Fix adding default attributes to subgraphs

Author: mdaines

packages/viz/CHANGELOG.md

@@ -2,6 +2,7 @@
 
 ## Unreleased
 
+* Fix that default attributes were added incorrectly, and would appear on the root graph as well as subgraphs.
 * For graph object input, fix that subgraphs without names were given the name "undefined", and reject nodes and edges without names.
 
 ## 3.22.0

packages/viz/backend/viz.c

@@ -139,16 +139,25 @@ Agraph_t *viz_add_subgraph(Agraph_t *g, char *name) {
 
 EMSCRIPTEN_KEEPALIVE
 void viz_set_default_graph_attribute(Agraph_t *graph, char *name, char *value) {
+  if (agattr(graph, AGRAPH, name, NULL) == NULL) {
+    agattr(graph, AGRAPH, name, "");
+  }
   agattr(graph, AGRAPH, name, value);
 }
 
 EMSCRIPTEN_KEEPALIVE
 void viz_set_default_node_attribute(Agraph_t *graph, char *name, char *value) {
+  if (agattr(graph, AGNODE, name, NULL) == NULL) {
+    agattr(graph, AGNODE, name, "");
+  }
   agattr(graph, AGNODE, name, value);
 }
 
 EMSCRIPTEN_KEEPALIVE
 void viz_set_default_edge_attribute(Agraph_t *graph, char *name, char *value) {
+  if (agattr(graph, AGEDGE, name, NULL) == NULL) {
+    agattr(graph, AGEDGE, name, "");
+  }
   agattr(graph, AGEDGE, name, value);
 }
 

packages/viz/test/graph-objects.test.js

@@ -280,6 +280,45 @@ describe("Viz", function() {
 			width=0.75];
 	}
 }
+`,
+        errors: []
+      });
+    });
+
+    it("applies subgraph attributes correctly", function() {
+      const result = viz.render({
+        subgraphs: [
+          {
+            graphAttributes: {
+              color: "red"
+            },
+            nodeAttributes: {
+              color: "green"
+            },
+            edgeAttributes: {
+              color: "blue"
+            },
+            nodes: [
+              { name: "a" }
+            ]
+          }
+        ]
+      });
+
+      assert.deepStrictEqual(result, {
+        status: "success",
+        output: `digraph {
+	graph [bb="0,0,54,36"];
+	node [label="\\N"];
+	{
+		graph [color=red];
+		node [color=green];
+		edge [color=blue];
+		a	[height=0.5,
+			pos="27,18",
+			width=0.75];
+	}
+}
 `,
         errors: []
       });