001////////////////////////////////////////////////////////////////////////////////
002// checkstyle: Checks Java source code for adherence to a set of rules.
003// Copyright (C) 2001-2020 the original author or authors.
004//
005// This library is free software; you can redistribute it and/or
006// modify it under the terms of the GNU Lesser General Public
007// License as published by the Free Software Foundation; either
008// version 2.1 of the License, or (at your option) any later version.
009//
010// This library is distributed in the hope that it will be useful,
011// but WITHOUT ANY WARRANTY; without even the implied warranty of
012// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
013// Lesser General Public License for more details.
014//
015// You should have received a copy of the GNU Lesser General Public
016// License along with this library; if not, write to the Free Software
017// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
018////////////////////////////////////////////////////////////////////////////////
019
020package com.puppycrawl.tools.checkstyle.checks.naming;
021
022import java.util.Objects;
023
024import com.puppycrawl.tools.checkstyle.api.DetailAST;
025import com.puppycrawl.tools.checkstyle.api.TokenTypes;
026import com.puppycrawl.tools.checkstyle.utils.TokenUtil;
027
028/**
029 * <p>
030 * Checks lambda parameter names.
031 * </p>
032 * <ul>
033 * <li>
034 * Property {@code format} - Specifies valid identifiers.
035 * Type is {@code java.util.regex.Pattern}.
036 * Default value is {@code "^[a-z][a-zA-Z0-9]*$"}.
037 * </li>
038 * </ul>
039 * <p>
040 * To configure the check:
041 * </p>
042 * <pre>
043 * &lt;module name="LambdaParameterName"/&gt;
044 * </pre>
045 * <p>Code Example:</p>
046 * <pre>
047 * Function&lt;String, String&gt; function1 = s -&gt; s.toLowerCase(); // OK
048 * Function&lt;String, String&gt; function2 = S -&gt; S.toLowerCase(); // violation, name 'S'
049 *                                                // must match pattern '^[a-z][a-zA-Z0-9]*$'
050 * </pre>
051 * <p>
052 * An example of how to configure the check for names that begin
053 * with a lower case letter, followed by letters is:
054 * </p>
055 * <pre>
056 * &lt;module name="LambdaParameterName"&gt;
057 *   &lt;property name="format" value="^[a-z]([a-zA-Z]+)*$"/&gt;
058 * &lt;/module&gt;
059 * </pre>
060 * <p>
061 * Code Example:
062 * </p>
063 * <pre>
064 * class MyClass {
065 *   Function&lt;String, String&gt; function1 = str -&gt; str.toUpperCase().trim(); // OK
066 *   Function&lt;String, String&gt; function2 = _s -&gt; _s.trim(); // violation, name '_s'
067 *                                              // must match pattern '^[a-z]([a-zA-Z]+)*$'
068 *
069 *   public boolean myMethod(String sentence) {
070 *     return Stream.of(sentence.split(" "))
071 *             .map(word -&gt; word.trim()) // OK
072 *             .anyMatch(Word -&gt; "in".equals(Word)); // violation, name 'Word'
073 *                                                      // must match pattern '^[a-z]([a-zA-Z]+)*$'
074 *   }
075 * }
076 *
077 * </pre>
078 * <p>
079 * Parent is {@code com.puppycrawl.tools.checkstyle.TreeWalker}
080 * </p>
081 * <p>
082 * Violation Message Keys:
083 * </p>
084 * <ul>
085 * <li>
086 * {@code name.invalidPattern}
087 * </li>
088 * </ul>
089 *
090 * @since 8.11
091 */
092public class LambdaParameterNameCheck extends AbstractNameCheck {
093
094    /** Creates new instance of {@code LambdaParameterNameCheck}. */
095    public LambdaParameterNameCheck() {
096        super("^[a-z][a-zA-Z0-9]*$");
097    }
098
099    @Override
100    public int[] getDefaultTokens() {
101        return getRequiredTokens();
102    }
103
104    @Override
105    public int[] getAcceptableTokens() {
106        return getRequiredTokens();
107    }
108
109    @Override
110    public int[] getRequiredTokens() {
111        return new int[] {
112            TokenTypes.LAMBDA,
113        };
114    }
115
116    @Override
117    public void visitToken(DetailAST ast) {
118        final boolean isInSwitchRule = ast.getParent().getType() == TokenTypes.SWITCH_RULE;
119
120        if (Objects.nonNull(ast.findFirstToken(TokenTypes.PARAMETERS))) {
121            final DetailAST parametersNode = ast.findFirstToken(TokenTypes.PARAMETERS);
122            TokenUtil.forEachChild(parametersNode, TokenTypes.PARAMETER_DEF, super::visitToken);
123        }
124        else if (!isInSwitchRule) {
125            super.visitToken(ast);
126        }
127    }
128
129    @Override
130    protected boolean mustCheckName(DetailAST ast) {
131        return true;
132    }
133
134}