[BUG] [Dart] additional properties of type: object doesn't generate with mapCastOfType

[0xNF]

Bug Report Checklist

• Have you provided a full/minimal spec to reproduce the issue?
• Have you validated the input using an OpenAPI validator (example)?
• Have you tested with the latest master to confirm the issue still exists?
• Have you searched for related issues/PRs?
• What's the actual output vs expected output?
• [Optional] Sponsorship to speed up the bug fix or feature request (example)

Description

The additionalProperties field, which specified a Map<T1, T2> in Dart, doesn't generate properly by fields defined by

schema:
   type: string
   additionalProperties:
      type: object

openapi-generator version

6.0.0

OpenAPI declaration file content or url

openapi: 3.0.3
info:
  version: "1.1"
  title: Dart MappedValue Fail
servers:
  - url: 'localhost'
    variables:
      host:
        default: localhost
components:
  schemas:
    ItemGood:
      type: object
      properties:
        mappedProps:
          type: string
          additionalProperties:
            type: string
    ItemBad:
      type: object
      properties:
        mappedProps:
          type: string
          additionalProperties:
            type: object
paths:
  /items:
    get:
      operationId: GetItems
      responses:
        "200":
          description: A list of Items
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/ItemGood'

Generation Details

1. java -jar ..\openapi-generator\modules\openapi-generator-cli\target\openapi-generator-cli.jar generate -i .\shadowspec.yaml -g dart -o mapped

Steps to reproduce

After generation, see the ./mapped/lib/model/item_good.dart and ./mapped/lib/model/item_bad.dart files.

ItemGood, defined as

    ItemGood:
      type: object
      properties:
        mappedProps:
          type: string
          additionalProperties:
            type: string

generates correctly with

      return ItemGood(
        mappedProps: mapCastOfType<String, String>(json, r'mappedProps') ?? const {},
      );

However, ItemBad, defined as

    ItemBad:
      type: object
      properties:
        mappedProps:
          type: string
          additionalProperties:
            type: object

generates incorrectly, using mapValueOfType instead of mapCastOfType:

      return ItemBad(
        mappedProps: mapValueOfType<Map<String, Object>>(json, r'mappedProps') ?? const {},
      );

Related issues/PRs

Suggest a fix

Maps should try to generate with mapValueOfType in as many situations as possible

[0xNF]

Slightly modifying the schema to look like this instead:

 ItemBad:
      type: object
      properties:
        mappedProps:
          type: string
          additionalProperties: true

and then inserting a check for additionalPropertiesIsAnyType into modules\openapi-generator\src\main\resources\dart2\serialization\native\native_class.mustache:173

                {{^items.isMap}}
                  {{#additionalPropertiesIsAnyType}}
        {{{name}}}: mapCastOfType<String, Object>(json, r'{{{baseName}}}'){{#required}}{{^isNullable}}!{{/isNullable}}{{/required}}{{^required}}{{#defaultValue}} ?? {{{.}}}{{/defaultValue}}{{/required}},
                  {{/additionalPropertiesIsAnyType}}
                  {{^additionalPropertiesIsAnyType}}
        {{{name}}}: mapValueOfType<{{{datatypeWithEnum}}}>(json, r'{{{baseName}}}'){{#required}}{{^isNullable}}!{{/isNullable}}{{/required}}{{^required}}{{#defaultValue}} ?? {{{.}}}{{/defaultValue}}{{/required}},
                  {{/additionalPropertiesIsAnyType}}
                {{/items.isMap}}

I can get the dart generators to correctly deserialize the value using mapCastOfType instead of mapValueOfType

But I don't know what the correct way to do this really is. Some issues I have include:

1. The existing examples for mapCastOfType use <String, dynamic> but because the instance member is generated as Map<String, Object> and not a Map<String, dynamic> I have to deviate from the pre-existing pattern.
2. I have to modify my schema to work around the generator. I don't see what the semantic difference is between additionalProperties: true and additionalProperties: type: object is, these should be equivalent (I think?), and so the generator shouldn't be distinguishing between the two in the way it does, but I don't know where to fix this.

