001///////////////////////////////////////////////////////////////////////////////////////////////
002// checkstyle: Checks Java source code and other text files for adherence to a set of rules.
003// Copyright (C) 2001-2024 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.modifier;
021
022import com.puppycrawl.tools.checkstyle.StatelessCheck;
023import com.puppycrawl.tools.checkstyle.api.AbstractCheck;
024import com.puppycrawl.tools.checkstyle.api.DetailAST;
025import com.puppycrawl.tools.checkstyle.api.TokenTypes;
026import com.puppycrawl.tools.checkstyle.utils.ScopeUtil;
027
028/**
029 * <div>
030 * Checks for implicit modifiers on interface members and nested types.
031 * </div>
032 *
033 * <p>
034 * This check is effectively the opposite of
035 * <a href="https://checkstyle.org/checks/modifier/redundantmodifier.html#RedundantModifier">
036 * RedundantModifier</a>.
037 * It checks the modifiers on interface members, ensuring that certain modifiers are explicitly
038 * specified even though they are actually redundant.
039 * </p>
040 *
041 * <p>
042 * Methods in interfaces are {@code public} by default, however from Java 9 they can also be
043 * {@code private}. This check provides the ability to enforce that {@code public} is explicitly
044 * coded and not implicitly added by the compiler.
045 * </p>
046 *
047 * <p>
048 * From Java 8, there are three types of methods in interfaces - static methods marked with
049 * {@code static}, default methods marked with {@code default} and abstract methods which do not
050 * have to be marked with anything. From Java 9, there are also private methods marked with
051 * {@code private}. This check provides the ability to enforce that {@code abstract} is
052 * explicitly coded and not implicitly added by the compiler.
053 * </p>
054 *
055 * <p>
056 * Fields in interfaces are always {@code public static final} and as such the compiler does not
057 * require these modifiers. This check provides the ability to enforce that these modifiers are
058 * explicitly coded and not implicitly added by the compiler.
059 * </p>
060 *
061 * <p>
062 * Nested types within an interface are always {@code public static} and as such the compiler
063 * does not require the {@code public static} modifiers. This check provides the ability to
064 * enforce that the {@code public} and {@code static} modifiers are explicitly coded and not
065 * implicitly added by the compiler.
066 * </p>
067 * <pre>
068 * public interface AddressFactory {
069 *   // check enforces code contains "public static final"
070 *   public static final String UNKNOWN = "Unknown";
071 *
072 *   String OTHER = "Other";  // violation
073 *
074 *   // check enforces code contains "public" or "private"
075 *   public static AddressFactory instance();
076 *
077 *   // check enforces code contains "public abstract"
078 *   public abstract Address createAddress(String addressLine, String city);
079 *
080 *   List&lt;Address&gt; findAddresses(String city);  // violation
081 *
082 *   // check enforces default methods are explicitly declared "public"
083 *   public default Address createAddress(String city) {
084 *     return createAddress(UNKNOWN, city);
085 *   }
086 *
087 *   default Address createOtherAddress() {  // violation
088 *     return createAddress(OTHER, OTHER);
089 *   }
090 * }
091 * </pre>
092 *
093 * <p>
094 * Rationale for this check: Methods, fields and nested types are treated differently
095 * depending on whether they are part of an interface or part of a class. For example, by
096 * default methods are package-scoped on classes, but public in interfaces. However, from
097 * Java 8 onwards, interfaces have changed to be much more like abstract classes.
098 * Interfaces now have static and instance methods with code. Developers should not have to
099 * remember which modifiers are required and which are implied. This check allows the simpler
100 * alternative approach to be adopted where the implied modifiers must always be coded explicitly.
101 * </p>
102 * <ul>
103 * <li>
104 * Property {@code violateImpliedAbstractMethod} - Control whether to enforce that {@code abstract}
105 * is explicitly coded on interface methods.
106 * Type is {@code boolean}.
107 * Default value is {@code true}.
108 * </li>
109 * <li>
110 * Property {@code violateImpliedFinalField} - Control whether to enforce that {@code final}
111 * is explicitly coded on interface fields.
112 * Type is {@code boolean}.
113 * Default value is {@code true}.
114 * </li>
115 * <li>
116 * Property {@code violateImpliedPublicField} - Control whether to enforce that {@code public}
117 * is explicitly coded on interface fields.
118 * Type is {@code boolean}.
119 * Default value is {@code true}.
120 * </li>
121 * <li>
122 * Property {@code violateImpliedPublicMethod} - Control whether to enforce that {@code public}
123 * is explicitly coded on interface methods.
124 * Type is {@code boolean}.
125 * Default value is {@code true}.
126 * </li>
127 * <li>
128 * Property {@code violateImpliedPublicNested} - Control whether to enforce that {@code public}
129 * is explicitly coded on interface nested types.
130 * Type is {@code boolean}.
131 * Default value is {@code true}.
