Merge pull request #3385 from SipanP/fix/discriminator-non-string-type-support

fix(shared): support non-string discriminator property types

.changeset/wicked-rings-march.md

···
+---
+"@hey-api/shared": patch
+---
+
+Support non-string discriminator property types (boolean, integer, number)

packages/openapi-ts-tests/main/test/3.0.x.test.ts

···
     },
     {
       config: createConfig({
+        input: 'discriminator-non-string.yaml',
+        output: 'discriminator-non-string',
+      }),
+      description: 'handles non-string discriminator property types',
+    },
+    {
+      config: createConfig({
         input: 'enum-escape.json',
         output: 'enum-escape',
       }),

packages/openapi-ts-tests/main/test/3.1.x.test.ts

···
     },
     {
       config: createConfig({
+        input: 'discriminator-non-string.yaml',
+        output: 'discriminator-non-string',
+      }),
+      description: 'handles non-string discriminator property types',
+    },
+    {
+      config: createConfig({
         input: 'discriminator-one-of-read-write.yaml',
         output: 'discriminator-one-of-read-write',
       }),

packages/openapi-ts-tests/main/test/__snapshots__/3.0.x/discriminator-non-string/index.ts

···
+// This file is auto-generated by @hey-api/openapi-ts
+
+export type { AutoConfig, BooleanAnyOf, BooleanOneOf, ClientOptions, CustomConfig, IntegerAllOfBase, IntegerAllOfChildA, IntegerAllOfChildB, IntegerOneOf, NumberOneOf, TypeOne, TypeTwo, VersionAlpha, VersionBeta } from './types.gen';

packages/openapi-ts-tests/main/test/__snapshots__/3.0.x/discriminator-non-string/types.gen.ts

···
+// This file is auto-generated by @hey-api/openapi-ts
+
+export type ClientOptions = {
+    baseUrl: `${string}://${string}` | (string & {});
+};
+
+export type BooleanOneOf = ({
+    use_custom: false;
+} & AutoConfig) | ({
+    use_custom: true;
+} & CustomConfig);
+
+export type AutoConfig = {
+    use_custom: boolean;
+    auto_setting: string;
+};
+
+export type CustomConfig = {
+    use_custom: boolean;
+    custom_value: number;
+};
+
+export type BooleanAnyOf = ({
+    use_custom?: false;
+} & AutoConfig) | ({
+    use_custom?: true;
+} & CustomConfig);
+
+export type IntegerOneOf = ({
+    type_id: 1;
+} & TypeOne) | ({
+    type_id: 2;
+} & TypeTwo);
+
+export type TypeOne = {
+    type_id: number;
+    one_data: string;
+};
+
+export type TypeTwo = {
+    type_id: number;
+    two_data: string;
+};
+
+export type NumberOneOf = ({
+    version: 1;
+} & VersionAlpha) | ({
+    version: 2.5;
+} & VersionBeta);
+
+export type VersionAlpha = {
+    version: number;
+    alpha_field: string;
+};
+
+export type VersionBeta = {
+    version: number;
+    beta_field: string;
+};
+
+export type IntegerAllOfBase = {
+    kind: number;
+};
+
+export type IntegerAllOfChildA = Omit<IntegerAllOfBase, 'kind'> & {
+    child_a_field: string;
+    kind: 1;
+};
+
+export type IntegerAllOfChildB = Omit<IntegerAllOfBase, 'kind'> & {
+    child_b_field: string;
+    kind: 2;
+};

packages/openapi-ts-tests/main/test/__snapshots__/3.1.x/discriminator-non-string/index.ts

···
+// This file is auto-generated by @hey-api/openapi-ts
+
+export type { AutoConfig, BooleanAnyOf, BooleanOneOf, ClientOptions, CustomConfig, IntegerAllOfBase, IntegerAllOfChildA, IntegerAllOfChildB, IntegerOneOf, NullableIntegerOneOf, NullableVariantX, NullableVariantY, NumberOneOf, TypeOne, TypeTwo, VersionAlpha, VersionBeta } from './types.gen';

packages/openapi-ts-tests/main/test/__snapshots__/3.1.x/discriminator-non-string/types.gen.ts

