Better error message

go/pkg/api/path.go

@@ -321,7 +321,7 @@ func patchValue(a *ast.Attribute, c change) error {
 	}
 	if a.ComplexValue != nil {
 		if c.method == "add" {
-			return fmt.Errorf("Can't add to complex value of '%s'", a.Name)
+			return fmt.Errorf("Can't add duplicate definition of '%s'", a.Name)
 		}
 		return fmt.Errorf("Can't delete from complex value of '%s'", a.Name)
 	}

go/testdata/api/path.t

@@ -770,7 +770,6 @@ area:a2 = {
 =INPUT=
 network:n1 = { ip = 10.1.1.0/24; }
 network:n2 = { ip = 10.1.2.0/24; }
-network:n3 = { ip = 10.1.3.0/24; }
 
 router:asa1 = {
  managed;
@@ -779,13 +778,6 @@ router:asa1 = {
  interface:n2 = { ip = 10.1.2.1; hardware = n2; }
 }
 
-router:asa2 = {
- managed;
- model = ASA;
- interface:n2 = { ip = 10.1.2.2; hardware = n2; }
- interface:n3 = { ip = 10.1.3.2; hardware = n3; }
-}
-
 area:a2 = {
  inclusive_border = interface:asa1.n1;
 }
@@ -809,4 +801,35 @@ Warning: Ignoring undefined owner:o1 of router_attributes of area:a2
 + }
   inclusive_border = interface:asa1.n1;
  }
+=END=
+
+############################################################
+=TITLE=Add duplicate router_attributes
+=INPUT=
+owner:o1 = { admins = a1@example.com; }
+network:n1 = { ip = 10.1.1.0/24; owner = o1; }
+network:n2 = { ip = 10.1.2.0/24; }
+
+router:asa1 = {
+ managed;
+ model = ASA;
+ interface:n1 = { ip = 10.1.1.1; hardware = n1; }
+ interface:n2 = { ip = 10.1.2.1; hardware = n2; }
+}
+
+area:a2 = {
+ router_attributes = { owner = o1; }
+ inclusive_border = interface:asa1.n1;
+}
+=JOB=
+{
+
+    "method": "add",
+    "params": {
+        "path": "area:a2,router_attributes",
+        "value": { "owner": "o2" }
+    }
+}
+=ERROR=
+Error: Can't add duplicate definition of 'router_attributes'
 =END=

go/testdata/api/topology.t

@@ -109,7 +109,7 @@ network:a = {
     }
 }
 =ERROR=
-Error: Can't add to complex value of 'host:name_10_1_1_4'
+Error: Can't add duplicate definition of 'host:name_10_1_1_4'
 =END=
 
 ############################################################