add discardOutput and discardError to redirector, apply, exec, java

WHATSNEW

@@ -69,6 +69,11 @@ Other changes:
    task.
    Bugzilla Report 65089
 
+ * added new disardOutput and discardError properties to redirector
+   and the exec, apply and java tasks which can be used to completely
+   discard any (error) output. This is a platform independent
+   alternative to directiong output to any kind of null device.
+
 Changes from Ant 1.10.8 TO Ant 1.10.9
 =====================================
 

manual/Tasks/apply.html

@@ -258,6 +258,27 @@ standard input.</p>
     <td>Whether to bypass timestamp comparisons for target files.  <em>Since Ant 1.6.3</em>.</td>
     <td>No; default is <q>false</q></td>
   </tr>
+  <tr>
+    <td>discardOutput</td>
+    <td>Whether output should completely be discarded. This setting is
+      incompatible with any setting that redirects output to files or
+      properties.<br/>
+      If you set this to <q>true</q> error output will be discared as
+      well unless you redirect error output to files, properties or
+      enable <q>logError</q>.
+      <em>Since Ant 1.10.10</em>
+    </td>
+    <td>No; defaults to <q>false</q></td>
+  </tr>
+  <tr>
+    <td>discardError</td>
+    <td>Whether error output should completely be discarded. This
+      setting is incompatible with any setting that redirects error
+      output to files or properties as well as <q>logError</q>.
+      <em>Since Ant 1.10.10</em>
+    </td>
+    <td>No; defaults to <q>false</q></td>
+  </tr>
 </table>
 <h3>Parameters specified as nested elements</h3>
 <h4>fileset</h4>

manual/Tasks/exec.html

@@ -262,6 +262,27 @@ standard input.</p>
       when resolving the location of the executable. <em>since Ant 1.6.3</em></td>
     <td>No; default is <q>false</q></td>
   </tr>
+  <tr>
+    <td>discardOutput</td>
+    <td>Whether output should completely be discarded. This setting is
+      incompatible with any setting that redirects output to files or
+      properties.<br/>
+      If you set this to <q>true</q> error output will be discared as
+      well unless you redirect error output to files, properties or
+      enable <q>logError</q>.
+      <em>Since Ant 1.10.10</em>
+    </td>
+    <td>No; defaults to <q>false</q></td>
+  </tr>
+  <tr>
+    <td>discardError</td>
+    <td>Whether error output should completely be discarded. This
+      setting is incompatible with any setting that redirects error
+      output to files or properties as well as <q>logError</q>.
+      <em>Since Ant 1.10.10</em>
+    </td>
+    <td>No; defaults to <q>false</q></td>
+  </tr>
 </table>
 <h3>Examples</h3>
 <pre>

manual/Tasks/java.html

@@ -218,6 +218,27 @@ because it tries to read from the standard input.</p>
       forked JVM will be the same as those of the JVM running Ant. <em>since Ant 1.7</em></td>
     <td>No; default is <q>false</q>, ignored if <var>fork</var> is <q>false</q></td>
   </tr>
+  <tr>
+    <td>discardOutput</td>
+    <td>Whether output should completely be discarded. This setting is
+      incompatible with any setting that redirects output to files or
+      properties.<br/>
+      If you set this to <q>true</q> error output will be discared as
+      well unless you redirect error output to files, properties or
+      enable <q>logError</q>.
+      <em>Since Ant 1.10.10</em>
+    </td>
+    <td>No; defaults to <q>false</q></td>
+  </tr>
+  <tr>
+    <td>discardError</td>
+    <td>Whether error output should completely be discarded. This
+      setting is incompatible with any setting that redirects error
+      output to files or properties as well as <q>logError</q>.
+      <em>Since Ant 1.10.10</em>
+    </td>
+    <td>No; defaults to <q>false</q></td>
+  </tr>
 </table>
 <h3>Parameters specified as nested elements</h3>
 <h4>arg and jvmarg</h4>

manual/Types/redirector.html

@@ -129,6 +129,27 @@ specify source (input) and destination (output/error) files.</p>
     </td>
     <td>No; default is <q>false</q></td>
   </tr>
+  <tr>
+    <td>discardOutput</td>
+    <td>Whether output should completely be discarded. This setting is
+      incompatible with any setting that redirects output to files or
+      properties.<br/>
+      If you set this to <q>true</q> error output will be discared as
+      well unless you redirect error output to files, properties or
+      enable <q>logError</q>.
+      <em>Since Ant 1.10.10</em>
+    </td>
+    <td>No; defaults to <q>false</q></td>
+  </tr>
+  <tr>
+    <td>discardError</td>
+    <td>Whether error output should completely be discarded. This
+      setting is incompatible with any setting that redirects error
+      output to files or properties as well as <q>logError</q>.
+      <em>Since Ant 1.10.10</em>
+    </td>
+    <td>No; defaults to <q>false</q></td>
+  </tr>
 </table>
 <h3>Parameters specified as nested elements</h3>
 <h4>inputmapper</h4>

