feat: alias single anyOf/allOf types

fixes #296

Author: perher

pkg/generator/config.go

@@ -40,6 +40,8 @@ type Config struct {
 	// DisableCustomTypesForMaps configures the generator to avoid creating a custom type for maps,
 	// and to use the map type directly.
 	DisableCustomTypesForMaps bool
+	// AliasSingleAllOfAnyOfRefs will convert types with a single nested anyOf or allOf ref type into a type alias.
+	AliasSingleAllOfAnyOfRefs bool
 }
 
 type SchemaMapping struct {

pkg/generator/schema_generator.go

@@ -849,6 +849,18 @@ func (g *schemaGenerator) generateAnyOfType(t *schemas.Type, scope nameScope) (c
 		return nil, errEmptyInAnyOf
 	}
 
+	if g.config.AliasSingleAllOfAnyOfRefs && len(t.AnyOf) == 1 && t.IsEmptyObject() {
+		childType := t.AnyOf[0]
+		if childType.Ref != "" {
+			resolvedType, err := g.resolveRef(childType)
+			if err == nil {
+				return g.generateTypeInline(resolvedType, scope)
+			} else {
+				g.warner(fmt.Sprintf("Could not resolve ref %q: %v", childType.Ref, err))
+			}
+		}
+	}
+
 	rAnyOf := g.resolveRefs(t.AnyOf)
 
 	var isCycle bool
@@ -902,6 +914,18 @@ func (g *schemaGenerator) generateAnyOfType(t *schemas.Type, scope nameScope) (c
 }
 
 func (g *schemaGenerator) generateAllOfType(t *schemas.Type, scope nameScope) (codegen.Type, error) {
+	if g.config.AliasSingleAllOfAnyOfRefs && len(t.AllOf) == 1 && t.IsEmptyObject() {
+		subType := t.AllOf[0]
+		if subType.Ref != "" {
+			resolvedType, err := g.resolveRef(subType)
+			if err == nil {
+				return g.generateTypeInline(resolvedType, scope)
+			} else {
+				g.warner(fmt.Sprintf("Could not resolve subtype ref %q: %v", subType.Ref, err))
+			}
+		}
+	}
+
 	rAllOf := g.resolveRefs(t.AllOf)
 
 	allOfType, err := schemas.AllOf(rAllOf, t)

pkg/schemas/model.go

@@ -208,6 +208,10 @@ type Type struct {
 	Dereferenced bool `json:"-"` // Marks that his type has been dereferenced.
 }
 
+func (value *Type) IsEmptyObject() bool {
+	return len(value.Properties) == 0 && value.AdditionalProperties == nil
+}
+
 func (value *Type) SetSubSchemaType(sst SubSchemaType) {
 	value.subSchemaType = sst
 }

tests/data/aliasSingleAllOfAnyOfRefs/allOf/allOf.go

@@ -0,0 +1,28 @@
+{
+  "$schema": "https://json-schema.org/draft/2019-09/schema",
+  "type": "object",
+  "allOf": [
+    {
+      "$ref": "#/definitions/Thing"
+    }
+  ],
+  "definitions": {
+    "Thing": {
+      "allOf": [
+        {
+          "properties": {
+            "values": {
+              "type": "array",
+              "items": {
+                "$ref": "#/definitions/Value"
+              }
+            }
+          }
+        }
+      ]
+    },
+    "Value": {
+      "type": "number"
+    }
+  }
+}

tests/data/aliasSingleAllOfAnyOfRefs/allOf/allOf.json

@@ -0,0 +1,28 @@
+{
+  "$schema": "https://json-schema.org/draft/2019-09/schema",
+  "type": "object",
+  "anyOf": [
+    {
+      "$ref": "#/definitions/Thing"
+    }
+  ],
+  "definitions": {
+    "Thing": {
+      "anyOf": [
+        {
+          "properties": {
+            "values": {
+              "type": "array",
+              "items": {
+                "$ref": "#/definitions/Value"
+              }
+            }
+          }
+        }
+      ]
+    },
+    "Value": {
+      "type": "number"
+    }
+  }
+}

tests/data/aliasSingleAllOfAnyOfRefs/anyOf/anyOf.go

@@ -0,0 +1,10 @@
+{
+  "$schema": "http://json-schema.org/draft-04/schema#",
+  "id": "https://example.com/refExternalFileAllOfNestedRefs",
+  "type": "object",
+  "allOf": [
+    {
+      "$ref": "../allOf/allOf.json#/$defs/Thing"
+    }
+  ]
+}

tests/data/aliasSingleAllOfAnyOfRefs/anyOf/anyOf.json

@@ -226,6 +226,15 @@ func TestMinSizeInt(t *testing.T) {
 	testExamples(t, cfg, "./data/minSizedInts")
 }
 
+func TestAliasSingleAllOfAnyOfRefs(t *testing.T) {
+	t.Parallel()
+
+	cfg := basicConfig
+	cfg.AliasSingleAllOfAnyOfRefs = true
+
+	testExamples(t, cfg, "./data/aliasSingleAllOfAnyOfRefs")
+}
+
 func TestSchemaExtensions(t *testing.T) {
 	t.Parallel()