A linter for parsing protobuf's Timestamps to DateTime. The goal is to always include isLocal: true when doing it.

timesamp_to_local_datetimes_linter.dart

import 'package:analyzer/dart/ast/ast.dart';
import 'package:analyzer/dart/element/type.dart';
import 'package:analyzer/error/error.dart';
import 'package:analyzer/error/listener.dart';
import 'package:analyzer/source/source_range.dart';
import 'package:custom_lint_builder/custom_lint_builder.dart';

class PreferTimestampsToLocalDateTimes extends DartLintRule {
  PreferTimestampsToLocalDateTimes() : super(code: _code);

  static const _code = LintCode(
    name: 'timestamp_to_date_time_is_local',
    problemMessage:
        'Parsing Timestamp to DateTime should always be to local time',
  );

  @override
  void run(
    CustomLintResolver resolver,
    ErrorReporter reporter,
    CustomLintContext context,
  ) {
    context.registry.addMethodInvocation((node) {
      if (node.isFromTimestamp &&
          node.isToDateTime &&
          !node.hasArgumentToLocalSetToTrue) {
        reporter.reportErrorForNode(_code, node);
      }
    });
  }

  @override
  List<Fix> getFixes() => [_AddIsLocalFix()];
}

class _AddIsLocalFix extends DartFix {
  @override
  void run(
    CustomLintResolver resolver,
    ChangeReporter reporter,
    CustomLintContext context,
    AnalysisError analysisError,
    List<AnalysisError> others,
  ) {
    context.registry.addMethodInvocation((node) {
      if (!analysisError.sourceRange.intersects(node.sourceRange) ||
          !node.isFromTimestamp && !node.isToDateTime) {
        return;
      }
      final leftParenthesisOffset = node.argumentList.leftParenthesis.offset;
      final rightParenthesisOffset = node.argumentList.rightParenthesis.offset;
      final fix = 'toLocal: true';
      if (node.hasArgumentToLocalSetToFalse) {
        final changeBuilder = reporter.createChangeBuilder(
          message: 'Replace with "toLocal: true"',
          priority: 1,
        );
        changeBuilder.addDartFileEdit((builder) {
          builder.addSimpleReplacement(
            SourceRange(
              leftParenthesisOffset + 1,
              rightParenthesisOffset - leftParenthesisOffset - 1,
            ),
            fix,
          );
        });
      } else {
        final changeBuilder = reporter.createChangeBuilder(
          message: 'Add "toLocal: true"',
          priority: 1,
        );
        changeBuilder.addDartFileEdit((builder) {
          builder.addSimpleInsertion(
            leftParenthesisOffset + 1,
            fix,
          );
        });
      }
    });
  }
}

extension on MethodInvocation {
  DartType? get targetType => target?.staticType;

  bool get isFromTimestamp =>
      targetType != null &&
      TypeChecker.fromName(
        'Timestamp',
        packageName: 'cheddar_api',
      ).isAssignableFromType(targetType!);

  bool get isToDateTime => methodName.name == 'toDateTime';

  bool get hasArgumentToLocalSetToTrue => hasArgumentToLocalSetToValue(true);

  bool get hasArgumentToLocalSetToFalse => hasArgumentToLocalSetToValue(false);

  bool hasArgumentToLocalSetToValue(bool value) =>
      argumentList.arguments.any((argument) =>
          argument is NamedExpression &&
          argument.name.label.name == 'toLocal' &&
          argument.expression.isBooleanWithValue(value));
}

extension on Expression {
  bool isBooleanWithValue(bool value) =>
      this is BooleanLiteral && (this as BooleanLiteral).value == value;
}

Make sure to check the package name too when using TypeChecker.fromName('Timestamp'). You wouldn't want a class with the Timestamp name from a different package to be impacted by your lint

Make sure to check the package name too when using TypeChecker.fromName('Timestamp'). You wouldn't want a class with the Timestamp name from a different package to be impacted by your lint

Right! Thanks! Updated :)