--- a/langtools/src/jdk.compiler/share/classes/com/sun/tools/javac/code/Lint.java	Mon Feb 06 09:25:31 2017 -0800
+++ b/langtools/src/jdk.compiler/share/classes/com/sun/tools/javac/code/Lint.java	Mon Feb 06 12:35:13 2017 -0800
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2005, 2016, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2005, 2017, 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
@@ -118,6 +118,7 @@
             if (source.compareTo(Source.JDK1_9) >= 0) {
                 values.add(LintCategory.DEP_ANN);
             }
+            values.add(LintCategory.OPENS);
             values.add(LintCategory.MODULE);
             values.add(LintCategory.REMOVAL);
         }
@@ -211,6 +212,11 @@
         MODULE("module"),
 
         /**
+         * Warn about issues regarding module opens.
+         */
+        OPENS("opens"),
+
+        /**
          * Warn about issues relating to use of command line options
          */
         OPTIONS("options"),

--- a/langtools/src/jdk.compiler/share/classes/com/sun/tools/javac/comp/Check.java	Mon Feb 06 09:25:31 2017 -0800
+++ b/langtools/src/jdk.compiler/share/classes/com/sun/tools/javac/comp/Check.java	Mon Feb 06 12:35:13 2017 -0800
@@ -3876,4 +3876,14 @@
         }
     }
 
+    void checkPackageExistsForOpens(final DiagnosticPosition pos, PackageSymbol packge) {
+        if (packge.members().isEmpty() &&
+            ((packge.flags() & Flags.HAS_RESOURCE) == 0)) {
+            deferredLintHandler.report(() -> {
+                if (lint.isEnabled(LintCategory.OPENS))
+                    log.warning(pos, Warnings.PackageEmptyOrNotFound(packge));
+            });
+        }
+    }
+
 }

--- a/langtools/src/jdk.compiler/share/classes/com/sun/tools/javac/comp/Modules.java	Mon Feb 06 09:25:31 2017 -0800
+++ b/langtools/src/jdk.compiler/share/classes/com/sun/tools/javac/comp/Modules.java	Mon Feb 06 12:35:13 2017 -0800
@@ -696,9 +696,6 @@
             PackageSymbol packge = syms.enterPackage(sym, name);
             attr.setPackageSymbols(tree.qualid, packge);
 
-            if (tree.hasTag(Tag.OPENS) && sym.flags.contains(ModuleFlags.OPEN)) {
-                log.error(tree.pos(), Errors.NoOpensUnlessStrong);
-            }
             List<ExportsDirective> exportsForPackage = allExports.computeIfAbsent(packge, p -> List.nil());
             for (ExportsDirective d : exportsForPackage) {
                 reportExportsConflict(tree, packge);
@@ -899,10 +896,7 @@
 
         @Override
         public void visitOpens(JCOpens tree) {
-            if (tree.directive.packge.members().isEmpty() &&
-                ((tree.directive.packge.flags() & Flags.HAS_RESOURCE) == 0)) {
-                log.error(tree.qualid.pos(), Errors.PackageEmptyOrNotFound(tree.directive.packge));
-            }
+            chk.checkPackageExistsForOpens(tree.qualid, tree.directive.packge);
             msym.directives = msym.directives.prepend(tree.directive);
         }
 

--- a/langtools/src/jdk.compiler/share/classes/com/sun/tools/javac/resources/compiler.properties	Mon Feb 06 09:25:31 2017 -0800
+++ b/langtools/src/jdk.compiler/share/classes/com/sun/tools/javac/resources/compiler.properties	Mon Feb 06 12:35:13 2017 -0800
@@ -2928,6 +2928,10 @@
 compiler.err.package.empty.or.not.found=\
     package is empty or does not exist: {0}
 
+# 0: symbol
+compiler.warn.package.empty.or.not.found=\
+    package is empty or does not exist: {0}
+
 compiler.err.no.output.dir=\
     no class output directory specified
 

--- a/langtools/src/jdk.compiler/share/classes/com/sun/tools/javac/resources/javac.properties	Mon Feb 06 09:25:31 2017 -0800
+++ b/langtools/src/jdk.compiler/share/classes/com/sun/tools/javac/resources/javac.properties	Mon Feb 06 12:35:13 2017 -0800
@@ -204,6 +204,9 @@
 javac.opt.Xlint.desc.module=\
     Warn about module system related issues.
 
+javac.opt.Xlint.desc.opens=\
+    Warn about issues regarding module opens.
+
 javac.opt.Xlint.desc.options=\
     Warn about issues relating to use of command line options.
 