···
+// This file is auto-generated by @hey-api/openapi-ts
+
+export type ClientOptions = {
+    baseUrl: `${string}://${string}` | (string & {});
+};
+
+export type BooleanOneOf = ({
+    use_custom: false;
+} & AutoConfig) | ({
+    use_custom: true;
+} & CustomConfig);
+
+export type AutoConfig = {
+    use_custom: false;
+    auto_setting: string;
+};
+
+export type CustomConfig = {
+    use_custom: true;
+    custom_value: number;
+};
+
+export type BooleanAnyOf = ({
+    use_custom?: false;
+} & AutoConfig) | ({
+    use_custom?: true;
+} & CustomConfig);
+
+export type IntegerOneOf = ({
+    type_id: 1;
+} & TypeOne) | ({
+    type_id: 2;
+} & TypeTwo);
+
+export type TypeOne = {
+    type_id: 1;
+    one_data: string;
+};
+
+export type TypeTwo = {
+    type_id: 2;
+    two_data: string;
+};
+
+export type NumberOneOf = ({
+    version: 1;
+} & VersionAlpha) | ({
+    version: 2.5;
+} & VersionBeta);
+
+export type VersionAlpha = {
+    version: 1;
+    alpha_field: string;
+};
+
+export type VersionBeta = {
+    version: 2.5;
+    beta_field: string;
+};
+
+export type IntegerAllOfBase = {
+    kind: number;
+};
+
+export type IntegerAllOfChildA = Omit<IntegerAllOfBase, 'kind'> & {
+    child_a_field: string;
+    kind: 1;
+};
+
+export type IntegerAllOfChildB = Omit<IntegerAllOfBase, 'kind'> & {
+    child_b_field: string;
+    kind: 2;
+};
+
+export type NullableIntegerOneOf = ({
+    tag: 10;
+} & NullableVariantX) | ({
+    tag: 20;
+} & NullableVariantY);
+
+export type NullableVariantX = {
+    tag: 10 | null;
+    x_data: string;
+};
+
+export type NullableVariantY = {
+    tag: 20 | null;
+    y_data: string;
+};

packages/shared/src/openApi/3.0.x/parser/schema.ts

···
   SchemaType,
   SchemaWithRequired,
 } from '../../../openApi/shared/types/schema';
-import { discriminatorValues } from '../../../openApi/shared/utils/discriminator';
+import {
+  convertDiscriminatorValue,
+  type DiscriminatorPropertyType,
+  discriminatorValues,
+} from '../../../openApi/shared/utils/discriminator';
 import { isTopLevelComponent, refToName } from '../../../utils/ref';
 import type { ReferenceObject, SchemaObject } from '../types/spec';
 
···
   }
 
   return;
+};
+
+/**
+ * Finds the type of a discriminator property by looking it up in the provided schemas.
+ * Searches through properties and allOf chains to find the property definition.
+ */
+const findDiscriminatorPropertyType = ({
+  context,
+  propertyName,
+  schemas,
+}: {
+  context: Context;
+  propertyName: string;
+  schemas: ReadonlyArray<SchemaObject | ReferenceObject>;
+}): DiscriminatorPropertyType => {
+  for (const schema of schemas) {
+    const resolved = '$ref' in schema ? context.resolveRef<SchemaObject>(schema.$ref) : schema;
+
+    // Check direct properties
+    const property = resolved.properties?.[propertyName];
+    if (property) {
+      const resolvedProperty =
+        '$ref' in property ? context.resolveRef<SchemaObject>(property.$ref) : property;
+      if (
+        resolvedProperty.type === 'boolean' ||
+        resolvedProperty.type === 'integer' ||
+        resolvedProperty.type === 'number'
+      ) {
+        return resolvedProperty.type;
+      }
+    }
+
+    // Check allOf chains
+    if (resolved.allOf) {
+      const foundType = findDiscriminatorPropertyType({
+        context,
+        propertyName,
+        schemas: resolved.allOf,
+      });
+      if (foundType !== 'string') {
+        return foundType;
+      }
+    }
+  }
+
+  return 'string';
 };
 
