Enum with Root Types Filtering Recursive Reference

Author: ParkerVR

.changeset/mighty-zebras-move.md

@@ -0,0 +1,5 @@
+---
+"openapi-typescript": patch
+---
+
+Fix behavior when using enum and export-type flags

packages/openapi-typescript/examples/enum-root-types.ts

@@ -0,0 +1,38 @@
+/**
+ * This file was auto-generated by openapi-typescript.
+ * Do not make direct changes to the file.
+ */
+
+export type paths = Record<string, never>;
+export type webhooks = Record<string, never>;
+export interface components {
+    schemas: {
+        /** @enum {string} */
+        Status: Status;
+        /** @enum {number} */
+        Priority: Priority;
+        Item: {
+            name?: string;
+            status?: components["schemas"]["Status"];
+            priority?: components["schemas"]["Priority"];
+        };
+    };
+    responses: never;
+    parameters: never;
+    requestBodies: never;
+    headers: never;
+    pathItems: never;
+}
+export type Item = components['schemas']['Item'];
+export type $defs = Record<string, never>;
+export enum Status {
+    active = "active",
+    inactive = "inactive",
+    pending = "pending"
+}
+export enum Priority {
+    Value1 = 1,
+    Value2 = 2,
+    Value3 = 3
+}
+export type operations = Record<string, never>;

packages/openapi-typescript/examples/enum-root-types.yaml

@@ -0,0 +1,21 @@
+openapi: 3.0.0
+info:
+  title: Enum Root Types Test
+  version: 1.0.0
+components:
+  schemas:
+    Status:
+      type: string
+      enum: [active, inactive, pending]
+    Priority:
+      type: number
+      enum: [1, 2, 3]
+    Item:
+      type: object
+      properties:
+        name:
+          type: string
+        status:
+          $ref: '#/components/schemas/Status'
+        priority:
+          $ref: '#/components/schemas/Priority'

packages/openapi-typescript/src/transform/components-object.ts

@@ -11,6 +11,34 @@ import transformRequestBodyObject from "./request-body-object.js";
 import transformResponseObject from "./response-object.js";
 import transformSchemaObject from "./schema-object.js";
 
+/**
+ * Determines if a schema object represents an enum type to prevent duplicate exports
+ * when using --root-types and --enum flags together.
+ *
+ * When both flags are enabled:
+ * - --enum flag generates TypeScript enums at the bottom of the file
+ * - --root-types flag would normally also export these as root type aliases
+ * - This results in duplicate exports (both enum and type alias for the same schema)
+ *
+ * This function identifies enum schemas so they can be excluded from root type generation,
+ * allowing only the TypeScript enum to be generated.
+ *
+ * @param schema The schema object to check
+ * @returns true if the schema represents an enum type
+ */
+export function isEnumSchema(schema: unknown): boolean {
+  return (
+    typeof schema === "object" &&
+    schema !== null &&
+    !Array.isArray(schema) &&
+    "enum" in schema &&
+    Array.isArray((schema as any).enum) &&
+    (!("type" in schema) || (schema as any).type !== "object") &&
+    !("properties" in schema) &&
+    !("additionalProperties" in schema)
+  );
+}
+
 type ComponentTransforms = keyof Omit<ComponentsObject, "examples" | "securitySchemes" | "links" | "callbacks">;
 
 const transformers: Record<ComponentTransforms, (node: any, options: TransformNodeOptions) => ts.TypeNode> = {
@@ -68,27 +96,32 @@ export default function transformComponentsObject(componentsObject: ComponentsOb
         items.push(property);
 
         if (ctx.rootTypes) {
-          const componentKey = changeCase.pascalCase(singularizeComponentKey(key));
-          let aliasName = `${componentKey}${changeCase.pascalCase(name)}`;
+          // Skip enum schemas when generating root types to prevent duplication (only when --enum flag is enabled)
+          const shouldSkipEnumSchema = ctx.enum && key === "schemas" && isEnumSchema(item);
 
-          // Add counter suffix (e.g. "_2") if conflict in name
-          let conflictCounter = 1;
+          if (!shouldSkipEnumSchema) {
+            const componentKey = changeCase.pascalCase(singularizeComponentKey(key));
+            let aliasName = `${componentKey}${changeCase.pascalCase(name)}`;
 
