error: MigrateCollectionsSingletonList recipe error

[kunli2]

Got this error when running recipe org.openrewrite.java.migrate.UpgradeToJava17 on repo https://github.com/spring-projects/spring-amqp

Error:

		connectionFactory.setConnectionListeners(Collections.singletonList(new ConnectionListener() {
			@Override
			public void onCreate(Connection connection) {
@ -79,7 +79,7 @@
				called.decrementAndGet();
			}
		})

Message:

Expected a template that would generate exactly one statement to replace one statement, but generated 2. Template:
List.of(__P__.<org.springframework.amqp.rabbit.connection.AbstractConnectionFactoryTests.1>/*__p0__*/p())

Detail:

java.lang.IllegalArgumentException: Expected a template that would generate exactly one statement to replace one statement, but generated 2. Template:
List.of(__P__.<org.springframework.amqp.rabbit.connection.AbstractConnectionFactoryTests.1>/*__p0__*/p())
org.openrewrite.java.internal.template.JavaTemplateJavaExtension$1.maybeReplaceStatement(JavaTemplateJavaExtension.java:462)
org.openrewrite.java.internal.template.JavaTemplateJavaExtension$1.visitMethodInvocation(JavaTemplateJavaExtension.java:428)
org.openrewrite.java.internal.template.JavaTemplateJavaExtension$1.visitMethodInvocation(JavaTemplateJavaExtension.java:59)
org.openrewrite.java.tree.J$MethodInvocation.acceptJava(J.java:3700)
org.openrewrite.java.tree.J.accept(J.java:64)
org.openrewrite.TreeVisitor.visit(TreeVisitor.java:276)
org.openrewrite.TreeVisitor.visit(TreeVisitor.java:172)
org.openrewrite.java.JavaTemplate.withTemplate(JavaTemplate.java:107)
...

[kunli2]

root cause

Source code

setConnectionListeners(Collections.singletonList(new ConnectionListener() {
         @Override
         public void onCreate() {
         }
     }));

this is the stub generated by BlockStatementTemplateGenerator.

class A {
    public void setConnectionListeners(List<? extends ConnectionListener> listeners) {
    }

    public void test() {
        __M__.any(
            /*__TEMPLATE__*/List.of(__P__.<A .1 >/*__p0__*/p())/*__TEMPLATE_STOP__*/
);
    }
}

since in the source, there is no assignment, the generic type of __P__ is not determined, and the code doesn't compile.

The stop comment is not able to be captured since it's somewhere before the target statement, so the order is the visitor caught /*__TEMPLATE_STOP__*/ first, and then caught /*__TEMPLATE__*/ (see the position in the tree below), the order is reversed than expected, and seems it's impossible to support this in current solution framework.

\---J.ClassDeclaration
    |---J.Identifier | "A"
    \---J.Block
        |-------J.MethodDeclaration | "MethodDeclaration{A{name=setConnectionListeners,return=void,parameters=[java.util.List<Generic{? extends {undefined}}..."
        |       |---J.Modifier | "public"
        |       |---J.Primitive | "void"
        |       |---J.Identifier | "setConnectionListeners"
        |       |-----------J.VariableDeclarations | "List<? extends ConnectionListener> listeners"
        |       |           |---J.ParameterizedType | "List<? extends ConnectionListener>"
        |       |           |   |---J.Identifier | "List"
        |       |           |   \-----------J.Wildcard | "? extends ConnectionListener"
        |       |           |               \---J.Identifier | "ConnectionListener"
        |       |           \-------J.VariableDeclarations.NamedVariable | "listeners"
        |       |                   \---J.Identifier | "listeners"
        |       \---J.Block
        \-------J.MethodDeclaration | "MethodDeclaration{A{name=test,return=void,parameters=[]}}"
                |---J.Modifier | "public"
                |---J.Primitive | "void"
                |---J.Identifier | "test"
                |-----------J.Empty
                \---J.Block
                    |-------J.MethodInvocation | "__M__.any( /*__TEMPLATE__*/List.of(__P__.<error><A.1>/*__p0__*/p())"        // JRightPadded.after = "/*__TEMPLATE_STOP__*/"
                    |       |-------J.Identifier | "__M__"
                    |       |---J.Identifier | "any"
                    |       \-----------J.MethodInvocation | "List.of(__P__.<error><A.1>/*__p0__*/p()"                        //  "/*__TEMPLATE__*/" is here, after the stop comment
                    |                   |-------J.Identifier | "List"
                    |                   |---J.Identifier | "of"
                    |                   \-----------J.FieldAccess | "__P__.<error>"
                    |                               |---J.Identifier | "__P__"
                    |                               \-------J.Identifier | "<error>"
                    \-------J.MethodInvocation | "p()"
                            |---J.Identifier | "p"
                            \-----------J.Empty

---

Compared to a working case:

List<LocalDate> list = Collections.singletonList(LocalDate.now());

The generated template stub is

class Test {
    List<String> list =
        /*__TEMPLATE__*/List.of(__P__.<String>/*__p0__*/p())/*__TEMPLATE_STOP__*/;
}

this works because there is no more statement to capture at the end, but not because the /*__TEMPLATE_STOP__*/ is successfully captured.