--- a/langtools/test/tools/javac/diags/examples/PackageEmptyOrNotFound/PackageEmptyOrNotFound.java	Mon Feb 06 09:25:31 2017 -0800
+++ /dev/null	Thu Jan 01 00:00:00 1970 +0000
@@ -1,24 +0,0 @@
-/*
- * Copyright (c) 2016, 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.
- *
- * 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.
- */
-
-// key: compiler.err.package.empty.or.not.found

--- a/langtools/test/tools/javac/diags/examples/PackageEmptyOrNotFound/modulesourcepath/m1x/module-info.java	Mon Feb 06 09:25:31 2017 -0800
+++ /dev/null	Thu Jan 01 00:00:00 1970 +0000
@@ -1,26 +0,0 @@
-/*
- * Copyright (c) 2016, 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.
- *
- * 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.
- */
-
-module m1x {
-    exports p1;
-}

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/langtools/test/tools/javac/diags/examples/PackageEmptyOrNotFoundError/PackageEmptyOrNotFound.java	Mon Feb 06 12:35:13 2017 -0800
@@ -0,0 +1,24 @@
+/*
+ * Copyright (c) 2016, 2017, 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.
+ *
+ * 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.
+ */
+
+// key: compiler.err.package.empty.or.not.found

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/langtools/test/tools/javac/diags/examples/PackageEmptyOrNotFoundError/modulesourcepath/m1x/module-info.java	Mon Feb 06 12:35:13 2017 -0800
@@ -0,0 +1,26 @@
+/*
+ * Copyright (c) 2016, 2017, 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.
+ *
+ * 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.
+ */
+
+module m1x {
+    exports p1;
+}

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/langtools/test/tools/javac/diags/examples/PackageEmptyOrNotFoundWarning/PackageEmptyOrNotFound.java	Mon Feb 06 12:35:13 2017 -0800
@@ -0,0 +1,24 @@
+/*
+ * Copyright (c) 2016, 2017, 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.
+ *
+ * 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.
+ */
+
+// key: compiler.warn.package.empty.or.not.found

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/langtools/test/tools/javac/diags/examples/PackageEmptyOrNotFoundWarning/modulesourcepath/m1x/module-info.java	Mon Feb 06 12:35:13 2017 -0800
@@ -0,0 +1,26 @@
+/*
+ * Copyright (c) 2016, 2017, 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.
+ *
+ * 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.
+ */
+
+module m1x {
+    opens p1;
+}

--- a/langtools/test/tools/javac/modules/ReportNonExistentPackageTest.java	Mon Feb 06 09:25:31 2017 -0800
+++ b/langtools/test/tools/javac/modules/ReportNonExistentPackageTest.java	Mon Feb 06 12:35:13 2017 -0800
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2015, 2016, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2015, 2017, 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
@@ -105,7 +105,7 @@
     }
 
     @Test
-    public void testExportPrivateEmptyPackage(Path base) throws Exception {
+    public void testOpensEmptyPackage(Path base) throws Exception {
         Path src = base.resolve("src");
         tb.writeJavaFiles(src,
                 "module m { opens p; }");
@@ -116,15 +116,34 @@
                 .options("-XDrawDiagnostics")
                 .outdir(classes)
                 .files(findJavaFiles(src))
-                .run(Task.Expect.FAIL)
+                .run(Task.Expect.SUCCESS)
                 .writeAll()
                 .getOutput(Task.OutputKind.DIRECT);
-        if (!log.contains("module-info.java:1:18: compiler.err.package.empty.or.not.found: p"))
+        if (!log.contains("module-info.java:1:18: compiler.warn.package.empty.or.not.found: p"))
             throw new Exception("expected output not found, actual output: " + log);
     }
 
     @Test
-    public void testExportPrivateOnlyWithResources(Path base) throws Exception {
+    public void testOpensEmptyPackageSuppressed(Path base) throws Exception {
+        Path src = base.resolve("src");
+        tb.writeJavaFiles(src,
+                "@SuppressWarnings(\"opens\") module m { opens p; }");
+        Path classes = base.resolve("classes");
+        Files.createDirectories(classes);
+
+        String log = new JavacTask(tb)
+                .options("-XDrawDiagnostics")
+                .outdir(classes)
+                .files(findJavaFiles(src))
+                .run(Task.Expect.SUCCESS)
+                .writeAll()
+                .getOutput(Task.OutputKind.DIRECT);
+        if (!log.equals(""))
+            throw new Exception("expected output not found, actual output: " + log);
+    }
+
+    @Test
+    public void testOpenOnlyWithResources(Path base) throws Exception {
         Path src = base.resolve("src");
         tb.writeJavaFiles(src,
                 "module m { opens p; }");