Add tests inspired by errorprone/bugpatterns/DirectReturnTest.java

Author: timtebeek

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

@@ -396,4 +396,264 @@ String getString() {
           )
         );
     }
+
+    @Test
+    void inlineAssignmentToParameter() {
+        rewriteRun(
+          //language=java
+          java(
+            """
+              class Test {
+                  String test(String param) {
+                      param = toString();
+                      return param;
+                  }
+              }
+              """,
+            """
+              class Test {
+                  String test(String param) {
+                      return toString();
+                  }
+              }
+              """
+          )
+        );
+    }
+
+    @Test
+    void inlineMultipleAssignmentsBeforeReturn() {
+        rewriteRun(
+          //language=java
+          java(
+            """
+              class Test {
+                  String test() {
+                      String variable = null;
+                      variable = toString();
+                      return variable;
+                  }
+              }
+              """,
+            """
+              class Test {
+                  String test() {
+                      String variable = null;
+                      return toString();
+                  }
+              }
+              """
+          )
+        );
+    }
+
+    @Test
+    void inlineAssignmentWithMethodCall() {
+        rewriteRun(
+          //language=java
+          java(
+            """
+              class Test {
+                  String spy() { return "spy"; }
+
+                  String test() {
+                      String variable = spy();
+                      return variable;
+                  }
+              }
+              """,
+            """
+              class Test {
+                  String spy() { return "spy"; }
+
+                  String test() {
+                      return spy();
+                  }
+              }
+              """
+          )
+        );
+    }
+
+    @Test
+    void inlineAssignmentInElseBlockWhilePreservingIfBlock() {
+        rewriteRun(
+          //language=java
+          java(
+            """
+              class Test {
+                  String test(boolean condition) {
+                      String variable = toString();
+                      if (condition) {
+                          return variable;
+                      } else {
+                          variable = "foo";
+                          return variable;
+                      }
+                  }
+              }
+              """,
+            """
+              class Test {
+                  String test(boolean condition) {
+                      String variable = toString();
+                      if (condition) {
+                          return variable;
+                      } else {
+                          return "foo";
+                      }
+                  }
+              }
+              """
+          )
+        );
+    }
+
+    @Test
+    void inlineVariableInElseBlock() {
+        rewriteRun(
+          //language=java
+          java(
+            """
+              class Test {
+                  String test(boolean condition) {
+                      if (condition) {
+                          return "bar";
+                      } else {
+                          String variable = "foo";
+                          return variable;
+                      }
+                  }
+              }
+              """,
+            """
+              class Test {
+                  String test(boolean condition) {
+                      if (condition) {
+                          return "bar";
+                      } else {
+                          return "foo";
+                      }
+                  }
+              }
+              """
+          )
+        );
+    }
+
+    @Test
+    void inlineAssignmentInTryBlock() {
+        rewriteRun(
+          //language=java
+          java(
+            """
+              class Test {
+                  String test() {
+                      try {
+                          String result = someMethod();
+                          return result;
+                      } catch (Exception e) {
+                          return null;
+                      }
+                  }
+
+                  String someMethod() throws Exception {
+                      return "value";
+                  }
+              }
+              """,
+            """
+              class Test {
+                  String test() {
+                      try {
+                          return someMethod();
+                      } catch (Exception e) {
+                          return null;
+                      }
+                  }
+
+                  String someMethod() throws Exception {
+                      return "value";
+                  }
+              }
+              """
+          )
+        );
+    }
+
+    @Test
+    void inlineVariableWithCast() {
+        rewriteRun(
+          //language=java
+          java(
+            """
+              class Test {
+                  Object test() {
+                      String str = (String) getObject();
+                      return str;
+                  }
+
+                  Object getObject() {
+                      return "string";
+                  }
+              }
+              """,
+            """
+              class Test {
+                  Object test() {
+                      return (String) getObject();
+                  }
+
+                  Object getObject() {
+                      return "string";
+                  }
+              }
+              """
+          )
+        );
+    }
+
+    @Test
+    void inlineVariableWithTernary() {
+        rewriteRun(
+          //language=java
+          java(
+            """
+              class Test {
+                  String test(boolean flag) {
+                      String result = flag ? "yes" : "no";
+                      return result;
+                  }
+              }
+              """,
+            """
+              class Test {
+                  String test(boolean flag) {
+                      return flag ? "yes" : "no";
+                  }
+              }
+              """
+          )
+        );
+    }
+
+    @Test
+    void doNotInlineWhenVariableIsReassigned() {
+        rewriteRun(
+          //language=java
+          java(
+            """
+              class Test {
+                  String test(boolean condition) {
+                      String result = "initial";
+                      if (condition) {
+                          result = "changed";
+                      }
+                      return result;
+                  }
+              }
+              """
+          )
+        );
+    }
 }