MVC Code generation fails to declare exception when constructor throws a checked exception

- fix #3737

Author: jknack

jooby/src/main/java/io/jooby/SneakyThrows.java

@@ -899,6 +899,28 @@ public static <V> Supplier<V> throwingSupplier(Supplier<V> fn) {
     return fn;
   }
 
+  /**
+   * Singleton supplier from existing instance.
+   *
+   * @param instance Singleton.
+   * @return Single supplier.
+   * @param <V> Resulting value.
+   */
+  public static <V> Supplier<V> singleton(V instance) {
+    return () -> instance;
+  }
+
+  /**
+   * Singleton supplier from another supplier.
+   *
+   * @param fn Supplier.
+   * @return Single supplier.
+   * @param <V> Resulting value.
+   */
+  public static <V> Supplier<V> singleton(Supplier<V> fn) {
+    return singleton(fn.get());
+  }
+
   /**
    * Factory method for {@link Function} and {@link java.util.function.Function}.
    *

modules/jooby-apt/src/main/java/io/jooby/internal/apt/MvcRouter.java

@@ -224,13 +224,22 @@ private StringBuilder constructors(String generatedName, boolean kt) {
             buffer,
             List.of(),
             (output, params) -> {
-              output
-                  .append("this(")
-                  .append(kt ? "" : "new ")
-                  .append(targetType)
-                  .append("())")
-                  .append(semicolon(kt))
-                  .append(System.lineSeparator());
+              if (kt) {
+                output
+                    .append("this(")
+                    .append(targetType)
+                    .append("())")
+                    .append(semicolon(true))
+                    .append(System.lineSeparator());
+              } else {
+                output
+                    .append("this(")
+                    .append("io.jooby.SneakyThrows.singleton(")
+                    .append(targetType)
+                    .append("::new))")
+                    .append(semicolon(false))
+                    .append(System.lineSeparator());
+              }
             });
       }
     }

modules/jooby-apt/src/test/java/tests/i3737/C3737.java

@@ -0,0 +1,20 @@
+/*
+ * Jooby https://jooby.io
+ * Apache License Version 2.0 https://jooby.io/LICENSE.txt
+ * Copyright 2014 Edgar Espina
+ */
+package tests.i3737;
+
+import io.jooby.annotation.GET;
+import io.jooby.annotation.Path;
+
+@Path("/3737")
+public class C3737 {
+
+  public C3737() throws Exception {}
+
+  @GET("/hello")
+  public String hello() {
+    return "hello world";
+  }
+}

modules/jooby-apt/src/test/java/tests/i3737/Issue3737.java

@@ -0,0 +1,28 @@
+/*
+ * Jooby https://jooby.io
+ * Apache License Version 2.0 https://jooby.io/LICENSE.txt
+ * Copyright 2014 Edgar Espina
+ */
+package tests.i3737;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+import org.junit.jupiter.api.Test;
+
+import io.jooby.apt.ProcessorRunner;
+
+public class Issue3737 {
+  @Test
+  public void shouldNotFail() throws Exception {
+    // must compile
+    new ProcessorRunner(new C3737())
+        .withRouter(
+            (app, source) -> {
+              var routes = app.getRoutes();
+              assertNotNull(routes);
+              assertFalse(routes.isEmpty());
+              var route = app.getRoutes().get(0);
+              assertNotNull(route);
+            });
+  }
+}