fix: make nullable work in components/schema

src/internal/OpenApiTools/components/Schema.ts

@@ -1,4 +1,4 @@
-import ts, { skipPartiallyEmittedExpressions } from "typescript";
+import ts from "typescript";
 
 import type { OpenApi } from "../../../types";
 import { FeatureDevelopmentError } from "../../Exception";
@@ -10,6 +10,20 @@ import type { AnySchema, ArraySchema, ObjectSchema, PrimitiveSchema } from "../t
 import type * as Walker from "../Walker";
 import * as ExternalDocumentation from "./ExternalDocumentation";
 
+const nullable = (factory: Factory.Type, typeNode: ts.TypeNode, nullable: boolean): ts.TypeNode => {
+  if (nullable) {
+    return factory.UnionTypeNode.create({
+      typeNodes: [
+        typeNode,
+        factory.TypeNode.create({
+          type: "null",
+        }),
+      ],
+    });
+  }
+  return typeNode;
+};
+
 export const generatePropertySignatures = (
   entryPoint: string,
   currentPoint: string,
@@ -42,6 +56,41 @@ export const generatePropertySignatures = (
   });
 };
 
+export const generateTypeAliasDeclarationForObject = (
+  entryPoint: string,
+  currentPoint: string,
+  factory: Factory.Type,
+  name: string,
+  schema: ObjectSchema,
+  context: ToTypeNode.Context,
+  convertContext: ConvertContext.Types,
+): ts.TypeAliasDeclaration => {
+  if (schema.type !== "object") {
+    throw new FeatureDevelopmentError("Please use generateTypeAlias");
+  }
+  let members: ts.TypeElement[] = [];
+  const propertySignatures = generatePropertySignatures(entryPoint, currentPoint, factory, schema, context, convertContext);
+  if (Guard.isObjectSchemaWithAdditionalProperties(schema)) {
+    const additionalProperties = ToTypeNode.convertAdditionalProperties(entryPoint, currentPoint, factory, schema, context, convertContext);
+    if (schema.additionalProperties === true) {
+      members = members.concat(additionalProperties);
+    } else {
+      members = [...propertySignatures, additionalProperties];
+    }
+  } else {
+    members = propertySignatures;
+  }
+  const typeNode = factory.TypeLiteralNode.create({
+    members,
+  });
+  return factory.TypeAliasDeclaration.create({
+    export: true,
+    name: convertContext.escapeDeclarationText(name),
+    comment: [schema.title, schema.description].filter(v => !!v).join("\n\n"),
+    type: nullable(factory, typeNode, schema.nullable === true),
+  });
+};
+
 export const generateInterface = (
   entryPoint: string,
   currentPoint: string,
@@ -164,11 +213,10 @@ export const generateTypeAlias = (
       type: schema.type,
     });
   }
-
   return factory.TypeAliasDeclaration.create({
     export: true,
     name: convertContext.escapeDeclarationText(name),
-    type,
+    type: nullable(factory, type, schema.nullable === true),
     comment: [schema.title, schema.description].filter(v => !!v).join("\n\n"),
   });
 };
@@ -239,11 +287,19 @@ export const addSchema = (
       value: generateArrayTypeAlias(entryPoint, currentPoint, factory, declarationName, schema, context, convertContext),
     });
   } else if (Guard.isObjectSchema(schema)) {
-    store.addStatement(targetPoint, {
-      kind: "interface",
-      name: convertContext.escapeDeclarationText(declarationName),
-      value: generateInterface(entryPoint, currentPoint, factory, declarationName, schema, context, convertContext),
-    });
+    if (schema.nullable) {
+      store.addStatement(targetPoint, {
+        kind: "typeAlias",
+        name: convertContext.escapeDeclarationText(declarationName),
+        value: generateTypeAliasDeclarationForObject(entryPoint, currentPoint, factory, declarationName, schema, context, convertContext),
+      });
+    } else {
+      store.addStatement(targetPoint, {
+        kind: "interface",
+        name: convertContext.escapeDeclarationText(declarationName),
+        value: generateInterface(entryPoint, currentPoint, factory, declarationName, schema, context, convertContext),
+      });
+    }
   } else if (Guard.isPrimitiveSchema(schema)) {
     store.addStatement(targetPoint, {
       kind: "typeAlias",