[ahmednfwela]

I am wondering if the spec itself is valid in your case
shouldn't additional properties be added to only type: object ?
a type string won't have properties in the first place, so how can it have additional properties?

docs: https://swagger.io/docs/specification/data-models/dictionaries/

[0xNF]

It's possibly not valid. I admit that I don't fully understand the OpenAPI spec format -- I've included it here in a simplified form because it's something I encountered in the wild at my current company.

Even if we take the type: object part away, I'm still having trouble generating a Map<String, Object> correctly when the more appropriate additionalProperties: true field is used.

[ahmednfwela]

does this schema not work for you?

type: object
additionalProperties: true

[0xNF]

I'll double check, but previously that was producing what looked like a valid Dart file, but would fail at runtime when actual access occurred on the generated map, since the generated object was some kind of _linkedInternalHashMap that doesn't permit indexing access.

[ahmednfwela]

if that happens please include a repro code of what causes the error

[0xNF]

I tried again with the latest master branch -- this time I don't actually get the error described above, but I do get a different and equally bad error.

When the check in castValueOfType<Map<String, Object>> occurs, the Map is successfully placed into a proper map, but the type assertion fails at api_helper.dart:73.

It's trying to assert that value is of type Map<String, Object> but it fails, because it's actually _InternalLinkedHashMap<String, dynamic>, which are not equal to each other, so it will return null instead.

You can try it for yourself here:
https://github.com/0xNF/openapi_dart_map

spec file:

openapi: 3.0.3
info:
  version: "1.1"
  title: Dart Bad Map
servers:
  - url: 'localhost'
    variables:
      host:
        default: localhost
components:
  schemas:
    ItemsWithMapStringAnyWithPropsTrue:
      type: object
      description: "map-string-any defined with `additionalProperties: true`"
      properties:
        objectMap:
          type: object
          additionalProperties: true
paths:
  /items:
    get:
      operationId: GetItemWithMapStringObjects
      responses:
        "200":
          description: A list of ItemWithMapStringObject
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/ItemsWithMapStringAnyWithPropsTrue'

the test file at test\item_with_map_string_any_with_props_object_test.dart will show the error:

  final String s = '{"objectMap": {"item_int": 1, "item_bool": true, "item_string": "str", "item_double": 4.3, "item_map": {"subProps": 1}, "item_array": [-1]}}';
    test('to test the property `objectMap`', () async {
      final m = JsonDecoder().convert(s);
      final i = ItemsWithMapStringAnyWithPropsTrue.fromJson(m)!;

      /* this fails because of the incorrect type assertion in mapValueOfType */
      assert(i.objectMap.isNotEmpty);

      assert(i.objectMap["item_int"] == 1);
      assert(i.objectMap["item_bool"] == true);
      assert(i.objectMap["item_string"] == "str");
      assert(i.objectMap["item_double"] == 4.3);
      assert((i.objectMap["item_map"] as Map)["subProps"] == 1);
      assert((i.objectMap["item_array"] as List)[0] == -1);
    });

[ahmednfwela]

that actually makes sense
it's because JsonDecoder().convert(s) decodes objectMap as just Map not Map<String, Object> so it fails
the fix is to replace

return ItemsWithMapStringAnyWithPropsTrue(
  objectMap: mapValueOfType<Map<String, Object>>(json, r'objectMap') ?? {},
);

with

return ItemsWithMapStringAnyWithPropsTrue(
  objectMap: mapCastOfType<String, Object>(json, r'objectMap') ?? {},
);

[0xNF]

Yes, that's what I was trying to solve with the PR -- the fix I included adds that mapCastOfType call to the mustache file for complex maps.

edit: my bad, I didn't realize this wasn't the PR thread. I was talking about this PR #12426

[ahmednfwela]

I am wondering tho, why would isMap be false in the first place

[ahmednfwela]

sounds like a problem with DefaultCodegen.java @wing328 can you confirm ?

[0xNF]

I also wondered about that, I figured it was some arcane thing that existed for a good reason -- it's from the core generator, so its beyond the scope of just the dart portion of the project.

I spent a long, long time debugging the issue to find out that isMap was false when I don't think it should have been.

I recall stepping through it that by that portion of the generator, it's looking at the inner map items instead of the map item itself, which is sees as just a generic object