only trigger deprecation warnings for non-empty attributes

A deprecation that targeted the use of an attributte would always trigger, now
we're only checking for deprecations on non-empty attributes.

deprecation_test.go

@@ -37,7 +37,7 @@ func TestDeprecation(t *testing.T) {
 		counts = make(map[string]int)
 	)
 
-	dfn := func(
+	deprecationHandler := func(
 		_ context.Context, _ *newsdoc.Document,
 		deprecation revisor.Deprecation,
 		c revisor.DeprecationContext,
@@ -57,7 +57,7 @@ func TestDeprecation(t *testing.T) {
 	ctx := context.Background()
 
 	res, err := testValidator.ValidateDocument(ctx, &document,
-		revisor.WithDeprecationHandler(dfn))
+		revisor.WithDeprecationHandler(deprecationHandler))
 	must(t, err, "validate document")
 
 	t.Run("FoundDeprecations", func(t *testing.T) {

testdata/constraints/geo.json

@@ -83,6 +83,20 @@
               }
             }
           }
+        },
+        {
+          "match": {
+            "type": {"const":"core/place"}
+          },
+          "attributes": {
+            "role": {
+              "allowEmpty": true,
+              "deprecated": {
+                "label": "no-roles",
+                "doc": "Let's just skip roles"
+              }
+            }
+          }
         }
       ]
     }

testdata/results-deprecation/geo.enforced.json

@@ -18,6 +18,21 @@
     "error": "enforced deprecation \"absurdity\": Why did we ever think this was a good idea?",
     "enforcedDeprecation": true
   },
+  {
+    "entity": [
+      {
+        "refType": "attribute",
+        "name": "role"
+      },
+      {
+        "refType": "block",
+        "kind": "meta",
+        "type": "core/place"
+      }
+    ],
+    "error": "enforced deprecation \"no-roles\": Let's just skip roles",
+    "enforcedDeprecation": true
+  },
   {
     "entity": [
       {

testdata/results-deprecation/geo.json

@@ -29,6 +29,29 @@
       "value": "absurd"
     }
   },
+  {
+    "Deprecation": {
+      "label": "no-roles",
+      "doc": "Let's just skip roles"
+    },
+    "Context": {
+      "entity": {
+        "refType": "attribute",
+        "name": "role"
+      },
+      "block": {
+        "type": "core/place",
+        "data": {
+          "area": "POLYGON ((30 10, 40 40, 20 40, 10 20, 30 10))",
+          "position": "POINT(12 15)",
+          "position_3d": "POINT Z (12 15 14)",
+          "road": "LINESTRING (30.123 10.15, 10.66 30.23, 40.23 40.66)"
+        },
+        "role": "absurd"
+      },
+      "value": "absurd"
+    }
+  },
   {
     "Deprecation": {
       "label": "3d-points",

validation.go

@@ -513,17 +513,20 @@ func validateDocumentAttributes(
 				})
 			}
 
-			res, err = checkDeprecation(
-				ctx, vCtx, res, d,
-				DeprecationContext{
-					Entity: &ref,
-					Value:  &value,
-				}, depr, check.Deprecated)
-			if err != nil {
-				return nil, err
-			}
-
 			if value != "" {
+				// As attributes always exist we only want to
+				// trigger a deprecation warning if they
+				// actually have a value.
+				res, err = checkDeprecation(
+					ctx, vCtx, res, d,
+					DeprecationContext{
+						Entity: &ref,
+						Value:  &value,
+					}, depr, check.Deprecated)
+				if err != nil {
+					return nil, err
+				}
+
 				vCtx.coll.CollectValue(ValueAnnotation{
 					Ref:   []EntityRef{ref},
 					Value: value,
@@ -808,17 +811,20 @@ func validateBlockAttributes(
 				})
 			}
 
-			res, err = checkDeprecation(
-				ctx, vCtx, res, doc, DeprecationContext{
-					Entity: &ref,
-					Block:  b,
-					Value:  &value,
-				}, check.Deprecated, depr)
-			if err != nil {
-				return nil, err
-			}
-
 			if value != "" {
+				// As attributes always exist we only want to
+				// trigger a deprecation warning if they
+				// actually have a value.
+				res, err = checkDeprecation(
+					ctx, vCtx, res, doc, DeprecationContext{
+						Entity: &ref,
+						Block:  b,
+						Value:  &value,
+					}, check.Deprecated, depr)
+				if err != nil {
+					return nil, err
+				}
+
 				vCtx.coll.CollectValue(ValueAnnotation{
 					Ref:        []EntityRef{ref},
 					Constraint: check,