 /**
···
     // Use allValues if we found children, otherwise use the original values
     const finalValues = allValues.length > 0 ? allValues : values;
 
-    const valueSchemas: ReadonlyArray<IR.SchemaObject> = finalValues.map((value) => ({
-      const: value,
-      type: 'string',
-    }));
+    // Detect the actual type of the discriminator property
+    const propertyType = findDiscriminatorPropertyType({
+      context,
+      propertyName: discriminator.propertyName,
+      schemas: compositionSchemas,
+    });
+
+    const valueSchemas: ReadonlyArray<IR.SchemaObject> = finalValues.map((value) =>
+      convertDiscriminatorValue(value, propertyType),
+    );
 
     const discriminatorProperty: IR.SchemaObject =
       valueSchemas.length > 1
···
 
   const compositionSchemas = schema.anyOf;
 
+  const discriminatorPropertyType = schema.discriminator
+    ? findDiscriminatorPropertyType({
+        context,
+        propertyName: schema.discriminator.propertyName,
+        schemas: compositionSchemas,
+      })
+    : undefined;
+
   for (const compositionSchema of compositionSchemas) {
     let irCompositionSchema = schemaToIrSchema({
       context,
···
     // `$ref` should be defined with discriminators
     if (schema.discriminator && irCompositionSchema.$ref != null) {
       const values = discriminatorValues(irCompositionSchema.$ref, schema.discriminator.mapping);
-      const valueSchemas: ReadonlyArray<IR.SchemaObject> = values.map((value) => ({
-        const: value,
-        type: 'string',
-      }));
+
+      const valueSchemas: ReadonlyArray<IR.SchemaObject> = values.map((value) =>
+        convertDiscriminatorValue(value, discriminatorPropertyType!),
+      );
       const irDiscriminatorSchema: IR.SchemaObject = {
         properties: {
           [schema.discriminator.propertyName]:
···
 
   const compositionSchemas = schema.oneOf;
 
+  const discriminatorPropertyType = schema.discriminator
+    ? findDiscriminatorPropertyType({
+        context,
+        propertyName: schema.discriminator.propertyName,
+        schemas: compositionSchemas,
+      })
+    : undefined;
+
   for (const compositionSchema of compositionSchemas) {
     let irCompositionSchema = schemaToIrSchema({
       context,
···
     // `$ref` should be defined with discriminators
     if (schema.discriminator && irCompositionSchema.$ref != null) {
       const values = discriminatorValues(irCompositionSchema.$ref, schema.discriminator.mapping);
-      const valueSchemas: ReadonlyArray<IR.SchemaObject> = values.map((value) => ({
-        const: value,
-        type: 'string',
-      }));
+
+      const valueSchemas: ReadonlyArray<IR.SchemaObject> = values.map((value) =>
+        convertDiscriminatorValue(value, discriminatorPropertyType!),
+      );
       const irDiscriminatorSchema: IR.SchemaObject = {
         properties: {
           [schema.discriminator.propertyName]:

packages/shared/src/openApi/3.1.x/parser/schema.ts

···
   SchemaType,
   SchemaWithRequired,
 } from '../../../openApi/shared/types/schema';
-import { discriminatorValues } from '../../../openApi/shared/utils/discriminator';
+import {
+  convertDiscriminatorValue,
+  type DiscriminatorPropertyType,
+  discriminatorValues,
+} from '../../../openApi/shared/utils/discriminator';
 import { isTopLevelComponent, refToName } from '../../../utils/ref';
 import type { SchemaObject } from '../types/spec';
 
