d2compiler: disallow non-sibling near keys

d2compiler/compile.go

@@ -1067,27 +1067,9 @@ func (c *compiler) validateNear(g *d2graph.Graph) {
 			nearObj, isKey := g.Root.HasChild(d2graph.Key(obj.NearKey))
 			_, isConst := d2graph.NearConstants[d2graph.Key(obj.NearKey)[0]]
 			if isKey {
-				// Doesn't make sense to set near to an ancestor or descendant
-				nearIsAncestor := false
-				for curr := obj; curr != nil; curr = curr.Parent {
-					if curr == nearObj {
-						nearIsAncestor = true
-						break
-					}
-				}
-				if nearIsAncestor {
-					c.errorf(obj.NearKey, "near keys cannot be set to an ancestor")
-					continue
-				}
-				nearIsDescendant := false
-				for curr := nearObj; curr != nil; curr = curr.Parent {
-					if curr == obj {
-						nearIsDescendant = true
-						break
-					}
-				}
-				if nearIsDescendant {
-					c.errorf(obj.NearKey, "near keys cannot be set to an descendant")
+				// Doesn't make sense to set near to a non-sibling
+				if obj.Parent != nearObj.Parent {
+					c.errorf(obj.NearKey, "near keys cannot be set to a non-sibling")
 					continue
 				}
 				if nearObj.OuterSequenceDiagram() != nil {

d2compiler/compile_test.go

@@ -1598,10 +1598,12 @@ b: {
 a: {
   near: a.b
   b
+	c.near: mongodb
 }
 `,
-			expErr: `d2/testdata/d2compiler/TestCompile/near-invalid.d2:9:11: near keys cannot be set to an ancestor
-d2/testdata/d2compiler/TestCompile/near-invalid.d2:14:9: near keys cannot be set to an descendant`,
+			expErr: `d2/testdata/d2compiler/TestCompile/near-invalid.d2:9:11: near keys cannot be set to a non-sibling
+d2/testdata/d2compiler/TestCompile/near-invalid.d2:14:9: near keys cannot be set to a non-sibling
+d2/testdata/d2compiler/TestCompile/near-invalid.d2:16:10: near keys cannot be set to a non-sibling`,
 		},
 		{
 			name: "near_bad_constant",
@@ -1619,7 +1621,7 @@ z: {
   x
 }
 `,
-			expErr: `d2/testdata/d2compiler/TestCompile/near_special.d2:1:9: near keys cannot be set to descendants of special objects, like grid cells`,
+			expErr: `d2/testdata/d2compiler/TestCompile/near_special.d2:1:9: near keys cannot be set to a non-sibling`,
 		},
 		{
 			name: "near_bad_connected",
@@ -2007,7 +2009,7 @@ dst.id <-> src.dst_id
 }
 b.near: x.a
 `,
-			expErr: `d2/testdata/d2compiler/TestCompile/near_sequence.d2:5:9: near keys cannot be set to an object within sequence diagrams`,
+			expErr: `d2/testdata/d2compiler/TestCompile/near_sequence.d2:5:9: near keys cannot be set to a non-sibling`,
 		},
 		{
 			name: "sequence-timestamp",