Guard UseJavaUtilBase64 from making changes when another "Base64" class is already present

Author: sambsnyd

src/main/java/org/openrewrite/java/migrate/UseJavaUtilBase64.java

@@ -22,8 +22,11 @@
 import org.openrewrite.java.search.UsesType;
 import org.openrewrite.java.tree.J;
 import org.openrewrite.java.tree.JavaSourceFile;
+import org.openrewrite.java.tree.JavaType;
+import org.openrewrite.marker.Markup;
 
 import java.util.Base64;
+import java.util.Objects;
 
 public class UseJavaUtilBase64 extends Recipe {
     private final String sunPackage;
@@ -79,6 +82,21 @@ protected JavaVisitor<ExecutionContext> getVisitor() {
                     .imports("java.util.Base64")
                     .build();
 
+            @Override
+            public J visitJavaSourceFile(JavaSourceFile cu, ExecutionContext ctx) {
+                if(alreadyUsingIncompatibleBase64(cu)) {
+                    return Markup.warn(cu, new IllegalStateException(
+                            "Already using a class named Base64 other than java.util.Base64. Manual intervention required."));
+                }
+                JavaSourceFile c = (JavaSourceFile) super.visitJavaSourceFile(cu, ctx);
+
+                c = (J.CompilationUnit) new ChangeType(sunPackage + ".BASE64Encoder", "java.util.Base64$Encoder", true)
+                        .getVisitor().visitNonNull(c, ctx);
+                c = (J.CompilationUnit) new ChangeType(sunPackage + ".BASE64Decoder", "java.util.Base64$Decoder", true)
+                        .getVisitor().visitNonNull(c, ctx);
+                return c;
+            }
+
             @Override
             public J visitMethodInvocation(J.MethodInvocation method, ExecutionContext ctx) {
                 J.MethodInvocation m = (J.MethodInvocation) super.visitMethodInvocation(method, ctx);
@@ -101,18 +119,6 @@ public J visitMethodInvocation(J.MethodInvocation method, ExecutionContext ctx)
                 return m;
             }
 
-            @Override
-            public J visitJavaSourceFile(JavaSourceFile cu, ExecutionContext ctx) {
-
-                JavaSourceFile c = (JavaSourceFile) super.visitJavaSourceFile(cu, ctx);
-
-                c = (J.CompilationUnit) new ChangeType(sunPackage + ".BASE64Encoder", "java.util.Base64$Encoder", true)
-                        .getVisitor().visitNonNull(c, ctx);
-                c = (J.CompilationUnit) new ChangeType(sunPackage + ".BASE64Decoder", "java.util.Base64$Decoder", true)
-                        .getVisitor().visitNonNull(c, ctx);
-                return c;
-            }
-
             @Override
             public J visitNewClass(J.NewClass newClass, ExecutionContext ctx) {
                 J.NewClass c = (J.NewClass) super.visitNewClass(newClass, ctx);
@@ -130,4 +136,14 @@ public J visitNewClass(J.NewClass newClass, ExecutionContext ctx) {
             }
         };
     }
+
+    private boolean alreadyUsingIncompatibleBase64(JavaSourceFile cu) {
+        return cu.getClasses().stream().anyMatch(it -> "Base64".equals(it.getSimpleName())) ||
+               cu.getTypesInUse().getTypesInUse().stream()
+                .filter(it -> it instanceof JavaType.FullyQualified)
+                .map(JavaType.FullyQualified.class::cast)
+                .map(JavaType.FullyQualified::getFullyQualifiedName)
+                .filter(it -> !"java.util.Base64".equals(it))
+                .anyMatch(it -> it.endsWith(".Base64"));
+    }
 }

src/test/java/org/openrewrite/java/migrate/UseJavaUtilBase64Test.java

@@ -17,6 +17,7 @@
 
 import org.junit.jupiter.api.Test;
 
+import org.openrewrite.Issue;
 import org.openrewrite.java.JavaParser;
 import org.openrewrite.test.RecipeSpec;
 import org.openrewrite.test.RewriteTest;
@@ -29,6 +30,7 @@ public class UseJavaUtilBase64Test implements RewriteTest {
     public void defaults(RecipeSpec spec) {
         spec.recipe(new UseJavaUtilBase64("test.sun.misc"))
           .parser(JavaParser.fromJavaVersion()
+            .logCompilationWarningsAndErrors(true)
             //language=java
             .dependsOn(
               """
@@ -168,4 +170,36 @@ void test(byte[] bBytes) {
           )
         );
     }
+
+    @Issue("https://github.com/openrewrite/rewrite-migrate-java/issues/212")
+    @Test
+    void otherBase64() {
+        //language=java
+        rewriteRun(
+          java("""
+              package test.sun.misc;
+              
+              public class App {
+                  public static void main(String[] args) {
+                      String encode = new BASE64Encoder().encode(new byte[16]);
+                  }
+              }
+              
+              class Base64 {
+              }
+              """,
+            """
+              /*~~(Already using a class named Base64 other than java.util.Base64. Manual intervention required.)~~>*/package test.sun.misc;
+              
+              public class App {
+                  public static void main(String[] args) {
+                      String encode = new BASE64Encoder().encode(new byte[16]);
+                  }
+              }
+              
+              class Base64 {
+              }
+              """)
+        );
+    }
 }