Fix faulty discriminator

Author: bombsimon

inferred_schema.go

@@ -136,14 +136,14 @@ func (i *InferredSchema) Infer(value any, hints Hints) *InferredSchema {
 
 		if discriminator, ok := hints.PeekActiveDiscriminator(); ok {
 			if mappingKey, ok := m[discriminator].(string); ok {
-				inferRest := NewInferredSchema().Infer(m, hints)
+				delete(m, discriminator)
 
 				return &InferredSchema{
 					SchemaType: SchemaTypeDiscriminator,
 					Discriminator: Discriminator{
 						Discriminator: discriminator,
 						Mapping: map[string]*InferredSchema{
-							mappingKey: inferRest,
+							mappingKey: NewInferredSchema().Infer(m, hints),
 						},
 					},
 				}
@@ -295,11 +295,15 @@ func (i *InferredSchema) Infer(value any, hints Hints) *InferredSchema {
 			return &InferredSchema{SchemaType: SchemaTypeAny}
 		}
 
+		delete(m, i.Discriminator.Discriminator)
+
 		if _, ok := i.Discriminator.Mapping[mappingKey]; !ok {
 			i.Discriminator.Mapping[mappingKey] = NewInferredSchema()
 		}
 
 		i.Discriminator.Mapping[mappingKey] = i.Discriminator.Mapping[mappingKey].Infer(m, hints)
+
+		return i
 	}
 
 	if i.SchemaType == SchemaTypeDiscriminator {

inferrer_test.go

@@ -72,3 +72,46 @@ func TestJTDInferrerWithHints(t *testing.T) {
 
 	assert.EqualValues(t, expectedSchema, gotSchema)
 }
+
+func TestJTDInferWithDiscriminatorHints(t *testing.T) {
+	hints := Hints{
+		Discriminator: HintSet{
+			Values: [][]string{
+				{"-", "type"},
+			},
+		},
+	}
+
+	rows := []string{
+		`[{"type": "s", "value": "foo"},{"type": "n", "value": 3.14}]`,
+	}
+
+	inferrer := NewInferrer(hints)
+
+	for _, row := range rows {
+		rowAsJSON := make([]any, 0)
+		require.NoError(t, json.Unmarshal([]byte(row), &rowAsJSON))
+		inferrer = inferrer.Infer(rowAsJSON)
+	}
+
+	expectedSchema := Schema{
+		Elements: &Schema{
+			Discriminator: "type",
+			Mapping: map[string]Schema{
+				"s": {
+					Properties: map[string]Schema{
+						"value": {Type: jtd.TypeString},
+					},
+				},
+				"n": {
+					Properties: map[string]Schema{
+						"value": {Type: jtd.TypeFloat64},
+					},
+				},
+			},
+		},
+	}
+	gotSchema := inferrer.IntoSchema()
+
+	assert.EqualValues(t, expectedSchema, gotSchema)
+}