-          while (rootTypeAliases[aliasName] !== undefined) {
-            conflictCounter++;
-            aliasName = `${componentKey}${changeCase.pascalCase(name)}_${conflictCounter}`;
-          }
-          const ref = ts.factory.createTypeReferenceNode(`components['${key}']['${name}']`);
-          if (ctx.rootTypesNoSchemaPrefix && key === "schemas") {
-            aliasName = aliasName.replace(componentKey, "");
+            // Add counter suffix (e.g. "_2") if conflict in name
+            let conflictCounter = 1;
+
+            while (rootTypeAliases[aliasName] !== undefined) {
+              conflictCounter++;
+              aliasName = `${componentKey}${changeCase.pascalCase(name)}_${conflictCounter}`;
+            }
+            const ref = ts.factory.createTypeReferenceNode(`components['${key}']['${name}']`);
+            if (ctx.rootTypesNoSchemaPrefix && key === "schemas") {
+              aliasName = aliasName.replace(componentKey, "");
+            }
+            const typeAlias = ts.factory.createTypeAliasDeclaration(
+              /* modifiers      */ tsModifiers({ export: true }),
+              /* name           */ aliasName,
+              /* typeParameters */ undefined,
+              /* type           */ ref,
+            );
+            rootTypeAliases[aliasName] = typeAlias;
           }
-          const typeAlias = ts.factory.createTypeAliasDeclaration(
-            /* modifiers      */ tsModifiers({ export: true }),
-            /* name           */ aliasName,
-            /* typeParameters */ undefined,
-            /* type           */ ref,
-          );
-          rootTypeAliases[aliasName] = typeAlias;
         }
       }
     }

packages/openapi-typescript/test/cli.test.ts

@@ -76,6 +76,14 @@ describe("CLI", () => {
         ci: { timeout: TIMEOUT },
       },
     ],
+    [
+      "snapshot > enum root types filtering",
+      {
+        given: ["./examples/enum-root-types.yaml", "--root-types", "--root-types-no-schema-prefix", "--enum"],
+        want: new URL("./examples/enum-root-types.ts", root),
+        ci: { timeout: TIMEOUT },
+      },
+    ],
   ];
 
   for (const [testName, { given, want, ci }] of tests) {

packages/openapi-typescript/test/transform/components-object.test.ts

@@ -1,7 +1,7 @@
 import { fileURLToPath } from "node:url";
 import ts from "typescript";
 import { NULL, astToString } from "../../src/lib/ts.js";
-import transformComponentsObject from "../../src/transform/components-object.js";
+import transformComponentsObject, { isEnumSchema } from "../../src/transform/components-object.js";
 import type { GlobalContext } from "../../src/types.js";
 import { DEFAULT_CTX, type TestCase } from "../test-helpers.js";
 
@@ -871,3 +871,69 @@ export type Error = components['schemas']['Error'];
     );
   }
 });
+
+describe("isEnumSchema", () => {
+  test("returns true for string enum schema", () => {
+    const schema = {
+      type: "string",
+      enum: ["active", "inactive", "pending"],
+    };
+    expect(isEnumSchema(schema)).toBe(true);
+  });
+
+  test("returns true for number enum schema", () => {
+    const schema = {
+      type: "number",
+      enum: [1, 2, 3],
+    };
+    expect(isEnumSchema(schema)).toBe(true);
+  });
+
+  test("returns true for mixed enum schema without explicit type", () => {
+    const schema = {
+      enum: ["high", 0, null],
+    };
+    expect(isEnumSchema(schema)).toBe(true);
+  });
+
+  test("returns false for object schema with properties", () => {
+    const schema = {
+      type: "object",
+      properties: {
+        name: { type: "string" },
+      },
+    };
+    expect(isEnumSchema(schema)).toBe(false);
+  });
+
+  test("returns false for object schema with enum (object enums not supported)", () => {
+    const schema = {
+      type: "object",
+      enum: [{ value: "test" }],
+    };
+    expect(isEnumSchema(schema)).toBe(false);
+  });
+
+  test("returns false for schema with additionalProperties", () => {
+    const schema = {
+      enum: ["test"],
+      additionalProperties: true,
+    };
+    expect(isEnumSchema(schema)).toBe(false);
+  });
+
+  test("returns false for schema without enum", () => {
+    const schema = {
+      type: "string",
+    };
+    expect(isEnumSchema(schema)).toBe(false);
+  });
+
+  test("returns false for null, undefined, or non-object inputs", () => {
+    expect(isEnumSchema(null)).toBe(false);
+    expect(isEnumSchema(undefined)).toBe(false);
+    expect(isEnumSchema("string")).toBe(false);
+    expect(isEnumSchema(123)).toBe(false);
+    expect(isEnumSchema([])).toBe(false);
+  });
+});

packages/openapi-typescript/tsconfig.examples.json

@@ -1,5 +1,5 @@
 {
   "extends": "./tsconfig.json",
   "include": ["examples"],
-  "exclude": ["examples/digital-ocean-api.ts"]
+  "exclude": ["examples/digital-ocean-api.ts", "examples/enum-root-types.ts"]
 }