test: verify origin tracking for mapping-valued schema fields

Adds TestOrigin_MappingFields covering dependentRequired,
dependentSchemas, and patternProperties — fields that were missing
from Origin.Fields before yaml3 v0.0.12.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: reuvenharrison

openapi3/origin_test.go

@@ -834,3 +834,50 @@ func TestOrigin_Disabled(t *testing.T) {
 	require.Nil(t, doc.Info.Origin)
 	require.Nil(t, doc.Paths.Origin)
 }
+
+// TestOrigin_MappingFields verifies that mapping-valued schema fields
+// (dependentRequired, dependentSchemas, patternProperties) have their
+// key locations tracked in Origin.Fields. Before yaml3 v0.0.12,
+// buildOriginSeq only tracked scalar and sequence values, so these
+// mapping-valued fields were missing from the origin and source
+// location lookups returned nil.
+func TestOrigin_MappingFields(t *testing.T) {
+	loader := NewLoader()
+	loader.IncludeOrigin = true
+
+	doc, err := loader.LoadFromFile("testdata/origin/mapping_fields.yaml")
+	require.NoError(t, err)
+
+	schema := doc.Paths.Find("/test").Get.Responses.Value("200").Value.
+		Content["application/json"].Schema.Value.Properties["metadata"].Value
+	require.NotNil(t, schema.Origin)
+
+	file := "testdata/origin/mapping_fields.yaml"
+
+	// dependentRequired is a map[string][]string — mapping-valued
+	require.Contains(t, schema.Origin.Fields, "dependentRequired")
+	require.Equal(t, Location{
+		File:   file,
+		Line:   18,
+		Column: 21,
+		Name:   "dependentRequired",
+	}, schema.Origin.Fields["dependentRequired"])
+
+	// dependentSchemas is a Schemas map — mapping-valued
+	require.Contains(t, schema.Origin.Fields, "dependentSchemas")
+	require.Equal(t, Location{
+		File:   file,
+		Line:   22,
+		Column: 21,
+		Name:   "dependentSchemas",
+	}, schema.Origin.Fields["dependentSchemas"])
+
+	// patternProperties is a Schemas map — mapping-valued
+	require.Contains(t, schema.Origin.Fields, "patternProperties")
+	require.Equal(t, Location{
+		File:   file,
+		Line:   25,
+		Column: 21,
+		Name:   "patternProperties",
+	}, schema.Origin.Fields["patternProperties"])
+}

openapi3/testdata/origin/mapping_fields.yaml

@@ -0,0 +1,27 @@
+openapi: "3.1.0"
+info:
+  title: Mapping Fields Origin Test
+  version: "1.0"
+paths:
+  /test:
+    get:
+      responses:
+        "200":
+          description: OK
+          content:
+            application/json:
+              schema:
+                type: object
+                properties:
+                  metadata:
+                    type: object
+                    dependentRequired:
+                      name:
+                        - age
+                        - email
+                    dependentSchemas:
+                      credit_card:
+                        type: object
+                    patternProperties:
+                      "^x-":
+                        type: string