Fix when first item is nullable.

Closes #2

Author: bombsimon

inferred_schema.go

@@ -75,7 +75,7 @@ func (i *InferredSchema) Infer(value any, hints Hints) *InferredSchema {
 	if i.SchemaType == SchemaTypeNullable {
 		return &InferredSchema{
 			SchemaType: SchemaTypeNullable,
-			Nullable:   i,
+			Nullable:   i.Nullable.Infer(value, hints),
 		}
 	}
 
@@ -258,7 +258,6 @@ func (i *InferredSchema) Infer(value any, hints Hints) *InferredSchema {
 			if subInfer, ok := i.Properties.Required[k]; ok {
 				i.Properties.Required[k] = subInfer.Infer(v, hints.SubHints(k))
 			} else if subInfer, ok := i.Properties.Optional[k]; ok {
-				i.Properties.Optional = ensureMap(i.Properties.Optional)
 				i.Properties.Optional[k] = subInfer.Infer(v, hints.SubHints(k))
 			} else {
 				i.Properties.Optional = ensureMap(i.Properties.Optional)

inferrer_test.go

@@ -43,6 +43,18 @@ func TestInferString(t *testing.T) {
 				},
 			},
 		},
+		{
+			description: "object first is null",
+			values:      []string{`{"name":null}`, `{"name":"Joe"}`},
+			expectedSchema: Schema{
+				Properties: map[string]Schema{
+					"name": {
+						Type:     jtd.TypeString,
+						Nullable: true,
+					},
+				},
+			},
+		},
 		{
 			description: "array",
 			values:      []string{`[1, 2, 3]`},