Quick fail if ImportTask is used with a ProjectHelper that doesn't

support imports. The original helper won't work ( because of eval order ),
and embed will fail too ( since it can't use 1.6 features - one of the
goals is to work in ant1.5 ).

I'm ready to move the dynamic properties and the component hooks - I'll
porbably do it this weekend ( most people are in vacation, so fewer
will feel any breakage ). In any case [embed] should now used only
if you want to use (some) new features in ant1.5.


git-svn-id: https://svn.apache.org/repos/asf/ant/core/trunk@273707 13f79535-47bb-0310-9956-ffa450edef68

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

@@ -100,6 +100,11 @@ public class ImportTask extends Task {
         ProjectHelper helper=
                 (ProjectHelper)project.getReference("ant.projectHelper");
         Vector importStack=helper.getImportStack();
+        if( importStack.size() == 0) {
+            // this happens if ant is used with a project
+            // helper that doesn't set the import.
+            throw new BuildException("import requires support in ProjectHelper");
+        }
         Object currentSource=importStack.elementAt(importStack.size() - 1);
 
 //        ProjectHelper2.AntXmlContext context;