Pr 43016 improved error reporting on nothing to compress.

git-svn-id: https://svn.apache.org/repos/asf/ant/core/trunk@566707 13f79535-47bb-0310-9956-ffa450edef68

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

@@ -88,9 +88,14 @@ public abstract class Pack extends Task {
      * @param a the resource to pack as a single element Resource collection.
      */
     public void addConfigured(ResourceCollection a) {
+        if (a.size() == 0) {
+            throw new BuildException("No resource selected, " + getTaskName()
+                    + " needs exactly one resource.");
+        }
         if (a.size() != 1) {
-            throw new BuildException("only single argument resource collections"
-                                     + " are supported as archives");
+            throw new BuildException(getTaskName()
+                    + " cannot handle multiple resources at once. (" + a.size()
+                    + " resources were selected.)");
         }
         setSrcResource((Resource) a.iterator().next());
     }

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

@@ -0,0 +1,36 @@
+<?xml version="1.0" encoding="utf-8"?>
+<project default="antunit" xmlns:au="antlib:org.apache.ant.antunit">
+
+    <!-- note relies on antunit built from svn trunk (1.1-alpha) -->
+    <import file="../antunit-base.xml" />
+
+    <target name="setUp">
+        <mkdir dir="${java.io.tmpdir}/gzip-test" />
+        <mkdir dir="${java.io.tmpdir}/gzip-test/empty" />
+        <touch file="${java.io.tmpdir}/gzip-test/fileone" />
+        <touch file="${java.io.tmpdir}/gzip-test/filetwo" />
+    </target>
+
+    <target name="tearDown">
+        <delete includeemptydirs="true">
+            <fileset dir="${java.io.tmpdir}/gzip-test" />
+        </delete>
+    </target>
+
+    <target name="testFailNone">
+        <au:expectfailure expectedmessage="No resource selected, gzip needs exactly one resource." message="Should have thrown an exception">
+            <gzip destfile="${java.io.tmpdir}/gzip-test/file.gz">
+                <fileset dir="${java.io.tmpdir}/gzip-test/empty" />
+            </gzip>
+        </au:expectfailure>
+    </target>
+
+    <target name="testFailTwo">
+        <au:expectfailure expectedmessage="gzip cannot handle multiple resources at once. (2 resources were selected.)" message="Should have thrown an exception">
+            <gzip destfile="${java.io.tmpdir}/gzip-test/file.gz">
+                <fileset dir="${java.io.tmpdir}/gzip-test" />
+            </gzip>
+        </au:expectfailure>
+    </target>
+
+</project>