fix: use self-closing tags when children are implictly hidden

Sources/XMLCoder/Auxiliaries/XMLCoderElement.swift

@@ -36,6 +36,11 @@ struct XMLCoderElement: Equatable, Sendable {
         return key.isEmpty
     }
 
+    private var isPracticallyEmpty: Bool {
+        guard stringValue == nil else { return false }
+        return elements.allSatisfy { $0.key.isEmpty && $0.isPracticallyEmpty }
+    }
+
     init(
         key: String,
         elements: [XMLCoderElement] = [],
@@ -313,7 +318,7 @@ struct XMLCoderElement: Equatable, Sendable {
             formatXMLAttributes(formatting, &string, escapedCharacters.attributes)
         }
 
-        if !elements.isEmpty || formatting.contains(.noEmptyElements) {
+        if !isPracticallyEmpty || formatting.contains(.noEmptyElements) {
             let hasOnlyIntrinsicContent = elements.allSatisfy { element in
                 element.key.isEmpty && !element.elements.contains { !$0.key.isEmpty }
             }

Tests/XMLCoderTests/AdvancedFeatures/InlinePropertyTests.swift

@@ -15,22 +15,25 @@ import XCTest
 private enum InlineChoice: Equatable, Codable {
     case simple(Nested1)
     case nested(Nested1, labeled: Nested2)
-
+    case attributesOnly(AttributesOnly)
+
     enum CodingKeys: String, CodingKey, XMLChoiceCodingKey {
-        case simple, nested
+        case simple, nested, attributesOnly
     }
-    
+
     enum SimpleCodingKeys: String, CodingKey { case _0 = "" }
-    
+
     enum NestedCodingKeys: String, CodingKey {
         case _0 = ""
         case labeled
     }
-
+
+    enum AttributesOnlyCodingKeys: String, CodingKey { case _0 = "" }
+
     struct Nested1: Equatable, Codable, DynamicNodeEncoding {
         var attr = "n1_a1"
         var val = "n1_v1"
-        
+
         public static func nodeEncoding(for key: CodingKey) -> XMLEncoder.NodeEncoding {
             switch key {
             case CodingKeys.attr: return .attribute
@@ -42,6 +45,18 @@ private enum InlineChoice: Equatable, Codable {
     struct Nested2: Equatable, Codable {
         var val = "n2_val"
     }
+
+    struct AttributesOnly: Equatable, Codable, DynamicNodeEncoding {
+        var name = "attr"
+
+        enum CodingKeys: String, CodingKey {
+            case name = "Name"
+        }
+
+        public static func nodeEncoding(for key: CodingKey) -> XMLEncoder.NodeEncoding {
+            return .attribute
+        }
+    }
 }
 
 final class InlinePropertyTests: XCTestCase {
@@ -75,9 +90,12 @@ final class InlinePropertyTests: XCTestCase {
         encoder.outputFormatting = .prettyPrinted
         encoder.prettyPrintIndentation = .spaces(4)
 
-        let original: [InlineChoice] = [.nested(.init(), labeled: .init()), .simple(.init())]
+        let original: [InlineChoice] = [
+            .nested(.init(), labeled: .init()),
+            .simple(.init()),
+            .attributesOnly(.init())
+        ]
         let encoded = try encoder.encode(original, withRootKey: "container")
-        print(String(data: encoded, encoding: .utf8)!)
         XCTAssertEqual(
             String(data: encoded, encoding: .utf8),
             """
@@ -91,6 +109,7 @@ final class InlinePropertyTests: XCTestCase {
                 <simple attr="n1_a1">
                     <val>n1_v1</val>
                 </simple>
+                <attributesOnly Name="attr" />
             </container>
             """
         )

Tests/XMLCoderTests/Auxiliary/XMLElementTests.swift

@@ -94,7 +94,7 @@ class XMLElementTests: XCTestCase {
         )
 
         XCTAssertEqual(result, """
-        <Input xmlns="https://example.com"><Nested xmlns:xsi="https://example.com" xsi:someName="nestedAttrValue"></Nested></Input>
+        <Input xmlns="https://example.com"><Nested xmlns:xsi="https://example.com" xsi:someName="nestedAttrValue" /></Input>
         """)
     }