fix(openapi-typescript): handle nullable schemas

Author: gduliscouet-ubitransport

.changeset/strange-cherries-collect.md

@@ -0,0 +1,5 @@
+---
+"openapi-typescript": minor
+---
+
+Allow all types except UNKNOWN to be nullable

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

@@ -257,24 +257,20 @@ export function transformSchemaObjectWithComposition(
     }
   }
 
-  // if final type could be generated, return intersection of all members
-  if (finalType) {
-    // deprecated nullable
-    if (schemaObject.nullable && !schemaObject.default) {
-      return tsNullable([finalType]);
+  // When no final type can be generated, fall back to unknown type (or related variants)
+  if (!finalType) {
+    if ("type" in schemaObject) {
+      finalType = tsRecord(STRING, options.ctx.emptyObjectsUnknown ? UNKNOWN : NEVER);
+    } else {
+      finalType = UNKNOWN;
     }
-    return finalType;
   }
-  // otherwise fall back to unknown type (or related variants)
-  else {
-    // fallback: unknown
-    if (!("type" in schemaObject)) {
-      return UNKNOWN;
-    }
 
-    // if no type could be generated, fall back to “empty object” type
-    return tsRecord(STRING, options.ctx.emptyObjectsUnknown ? UNKNOWN : NEVER);
+  if (finalType !== UNKNOWN && schemaObject.nullable && !schemaObject.default) {
+    finalType = tsNullable([finalType]);
   }
+
+  return finalType;
 }
 
 /**

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

@@ -759,6 +759,119 @@ export enum ApiPaths {
         },
       },
     ],
+    [
+      "nullable > 3.0 syntax",
+      {
+        given: {
+          openapi: "3.0.3",
+          info: {
+            title: "Test",
+            version: "0",
+          },
+          paths: {},
+          components: {
+            schemas: {
+              obj1: {
+                title: "Nullable object",
+                type: "object",
+                properties: {
+                  id: {
+                    type: "string",
+                  },
+                },
+                nullable: true,
+              },
+              obj2: {
+                title: "Nullable empty object",
+                type: "object",
+                nullable: true,
+              },
+              str: {
+                title: "Nullable string",
+                type: "string",
+                nullable: true,
+              },
+            },
+          },
+        },
+        want: `export type paths = Record<string, never>;
+export type webhooks = Record<string, never>;
+export interface components {
+    schemas: {
+        /** Nullable object */
+        obj1: {
+            id?: string;
+        } | null;
+        /** Nullable empty object */
+        obj2: Record<string, never> | null;
+        /** Nullable string */
+        str: string | null;
+    };
+    responses: never;
+    parameters: never;
+    requestBodies: never;
+    headers: never;
+    pathItems: never;
+}
+export type $defs = Record<string, never>;
+export type operations = Record<string, never>;`,
+      },
+    ],
+    [
+      "nullable > 3.1 syntax",
+      {
+        given: {
+          openapi: "3.1.0",
+          info: {
+            title: "Test",
+            version: "0",
+          },
+          paths: {},
+          components: {
+            schemas: {
+              obj1: {
+                title: "Nullable object",
+                type: ["object", "null"],
+                properties: {
+                  id: {
+                    type: "string",
+                  },
+                },
+              },
+              obj2: {
+                title: "Nullable empty object",
+                type: ["object", "null"],
+              },
+              str: {
+                title: "Nullable string",
+                type: ["string", "null"],
+              },
+            },
+          },
+        },
+        want: `export type paths = Record<string, never>;
+export type webhooks = Record<string, never>;
+export interface components {
+    schemas: {
+        /** Nullable object */
+        obj1: {
+            id?: string;
+        } | null;
+        /** Nullable empty object */
+        obj2: Record<string, never> | null;
+        /** Nullable string */
+        str: string | null;
+    };
+    responses: never;
+    parameters: never;
+    requestBodies: never;
+    headers: never;
+    pathItems: never;
+}
+export type $defs = Record<string, never>;
+export type operations = Record<string, never>;`,
+      },
+    ],
   ];
 
   for (const [testName, { given, want, options, ci }] of tests) {