Simplify else branch if it only has a single if (#666) (#726)

* Simplify `else` branch if it only has a single `if` (#666)

* Update License to MSAL

Co-authored-by: Tim te Beek <[email protected]>

* Update License to MSAL

Co-authored-by: Tim te Beek <[email protected]>

* Polish

* Verify handling of somewhat exotic newline placement

* Add placeholder to enable recipe once we've seen it at scale

---------

Co-authored-by: Tim te Beek <[email protected]>
Co-authored-by: Tim te Beek <[email protected]>

Author: olwispe

src/main/java/org/openrewrite/staticanalysis/SimplifyElseBranch.java

@@ -0,0 +1,66 @@
+/*
+ * Copyright 2025 the original author or authors.
+ * <p>
+ * Licensed under the Moderne Source Available License (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ * <p>
+ * https://docs.moderne.io/licensing/moderne-source-available-license
+ * <p>
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.openrewrite.staticanalysis;
+
+import org.openrewrite.ExecutionContext;
+import org.openrewrite.Recipe;
+import org.openrewrite.internal.ListUtils;
+import org.openrewrite.java.JavaIsoVisitor;
+import org.openrewrite.java.tree.J;
+import org.openrewrite.java.tree.Space;
+import org.openrewrite.java.tree.Statement;
+
+import static org.openrewrite.java.format.ShiftFormat.indent;
+
+public class SimplifyElseBranch extends Recipe {
+
+    @Override
+    public String getDisplayName() {
+        // language=markdown
+        return "Simplify `else` branch if it only has a single `if`";
+    }
+
+    @Override
+    public String getDescription() {
+        // language=markdown
+        return "Simplify `else` branch if it only has a single `if`.";
+    }
+
+    @Override
+    public JavaIsoVisitor<ExecutionContext> getVisitor() {
+        return new JavaIsoVisitor<ExecutionContext>() {
+            @Override
+            public J.If.Else visitElse(J.If.Else else_, ExecutionContext ctx) {
+                J.If.Else elseStatement = super.visitElse(else_, ctx);
+                Statement body = elseStatement.getBody();
+                if (body instanceof J.Block) {
+                    J.Block block = (J.Block) body;
+                    if (block.getStatements().size() == 1) {
+                        Statement firstStatement = block.getStatements().get(0);
+                        if (firstStatement instanceof J.If) {
+                            // Combine comments from the block and the if statement
+                            J.If ifStatement = firstStatement
+                                    .withPrefix(Space.SINGLE_SPACE)
+                                    .withComments(ListUtils.concatAll(block.getComments(), firstStatement.getComments()));
+                            return elseStatement.withBody(indent(ifStatement, getCursor(), -1));
+                        }
+                    }
+                }
+                return elseStatement;
+            }
+        };
+    }
+}

src/main/resources/META-INF/rewrite/common-static-analysis.yml

@@ -84,6 +84,7 @@ recipeList:
   - org.openrewrite.staticanalysis.SimplifyArraysAsList
   - org.openrewrite.staticanalysis.SimplifyBooleanExpression
   - org.openrewrite.staticanalysis.SimplifyBooleanReturn
+#  - org.openrewrite.staticanalysis.SimplifyElseBranch # TODO Add once we've tried this out at scale
 #  - org.openrewrite.staticanalysis.SimplifyTernaryRecipes
   - org.openrewrite.staticanalysis.StaticMethodNotFinal
   - org.openrewrite.staticanalysis.StringLiteralEquality