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 com.puppycrawl.tools.checkstyle.api.DetailAST;
023import com.puppycrawl.tools.checkstyle.api.TokenTypes;
024
025/**
026 * <p>
027 * Checks lambda parameter names.
028 * </p>
029 * <ul>
030 * <li>
031 * Property {@code format} - Specifies valid identifiers.
032 * Type is {@code java.util.regex.Pattern}.
033 * Default value is {@code "^[a-z][a-zA-Z0-9]*$"}.
034 * </li>
035 * </ul>
036 * <p>
037 * An example of how to configure the check is:
038 * </p>
039 * <pre>
040 * &lt;module name="LambdaParameterName"/&gt;
041 * </pre>
042 * <p>Code Example:</p>
043 * <pre>
044 * Function&lt;String, String&gt; function1 = s -&gt; s.toLowerCase(); // OK
045 * Function&lt;String, String&gt; function2 = S -&gt; S.toLowerCase(); // violation, name 'S'
046 *                                                // must match pattern '^[a-z][a-zA-Z0-9]*$'
047 * </pre>
048 * <p>
049 * An example of how to configure the check for names that begin
050 * with a lower case letter, followed by letters is:
051 * </p>
052 * <pre>
053 * &lt;module name="LambdaParameterName"&gt;
054 *   &lt;property name="format" value="^[a-z]([a-zA-Z]+)*$"/&gt;
055 * &lt;/module&gt;
056 * </pre>
057 * <p>
058 * Code Example:
059 * </p>
060 * <pre>
061 * class MyClass {
062 *   Function&lt;String, String&gt; function1 = str -&gt; str.toUpperCase().trim(); // OK
063 *   Function&lt;String, String&gt; function2 = _s -&gt; _s.trim(); // violation, name '_s'
064 *                                              // must match pattern '^[a-z]([a-zA-Z]+)*$'
065 *
066 *   public boolean myMethod(String sentence) {
067 *     return Stream.of(sentence.split(" "))
068 *             .map(word -&gt; word.trim()) // OK
069 *             .anyMatch(Word -&gt; "in".equals(Word)); // violation, name 'Word'
070 *                                                      // must match pattern '^[a-z]([a-zA-Z]+)*$'
071 *   }
072 * }
073 *
074 * </pre>
075 * <p>
076 * Parent is {@code com.puppycrawl.tools.checkstyle.TreeWalker}
077 * </p>
078 * <p>
079 * Violation Message Keys:
080 * </p>
081 * <ul>
082 * <li>
083 * {@code name.invalidPattern}
084 * </li>
085 * </ul>
086 *
087 * @since 8.11
088 */
089public class LambdaParameterNameCheck extends AbstractNameCheck {
090
091    /** Creates new instance of {@code LambdaParameterNameCheck}. */
092    public LambdaParameterNameCheck() {
093        super("^[a-z][a-zA-Z0-9]*$");
094    }
095
096    @Override
097    public int[] getDefaultTokens() {
098        return getRequiredTokens();
099    }
100
101    @Override
102    public int[] getAcceptableTokens() {
103        return getRequiredTokens();
104    }
105
106    @Override
107    public int[] getRequiredTokens() {
108        return new int[] {
109            TokenTypes.LAMBDA,
110        };
111    }
112
113    @Override
114    public void visitToken(DetailAST ast) {
115        final DetailAST parametersNode = ast.findFirstToken(TokenTypes.PARAMETERS);
116        if (parametersNode == null) {
117            super.visitToken(ast);
118        }
119        else {
120            for (DetailAST parameterDef = parametersNode.getFirstChild();
121                 parameterDef != null;
122                 parameterDef = parameterDef.getNextSibling()) {
123                if (parameterDef.getType() == TokenTypes.PARAMETER_DEF) {
124                    super.visitToken(parameterDef);
125                }
126            }
127        }
128    }
129
130    @Override
131    protected boolean mustCheckName(DetailAST ast) {
132        return true;
133    }
134
135}