···
   }
 
   return [];
+};
+
+/**
+ * Finds the type of a discriminator property by looking it up in the provided schemas.
+ * Searches through properties and allOf chains to find the property definition.
+ */
+const findDiscriminatorPropertyType = ({
+  context,
+  propertyName,
+  schemas,
+}: {
+  context: Context;
+  propertyName: string;
+  schemas: ReadonlyArray<SchemaObject>;
+}): DiscriminatorPropertyType => {
+  for (const schema of schemas) {
+    const resolved = schema.$ref ? context.resolveRef<SchemaObject>(schema.$ref) : schema;
+
+    // Check direct properties
+    const property = resolved.properties?.[propertyName];
+    if (property === true) {
+      continue;
+    }
+    if (property) {
+      const resolvedProperty = property.$ref
+        ? context.resolveRef<SchemaObject>(property.$ref)
+        : property;
+      // Handle both single type and array of types (3.1.x supports type arrays)
+      const propertyTypes = Array.isArray(resolvedProperty.type)
+        ? resolvedProperty.type
+        : resolvedProperty.type
+          ? [resolvedProperty.type]
+          : [];
+      for (const propType of propertyTypes) {
+        if (propType === 'boolean' || propType === 'integer' || propType === 'number') {
+          return propType;
+        }
+      }
+    }
+
+    // Check allOf chains
+    if (resolved.allOf) {
+      const foundType = findDiscriminatorPropertyType({
+        context,
+        propertyName,
+        schemas: resolved.allOf,
+      });
+      if (foundType !== 'string') {
+        return foundType;
+      }
+    }
+  }
+
+  return 'string';
 };
 
 /**
···
     // Use allValues if we found children, otherwise use the original values
     const finalValues = allValues.length > 0 ? allValues : values;
 
-    const valueSchemas: ReadonlyArray<IR.SchemaObject> = finalValues.map((value) => ({
-      const: value,
-      type: 'string',
-    }));
+    // Detect the actual type of the discriminator property
+    const propertyType = findDiscriminatorPropertyType({
+      context,
+      propertyName: discriminator.propertyName,
+      schemas: compositionSchemas,
+    });
+
+    const valueSchemas: ReadonlyArray<IR.SchemaObject> = finalValues.map((value) =>
+      convertDiscriminatorValue(value, propertyType),
+    );
 
     const discriminatorProperty: IR.SchemaObject =
       valueSchemas.length > 1
···
 
   const compositionSchemas = schema.anyOf;
 
+  const discriminatorPropertyType = schema.discriminator
+    ? findDiscriminatorPropertyType({
+        context,
+        propertyName: schema.discriminator.propertyName,
+        schemas: compositionSchemas,
+      })
+    : undefined;
+
   for (const compositionSchema of compositionSchemas) {
     let irCompositionSchema = schemaToIrSchema({
       context,
···
     // `$ref` should be defined with discriminators
     if (schema.discriminator && irCompositionSchema.$ref != null) {
       const values = discriminatorValues(irCompositionSchema.$ref, schema.discriminator.mapping);
-      const valueSchemas: ReadonlyArray<IR.SchemaObject> = values.map((value) => ({
-        const: value,
-        type: 'string',
-      }));
+
+      const valueSchemas: ReadonlyArray<IR.SchemaObject> = values.map((value) =>
+        convertDiscriminatorValue(value, discriminatorPropertyType!),
+      );
       const irDiscriminatorSchema: IR.SchemaObject = {
         properties: {
           [schema.discriminator.propertyName]:
···
 
   const compositionSchemas = schema.oneOf;
 