132 * </li>
133 * <li>
134 * Property {@code violateImpliedStaticField} - Control whether to enforce that {@code static}
135 * is explicitly coded on interface fields.
136 * Type is {@code boolean}.
137 * Default value is {@code true}.
138 * </li>
139 * <li>
140 * Property {@code violateImpliedStaticNested} - Control whether to enforce that {@code static}
141 * is explicitly coded on interface nested types.
142 * Type is {@code boolean}.
143 * Default value is {@code true}.
144 * </li>
145 * </ul>
146 *
147 * <p>
148 * Parent is {@code com.puppycrawl.tools.checkstyle.TreeWalker}
149 * </p>
150 *
151 * <p>
152 * Violation Message Keys:
153 * </p>
154 * <ul>
155 * <li>
156 * {@code interface.implied.modifier}
157 * </li>
158 * </ul>
159 *
160 * @since 8.12
161 */
162@StatelessCheck
163public class InterfaceMemberImpliedModifierCheck
164    extends AbstractCheck {
165
166    /**
167     * A key is pointing to the warning message text in "messages.properties" file.
168     */
169    public static final String MSG_KEY = "interface.implied.modifier";
170
171    /** Name for 'public' access modifier. */
172    private static final String PUBLIC_ACCESS_MODIFIER = "public";
173
174    /** Name for 'abstract' keyword. */
175    private static final String ABSTRACT_KEYWORD = "abstract";
176
177    /** Name for 'static' keyword. */
178    private static final String STATIC_KEYWORD = "static";
179
180    /** Name for 'final' keyword. */
181    private static final String FINAL_KEYWORD = "final";
182
183    /**
184     * Control whether to enforce that {@code public} is explicitly coded
185     * on interface fields.
186     */
187    private boolean violateImpliedPublicField = true;
188
189    /**
190     * Control whether to enforce that {@code static} is explicitly coded
191     * on interface fields.
192     */
193    private boolean violateImpliedStaticField = true;
194
195    /**
196     * Control whether to enforce that {@code final} is explicitly coded
197     * on interface fields.
198     */
199    private boolean violateImpliedFinalField = true;
200
201    /**
202     * Control whether to enforce that {@code public} is explicitly coded
203     * on interface methods.
204     */
205    private boolean violateImpliedPublicMethod = true;
206
207    /**
208     * Control whether to enforce that {@code abstract} is explicitly coded
209     * on interface methods.
210     */
211    private boolean violateImpliedAbstractMethod = true;
212
213    /**
214     * Control whether to enforce that {@code public} is explicitly coded
215     * on interface nested types.
216     */
217    private boolean violateImpliedPublicNested = true;
218
219    /**
220     * Control whether to enforce that {@code static} is explicitly coded
221     * on interface nested types.
222     */
223    private boolean violateImpliedStaticNested = true;
224
225    /**
226     * Setter to control whether to enforce that {@code public} is explicitly coded
227     * on interface fields.
228     *
229     * @param violateImpliedPublicField
230     *        True to perform the check, false to turn the check off.
231     * @since 8.12
232     */
233    public void setViolateImpliedPublicField(boolean violateImpliedPublicField) {
234        this.violateImpliedPublicField = violateImpliedPublicField;
235    }
236
237    /**
238     * Setter to control whether to enforce that {@code static} is explicitly coded
239     * on interface fields.
240     *
241     * @param violateImpliedStaticField
242     *        True to perform the check, false to turn the check off.
243     * @since 8.12
244     */
245    public void setViolateImpliedStaticField(boolean violateImpliedStaticField) {
246        this.violateImpliedStaticField = violateImpliedStaticField;
247    }
248
249    /**
250     * Setter to control whether to enforce that {@code final} is explicitly coded
251     * on interface fields.
252     *
253     * @param violateImpliedFinalField
254     *        True to perform the check, false to turn the check off.
255     * @since 8.12
256     */
257    public void setViolateImpliedFinalField(boolean violateImpliedFinalField) {
258        this.violateImpliedFinalField = violateImpliedFinalField;
259    }
260
261    /**
262     * Setter to control whether to enforce that {@code public} is explicitly coded
263     * on interface methods.
264     *
265     * @param violateImpliedPublicMethod
266     *        True to perform the check, false to turn the check off.
267     * @since 8.12
268     */
269    public void setViolateImpliedPublicMethod(boolean violateImpliedPublicMethod) {
270        this.violateImpliedPublicMethod = violateImpliedPublicMethod;
271    }
272
273    /**
274     * Setter to control whether to enforce that {@code abstract} is explicitly coded
275     * on interface methods.
276     *
277     * @param violateImpliedAbstractMethod
278     *        True to perform the check, false to turn the check off.
279     * @since 8.12
280     */
281    public void setViolateImpliedAbstractMethod(boolean violateImpliedAbstractMethod) {
282        this.violateImpliedAbstractMethod = violateImpliedAbstractMethod;
283    }
284
285    /**
286     * Setter to control whether to enforce that {@code public} is explicitly coded
287     * on interface nested types.
