8216064: -XX:StartFlightRecording:settings= doesn't work properly

Reviewed-by: mgronlun

src/share/classes/jdk/jfr/internal/dcmd/DCmdStart.java

@@ -24,6 +24,7 @@
  */
 package jdk.jfr.internal.dcmd;
 
+import java.io.FileNotFoundException;
 import java.io.IOException;
 import java.nio.file.Files;
 import java.nio.file.InvalidPathException;
@@ -105,8 +106,9 @@ final class DCmdStart extends AbstractDCmd {
         if (duration == null && Boolean.FALSE.equals(dumpOnExit) && path != null) {
             throw new DCmdException("Filename can only be set for a time bound recording or if dumponexit=true. Set duration/dumponexit or omit filename.");
         }
-
-
+        if (settings.length == 1 && settings[0].length() == 0) {
+            throw new DCmdException("No settings specified. Use settings=none to start without any settings");
+        }
         Map<String, String> s = new HashMap<>();
 
         if (settings == null || settings.length == 0) {
@@ -116,8 +118,10 @@ final class DCmdStart extends AbstractDCmd {
         for (String configName : settings) {
             try {
                 s.putAll(JFC.createKnown(configName).getSettings());
+            } catch(FileNotFoundException e) {
+                throw new DCmdException("Could not find settings file'" + configName + "'", e);
             } catch (IOException | ParseException e) {
-                throw new DCmdException("Could not parse setting " + settings[0], e);
+                throw new DCmdException("Could not parse settings file '" + settings[0] + "'", e);
             }
         }
 

src/share/classes/jdk/jfr/internal/jfc/JFC.java

@@ -127,7 +127,11 @@ public final class JFC {
 
     public static String nameFromPath(Path file) throws IOException {
         String f = nullSafeFileName(file);
-        return f.substring(0, f.length() - JFCParser.FILE_EXTENSION.length());
+        if (f.endsWith(JFCParser.FILE_EXTENSION)) {
+            return f.substring(0, f.length() - JFCParser.FILE_EXTENSION.length());
+        } else  {
+            return f;
+        }
     }
 
     // Invoked by DCmdStart

test/jdk/jfr/startupargs/TestStartNoSettings.java

+/*
+ * Copyright (c) 2019, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.  Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+package jdk.jfr.startupargs;
+
+import jdk.jfr.Event;
+import jdk.jfr.EventType;
+import jdk.jfr.FlightRecorder;
+import jdk.jfr.Name;
+import jdk.jfr.Recording;
+
+/**
+ * @test
+ * @summary Start a FlightRecording without any settings (not even default).
+ * @key jfr
+ * @library /lib /
+ * @run main/othervm jdk.jfr.startupargs.TestStartNoSettings
+ *      -XX:StartFlightRecording=settings=none
+ */
+public class TestStartNoSettings {
+
+    @Name("UserEvent")
+    static class UserEvent extends Event {
+    }
+
+    public static void main(String[] a) throws Exception {
+        boolean userEnabled = false;
+        try (Recording r = new Recording()) {
+            r.start();
+            UserEvent e = new UserEvent();
+            e.commit();
+            for (EventType et : FlightRecorder.getFlightRecorder().getEventTypes()) {
+                if (et.isEnabled()) {
+                    if (!et.getName().equals("UserEvent")) {
+                        throw new Exception("Only 'UserEvent' should be enabled");
+                    }
+                    userEnabled = true;
+                }
+            }
+        }
+
+        if (!userEnabled)  {
+            throw new Exception("Expected 'UserEvent' to be enabled with -XX:StartFlightRecording=settings=none");
+        }
+    }
+}