pkg/analysis_server/lib/src/services/correction/dart/remove_unused_parameter.dart

// Copyright (c) 2020, the Dart project authors. Please see the AUTHORS file
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.

import 'package:analysis_server/src/services/correction/dart/abstract_producer.dart';
import 'package:analysis_server/src/services/correction/fix.dart';
import 'package:analyzer/dart/ast/ast.dart';
import 'package:analyzer/dart/ast/token.dart';
import 'package:analyzer_plugin/utilities/change_builder/change_builder_core.dart';
import 'package:analyzer_plugin/utilities/fixes/fixes.dart';
import 'package:analyzer_plugin/utilities/range_factory.dart';

class RemoveUnusedParameter extends CorrectionProducer {
  @override
  FixKind get fixKind => DartFixKind.REMOVE_UNUSED_PARAMETER;

  @override
  Future<void> compute(ChangeBuilder builder) async {
    if (node is FormalParameter) {
      var parameter = node as FormalParameter;
      if (parameter.parent is DefaultFormalParameter) {
        parameter = parameter.parent;
      }

      var parameterList = parameter.parent as FormalParameterList;
      var parameters = parameterList.parameters;
      var index = parameters.indexOf(parameter);
      await builder.addDartFileEdit(file, (builder) {
        if (index == 0) {
          // Remove the first parameter in the list.
          if (parameters.length == 1) {
            // There is only one parameter. By removing everything inside the
            // parentheses we also remove any square brackets or curly braces.
            builder.addDeletion(range.endStart(
                parameterList.leftParenthesis, parameterList.rightParenthesis));
          } else {
            var following = parameters[1];
            if (parameter.isRequiredPositional &&
                !following.isRequiredPositional) {
              // The parameter to be removed and the following parameter are not
              // of the same kind, so there is a delimiter between them that we
              // can't delete.
              var leftDelimiter = parameterList.leftDelimiter;
              if (leftDelimiter != null) {
                builder.addDeletion(range.startStart(parameter, leftDelimiter));
              } else {
                // Invalid code `C(foo, bar = 1)`.
                builder.addDeletion(range.startStart(parameter, following));
              }
            } else {
              // The parameter to be removed and the following parameter are of
              // the same kind, so there is no delimiter between them.
              builder.addDeletion(range.startStart(parameter, following));
            }
          }
        } else {
          var preceding = parameters[index - 1];
          if (preceding.isRequiredPositional &&
              !parameter.isRequiredPositional) {
            // The parameter to be removed and the preceding parameter are not
            // of the same kind, so there is a delimiter between them.
            if (index == parameters.length - 1) {
              // The parameter to be removed is the only parameter between the
              // delimiters, so remove the delimiters with the parameter.
              var trailingToken = parameterList.rightParenthesis;
              if (trailingToken.previous.type == TokenType.COMMA) {
                // Leave the trailing comma if there is one.
                trailingToken = trailingToken.previous;
              }
              builder.addDeletion(range.endStart(preceding, trailingToken));
            } else {
              // The parameter to be removed is the first inside the delimiters
              // but the delimiters should be left.
              var following = parameters[index + 1];
              builder.addDeletion(range.startStart(parameter, following));
            }
          } else {
            // The parameter to be removed and the preceding parameter are of
            // the same kind, so there is no delimiter between them.
            builder.addDeletion(range.endEnd(preceding, parameter));
          }
        }
      });
    }
  }

  /// Return an instance of this class. Used as a tear-off in `FixProcessor`.
  static RemoveUnusedParameter newInstance() => RemoveUnusedParameter();
}