[BUG] [Dart] Recent addition of copy_with_extension breaks code generation due to wrong SDK version constraint

[MichaelMarner]

Bug Report Checklist

• Have you provided a full/minimal spec to reproduce the issue?
• Have you validated the input using an OpenAPI validator?
• 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 recent addition of copy_with_extension has caused code generation to fail. This is because copy_with_extension requires Dart 3.8, but the version constraint in the templated pubspec.yaml is 3.5.0.

Example error:

log output for json_serializable on lib/src/model/additional_properties_class.dart
W The language version (3.5.0) of this package (openapi) does not match the required range `^3.8.0`.
  Edit pubspec.yaml to include an SDK constraint of at least ^3.8.0.
  environment:
    sdk: ^3.8.0
E An error `FormatterException` occurred while formatting the generated source for
    `package:openapi/src/model/additional_properties_class.dart`
  which was output to
    `lib/src/model/additional_properties_class.json_serializable.g.part`.
  This may indicate an issue in the generator, the input source code, or in the
  source formatter.
  Could not format because the source could not be parsed:
  line 19, column 25 of .: This requires the 'null-aware-elements' language feature to be enabled.
     ╷
  19 │         'map_property': ?instance.mapProperty,
     │                         ^
     ╵

openapi-generator version

7.15.0, and this issue exists on master branch,

OpenAPI declaration file content or url

N/A - this issue can be verified with the petstore example in the repo.

Steps to reproduce

This issue can be verified using the petstore sample

1. Checkout OpenAPI Generator on master
2. cd samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable
3. dart pub get
4. dart run build_runner build --delete-conflicting-outputs

See the errors

Related issues/PRs

#21667
#21665

Suggest a fix

Requiring a minimum of Dart 3.8.0 fixes the issue for us. Unfortunately it looks like the petstore example still has other build issues. eg:

pubspec.mustache

environment:
  sdk: '>={{^useJsonSerializable}}2.18.0{{/useJsonSerializable}}{{#useJsonSerializable}}3.8.0{{/useJsonSerializable}} <4.0.0'

[wing328]

I'll add an option shortly to allow fallback to previous behavior

cc @LahaLuhem

[wing328]

update: filed #21816

please have a look when you've time

[wing328]

PR merged.

please give it a try with the latest master, e.g. https://hub.docker.com/r/openapitools/openapi-generator-cli (tag: latest)

[LahaLuhem]

@wing328 I feel that your solution is a better fix for the previous issue. For this issue, @MichaelMarner's fix is better. However then this change is going to be once again conditionally dependent on the 'shouldUseThisFeature' flag of your current solution.
That we need to upgrade the sdk constraints if the user want to opt-in into the CopyWith feature, otherwise keep it as is.

I have only a limited experience with mustache template syntax, so I'd prefer someone else (maybe @MichaelMarner ?) to take out a PR for this?

[gratzl-dev]

I was going insane figuring out how I can fix this null-aware-elements issue.

Turns out the fix was right there in the bug report all along

[Christiaan-EPSza]

@wing328 I am still having issues with this even when specifying the skipCopyWith: true part.

I still get the following errors:

This requires the 'null-aware-elements' language feature to be enabled.