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/*
 * SonarQube Python Plugin
 * Copyright (C) 2011-2024 SonarSource SA
 * mailto:info AT sonarsource DOT com
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the Sonar Source-Available License Version 1, as published by SonarSource SA.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
 * See the Sonar Source-Available License for more details.
 *
 * You should have received a copy of the Sonar Source-Available License
 * along with this program; if not, see https://sonarsource.com/license/ssal/
 */
package org.sonar.python.checks;

import org.sonar.check.Rule;
import org.sonar.plugins.python.api.PythonSubscriptionCheck;
import org.sonar.plugins.python.api.SubscriptionContext;
import org.sonar.plugins.python.api.tree.Expression;
import org.sonar.plugins.python.api.tree.KeyValuePair;
import org.sonar.plugins.python.api.tree.SetLiteral;
import org.sonar.plugins.python.api.types.InferredType;
import org.sonar.python.semantic.SymbolImpl;

import static org.sonar.plugins.python.api.tree.Tree.Kind.KEY_VALUE_PAIR;
import static org.sonar.plugins.python.api.tree.Tree.Kind.SET_LITERAL;
import static org.sonar.plugins.python.api.types.BuiltinTypes.NONE_TYPE;

@Rule(key = "S6662")
public class HashMethodCheck extends PythonSubscriptionCheck {

  private static final String MESSAGE = "Make sure this expression is hashable.";

  @Override
  public void initialize(Context context) {
    context.registerSyntaxNodeConsumer(SET_LITERAL, ctx -> ((SetLiteral) ctx.syntaxNode()).elements().forEach(elem -> checkHashMethod(elem, ctx)));
    context.registerSyntaxNodeConsumer(KEY_VALUE_PAIR, ctx -> checkHashMethod(((KeyValuePair) ctx.syntaxNode()).key(), ctx));
  }

  /**
   Note that, by default "object" itself defines a __hash__ method, and it is removed from classes whenever one of those two things happen (see Python
   documentation):
   
   A class implements __eq__ without implementing __hash__
   __hash__ is manually set to None (common in mutable sequences like list)
   

   The implementation will only focus on 2., because 1. is causing too many FPs for typeshed symbols (e.g. int)
   */
  private static void checkHashMethod(Expression expression, SubscriptionContext ctx) {
    InferredType type = expression.type();
    boolean hashIsManuallySetToNone = type.resolveMember("__hash__")
      .filter(symbol -> ((SymbolImpl) symbol).inferredType().canOnlyBe(NONE_TYPE))
      .isPresent();
    if (hashIsManuallySetToNone) {
      ctx.addIssue(expression, MESSAGE);
    }
  }
}