fix setting board label with primary

ci/release/changelogs/next.md

@@ -12,3 +12,4 @@
 #### Bugfixes ⛑️
 
 - Render: fixes edge case of a 3d shape with outside label being cut off [#2132](https://github.com/terrastruct/d2/pull/2132)
+- Composition: labels for boards set with shorthand `x: y` was not applied [#2182](https://github.com/terrastruct/d2/pull/2182)

d2compiler/compile.go

@@ -129,6 +129,9 @@ func (c *compiler) compileBoardsField(g *d2graph.Graph, ir *d2ir.Map, fieldName
 			g2.BaseAST = findFieldAST(g.BaseAST, f)
 		}
 		c.compileBoard(g2, m)
+		if f.Primary() != nil {
+			c.compileLabel(&g2.Root.Attributes, f)
+		}
 		g2.Name = f.Name
 		switch fieldName {
 		case "layers":

d2compiler/compile_test.go

@@ -3511,6 +3511,24 @@ steps: {
 				assert.True(t, g.IsFolderOnly)
 			},
 		},
+		{
+			name: "board-label-primary",
+			run: func(t *testing.T) {
+				g, _ := assertCompile(t, `hi
+layers: {
+  1: one {
+    RJ
+  }
+  2: {
+    label: two
+    RJ
+  }
+}
+`, "")
+				assert.Equal(t, "one", g.Layers[0].Root.Label.Value)
+				assert.Equal(t, "two", g.Layers[1].Root.Label.Value)
+			},
+		},
 		{
 			name: "no-inherit-label",
 			run: func(t *testing.T) {