bugfix: correctly determine fragment usage

In previous versions of this code, this validation would exit when it
encountered a fragment legitimately used twice. This bugfix skips the recursion
but does not stop progress altogether allowing other fragments to be marked as
used.

Author: seansorr

internal/validation/testdata/tests.json

@@ -1464,6 +1464,13 @@
       "query": "\n      query Foo($a: String, $b: String, $c: String) {\n        ... on Type {\n          field(a: $a) {\n            field(b: $b) {\n              ... on Type {\n                field(c: $c)\n              }\n            }\n          }\n        }\n      }\n    ",
       "errors": []
     },
+    {
+      "name": "Validate: fragments are used even when they are nested",
+      "rule": "NoUnusedFragments",
+      "schema": 1,
+      "query": "\n        query Foo() {\n ...StringFragment\n stringBox {\n ...StringFragment\n ...StringFragmentPrime\n}\n}\n\n\n fragment StringFragment on StringBox {\n scalar\n}\n\n fragment StringFragmentPrime on StringBox {\n unrelatedField\n}\n",
+      "errors": []
+    },
     {
       "name": "Validate: No unused variables/uses all variables in fragments",
       "rule": "NoUnusedVariables",
@@ -3853,4 +3860,4 @@
       ]
     }
   ]
-}
+}

internal/validation/validation.go

@@ -418,8 +418,9 @@ func markUsedFragments(c *context, sels []query.Selection, fragUsed map[*query.F
 			}
 
 			if _, ok := fragUsed[frag]; ok {
-				return
+				continue
 			}
+
 			fragUsed[frag] = struct{}{}
 			markUsedFragments(c, frag.Selections, fragUsed)