The list must add default values ​​or nullable.

[hmshohrab]

Need to add list default value or nullable.
Json sample:
{
"userImage": "Shohrab",
"socialMediaInfoess": [
{
"ProfileID": 2,
"SocialMediaURL": "http://facebook.com"
}
]
}

Output sample:
class ProfileInfo {
final String userImage;
final List socialMediaInfoess;

ProfileInfo({
this.userImage = "",
required this.socialMediaInfoess, //remove required and add default value or nullable (if possible)
});

factory ProfileInfo.fromJson(Map<String, dynamic>? json) => ProfileInfo(
userImage: asT(json, 'userImage'),
socialMediaInfoess: asT(json, 'socialMediaInfoess').map((e) => SocialMediaInfoessItem.fromJson(e)).toList(),
);

Map<String, dynamic> toJson() => {
'userImage': userImage,
'socialMediaInfoess': socialMediaInfoess.map((e) => e.toJson()).toList(),
};

ProfileInfo copyWith({
String? userImage,
List? socialMediaInfoess,
}) {
return ProfileInfo(
userImage: userImage ?? this.userImage,
socialMediaInfoess: socialMediaInfoess ?? this.socialMediaInfoess,
);
}
}

class SocialMediaInfoessItem {
final int profileID;
final String socialMediaURL;

SocialMediaInfoessItem({
this.profileID = 0,
this.socialMediaURL = "",
});

factory SocialMediaInfoessItem.fromJson(Map<String, dynamic>? json) => SocialMediaInfoessItem(
profileID: asT(json, 'ProfileID'),
socialMediaURL: asT(json, 'SocialMediaURL'),
);

Map<String, dynamic> toJson() => {
'ProfileID': profileID,
'SocialMediaURL': socialMediaURL,
};

SocialMediaInfoessItem copyWith({
int? profileID,
String? socialMediaURL,
}) {
return SocialMediaInfoessItem(
profileID: profileID ?? this.profileID,
socialMediaURL: socialMediaURL ?? this.socialMediaURL,
);
}
}

[windows7lake]

@hmshohrab
Deselect Enable Null Safety, and list can be nullable

class ProfileInfo {
  final String userImage;
  final List<SocialMediaInfoessItem>? socialMediaInfoess;

  ProfileInfo({
    this.userImage = "",
    this.socialMediaInfoess,
  });

  factory ProfileInfo.fromJson(Map<String, dynamic> json) => ProfileInfo(
    userImage: asString(json, 'userImage'),
    socialMediaInfoess: asList(json, 'socialMediaInfoess').map((e) => SocialMediaInfoessItem.fromJson(e)).toList(),
  );

  Map<String, dynamic> toJson() => {
    'userImage': userImage,
    'socialMediaInfoess': socialMediaInfoess?.map((e) => e.toJson()).toList(),
  };
}

class SocialMediaInfoessItem {
  final int profileID;
  final String socialMediaURL;

  SocialMediaInfoessItem({
    this.profileID = 0,
    this.socialMediaURL = "",
  });

  factory SocialMediaInfoessItem.fromJson(Map<String, dynamic> json) => SocialMediaInfoessItem(
    profileID: asInt(json, 'ProfileID'),
    socialMediaURL: asString(json, 'SocialMediaURL'),
  );

  Map<String, dynamic> toJson() => {
    'ProfileID': profileID,
    'SocialMediaURL': socialMediaURL,
  };
}

[windows7lake]

json2dart-1.2.4.zip
1.2.4 support to add default value for list type property in construction method.