Preserve statement order in UseTryWithResources (#866)

Refuse to merge a `close()` into try-with-resources when non-close
statements precede it in the finally block. Try-with-resources runs the
auto-close before the finally, so those statements would otherwise move
from before to after the close, changing semantics.

Author: timtebeek

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

@@ -306,10 +306,18 @@ private static boolean isReassignedBetween(String varName, List<Statement> stmts
     }
 
     private static boolean finallyContainsClose(J.Block finallyBlock, String varName) {
+        // The target close must be reachable without any non-close statements before it.
+        // Try-with-resources closes the resource before the finally block runs, so any
+        // statement that originally ran before the close in the finally would otherwise
+        // run after it. Other close statements (for variables that will also be merged
+        // into the try-with-resources) are tolerated.
         for (Statement stmt : finallyBlock.getStatements()) {
             if (isCloseStatement(stmt, varName)) {
                 return true;
             }
+            if (extractVarNameFromCloseStatement(stmt) == null) {
+                return false;
+            }
         }
         return false;
     }

src/test/java/org/openrewrite/staticanalysis/UseTryWithResourcesTest.java

@@ -17,6 +17,7 @@
 
 import org.junit.jupiter.api.Test;
 import org.openrewrite.DocumentExample;
+import org.openrewrite.Issue;
 import org.openrewrite.test.RecipeSpec;
 import org.openrewrite.test.RewriteTest;
 
@@ -343,7 +344,7 @@ void method() throws IOException {
     }
 
     @Test
-    void finallyWithExtraLogicKeepsRemainingStatements() {
+    void finallyWithExtraLogicAfterCloseKeepsRemainingStatements() {
         rewriteRun(
           //language=java
           java(
@@ -356,8 +357,8 @@ void method() throws IOException {
                       try {
                           int data = in.read();
                       } finally {
-                          System.out.println("closing");
                           in.close();
+                          System.out.println("closed");
                       }
                   }
               }
@@ -369,8 +370,62 @@ class Test {
                   void method() throws IOException {
                       try (InputStream in = new FileInputStream("file.txt")) {
                           int data = in.read();
+                      } finally {
+                          System.out.println("closed");
+                      }
+                  }
+              }
+              """
+          )
+        );
+    }
+
+    @Test
+    @Issue("https://github.com/moderneinc/rewrite-java-application-server/issues/19")
+    void doNotChangeWhenStatementsBeforeClose() {
+        rewriteRun(
+          //language=java
+          java(
+            """
+              import java.io.*;
+
+              class Test {
+                  void method() throws IOException {
+                      InputStream in = new FileInputStream("file.txt");
+                      try {
+                          int data = in.read();
                       } finally {
                           System.out.println("closing");
+                          in.close();
+                      }
+                  }
+              }
+              """
+          )
+        );
+    }
+
+    @Test
+    @Issue("https://github.com/moderneinc/rewrite-java-application-server/issues/19")
+    void doNotChangeWhenCleanupBeforeClose() {
+        rewriteRun(
+          //language=java
+          java(
+            """
+              import java.io.*;
+
+              class Test {
+                  interface CancellationTokenSource {
+                      void cancel();
+                  }
+
+                  void method(CancellationTokenSource cancellation) throws IOException {
+                      InputStream in = new FileInputStream("file.txt");
+                      try {
+                          int data = in.read();
+                      } finally {
+                          cancellation.cancel();
+                          in.close();
                       }
                   }
               }