fix(parser-3.0.x): prevent [key: string]: never in allOf with additionalProperties: false

Applies same fix as 2.0.x parser - detects empty objects with additionalProperties: false
inside allOf compositions and skips never index signature generation.
Ensures consistent behavior across all OpenAPI parser versions.

Author: Mxwllas

packages/openapi-ts/src/openApi/3.0.x/parser/schema.ts

@@ -248,31 +248,24 @@ const parseObject = ({
     irSchema.properties = schemaProperties;
   }
 
-  // --- PATCH: Avoid [key: string]: never for empty objects in allOf ---
-  // If this object is empty (no properties, no required, no patternProperties, no min/maxProperties)
-  // and additionalProperties is false, and we are inside an allOf composition,
-  // then do NOT emit additionalProperties: { type: 'never' }.
-  // Instead, let the composition enforce the restriction.
-  const isEmptyObject =
-    (!schema.properties || Object.keys(schema.properties).length === 0) &&
-    (!schema.required || schema.required.length === 0) &&
-    schema.minProperties === undefined &&
-    schema.maxProperties === undefined;
-
-  // Heuristic: if state has a marker for "inAllOf", skip [key: string]: never for empty objects
-  const inAllOf = (state as any)?.inAllOf;
-
   if (schema.additionalProperties === undefined) {
     if (!irSchema.properties) {
       irSchema.additionalProperties = {
         type: 'unknown',
       };
     }
   } else if (typeof schema.additionalProperties === 'boolean') {
-    if (schema.additionalProperties === false && isEmptyObject && inAllOf) {
-      // Do not emit [key: string]: never for empty object in allOf
-      // Just skip setting additionalProperties
-    } else {
+    // Avoid [key: string]: never for empty objects with additionalProperties: false inside allOf
+    // This would override inherited properties from other schemas in the composition
+    const isEmptyObjectInAllOf =
+      state.inAllOf &&
+      schema.additionalProperties === false &&
+      (!schema.properties || Object.keys(schema.properties).length === 0) &&
+      !schema.allOf &&
+      !schema.anyOf &&
+      !schema.oneOf;
+
+    if (!isEmptyObjectInAllOf) {
       irSchema.additionalProperties = {
         type: schema.additionalProperties ? 'unknown' : 'never',
       };
@@ -338,26 +331,20 @@ const parseAllOf = ({
   const compositionSchemas = schema.allOf;
 
   for (const compositionSchema of compositionSchemas) {
-    // Mark that we are inside an allOf for parseObject
-    // Only pass inAllOf directly to the schema in allOf if it is NOT a $ref.
-    let irCompositionSchema;
-    if (
-      compositionSchema &&
-      typeof compositionSchema === 'object' &&
-      !('$ref' in compositionSchema)
-    ) {
-      irCompositionSchema = schemaToIrSchema({
-        context,
-        schema: compositionSchema,
-        state: { ...state, inAllOf: true },
-      });
-    } else {
-      irCompositionSchema = schemaToIrSchema({
-        context,
-        schema: compositionSchema,
-        state,
-      });
-    }
+    // Don't propagate inAllOf flag to $ref schemas to avoid issues with reusable components
+    const isRef = '$ref' in compositionSchema;
+    const schemaState = isRef
+      ? state
+      : {
+          ...state,
+          inAllOf: true,
+        };
+
+    const irCompositionSchema = schemaToIrSchema({
+      context,
+      schema: compositionSchema,
+      state: schemaState,
+    });
 
     irSchema.accessScopes = mergeSchemaAccessScopes(
       irSchema.accessScopes,