Fail Macro Expansion if JavaStaticField is used in non-class (#174)

Author: jrosen081

Sources/JavaKitMacros/JavaFieldMacro.swift

@@ -33,6 +33,11 @@ extension JavaFieldMacro: AccessorMacro {
       return []
     }
 
+    let isStatic = node.attributeName.trimmedDescription == "JavaStaticField"
+    guard !isStatic || isInJavaClassContext(context: context) else {
+      throw MacroExpansionErrorMessage("Cannot use @JavaStaticField outside of a JavaClass instance")
+    }
+
     // Dig out the Java field name, if provided. Otherwise, use the name as written.
     let fieldName =
       if case .argumentList(let arguments) = node.arguments,
@@ -79,4 +84,14 @@ extension JavaFieldMacro: AccessorMacro {
 
     return accessors
   }
+
+  private static func isInJavaClassContext(context: some MacroExpansionContext) -> Bool {
+    for lexicalContext in context.lexicalContext {
+      if let classSyntax = lexicalContext.as(ExtensionDeclSyntax.self) {
+        return classSyntax.extendedType.trimmedDescription.starts(with: "JavaClass")
+      }
+    }
+
+    return false
+  }
 }

Tests/JavaKitMacroTests/JavaClassMacroTests.swift

@@ -23,9 +23,64 @@ class JavaKitMacroTests: XCTestCase {
   static let javaKitMacros: [String: any Macro.Type] = [
     "JavaClass": JavaClassMacro.self,
     "JavaMethod": JavaMethodMacro.self,
-    "JavaField": JavaFieldMacro.self
+    "JavaField": JavaFieldMacro.self,
+    "JavaStaticField": JavaFieldMacro.self
   ]
 
+  func testJavaStaticMethodFailure() throws {
+    assertMacroExpansion(
+      """
+        @JavaClass("org.swift.example.HelloWorld")
+        public class HelloWorld {
+          @JavaStaticField
+          public var test: String
+        }
+      """,
+      expandedSource: """
+      
+        public class HelloWorld {
+          public var test: String
+      
+            /// The full Java class name for this Swift type.
+            open override class var fullJavaClassName: String {
+                "org.swift.example.HelloWorld"
+            }
+      
+            public required init(javaHolder: JavaObjectHolder) {
+                super.init(javaHolder: javaHolder)
+            }
+        }
+      """,
+      diagnostics: [DiagnosticSpec(message: "Cannot use @JavaStaticField outside of a JavaClass instance", line: 3, column: 5)],
+      macros: Self.javaKitMacros
+    )
+  }
+
+  func testJavaStaticMethodSuccess() throws {
+    assertMacroExpansion(
+      """
+        extension JavaClass<HelloWorld> {
+          @JavaStaticField
+          public var test: String
+        }
+      """,
+      expandedSource: """
+      
+        extension JavaClass<HelloWorld> {
+          public var test: String {
+              get {
+                  self[javaFieldName: "test", fieldType: String.self]
+              }
+              set {
+                  self[javaFieldName: "test", fieldType: String.self] = newValue
+              }
+          }
+        }
+      """,
+      macros: Self.javaKitMacros
+    )
+  }
+
   func testJavaClass() throws {
     assertMacroExpansion("""
         @JavaClass("org.swift.example.HelloWorld")