WIP Fix behavior of names in graph objects

- Nodes must have a name
- Edges must have a tail and head
- Subgraphs may have no name

The subgraph test currently fails because for some reason, the attributes for one of the subgraphs are being set on the containing graph as well.

Author: mdaines

packages/viz/src/wrapper.js

@@ -195,6 +195,10 @@ function readGraph(module, graphPointer, graphData) {
 
   if (graphData.nodes) {
     graphData.nodes.forEach(nodeData => {
+      if (typeof nodeData.name === "undefined") {
+        throw new Error("nodes must have a name");
+      }
+
       const nodePointer = module.ccall("viz_add_node", "number", ["number", "string"], [graphPointer, String(nodeData.name)]);
 
       if (nodeData.attributes) {
@@ -205,6 +209,14 @@ function readGraph(module, graphPointer, graphData) {
 
   if (graphData.edges) {
     graphData.edges.forEach(edgeData => {
+      if (typeof edgeData.tail === "undefined") {
+        throw new Error("edges must have a tail");
+      }
+
+      if (typeof edgeData.head === "undefined") {
+        throw new Error("edges must have a head");
+      }
+
       const edgePointer = module.ccall("viz_add_edge", "number", ["number", "string", "string"], [graphPointer, String(edgeData.tail), String(edgeData.head)]);
 
       if (edgeData.attributes) {
@@ -215,7 +227,7 @@ function readGraph(module, graphPointer, graphData) {
 
   if (graphData.subgraphs) {
     graphData.subgraphs.forEach(subgraphData => {
-      const subgraphPointer = module.ccall("viz_add_subgraph", "number", ["number", "string"], [graphPointer, String(subgraphData.name)]);
+      const subgraphPointer = module.ccall("viz_add_subgraph", "number", ["number", "string"], [graphPointer, typeof subgraphData.name !== "undefined" ? String(subgraphData.name) : 0]);
 
       readGraph(module, subgraphPointer, subgraphData);
     });

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

@@ -207,6 +207,99 @@ describe("Viz", function() {
 		lp="136.52,50.4",
 		pos="e,157.62,42 115.49,42 124.55,42 135.85,42 146.16,42"];
 }
+`,
+        errors: []
+      });
+    });
+
+    it("throws for a node without a name", function() {
+      assert.throws(() => {
+        viz.render({
+          nodes: [
+            {}
+          ]
+        });
+      });
+    });
+
+    it("throws for an edge without tail or head", function() {
+      assert.throws(() => {
+        viz.render({
+          edges: [
+            {}
+          ]
+        });
+      });
+
+      assert.throws(() => {
+        viz.render({
+          edges: [
+            { tail: "a" }
+          ]
+        });
+      });
+
+      assert.throws(() => {
+        viz.render({
+          edges: [
+            { head: "b" }
+          ]
+        });
+      });
+    });
+
+    it("accepts a subgraph without a name", function() {
+      const result = viz.render({
+        edges: [
+          { tail: "a", head: "b" }
+        ],
+        subgraphs: [
+          {
+            graphAttributes: {
+              cluster: true,
+              color: "red"
+            },
+            nodes: [
+              { name: "a" }
+            ]
+          },
+          {
+            graphAttributes: {
+              cluster: true,
+              color: "green"
+            },
+            nodes: [
+              { name: "b" }
+            ]
+          }
+        ]
+      });
+
+      assert.deepStrictEqual(result, {
+        status: "success",
+        output: `digraph {
+	graph [bb="0,0,86,140"];
+	node [label="\\N"];
+	{
+		graph [bb="8,80,78,132",
+			cluster=true,
+			color=red
+		];
+		a	[height=0.5,
+			pos="43,106",
+			width=0.75];
+	}
+	{
+		graph [bb="8,8,78,60",
+			cluster=true,
+			color=green
+		];
+		b	[height=0.5,
+			pos="43,34",
+			width=0.75];
+	}
+	a -> b	[pos="e,43,52.104 43,87.697 43,80.407 43,71.726 43,63.536"];
+}
 `,
         errors: []
       });