src/internal/OpenApiTools/components/Schemas.ts

@@ -137,17 +137,17 @@ export const generateNamespace = (
       );
     }
     if (Guard.isObjectSchema(schema)) {
-      return store.addStatement(
-        path,
-        {
-          kind: "interface",
-          name: convertContext.escapeDeclarationText(name),
-          value: Schema.generateInterface(entryPoint, currentPoint, factory, name, schema, context, convertContext),
-        },
-        { override: true },
-      );
-    }
-    if (Guard.isObjectSchema(schema)) {
+      if (schema.nullable) {
+        return store.addStatement(
+          path,
+          {
+            kind: "typeAlias",
+            name: convertContext.escapeDeclarationText(name),
+            value: Schema.generateTypeAliasDeclarationForObject(entryPoint, currentPoint, factory, name, schema, context, convertContext),
+          },
+          { override: true },
+        );
+      }
       return store.addStatement(
         path,
         {

test/__tests__/__snapshots__/spit-code-test.ts.snap

@@ -340,6 +340,13 @@ export namespace Schemas {
     export type RemoteRefArray = Schemas.Level1.Level2.Level3.RemoteArray;
     /** Level 4 */
     export type RemoteRefObject = Schemas.Level1.Level2.Level3.Level4.RemoteObject;
+    export type NullableString = string | null;
+    export type NullableBoolean = boolean | null;
+    export type NullableNumber = number | null;
+    export type NullableArray = string[] | null;
+    export type NullableObject = {
+        gt?: string;
+    } | null;
     export namespace DirectRef {
         export type ForHeader = string;
         export interface ForResponse {

test/__tests__/__snapshots__/typedef-only-test.ts.snap

@@ -141,6 +141,13 @@ export namespace Schemas {
     export type RemoteRefArray = Schemas.Level1.Level2.Level3.RemoteArray;
     /** Level 4 */
     export type RemoteRefObject = Schemas.Level1.Level2.Level3.Level4.RemoteObject;
+    export type NullableString = string | null;
+    export type NullableBoolean = boolean | null;
+    export type NullableNumber = number | null;
+    export type NullableArray = string[] | null;
+    export type NullableObject = {
+        gt?: string;
+    } | null;
     export namespace DirectRef {
         export type ForHeader = string;
         export interface ForResponse {

test/__tests__/__snapshots__/typedef-with-template-test.ts.snap

@@ -107,6 +107,13 @@ export namespace Schemas {
     export type RemoteRefArray = Schemas.Level1.Level2.Level3.RemoteArray;
     /** Level 4 */
     export type RemoteRefObject = Schemas.Level1.Level2.Level3.Level4.RemoteObject;
+    export type NullableString = string | null;
+    export type NullableBoolean = boolean | null;
+    export type NullableNumber = number | null;
+    export type NullableArray = string[] | null;
+    export type NullableObject = {
+        gt?: string;
+    } | null;
     export namespace DirectRef {
         export type ForHeader = string;
         export interface ForResponse {
@@ -650,6 +657,13 @@ export namespace Schemas {
     export type RemoteRefArray = Schemas.Level1.Level2.Level3.RemoteArray;
     /** Level 4 */
     export type RemoteRefObject = Schemas.Level1.Level2.Level3.Level4.RemoteObject;
+    export type NullableString = string | null;
+    export type NullableBoolean = boolean | null;
+    export type NullableNumber = number | null;
+    export type NullableArray = string[] | null;
+    export type NullableObject = {
+        gt?: string;
+    } | null;
     export namespace DirectRef {
         export type ForHeader = string;
         export interface ForResponse {

test/api.test.domain/index.yml

@@ -207,6 +207,26 @@ components:
       $ref: "./components/schemas/Level1/Level2/Level3/RemoteArray.yml"
     RemoteRefObject:
       $ref: "./components/schemas/Level1/Level2/Level3/Level4/RemoteObject.yml"
+    NullableString:
+      type: string
+      nullable: true
+    NullableBoolean:
+      type: boolean
+      nullable: true
+    NullableNumber:
+      type: number
+      nullable: true
+    NullableArray:
+      type: array
+      items:
+        type: string
+      nullable: true
+    NullableObject:
+      type: object
+      nullable: true
+      properties:
+        gt:
+          type: string
   headers:
     StringHeader:
       schema: