update after feedback

Pontus Lundin · Pontus Lundin · commit 50ad58635f0b · 2025-08-19T10:28:03.000+02:00
diff --git a/packages/openapi-typescript/src/transform/schema-object.ts b/packages/openapi-typescript/src/transform/schema-object.ts
@@ -547,18 +547,27 @@ function transformSchemaObjectCore(schemaObject: SchemaObject, options: Transfor
     if (schemaObject.additionalProperties || options.ctx.additionalProperties || schemaObject.patternProperties) {
       const hasExplicitAdditionalProperties =
         typeof schemaObject.additionalProperties === "object" && Object.keys(schemaObject.additionalProperties).length;
+      const hasImplicitAdditionalProperties =
+      schemaObject.additionalProperties === true || (typeof schemaObject.additionalProperties === "object" && Object.keys(schemaObject.additionalProperties).length === 0);
       const hasExplicitPatternProperties =
         typeof schemaObject.patternProperties === "object" && Object.keys(schemaObject.patternProperties).length;
       const addlTypes = [];
       if (hasExplicitAdditionalProperties) {
         addlTypes.push(transformSchemaObject(schemaObject.additionalProperties as SchemaObject, options));
       }
+      if (hasImplicitAdditionalProperties || (!schemaObject.additionalProperties && options.ctx.additionalProperties)) {
+        addlTypes.push(UNKNOWN);
+      }
       if (hasExplicitPatternProperties) {
         for (const [_, v] of getEntries(schemaObject.patternProperties ?? {}, options.ctx)) {
           addlTypes.push(transformSchemaObject(v, options));
         }
       }
-      const addlType = addlTypes.length === 0 ? UNKNOWN : tsUnion(addlTypes);
+
+      if (addlTypes.length === 0) return;
+
+      const addlType = tsUnion(addlTypes);
+
       return tsIntersection([
         ...(coreObjectType.length ? [ts.factory.createTypeLiteralNode(coreObjectType)] : []),
         ts.factory.createTypeLiteralNode([
diff --git a/packages/openapi-typescript/test/transform/schema-object/object.test.ts b/packages/openapi-typescript/test/transform/schema-object/object.test.ts
@@ -101,11 +101,22 @@ describe("transformSchemaObject > object", () => {
     ],
     [
       "patternProperties > empty object",
+      {
+        given: { type: "object", patternProperties: {} },
+        want: `Record<string, never>`,
+      },
+    ],
+    [
+      "patternProperties > empty object with options.additionalProperties=true",
       {
         given: { type: "object", patternProperties: {} },
         want: `{
     [key: string]: unknown;
 }`,
+      options: {
+        ...DEFAULT_OPTIONS,
+        ctx: { ...DEFAULT_CTX, additionalProperties: true },
+      }
       },
     ],
     [
@@ -132,6 +143,19 @@ describe("transformSchemaObject > object", () => {
         given: { type: "object", patternProperties: { "^a": { type: "string" }, "^b": { type: "number" } } },
         want: `{
     [key: string]: string | number;
+}`,
+      },
+    ],
+    [
+      "patternProperties > additional=true and patterns",
+      {
+        given: {
+          type: "object",
+          additionalProperties: true,
+          patternProperties: { "^a": { type: "string" } },
+        },
+        want: `{
+    [key: string]: unknown | string;
 }`,
       },
     ],
@@ -148,6 +172,22 @@ describe("transformSchemaObject > object", () => {
 }`,
       },
     ],
+    [
+      "patternProperties > patterns with options.additionalProperties=true",
+      {
+        given: {
+          type: "object",
+          patternProperties: { "^a": { type: "string" } },
+        },
+        want: `{
+    [key: string]: unknown | string;
+}`,
+      options: {
+        ...DEFAULT_OPTIONS,
+        ctx: { ...DEFAULT_CTX, additionalProperties: true },
+      }
+      },
+    ],
     [
       "nullable",
       {