src/main/org/apache/tools/ant/taskdefs/ExecTask.java

@@ -380,6 +380,36 @@ public class ExecTask extends Task {
         incompatibleWithSpawn |= append;
     }
 
+    /**
+     * Whether output should be discarded.
+     *
+     * <p>Defaults to false.</p>
+     *
+     * @param discard
+     *            if true output streams are discarded.
+     *
+     * @since Ant 1.10.10
+     * @see #setDiscardError
+     */
+    public void setDiscardOutput(final boolean discard) {
+        redirector.setDiscardOutput(discard);
+    }
+
+    /**
+     * Whether error output should be discarded.
+     *
+     * <p>Defaults to false.</p>
+     *
+     * @param discard
+     *            if true error streams are discarded.
+     *
+     * @since Ant 1.10.10
+     * @see #setDiscardOutput
+     */
+    public void setDiscardError(final boolean discard) {
+        redirector.setDiscardError(discard);
+    }
+
     /**
      * Add a <code>RedirectorElement</code> to this task.
      *

src/main/org/apache/tools/ant/taskdefs/Java.java

@@ -707,6 +707,36 @@ public class Java extends Task {
         incompatibleWithSpawn |= append;
     }
 
+    /**
+     * Whether output should be discarded.
+     *
+     * <p>Defaults to false.</p>
+     *
+     * @param discard
+     *            if true output streams are discarded.
+     *
+     * @since Ant 1.10.10
+     * @see #setDiscardError
+     */
+    public void setDiscardOutput(final boolean discard) {
+        redirector.setDiscardOutput(discard);
+    }
+
+    /**
+     * Whether error output should be discarded.
+     *
+     * <p>Defaults to false.</p>
+     *
+     * @param discard
+     *            if true error streams are discarded.
+     *
+     * @since Ant 1.10.10
+     * @see #setDiscardOutput
+     */
+    public void setDiscardError(final boolean discard) {
+        redirector.setDiscardError(discard);
+    }
+
     /**
      * Set the timeout in milliseconds after which the process will be killed.
      *

src/main/org/apache/tools/ant/taskdefs/Redirector.java

@@ -45,6 +45,7 @@ import org.apache.tools.ant.util.KeepAliveOutputStream;
 import org.apache.tools.ant.util.LazyFileOutputStream;
 import org.apache.tools.ant.util.LeadPipeInputStream;
 import org.apache.tools.ant.util.LineOrientedOutputStreamRedirector;
+import org.apache.tools.ant.util.NullOutputStream;
 import org.apache.tools.ant.util.OutputStreamFunneler;
 import org.apache.tools.ant.util.ReaderInputStream;
 import org.apache.tools.ant.util.TeeOutputStream;
@@ -197,6 +198,11 @@ public class Redirector {
     /** Is the output binary or can we safely split it into lines? */
     private boolean outputIsBinary = false;
 
+    /** Flag which indicates if error and output files are to be discarded. */
+    private boolean discardOut = false;
+
+    private boolean discardErr = false;
+
     /**
      * Create a redirector instance for the given task
      *
@@ -442,6 +448,40 @@ public class Redirector {
         }
     }
 
+    /**
+     * Whether output should be discarded.
+     *
+     * <p>Defaults to false.</p>
+     *
+     * @param discard
+     *            if true output streams are discarded.
+     *
+     * @since Ant 1.10.10
+     * @see #setDiscardError
+     */
+    public void setDiscardOutput(final boolean discard) {
+        synchronized (outMutex) {
+            discardOut = discard;
+        }
+    }
+
+    /**
+     * Whether error output should be discarded.
+     *
+     * <p>Defaults to false.</p>
+     *
+     * @param discard
+     *            if true error streams are discarded.
+     *
+     * @since Ant 1.10.10
+     * @see #setDiscardOutput
+     */
+    public void setDiscardError(final boolean discard) {
+        synchronized (errMutex) {
+            discardErr = discard;
+        }
+    }
+
     /**
      * If true, (error and non-error) output will be "teed", redirected as
      * specified while being sent to Ant's logging mechanism as if no
@@ -694,7 +734,17 @@ public class Redirector {
 
