make reuse of CreationContext possible

Signed-off-by: Stefan Niederhauser <[email protected]>

Author: nidi3

graphviz-java/src/main/java/guru/nidi/graphviz/model/CreationContext.java

@@ -47,6 +47,15 @@ public static <T> T use(@Nullable MutableGraph graph, ThrowingFunction<CreationC
         }
     }
 
+    public <T> T reuse(ThrowingFunction<CreationContext, T> actions) {
+        CONTEXT.get().push(this);
+        try {
+            return actions.applyNotThrowing(this);
+        } finally {
+            end();
+        }
+    }
+
     public static Optional<CreationContext> current() {
         final Stack<CreationContext> cs = CONTEXT.get();
         return cs.empty() ? Optional.empty() : Optional.of(cs.peek());

graphviz-java/src/main/java/guru/nidi/graphviz/model/MutableGraph.java

@@ -25,6 +25,8 @@
 
 public class MutableGraph implements LinkSource, LinkTarget {
     private static final SafeRecursion<MutableGraph> RECURSION = new SafeRecursion<>();
+    private static final String CONTEXT = "$context";
+
     protected boolean strict;
     protected boolean directed;
     protected boolean cluster;
@@ -71,11 +73,23 @@ public Graph toImmutable() {
 
     public MutableGraph use(ThrowingBiConsumer<MutableGraph, CreationContext> actions) {
         return CreationContext.use(this, ctx -> {
+            graphAttrs.add(CONTEXT, ctx);
             actions.accept(this, ctx);
             return this;
         });
     }
 
+    public MutableGraph reuse(ThrowingBiConsumer<MutableGraph, CreationContext> actions) {
+        final Object c = graphAttrs.get(CONTEXT);
+        if (c instanceof CreationContext) {
+            return ((CreationContext) c).reuse(ctx -> {
+                actions.accept(this, ctx);
+                return this;
+            });
+        }
+        return use(actions);
+    }
+
     public MutableGraph setStrict(boolean strict) {
         this.strict = strict;
         return this;

graphviz-java/src/main/java/guru/nidi/graphviz/model/SerializerImpl.java

@@ -124,9 +124,12 @@ private int indexOfName(List<MutableNode> nodes, Label name) {
     }
 
     private void attributes(String name, Attributes<?> attributed, Scope scope, Location location) {
-        if (!attributed.isEmpty()) {
-            str.append(name);
-            attrs(attributed, scope, location);
+        final int len = str.length();
+        str.append(name);
+        attrs(attributed, scope, location);
+        if (str.length() == len + name.length()) {
+            str.delete(len, str.length());
+        } else {
             str.append('\n');
         }
     }
@@ -235,19 +238,19 @@ private void port(ImmutablePortNode portNode) {
     }
 
     private void attrs(Attributes<?> attrs, Scope scope, Location location) {
-        if (!attrs.isEmpty()) {
-            str.append(" [");
-            boolean first = true;
-            for (final Entry<String, Object> attr : attrs) {
-                if (attr.getValue() != null) {
-                    if (first) {
-                        first = false;
-                    } else {
-                        str.append(',');
-                    }
-                    attr(attr.getKey(), attr.getValue(), scope, location);
+        boolean first = true;
+        for (final Entry<String, Object> attr : attrs) {
+            if (!attr.getKey().startsWith("$") && attr.getValue() != null) {
+                if (first) {
+                    str.append(" [");
+                    first = false;
+                } else {
+                    str.append(',');
                 }
+                attr(attr.getKey(), attr.getValue(), scope, location);
             }
+        }
+        if (!first) {
             str.append(']');
         }
     }

graphviz-java/src/test/java/guru/nidi/graphviz/model/SerializerTest.java

@@ -214,6 +214,12 @@ void mixedDirected() {
                 "digraph {\nedge ['dir'='none']\n'a' -> {\nedge ['dir'='forward']\n'b' -> 'c'\n}\n}");
     }
 
+    @Test
+    void privateAttribute() {
+        assertSerialize(graph().graphAttr().with("$a", "b").with(node("a").with("$b", "c")),
+                "graph {\n'a'\n}");
+    }
+
     private void assertSerialize(Graph graph, String expectedString, ValidatorMessage... expectedMessages) {
         assertEquals(expectedString.replace("'", "\""), ser.serializer.serialize(graph));
         assertEquals(asList(expectedMessages), ser.messages);