Add flag to control when headers are reset on error

- fix #1383
- fix #1299

Author: jknack

jooby/src/main/java/org/jooby/Response.java

@@ -416,6 +416,14 @@ public String toString() {
       return rsp.toString();
     }
 
+    @Override public boolean isResetHeadersOnError() {
+      return rsp.isResetHeadersOnError();
+    }
+
+    @Override public void setResetHeadersOnError(boolean value) {
+      this.setResetHeadersOnError(value);
+    }
+
     /**
      * Unwrap a response in order to find out the target instance.
      *
@@ -848,4 +856,18 @@ default Response status(final int status) {
    * @see Route.After
    */
   void complete(Route.Complete handler);
+
+  /**
+   * Indicates if headers are cleared/reset on error.
+   *
+   * @return Indicates if headers are cleared/reset on error. Default is true.
+   */
+  boolean isResetHeadersOnError();
+
+  /**
+   * Indicates if headers are cleared/reset on error.
+   *
+   * @param value True to reset.
+   */
+  void setResetHeadersOnError(boolean value);
 }

jooby/src/main/java/org/jooby/internal/ResponseImpl.java

@@ -280,6 +280,8 @@ public class ResponseImpl implements Response {
 
   private Optional<String> byteRange;
 
+  private boolean resetHeadersOnError = true;
+
   public ResponseImpl(final RequestImpl req, final ParserExecutor parserExecutor,
       final NativeResponse rsp, final Route route, final List<Renderer> renderers,
       final Map<String, Renderer> rendererMap, final Map<String, Object> locals,
@@ -296,6 +298,14 @@ public ResponseImpl(final RequestImpl req, final ParserExecutor parserExecutor,
     this.byteRange = byteRange;
   }
 
+  @Override public boolean isResetHeadersOnError() {
+    return resetHeadersOnError;
+  }
+
+  @Override public void setResetHeadersOnError(boolean resetHeadersOnError) {
+    this.resetHeadersOnError = resetHeadersOnError;
+  }
+
   @Override
   public void download(final String filename, final InputStream stream) throws Throwable {
     requireNonNull(filename, "A file's name is required.");
@@ -585,9 +595,11 @@ private void writeCookies() {
   }
 
   public void reset() {
-    status = null;
-    this.cookies.clear();
-    rsp.reset();
+    if (resetHeadersOnError) {
+      status = null;
+      this.cookies.clear();
+      rsp.reset();
+    }
   }
 
   void route(final Route route) {

jooby/src/test/java/org/jooby/ResponseTest.java

@@ -17,6 +17,14 @@
 public class ResponseTest {
   public static class ResponseMock implements Response {
 
+    @Override public boolean isResetHeadersOnError() {
+      throw new UnsupportedOperationException();
+    }
+
+    @Override public void setResetHeadersOnError(boolean value) {
+      throw new UnsupportedOperationException();
+    }
+
     @Override
     public void download(final String filename, final InputStream stream) throws Exception {
       throw new UnsupportedOperationException();

modules/coverage-report/src/test/java/org/jooby/issues/Issue1299.java

@@ -0,0 +1,32 @@
+package org.jooby.issues;
+
+import org.jooby.test.ServerFeature;
+import org.junit.Test;
+
+public class Issue1299 extends ServerFeature {
+
+  {
+    use("*", (req, rsp) -> {
+      if (req.param("noreset").booleanValue(false)) {
+        rsp.setResetHeadersOnError(false);
+      }
+    });
+    get("/1299", req -> {
+      req.flash("error", "error");
+      return req.param("missing").value();
+    });
+
+    err((req, rsp, x) -> {
+      rsp.status(200).end();
+    });
+  }
+
+  @Test
+  public void shouldNotResetHeaders() throws Exception {
+    request()
+        .get("/1299")
+        .expect(200)
+        .header("Set-Cookie", (String) null);
+  }
+
+}