zest: rely on script context writer (#1889)

Change ZestZapRunner to not set the script console writer as output
writer if the script context writer is already set, while both end up in
the script console the latter allows the core to intercept the writes.
For the cases the context writer is not set the writes are not
intercepted.
Update changes in ZapAddOn.xml file.

Related to zaproxy/zaproxy#5113 - Allow to differentiate scripts' output

src/org/zaproxy/zap/extension/zest/ZapAddOn.xml

@@ -7,6 +7,7 @@
 	<url>https://github.com/zaproxy/zap-core-help/wiki/HelpAddonsZestZest</url>
 	<changes>
 	<![CDATA[
+	Rely on script context writer for script output.<br>
 	]]>
 	</changes>
 	<dependencies>

src/org/zaproxy/zap/extension/zest/ZestZapRunner.java

@@ -21,6 +21,7 @@
 package org.zaproxy.zap.extension.zest;
 
 import java.io.IOException;
+import java.lang.reflect.Field;
 import java.util.ArrayList;
 import java.util.List;
 import java.util.Map;
@@ -69,6 +70,8 @@ public class ZestZapRunner extends ZestBasicRunner implements ScannerListener {
 
 	private static final int ZEST_HISTORY_REFERENCE_TYPE = HistoryReference.TYPE_ZEST_SCRIPT;
 	private static final int FAIL_ACTION_PLUGIN_ID = 50004;
+
+	private static Field fieldOutputWriter;
 
 	private ExtensionZest extension;
 	private ZestScriptWrapper wrapper = null;
@@ -126,24 +129,36 @@ public String run(ZestScript script, Map<String, String> params) throws ZestAsse
 			this.target = null;
 			if (wrapper.getWriter() != null) {
 				super.setOutputWriter(wrapper.getWriter());
-			} else if (extension.getExtScript().getScriptUI() != null) {
-				super.setOutputWriter(extension.getExtScript().getScriptUI().getOutputWriter());
+			} else if (scriptUI != null && !hasOutputWriter()) {
+				super.setOutputWriter(scriptUI.getOutputWriter());
 			}
 			this.setDebug(this.wrapper.isDebug());
 
 			return super.run(script, params);
     	}
 	}
 
+	private boolean hasOutputWriter() {
+		try {
+			if (fieldOutputWriter == null) {
+				fieldOutputWriter = ZestBasicRunner.class.getDeclaredField("outputWriter");
+				fieldOutputWriter.setAccessible(true);
+			}
+			return fieldOutputWriter.get(this) != null;
+		} catch (IllegalAccessException | NoSuchFieldException e) {
+			return false;
+		}
+	}
+
 	@Override
 	public String run (ZestScript script, ZestRequest target, Map<String, String> params) 
 			throws ZestAssertFailException, ZestActionFailException, IOException,
 			ZestInvalidCommonTestException, ZestAssignFailException, ZestClientFailException {
     	log.debug("Run script " + script.getTitle());
 		if (wrapper.getWriter() != null) {
 			super.setOutputWriter(wrapper.getWriter());
-		} else if (extension.getExtScript().getScriptUI() != null) {
-			super.setOutputWriter(extension.getExtScript().getScriptUI().getOutputWriter());
+		} else if (scriptUI != null && !hasOutputWriter()) {
+			super.setOutputWriter(scriptUI.getOutputWriter());
 		}
 		this.setDebug(this.wrapper.isDebug());
 		String result = super.run(script, target, params);