+  const discriminatorPropertyType = schema.discriminator
+    ? findDiscriminatorPropertyType({
+        context,
+        propertyName: schema.discriminator.propertyName,
+        schemas: compositionSchemas,
+      })
+    : undefined;
+
   for (const compositionSchema of compositionSchemas) {
     let irCompositionSchema = schemaToIrSchema({
       context,
···
     // `$ref` should be defined with discriminators
     if (schema.discriminator && irCompositionSchema.$ref != null) {
       const values = discriminatorValues(irCompositionSchema.$ref, schema.discriminator.mapping);
-      const valueSchemas: ReadonlyArray<IR.SchemaObject> = values.map((value) => ({
-        const: value,
-        type: 'string',
-      }));
+
+      const valueSchemas: ReadonlyArray<IR.SchemaObject> = values.map((value) =>
+        convertDiscriminatorValue(value, discriminatorPropertyType!),
+      );
       const irDiscriminatorSchema: IR.SchemaObject = {
         properties: {
           [schema.discriminator.propertyName]:

packages/shared/src/openApi/shared/utils/discriminator.ts

···
+import type { IR } from '../../../ir/types';
 import { refToName } from '../../../utils/ref';
+
+/**
+ * Supported types for discriminator properties.
+ */
+export type DiscriminatorPropertyType = 'boolean' | 'integer' | 'number' | 'string';
+
+/**
+ * Converts a string discriminator mapping value to the appropriate type based on
+ * the actual property type in the schema.
+ *
+ * OpenAPI discriminator mappings always use string keys, but the actual discriminator
+ * property may be a boolean, number, or integer. This function converts the string
+ * key to the correct runtime value and IR type.
+ */
+export const convertDiscriminatorValue = (
+  value: string,
+  propertyType: DiscriminatorPropertyType,
+): { const: IR.SchemaObject['const']; type: IR.SchemaObject['type'] } => {
+  switch (propertyType) {
+    case 'boolean': {
+      const lowerValue = value.toLowerCase();
+      if (lowerValue !== 'true' && lowerValue !== 'false') {
+        console.warn(
+          '🚨',
+          `non-boolean discriminator mapping value "${value}" for boolean property, falling back to string`,
+        );
+        return {
+          const: value,
+          type: 'string',
+        };
+      }
+      return {
+        const: lowerValue === 'true',
+        type: 'boolean',
+      };
+    }
+    case 'integer': {
+      const parsed = parseInt(value, 10);
+      if (Number.isNaN(parsed)) {
+        console.warn(
+          '🚨',
+          `non-numeric discriminator mapping value "${value}" for integer property, falling back to string`,
+        );
+        return {
+          const: value,
+          type: 'string',
+        };
+      }
+      return {
+        const: parsed,
+        type: 'integer',
+      };
+    }
+    case 'number': {
+      const parsed = parseFloat(value);
+      if (Number.isNaN(parsed)) {
+        console.warn(
+          '🚨',
+          `non-numeric discriminator mapping value "${value}" for number property, falling back to string`,
+        );
+        return {
+          const: value,
+          type: 'string',
+        };
+      }
+      return {
+        const: parsed,
+        type: 'number',
+      };
+    }
+    default:
+      return {
+        const: value,
+        type: 'string',
+      };
+  }
+};
 
