Tests for an empty field name

A field named "" loads, and a bare {} token renders it, but no dot path can
reach it — List hides it and Fake cannot ask for it. {a.} is already rejected
for the same reason, so the two spellings disagree about the same mistake.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

bound_test.go

@@ -656,12 +656,13 @@ func TestDeepPathsUnderOneHeadStayIndependentWhereTheyDiverge(t *testing.T) {
 }
 
 func TestEmptyPathSegmentIsRejected(t *testing.T) {
-	// "{a.}", "{.b}" and "{a..b}" are unfinished paths. A field really named ""
-	// would otherwise make them resolve, which reads as a typo that worked.
+	// "{a.}", "{.b}" and "{a..b}" are unfinished paths, and the segment naming
+	// nothing is reported as that rather than as a missing field. An empty name is
+	// rejected where it is authored, so no data can make these resolve.
 	rejected := map[string]string{
-		"trailing dot": `{"format":"[{a.}]","a":{"format":"x","":["V"]}}`,
-		"leading dot":  `{"format":"[{.b}]","":{"format":"{b}","b":["V"]}}`,
-		"double dot":   `{"format":"[{a..b}]","a":{"format":"x","":{"format":"{b}","b":["V"]}}}`,
+		"trailing dot": `{"format":"[{a.}]","a":{"format":"x"}}`,
+		"leading dot":  `{"format":"[{.b}]","a":{"format":"{b}","b":["V"]}}`,
+		"double dot":   `{"format":"[{a..b}]","a":{"format":"x"}}`,
 	}
 	for name, file := range rejected {
 		_, err := New([]string{writeData(t, map[string]string{"cat": file})})

edge_test.go

@@ -120,6 +120,13 @@ func TestNewErrors(t *testing.T) {
 			map[string]string{"a|b": `["1"]`},
 			`category "a|b" contains "|"`,
 		},
+		// An empty name is reachable by no dot path, so List cannot advertise it and
+		// Fake cannot ask for it — {} is the one spelling that reaches it, which is
+		// the same trap {a.} is already rejected for.
+		"empty field name": {
+			map[string]string{"a": `{"format":"[{}]","":"VALUE"}`},
+			`field "" is empty`,
+		},
 		"folder name with a paren": {
 			map[string]string{"a(b/cat": `["1"]`},
 			`folder "a(b" contains "("`,