Fix nullable QueryMap fails to compile

[techouse]

This addresses #343

I've used Expression.ifNullThen to additionally check for a nullable QueryMap.

This should be able to take

@Get(path: 'query_map')
Future<Response> getQueryMapTest4({
  @Query('name') String name = '',
  @Query('number') int? number,
  @QueryMap() Map<String, dynamic>? filters, // <-- nullable / optional filters
});

and generate

@override
Future<Response<dynamic>> getQueryMapTest4(
    {String name = '', int? number, Map<String, dynamic>? filters}) {
  final $url = '/test/query_map';
  final $params = <String, dynamic>{'name': name, 'number': number};
  $params.addAll(filters ?? {}); // <-- because Map.addAll expects a non-nullable Map
  final $request = Request('GET', $url, client.baseUrl, parameters: $params);
  return client.send<dynamic, dynamic>($request);
}

without any subsequent compilation errors.

Before this hotfix one had to use a default const {} like this in order to omit the QueryMap and avoid a compilation error

@Get(path: 'query_map')
Future<Response> getQueryMapTest3({
  @Query('name') String name = '',
  @Query('number') int? number,
  @QueryMap() Map<String, dynamic> filters = const {}, // <-- default
});

which would generate

@override
Future<Response<dynamic>> getQueryMapTest3(
    {String name = '',
    int? number,
    Map<String, dynamic> filters = const {}}) { // <-- default
  final $url = '/test/query_map';
  final $params = <String, dynamic>{'name': name, 'number': number};
  $params.addAll(filters);
  final $request = Request('GET', $url, client.baseUrl, parameters: $params);
  return client.send<dynamic, dynamic>($request);
}

However, this fix will also add a null check ?? when the value is not nullable and that's why I've added the extra ignore flag dead_null_aware_expression in order to silence the linter in a case like this

@Get(path: 'query_map')
Future<Response> getQueryMapTest2(
  @QueryMap() Map<String, dynamic> query, {
  @Query('test') bool? test,
});

which generates

@override
Future<Response<dynamic>> getQueryMapTest2(Map<String, dynamic> query,
    {bool? test}) {
  final $url = '/test/query_map';
  final $params = <String, dynamic>{'test': test};
  $params.addAll(query ?? {}); // <-- dead_null_aware_expression because `query` is not nullable
  final $request = Request('GET', $url, client.baseUrl, parameters: $params);
  return client.send<dynamic, dynamic>($request);
}

As such, this should be regarded more or less as a hotfix as some more robust null checking should be performed on the QueryMap itself. At this point, I lack the expertise to do this with source_gen and would appreciate any further guidance 😊

EDIT: This issue has now been rectified. See #344 (comment)

Oh, and of course, I've added a few test cases. ☑️

[JEuler]

Thank you sooooooo much!

[JEuler]

Please reformat code :)

[techouse]

Please reformat code :)

Done. My bad :)

[techouse]

I just found out how to do a more precise null check on the parameters.

In essence, I built an Iterable of all the positional optional and named parameters like

// Build an iterable of all the parameters that are nullable
final Iterable<String> optionalNullableParameters = [
  ...m.parameters.where((p) => p.isOptionalPositional),
  ...m.parameters.where((p) => p.isNamed),
].where((el) => el.type.isNullable).map((el) => el.name);

which in the case of building a QueryMap I can simply check

if (optionalNullableParameters.contains(queryMap.keys.first)) {
  // do nullable stuff
} else {
  // do non nullable stuff
}

This way I can remove dead_null_aware_expression as this update to the fix will prevent it from happening.

This means that

@Get(path: 'query_map')
Future<Response> getQueryMapTest2(
  @QueryMap() Map<String, dynamic> query, {
  @Query('test') bool? test,
});

will correctly produce

@override
Future<Response<dynamic>> getQueryMapTest2(Map<String, dynamic> query,
    {bool? test}) {
  final $url = '/test/query_map';
  final $params = <String, dynamic>{'test': test};
  $params.addAll(query);
  final $request = Request('GET', $url, client.baseUrl, parameters: $params);
  return client.send<dynamic, dynamic>($request);
}

and

@Get(path: 'query_map')
Future<Response> getQueryMapTest4({
  @Query('name') String name = '',
  @Query('number') int? number,
  @QueryMap() Map<String, dynamic>? filters, // <-- nullable / optional filters
});

will correctly produce

@override
Future<Response<dynamic>> getQueryMapTest4(
    {String name = '', int? number, Map<String, dynamic>? filters}) {
  final $url = '/test/query_map';
  final $params = <String, dynamic>{'name': name, 'number': number};
  $params.addAll(filters ?? {});
  final $request = Request('GET', $url, client.baseUrl, parameters: $params);
  return client.send<dynamic, dynamic>($request);
}