288     *
289     * @param violateImpliedPublicNested
290     *        True to perform the check, false to turn the check off.
291     * @since 8.12
292     */
293    public void setViolateImpliedPublicNested(boolean violateImpliedPublicNested) {
294        this.violateImpliedPublicNested = violateImpliedPublicNested;
295    }
296
297    /**
298     * Setter to control whether to enforce that {@code static} is explicitly coded
299     * on interface nested types.
300     *
301     * @param violateImpliedStaticNested
302     *        True to perform the check, false to turn the check off.
303     * @since 8.12
304     */
305    public void setViolateImpliedStaticNested(boolean violateImpliedStaticNested) {
306        this.violateImpliedStaticNested = violateImpliedStaticNested;
307    }
308
309    @Override
310    public int[] getDefaultTokens() {
311        return getAcceptableTokens();
312    }
313
314    @Override
315    public int[] getRequiredTokens() {
316        return getAcceptableTokens();
317    }
318
319    @Override
320    public int[] getAcceptableTokens() {
321        return new int[] {
322            TokenTypes.METHOD_DEF,
323            TokenTypes.VARIABLE_DEF,
324            TokenTypes.INTERFACE_DEF,
325            TokenTypes.CLASS_DEF,
326            TokenTypes.ENUM_DEF,
327        };
328    }
329
330    @Override
331    public void visitToken(DetailAST ast) {
332        if (ScopeUtil.isInInterfaceBlock(ast) && !ScopeUtil.isInCodeBlock(ast)) {
333            switch (ast.getType()) {
334                case TokenTypes.METHOD_DEF:
335                    processMethod(ast);
336                    break;
337                case TokenTypes.VARIABLE_DEF:
338                    processField(ast);
339                    break;
340                case TokenTypes.CLASS_DEF:
341                case TokenTypes.INTERFACE_DEF:
342                case TokenTypes.ENUM_DEF:
343                    processNestedType(ast);
344                    break;
345                default:
346                    throw new IllegalStateException(ast.toString());
347            }
348        }
349    }
350
351    /**
352     * Check method in interface.
353     *
354     * @param ast the method AST
355     */
356    private void processMethod(DetailAST ast) {
357        final DetailAST modifiers = ast.findFirstToken(TokenTypes.MODIFIERS);
358        if (violateImpliedPublicMethod
359                && modifiers.findFirstToken(TokenTypes.LITERAL_PRIVATE) == null
360                && modifiers.findFirstToken(TokenTypes.LITERAL_PUBLIC) == null) {
361            log(ast, MSG_KEY, PUBLIC_ACCESS_MODIFIER);
362        }
363        if (violateImpliedAbstractMethod
364                && modifiers.findFirstToken(TokenTypes.LITERAL_PRIVATE) == null
365                && modifiers.findFirstToken(TokenTypes.LITERAL_STATIC) == null
366                && modifiers.findFirstToken(TokenTypes.LITERAL_DEFAULT) == null
367                && modifiers.findFirstToken(TokenTypes.ABSTRACT) == null) {
368            log(ast, MSG_KEY, ABSTRACT_KEYWORD);
369        }
370    }
371
372    /**
373     * Check field in interface.
374     *
375     * @param ast the field AST
376     */
377    private void processField(DetailAST ast) {
378        final DetailAST modifiers = ast.findFirstToken(TokenTypes.MODIFIERS);
379        if (violateImpliedPublicField
380                && modifiers.findFirstToken(TokenTypes.LITERAL_PUBLIC) == null) {
381            log(ast, MSG_KEY, PUBLIC_ACCESS_MODIFIER);
382        }
383        if (violateImpliedStaticField
384                && modifiers.findFirstToken(TokenTypes.LITERAL_STATIC) == null) {
385            log(ast, MSG_KEY, STATIC_KEYWORD);
386        }
387        if (violateImpliedFinalField
388                && modifiers.findFirstToken(TokenTypes.FINAL) == null) {
389            log(ast, MSG_KEY, FINAL_KEYWORD);
390        }
391    }
392
393    /**
394     * Check nested types in interface.
395     *
396     * @param ast the nested type AST
397     */
398    private void processNestedType(DetailAST ast) {
399        final DetailAST modifiers = ast.findFirstToken(TokenTypes.MODIFIERS);
400        if (violateImpliedPublicNested
401                && modifiers.findFirstToken(TokenTypes.LITERAL_PUBLIC) == null) {
402            log(ast, MSG_KEY, PUBLIC_ACCESS_MODIFIER);
403        }
404        if (violateImpliedStaticNested
405                && modifiers.findFirstToken(TokenTypes.LITERAL_STATIC) == null) {
406            log(ast, MSG_KEY, STATIC_KEYWORD);
407        }
408    }
409
410}