     /** outStreams */
     private void outStreams() {
-        if (out != null && out.length > 0) {
+        final boolean haveOutputFiles = out != null && out.length > 0;
+        if (discardOut) {
+            if (haveOutputFiles || outputProperty != null) {
+                throw new BuildException("Cant discard output when output or outputProperty"
+                        + " are set");
+            }
+            managingTask.log("Discarding output", Project.MSG_VERBOSE);
+            outputStream = NullOutputStream.INSTANCE;
+            return;
+        }
+        if (haveOutputFiles) {
             final String logHead = "Output "
                     + ((appendOut) ? "appended" : "redirected") + " to ";
             outputStream = foldFiles(out, logHead, Project.MSG_VERBOSE,
@@ -716,7 +766,17 @@ public class Redirector {
     }
 
     private void errorStreams() {
-        if (error != null && error.length > 0) {
+        final boolean haveErrorFiles = error != null && error.length > 0;
+        if (discardErr) {
+            if (haveErrorFiles || errorProperty != null || logError) {
+                throw new BuildException("Cant discard error output when error, errorProperty"
+                        + " or logError are set");
+            }
+            managingTask.log("Discarding error output", Project.MSG_VERBOSE);
+            errorStream = NullOutputStream.INSTANCE;
+            return;
+        }
+        if (haveErrorFiles) {
             final String logHead = "Error "
                     + ((appendErr) ? "appended" : "redirected") + " to ";
             errorStream = foldFiles(error, logHead, Project.MSG_VERBOSE,

src/main/org/apache/tools/ant/util/NullOutputStream.java

@@ -0,0 +1,53 @@
+/*
+ *  Licensed to the Apache Software Foundation (ASF) under one or more
+ *  contributor license agreements.  See the NOTICE file distributed with
+ *  this work for additional information regarding copyright ownership.
+ *  The ASF licenses this file to You under the Apache License, Version 2.0
+ *  (the "License"); you may not use this file except in compliance with
+ *  the License.  You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ *  Unless required by applicable law or agreed to in writing, software
+ *  distributed under the License is distributed on an "AS IS" BASIS,
+ *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ *  See the License for the specific language governing permissions and
+ *  limitations under the License.
+ *
+ */
+
+package org.apache.tools.ant.util;
+
+import java.io.OutputStream;
+
+/**
+ * OutputStream that completely discards all data written to it.
+ *
+ * @since Ant 1.10.10
+ */
+public class NullOutputStream extends OutputStream {
+
+    /**
+     * Shared instance which is safe to use concurrently as the stream
+     * doesn't hold any state at all.
+     */
+    public static NullOutputStream INSTANCE = new NullOutputStream();
+
+    /**
+     * Doesn't do anything.
+     */
+    @Override
+    public void write(byte[] b) { }
+
+    /**
+     * Doesn't do anything.
+     */
+    @Override
+    public void write(byte[] b, int off, int len) { }
+
+    /**
+     * Doesn't do anything.
+     */
+    @Override
+    public void write(int i) { }
+}

src/tests/antunit/taskdefs/exec/exec-test.xml

@@ -707,4 +707,31 @@ public class Hello {
         </au:assertTrue>
     </target>
 
+    <target name="test-discard-output" depends="setUp" if="test.can.run">
+        <exec executable="sh" discardOutput="true">
+            <arg value="parrot.sh" />
+            <arg value="${ant.file}" />
+        </exec>
+        <au:assertLogDoesntContain text="${ant.file} out" />
+        <au:assertLogDoesntContain text="${ant.file} err" />
+    </target>
+
+    <target name="test-discard-output-only" depends="setUp" if="test.can.run">
+        <exec executable="sh" discardOutput="true" logError="true">
+            <arg value="parrot.sh" />
+            <arg value="${ant.file}" />
+        </exec>
+        <au:assertLogDoesntContain text="${ant.file} out" />
+        <au:assertLogContains text="${ant.file} err" />
+    </target>
+
+    <target name="test-discard-error" depends="setUp" if="test.can.run">
+        <exec executable="sh" discardError="true">
+            <arg value="parrot.sh" />
+            <arg value="${ant.file}" />
+        </exec>
+        <au:assertLogContains text="${ant.file} out" />
+        <au:assertLogDoesntContain text="${ant.file} err" />
+    </target>
+
 </project>