRequired(
+            testStructPrettyData,
+            headerFields: &headerFields,
+            transforming: { .init(value: $0, contentType: "application/octet-stream") }
+        )
+        XCTAssertEqual(data, testStructPrettyData)
+        XCTAssertEqual(
+            headerFields,
+            [
+                .init(name: "content-type", value: "application/octet-stream")
+            ]
+        )
+    }
+
+    func testBodyAddStringOptional_success() throws {
+        var headerFields: [HeaderField] = []
+        let data = try converter.bodyAddOptional(
+            testString,
+            headerFields: &headerFields,
+            transforming: { .init(value: $0, contentType: "text/plain") }
+        )
+        XCTAssertEqual(data, testStringData)
+        XCTAssertEqual(
+            headerFields,
+            [
+                .init(name: "content-type", value: "text/plain")
+            ]
+        )
+    }
+
+    func testBodyAddStringRequired_success() throws {
+        var headerFields: [HeaderField] = []
+        let data = try converter.bodyAddRequired(
+            testString,
+            headerFields: &headerFields,
+            transforming: { .init(value: $0, contentType: "text/plain") }
+        )
+        XCTAssertEqual(data, testStringData)
+        XCTAssertEqual(
+            headerFields,
+            [
+                .init(name: "content-type", value: "text/plain")
+            ]
+        )
+    }
 }

Tests/OpenAPIRuntimeTests/Conversion/Test_Converter+Server.swift

@@ -538,6 +538,38 @@ final class Test_ServerConverterExtensions: Test_Runtime {
         )
     }
 
+    func testBodyAddString() throws {
+        var headers: [HeaderField] = []
+        let data = try converter.bodyAdd(
+            testString,
+            headerFields: &headers,
+            transforming: { .init(value: $0, contentType: "text/plain") }
+        )
+        XCTAssertEqual(String(data: data, encoding: .utf8)!, testString)
+        XCTAssertEqual(
+            headers,
+            [
+                .init(name: "content-type", value: "text/plain")
+            ]
+        )
+    }
+
+    func testBodyAddData() throws {
+        var headers: [HeaderField] = []
+        let data = try converter.bodyAdd(
+            testStructPrettyData,
+            headerFields: &headers,
+            transforming: { .init(value: $0, contentType: "application/octet-stream") }
+        )
+        XCTAssertEqual(data, testStructPrettyData)
+        XCTAssertEqual(
+            headers,
+            [
+                .init(name: "content-type", value: "application/octet-stream")
+            ]
+        )
+    }
+
     func testBodyGetComplexOptional_success() throws {
         let body = try converter.bodyGetOptional(
             TestPet.self,
@@ -584,4 +616,40 @@ final class Test_ServerConverterExtensions: Test_Runtime {
             }
         )
     }
+
+    func testBodyGetDataOptional_success() throws {
+        let body = try converter.bodyGetOptional(
+            Data.self,
+            from: testStructPrettyData,
+            transforming: { $0 }
+        )
+        XCTAssertEqual(body, testStructPrettyData)
+    }
+
+    func testBodyGetDataRequired_success() throws {
+        let body = try converter.bodyGetOptional(
+            Data.self,
+            from: testStructPrettyData,
+            transforming: { $0 }
+        )
+        XCTAssertEqual(body, testStructPrettyData)
+    }
+
+    func testBodyGetStringOptional_success() throws {
+        let body = try converter.bodyGetOptional(
+            String.self,
+            from: testStringData,
+            transforming: { $0 }
+        )
+        XCTAssertEqual(body, testString)
+    }
+
+    func testBodyGetStringRequired_success() throws {
+        let body = try converter.bodyGetOptional(
+            String.self,
+            from: testStringData,
+            transforming: { $0 }
+        )
+        XCTAssertEqual(body, testString)
+    }
 }

Tests/OpenAPIRuntimeTests/Test_Runtime.swift

@@ -54,6 +54,14 @@ class Test_Runtime: XCTestCase {
         "2023-01-18T10:04:11Z"
     }
 
+    var testString: String {
+        "hello"
+    }
+
+    var testStringData: Data {
+        "hello".data(using: .utf8)!
+    }
+
     var testStruct: TestPet {
         .init(name: "Fluffz")
     }