Fixes #1494

Converted dependencies from a Set to a List, so the order of dependencies
can be used to help select between multiple provides.  More specifically,
stop an unordered Set allowing one dependency to trigger a default provider
when an earlier specified dependency enables a specific provider.

jetty-start/src/main/java/org/eclipse/jetty/start/Module.java

@@ -116,7 +116,7 @@ public class Module implements Comparable<Module>
     private final List<String> _license=new ArrayList<>();
     
     /** Dependencies */
-    private final Set<String> _depends=new HashSet<>();
+    private final List<String> _depends=new ArrayList<>();
     
     /** Optional */
     private final Set<String> _optional=new HashSet<>();
@@ -183,10 +183,10 @@ public class Module implements Comparable<Module>
     {
         Function<String,String> expander = d->{return props.expand(d);};
         
-        Set<String> tmp=_depends.stream().map(expander).collect(Collectors.toSet());
+        List<String> tmp=_depends.stream().map(expander).collect(Collectors.toList());
         _depends.clear();
         _depends.addAll(tmp);
-        tmp=_optional.stream().map(expander).collect(Collectors.toSet());
+        tmp=_optional.stream().map(expander).collect(Collectors.toList());
         _optional.clear();
         _optional.addAll(tmp);
     }
@@ -329,7 +329,8 @@ public class Module implements Comparable<Module>
                                 break;
                             case "DEPEND":  
                             case "DEPENDS":
-                                _depends.add(line);
+                                if (!_depends.contains(line))
+                                    _depends.add(line);
                                 break;
                             case "FILE":
                             case "FILES":
@@ -437,9 +438,9 @@ public class Module implements Comparable<Module>
         return str.toString();
     }
 
-    public Set<String> getDepends()
+    public List<String> getDepends()
     {
-        return new HashSet<>(_depends);
+        return new ArrayList<>(_depends);
     }
 
     public Set<String>  getProvides()

jetty-start/src/main/java/org/eclipse/jetty/start/Modules.java

@@ -335,12 +335,13 @@ public class Modules implements Iterable<Module>
         }
         
         // Process module dependencies (always processed as may be dynamic)
+        StartLog.debug("Enabled module %s depends on %s",module.getName(),module.getDepends());
         for(String dependsOn:module.getDepends())
         {
             // Look for modules that provide that dependency
             Set<Module> providers = getAvailableProviders(dependsOn);
                 
-            StartLog.debug("Module %s depends on %s provided by ",module,dependsOn,providers);
+            StartLog.debug("Module %s depends on %s provided by %s",module,dependsOn,providers);
             
             // If there are no known providers of the module
             if (providers.isEmpty())
@@ -381,11 +382,11 @@ public class Modules implements Iterable<Module>
     private Set<Module> getAvailableProviders(String name)
     {
         // Get all available providers 
-        
         Set<Module> providers = _provided.get(name);
+        StartLog.debug("Providers of %s are %s",name,providers);
         if (providers==null || providers.isEmpty())
             return Collections.emptySet();
-        
+
         providers = new HashSet<>(providers);
         
         // find all currently provided names by other modules
@@ -409,13 +410,15 @@ public class Modules implements Iterable<Module>
                 {
                     if (provided.contains(p))
                     {
+                        StartLog.debug("Removing provider %s because %s already enabled",provider,p);
                         i.remove();
                         break;
                     }
                 }
             }
         }
-        
+
+        StartLog.debug("Available providers of %s are %s",name,providers);
         return providers;
     }
 

jetty-start/src/test/resources/usecases/ordered.default.assert.txt

@@ -0,0 +1,12 @@
+## The XMLs we expect (order is important)
+XML|${jetty.home}/etc/base.xml
+XML|${jetty.home}/etc/main.xml
+
+# The LIBs we expect (order is irrelevant)
+LIB|${jetty.home}/lib/base.jar
+LIB|${jetty.home}/lib/main.jar
+LIB|${jetty.home}/lib/other.jar
+
+# The Properties we expect (order is irrelevant)
+PROP|main.prop=value0
+PROP|impl=replacement

jetty-start/src/test/resources/usecases/ordered.default.cmdline.txt

@@ -0,0 +1,2 @@
+--module=main,convenience
+

jetty-start/src/test/resources/usecases/ordered/modules/convenience.mod

@@ -0,0 +1,4 @@
+
+[depends]
+replacement
+something-else

jetty-start/src/test/resources/usecases/ordered/modules/original.mod

@@ -0,0 +1,4 @@
+
+
+[ini]
+impl=original

jetty-start/src/test/resources/usecases/ordered/modules/replacement.mod

@@ -0,0 +1,7 @@
+
+
+[provides]
+original
+
+[ini]
+impl=replacement

jetty-start/src/test/resources/usecases/ordered/modules/something-else.mod

@@ -0,0 +1,3 @@
+
+[depends]
+original