 export const discriminatorValues = (
   $ref: string,

specs/3.0.x/discriminator-non-string.yaml

···
+openapi: 3.0.3
+info:
+  title: Non-string discriminator test
+  version: 1
+components:
+  schemas:
+    # --- Boolean discriminator (oneOf) ---
+    BooleanOneOf:
+      oneOf:
+        - $ref: '#/components/schemas/AutoConfig'
+        - $ref: '#/components/schemas/CustomConfig'
+      discriminator:
+        propertyName: use_custom
+        mapping:
+          'False': '#/components/schemas/AutoConfig'
+          'True': '#/components/schemas/CustomConfig'
+
+    AutoConfig:
+      type: object
+      required:
+        - use_custom
+        - auto_setting
+      properties:
+        use_custom:
+          type: boolean
+          const: false
+        auto_setting:
+          type: string
+
+    CustomConfig:
+      type: object
+      required:
+        - use_custom
+        - custom_value
+      properties:
+        use_custom:
+          type: boolean
+          const: true
+        custom_value:
+          type: integer
+
+    # --- Boolean discriminator (anyOf) ---
+    BooleanAnyOf:
+      anyOf:
+        - $ref: '#/components/schemas/AutoConfig'
+        - $ref: '#/components/schemas/CustomConfig'
+      discriminator:
+        propertyName: use_custom
+        mapping:
+          'False': '#/components/schemas/AutoConfig'
+          'True': '#/components/schemas/CustomConfig'
+
+    # --- Integer discriminator (oneOf) ---
+    IntegerOneOf:
+      oneOf:
+        - $ref: '#/components/schemas/TypeOne'
+        - $ref: '#/components/schemas/TypeTwo'
+      discriminator:
+        propertyName: type_id
+        mapping:
+          '1': '#/components/schemas/TypeOne'
+          '2': '#/components/schemas/TypeTwo'
+
+    TypeOne:
+      type: object
+      required:
+        - type_id
+        - one_data
+      properties:
+        type_id:
+          type: integer
+          const: 1
+        one_data:
+          type: string
+
+    TypeTwo:
+      type: object
+      required:
+        - type_id
+        - two_data
+      properties:
+        type_id:
+          type: integer
+          const: 2
+        two_data:
+          type: string
+
+    # --- Number (float) discriminator (oneOf) ---
+    NumberOneOf:
+      oneOf:
+        - $ref: '#/components/schemas/VersionAlpha'
+        - $ref: '#/components/schemas/VersionBeta'
+      discriminator:
+        propertyName: version
+        mapping:
+          '1.0': '#/components/schemas/VersionAlpha'
+          '2.5': '#/components/schemas/VersionBeta'
+
+    VersionAlpha:
+      type: object
+      required:
+        - version
+        - alpha_field
+      properties:
+        version:
+          type: number
+          const: 1.0
+        alpha_field:
+          type: string
+
+    VersionBeta:
+      type: object
+      required:
+        - version
+        - beta_field
+      properties:
+        version:
+          type: number
+          const: 2.5
+        beta_field:
+          type: string
+
+    # --- Integer discriminator (allOf) ---
+    IntegerAllOfBase:
+      type: object
+      required:
+        - kind
+      properties:
+        kind:
+          type: integer
+      discriminator:
+        propertyName: kind
+        mapping:
+          '1': '#/components/schemas/IntegerAllOfChildA'
+          '2': '#/components/schemas/IntegerAllOfChildB'
+
+    IntegerAllOfChildA:
+      allOf:
+        - $ref: '#/components/schemas/IntegerAllOfBase'
+        - type: object
+          required:
+            - child_a_field
+          properties:
+            child_a_field:
+              type: string
+
+    IntegerAllOfChildB:
+      allOf:
+        - $ref: '#/components/schemas/IntegerAllOfBase'
+        - type: object
+          required:
+            - child_b_field
+          properties:
+            child_b_field:
+              type: string

