[dart-dio] Fix json_serializable serialize template to support hasFormParams

[Bazni]

Summary

The json_serializable dart-dio serialize template only handled {{#bodyParam}}, so any operation whose request body was application/x-www-form-urlencoded or multipart/form-data produced an empty try {} block: _bodyData was declared but never assigned, and the form fields were silently dropped. Only the built_value serialization library was correctly handling form params.

This PR adds the missing {{#hasFormParams}} handling to serialization/json_serializable/api/serialize.mustache, mirroring the pattern from the built_value counterpart but without built_value-specific encodeFormParameter / _serializers calls (consistent with how json_serializable's query_param.mustache already just outputs {{{paramName}}}).

Similar to #20314, but for the dart-dio generator.

Before

// updatePetWithForm — application/x-www-form-urlencoded
dynamic _bodyData;

try {
  // empty — form fields lost
} catch (error, stackTrace) { ... }

final _response = await _dio.request<Object>(
  _path,
  data: _bodyData, // always null
  ...
);

After

dynamic _bodyData;

try {
  _bodyData = <String, dynamic>{
    if (name != null) r'name': name,
    if (status != null) r'status': status,
  };
} catch (error, stackTrace) { ... }

For multipart/form-data (uploadFile), the map is wrapped in FormData.fromMap(...) from the dio package, and MultipartFile values are passed through directly ({{#isFile}}).

Reproduction

Minimal spec with an application/x-www-form-urlencoded body (e.g. updatePetWithForm from the petstore fake spec) generated with:

-g dart-dio --additional-properties=serializationLibrary=json_serializable

Before this PR, the generated _bodyData is always null. After, it is a populated Map<String, dynamic> (or FormData).

Changes

• modules/openapi-generator/src/main/resources/dart/libraries/dio/serialization/json_serializable/api/serialize.mustache: add hasFormParams handling for both isMultipart and non-multipart cases; preserve the existing bodyParam branch (with proper indentation so the generated code is consistent with built_value).
• Regenerate samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/** via ./bin/generate-samples.sh bin/configs/dart-dio*. Previously broken operations (updatePetWithForm, uploadFile, uploadFileWithRequiredFile, testEndpointParameters, testEnumParameters, testQueryParameterCollectionFormat) now serialize the form body correctly.
• built_value samples, docs, and other generators are unaffected.

PR checklist

• Read the contribution guidelines.
• PR title clearly describes the work.
• ./mvnw clean package -DskipTests -Dmaven.javadoc.skip=true (built via -pl modules/openapi-generator-cli -am).
• ./bin/generate-samples.sh bin/configs/dart-dio*
• ./bin/utils/export_docs_generators.sh (no diff).
• All changed files committed.
• Targets master.

cc @kuhnroyal @josh-burton @amondnet @ahmednfwela (dart-dio technical committee)

---

Summary by cubic

Fixes form parameter serialization in dart-dio with json_serializable, so application/x-www-form-urlencoded and multipart/form-data requests set _bodyData correctly instead of sending null.

• Bug Fixes
  • Add {{#hasFormParams}} handling in serialization/json_serializable/api/serialize.mustache: build <String, dynamic>{...} for urlencoded, FormData.fromMap(...) for multipart; pass MultipartFile values (and arrays) through; include optional params only when non-null.
  • Preserve the existing {{#bodyParam}} branch and align indentation.
  • Regenerate petstore_client_lib_fake-json_serializable samples; operations like updatePetWithForm, uploadFile, testEndpointParameters, and testEnumParameters now serialize form bodies correctly.

^{Written for commit 23b1b94. Summary will update on new commits.}

[cubic-dev-ai]

No issues found across 7 files

[wing328]

Thanks for the PR but your commit (as shown in the Commits tab) is not linked to your Github account, which means this PR won't count as your contribution in https://github.com/OpenAPITools/openapi-generator/graphs/contributors.

Let me know if you need help fixing it.

Ref: https://github.com/OpenAPITools/openapi-generator/wiki/FAQ#how-can-i-update-commits-that-are-not-linked-to-my-github-account

[Bazni]

Thx I will do that asap.

Edit: @wing328 Should be better now

[wing328]

thanks for the PR which has been merged