Support custom JSON coders (vapor#127)

* Support non Foundation JSON coders

* add a `PostgresJSONEncoder` protocol with an API that mirrors the Foundation `JSONEncoder`'s decoding function

* add global `_defaultJSONEncoder` variable used in the JSON and JSONB type and that is defaulted to a Foundation `JSONEncoder`

* add a `PostgresJSONDecoder` protocol with an API that mirrors the Foundation `JSONDecoder`'s decoding function

* add global `_defaultJSONDecoder` variable used in the JSON and JSONB type and that is defaulted to a Foundation `JSONDecoder`

* Add docblocks for _defaultJSON{encoder,decoder} and their respective unit tests

Author: jordanebelanger

Diff for: Sources/PostgresNIO/Data/PostgresData+JSON.swift

@@ -11,7 +11,7 @@ extension PostgresData {
     }
 
     public init<T>(json value: T) throws where T: Encodable {
-        let jsonData = try JSONEncoder().encode(value)
+        let jsonData = try PostgresNIO._defaultJSONEncoder.encode(value)
         self.init(json: jsonData)
     }
 
@@ -32,7 +32,7 @@ extension PostgresData {
         guard let data = self.json else {
             return nil
         }
-        return try JSONDecoder().decode(T.self, from: data)
+        return try PostgresNIO._defaultJSONDecoder.decode(T.self, from: data)
     }
 }
 

Diff for: Sources/PostgresNIO/Data/PostgresData+JSONB.swift

@@ -15,7 +15,7 @@ extension PostgresData {
     }
 
     public init<T>(jsonb value: T) throws where T: Encodable {
-        let jsonData = try JSONEncoder().encode(value)
+        let jsonData = try PostgresNIO._defaultJSONEncoder.encode(value)
         self.init(jsonb: jsonData)
     }
 
@@ -43,7 +43,7 @@ extension PostgresData {
             return nil
         }
 
-        return try JSONDecoder().decode(T.self, from: data)
+        return try PostgresNIO._defaultJSONDecoder.decode(T.self, from: data)
     }
 }
 

Diff for: Sources/PostgresNIO/Utilities/PostgresJSONDecoder.swift

@@ -0,0 +1,16 @@
+import Foundation
+
+/// A protocol that mimmicks the Foundation `JSONDecoder.decode(_:from:)` function.
+/// Conform a non-Foundation JSON decoder to this protocol if you want PostgresNIO to be
+/// able to use it when decoding JSON & JSONB values (see `PostgresNIO._defaultJSONDecoder`)
+public protocol PostgresJSONDecoder {
+    func decode<T>(_ type: T.Type, from data: Data) throws -> T where T : Decodable
+}
+
+extension JSONDecoder: PostgresJSONDecoder {}
+
+/// The default JSON decoder used by PostgresNIO when decoding JSON & JSONB values.
+/// As `_defaultJSONDecoder` will be reused for decoding all JSON & JSONB values
+/// from potentially multiple threads at once, you must ensure your custom JSON decoder is
+/// thread safe internally like `Foundation.JSONDecoder`.
+public var _defaultJSONDecoder: PostgresJSONDecoder = JSONDecoder()

Diff for: Sources/PostgresNIO/Utilities/PostgresJSONEncoder.swift

@@ -0,0 +1,16 @@
+import Foundation
+
+/// A protocol that mimmicks the Foundation `JSONEncoder.encode(_:)` function.
+/// Conform a non-Foundation JSON encoder to this protocol if you want PostgresNIO to be
+/// able to use it when encoding JSON & JSONB values (see `PostgresNIO._defaultJSONEncoder`)
+public protocol PostgresJSONEncoder {
+    func encode<T>(_ value: T) throws -> Data where T : Encodable
+}
+
+extension JSONEncoder: PostgresJSONEncoder {}
+
+/// The default JSON encoder used by PostgresNIO when encoding JSON & JSONB values.
+/// As `_defaultJSONEncoder` will be reused for encoding all JSON & JSONB values
+/// from potentially multiple threads at once, you must ensure your custom JSON encoder is
+/// thread safe internally like `Foundation.JSONEncoder`.
+public var _defaultJSONEncoder: PostgresJSONEncoder = JSONEncoder()

Diff for: Tests/PostgresNIOTests/PostgresNIOTests.swift

@@ -1004,6 +1004,62 @@ final class PostgresNIOTests: XCTestCase {
         XCTAssertEqual(rows[0].column("min64")?.int64, .min)
         XCTAssertEqual(rows[0].column("max64")?.int64, .max)
     }
+    
+    // https://github.com/vapor/postgres-nio/issues/126
+    func testCustomJSONEncoder() throws {
+        let previousDefaultJSONEncoder = PostgresNIO._defaultJSONEncoder
+        defer {
+            PostgresNIO._defaultJSONEncoder = previousDefaultJSONEncoder
+        }
+        final class CustomJSONEncoder: PostgresJSONEncoder {
+            var didEncode = false
+            func encode<T>(_ value: T) throws -> Data where T : Encodable {
+                self.didEncode = true
+                return try JSONEncoder().encode(value)
+            }
+        }
+        struct Object: Codable {
+            var foo: Int
+            var bar: Int
+        }
+        let customJSONEncoder = CustomJSONEncoder()
+        PostgresNIO._defaultJSONEncoder = customJSONEncoder
+        let _ = try PostgresData(json: Object(foo: 1, bar: 2))
+        XCTAssert(customJSONEncoder.didEncode)
+        
+        let customJSONBEncoder = CustomJSONEncoder()
+        PostgresNIO._defaultJSONEncoder = customJSONBEncoder
+        let _ = try PostgresData(jsonb: Object(foo: 1, bar: 2))
+        XCTAssert(customJSONBEncoder.didEncode)
+    }
+    
+    // https://github.com/vapor/postgres-nio/issues/126
+    func testCustomJSONDecoder() throws {
+        let previousDefaultJSONDecoder = PostgresNIO._defaultJSONDecoder
+        defer {
+            PostgresNIO._defaultJSONDecoder = previousDefaultJSONDecoder
+        }
+        final class CustomJSONDecoder: PostgresJSONDecoder {
+            var didDecode = false
+            func decode<T>(_ type: T.Type, from data: Data) throws -> T where T : Decodable {
+                self.didDecode = true
+                return try JSONDecoder().decode(type, from: data)
+            }
+        }
+        struct Object: Codable {
+            var foo: Int
+            var bar: Int
+        }
+        let customJSONDecoder = CustomJSONDecoder()
+        PostgresNIO._defaultJSONDecoder = customJSONDecoder
+        let _ = try PostgresData(json: Object(foo: 1, bar: 2)).json(as: Object.self)
+        XCTAssert(customJSONDecoder.didDecode)
+        
+        let customJSONBDecoder = CustomJSONDecoder()
+        PostgresNIO._defaultJSONDecoder = customJSONBDecoder
+        let _ = try PostgresData(json: Object(foo: 1, bar: 2)).json(as: Object.self)
+        XCTAssert(customJSONBDecoder.didDecode)
+    }
 }
 
 func env(_ name: String) -> String? {