specs/3.1.x/discriminator-non-string.yaml

···
+openapi: 3.1.0
+info:
+  title: Non-string discriminator test
+  version: 1
+components:
+  schemas:
+    # --- Boolean discriminator (oneOf) ---
+    BooleanOneOf:
+      oneOf:
+        - $ref: '#/components/schemas/AutoConfig'
+        - $ref: '#/components/schemas/CustomConfig'
+      discriminator:
+        propertyName: use_custom
+        mapping:
+          'False': '#/components/schemas/AutoConfig'
+          'True': '#/components/schemas/CustomConfig'
+
+    AutoConfig:
+      type: object
+      required:
+        - use_custom
+        - auto_setting
+      properties:
+        use_custom:
+          type: boolean
+          const: false
+        auto_setting:
+          type: string
+
+    CustomConfig:
+      type: object
+      required:
+        - use_custom
+        - custom_value
+      properties:
+        use_custom:
+          type: boolean
+          const: true
+        custom_value:
+          type: integer
+
+    # --- Boolean discriminator (anyOf) ---
+    BooleanAnyOf:
+      anyOf:
+        - $ref: '#/components/schemas/AutoConfig'
+        - $ref: '#/components/schemas/CustomConfig'
+      discriminator:
+        propertyName: use_custom
+        mapping:
+          'False': '#/components/schemas/AutoConfig'
+          'True': '#/components/schemas/CustomConfig'
+
+    # --- Integer discriminator (oneOf) ---
+    IntegerOneOf:
+      oneOf:
+        - $ref: '#/components/schemas/TypeOne'
+        - $ref: '#/components/schemas/TypeTwo'
+      discriminator:
+        propertyName: type_id
+        mapping:
+          '1': '#/components/schemas/TypeOne'
+          '2': '#/components/schemas/TypeTwo'
+
+    TypeOne:
+      type: object
+      required:
+        - type_id
+        - one_data
+      properties:
+        type_id:
+          type: integer
+          const: 1
+        one_data:
+          type: string
+
+    TypeTwo:
+      type: object
+      required:
+        - type_id
+        - two_data
+      properties:
+        type_id:
+          type: integer
+          const: 2
+        two_data:
+          type: string
+
+    # --- Number (float) discriminator (oneOf) ---
+    NumberOneOf:
+      oneOf:
+        - $ref: '#/components/schemas/VersionAlpha'
+        - $ref: '#/components/schemas/VersionBeta'
+      discriminator:
+        propertyName: version
+        mapping:
+          '1.0': '#/components/schemas/VersionAlpha'
+          '2.5': '#/components/schemas/VersionBeta'
+
+    VersionAlpha:
+      type: object
+      required:
+        - version
+        - alpha_field
+      properties:
+        version:
+          type: number
+          const: 1.0
+        alpha_field:
+          type: string
+
+    VersionBeta:
+      type: object
+      required:
+        - version
+        - beta_field
+      properties:
+        version:
+          type: number
+          const: 2.5
+        beta_field:
+          type: string
+
+    # --- Integer discriminator (allOf) ---
+    IntegerAllOfBase:
+      type: object
+      required:
+        - kind
+      properties:
+        kind:
+          type: integer
+      discriminator:
+        propertyName: kind
+        mapping:
+          '1': '#/components/schemas/IntegerAllOfChildA'
+          '2': '#/components/schemas/IntegerAllOfChildB'
+
+    IntegerAllOfChildA:
+      allOf:
+        - $ref: '#/components/schemas/IntegerAllOfBase'
+        - type: object
+          required:
+            - child_a_field
+          properties:
+            child_a_field:
+              type: string
+
+    IntegerAllOfChildB:
+      allOf:
+        - $ref: '#/components/schemas/IntegerAllOfBase'
+        - type: object
+          required:
+            - child_b_field
+          properties:
+            child_b_field:
+              type: string
+
+    # --- 3.1.x-specific: discriminator property with type array (e.g. nullable integer) ---
+    NullableIntegerOneOf:
+      oneOf:
+        - $ref: '#/components/schemas/NullableVariantX'
+        - $ref: '#/components/schemas/NullableVariantY'
+      discriminator:
+        propertyName: tag
+        mapping:
+          '10': '#/components/schemas/NullableVariantX'
+          '20': '#/components/schemas/NullableVariantY'
+
+    NullableVariantX:
+      type: object
+      required:
+        - tag
+        - x_data
+      properties:
+        tag:
+          type:
+            - integer
+            - 'null'
+          const: 10
+        x_data:
+          type: string
+
+    NullableVariantY:
+      type: object
+      required:
+        - tag
+        - y_data
+      properties:
+        tag:
+          type:
+            - integer
+            - 'null'
+          const: 20
+        y_data:
+          type: string