Fix reading first enum case and add tests

Author: Alexander Schmutz

Sources/StructBuilderClient/main.swift

@@ -36,5 +36,6 @@ struct MyObject {
 
 @Buildable
 enum MyEnum {
+    case `none`
     case myCase
 }

Sources/StructBuilderMacro/Enum/Helper/GetFirstEnumCaseName.swift

@@ -8,7 +8,8 @@
 import SwiftSyntax
 
 func getFirstEnumCaseName(from enumDecl: EnumDeclSyntax) throws -> TokenSyntax {
-    guard let firstCaseName = enumDecl.memberBlock.members.first?.decl.as(EnumCaseDeclSyntax.self)?.elements.first?.name else {
+    let enumCaseDecls = enumDecl.memberBlock.members.compactMap { $0.decl.as(EnumCaseDeclSyntax.self) }
+    guard let firstCaseName = enumCaseDecls.first?.elements.first?.name else {
         throw "Missing enum case"
     }
     return firstCaseName

Tests/StructBuilderMacroTests/BuildableEnumTests.swift

@@ -35,5 +35,117 @@ class BuildableEnumTests: XCTestCase {
             macros: testMacros
         )
     }
+
+    func test_should_set_first_enum_case_as_default_value() {
+        assertMacroExpansion(
+            """
+            @Buildable
+            enum MyEnum {
+                case myCase, mySecondCase
+            }
+            """,
+            expandedSource: """
+
+            enum MyEnum {
+                case myCase, mySecondCase
+            }
+
+            struct MyEnumBuilder {
+                var value: MyEnum = .myCase
+
+                func build() -> MyEnum {
+                    return value
+                }
+            }
+
+            """,
+            macros: testMacros
+        )
+    }
+
+    func test_should_set_first_enum_case_as_default_value_when_enum_has_rawvalue() {
+        assertMacroExpansion(
+            """
+            @Buildable
+            enum MyEnum: String {
+                case myCase = "a"
+                case mySecondCase = "b"
+            }
+            """,
+            expandedSource: """
+
+            enum MyEnum: String {
+                case myCase = "a"
+                case mySecondCase = "b"
+            }
+
+            struct MyEnumBuilder {
+                var value: MyEnum = .myCase
+
+                func build() -> MyEnum {
+                    return value
+                }
+            }
+
+            """,
+            macros: testMacros
+        )
+    }
+
+    func test_should_set_first_enum_case_as_default_value_when_identifier_uses_special_keyword() {
+        assertMacroExpansion(
+            """
+            @Buildable
+            enum MyEnum {
+                case `none`
+            }
+            """,
+            expandedSource: """
+
+            enum MyEnum {
+                case `none`
+            }
+
+            struct MyEnumBuilder {
+                var value: MyEnum = .`none`
+
+                func build() -> MyEnum {
+                    return value
+                }
+            }
+
+            """,
+            macros: testMacros
+        )
+    }
+
+    func test_should_set_first_enum_case_as_default_value_when_first_enum_member_is_no_case_declaration() {
+        assertMacroExpansion(
+            """
+            @Buildable
+            enum MyEnum {
+                var someVariable: String? { nil }
+                case myCase
+            }
+            """,
+            expandedSource: """
+
+            enum MyEnum {
+                var someVariable: String? { nil }
+                case myCase
+            }
+
+            struct MyEnumBuilder {
+                var value: MyEnum = .myCase
+
+                func build() -> MyEnum {
+                    return value
+                }
+            }
+
+            """,
+            macros: testMacros
+        )
+    }
 }