restrict edges in grid diagrams to between direct children (nested not implemented yet)

d2compiler/compile.go

@@ -1074,9 +1074,16 @@ func (c *compiler) validateEdges(g *d2graph.Graph) {
 	for _, edge := range g.Edges {
 		srcGrid := edge.Src.Parent.ClosestGridDiagram()
 		dstGrid := edge.Dst.Parent.ClosestGridDiagram()
-		if (srcGrid != nil || dstGrid != nil) && srcGrid != dstGrid {
+		if srcGrid != nil || dstGrid != nil {
+			if srcGrid != dstGrid {
 				c.errorf(edge.GetAstEdge(), "edges into grid diagrams are not supported yet")
 				continue
+			} else {
+				if srcGrid != edge.Src.Parent || dstGrid != edge.Dst.Parent {
+					c.errorf(edge.GetAstEdge(), "grid diagrams can only have edges between children right now")
+					continue
+				}
+			}
 		}
 	}
 }

d2compiler/compile_test.go

@@ -2488,6 +2488,18 @@ d2/testdata/d2compiler/TestCompile/grid_gap_negative.d2:3:16: vertical-gap must
 d2/testdata/d2compiler/TestCompile/grid_edge.d2:6:2: edges into grid diagrams are not supported yet
 d2/testdata/d2compiler/TestCompile/grid_edge.d2:7:2: edges into grid diagrams are not supported yet`,
 		},
+		{
+			name: "grid_deeper_edge",
+			text: `hey: {
+	grid-rows: 1
+	a -> b: ok
+	b: {
+		c -> d: not yet
+	}
+}
+`,
+			expErr: `d2/testdata/d2compiler/TestCompile/grid_deeper_edge.d2:5:3: grid diagrams can only have edges between children right now`,
+		},
 		{
 			name: "grid_nested",
 			text: `hey: {

testdata/d2compiler/TestCompile/grid_deeper_edge.exp.json

@@ -0,0 +1,11 @@
+{
+  "graph": null,
+  "err": {
+    "errs": [
+      {
+        "range": "d2/testdata/d2compiler/TestCompile/grid_deeper_edge.d2,4:2:41-4:8:47",
+        "errmsg": "d2/testdata/d2compiler/TestCompile/grid_deeper_edge.d2:5:3: grid diagrams can only have edges between children right now"
+      }
+    ]
+  }
+}