1 ///////////////////////////////////////////////////////////////////////////////////////////////
2 // checkstyle: Checks Java source code and other text files for adherence to a set of rules.
3 // Copyright (C) 2001-2024 the original author or authors.
4 //
5 // This library is free software; you can redistribute it and/or
6 // modify it under the terms of the GNU Lesser General Public
7 // License as published by the Free Software Foundation; either
8 // version 2.1 of the License, or (at your option) any later version.
9 //
10 // This library is distributed in the hope that it will be useful,
11 // but WITHOUT ANY WARRANTY; without even the implied warranty of
12 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 // Lesser General Public License for more details.
14 //
15 // You should have received a copy of the GNU Lesser General Public
16 // License along with this library; if not, write to the Free Software
17 // Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
18 ///////////////////////////////////////////////////////////////////////////////////////////////
19
20 package com.puppycrawl.tools.checkstyle.checks.coding;
21
22 import java.util.ArrayDeque;
23 import java.util.Deque;
24 import java.util.regex.Pattern;
25
26 import com.puppycrawl.tools.checkstyle.FileStatefulCheck;
27 import com.puppycrawl.tools.checkstyle.api.AbstractCheck;
28 import com.puppycrawl.tools.checkstyle.api.DetailAST;
29 import com.puppycrawl.tools.checkstyle.api.TokenTypes;
30
31 /**
32 * <p>
33 * Restricts the number of return statements in methods, constructors and lambda expressions.
34 * Ignores specified methods ({@code equals} by default).
35 * </p>
36 * <p>
37 * <b>max</b> property will only check returns in methods and lambdas that
38 * return a specific value (Ex: 'return 1;').
39 * </p>
40 * <p>
41 * <b>maxForVoid</b> property will only check returns in methods, constructors,
42 * and lambdas that have no return type (IE 'return;'). It will only count
43 * visible return statements. Return statements not normally written, but
44 * implied, at the end of the method/constructor definition will not be taken
45 * into account. To disallow "return;" in void return type methods, use a value
46 * of 0.
47 * </p>
48 * <p>
49 * Rationale: Too many return points can mean that code is
50 * attempting to do too much or may be difficult to understand.
51 * </p>
52 * <ul>
53 * <li>
54 * Property {@code format} - Specify method names to ignore.
55 * Type is {@code java.util.regex.Pattern}.
56 * Default value is {@code "^equals$"}.
57 * </li>
58 * <li>
59 * Property {@code max} - Specify maximum allowed number of return statements
60 * in non-void methods/lambdas.
61 * Type is {@code int}.
62 * Default value is {@code 2}.
63 * </li>
64 * <li>
65 * Property {@code maxForVoid} - Specify maximum allowed number of return statements
66 * in void methods/constructors/lambdas.
67 * Type is {@code int}.
68 * Default value is {@code 1}.
69 * </li>
70 * <li>
71 * Property {@code tokens} - tokens to check
72 * Type is {@code java.lang.String[]}.
73 * Validation type is {@code tokenSet}.
74 * Default value is:
75 * <a href="https://checkstyle.org/apidocs/com/puppycrawl/tools/checkstyle/api/TokenTypes.html#CTOR_DEF">
76 * CTOR_DEF</a>,
77 * <a href="https://checkstyle.org/apidocs/com/puppycrawl/tools/checkstyle/api/TokenTypes.html#METHOD_DEF">
78 * METHOD_DEF</a>,
79 * <a href="https://checkstyle.org/apidocs/com/puppycrawl/tools/checkstyle/api/TokenTypes.html#LAMBDA">
80 * LAMBDA</a>.
81 * </li>
82 * </ul>
83 * <p>
84 * Parent is {@code com.puppycrawl.tools.checkstyle.TreeWalker}
85 * </p>
86 * <p>
87 * Violation Message Keys:
88 * </p>
89 * <ul>
90 * <li>
91 * {@code return.count}
92 * </li>
93 * <li>
94 * {@code return.countVoid}
95 * </li>
96 * </ul>
97 *
98 * @since 3.2
99 */
100 @FileStatefulCheck
101 public final class ReturnCountCheck extends AbstractCheck {
102
103 /**
104 * A key is pointing to the warning message text in "messages.properties"
105 * file.
106 */
107 public static final String MSG_KEY = "return.count";
108 /**
109 * A key pointing to the warning message text in "messages.properties"
110 * file.
111 */
112 public static final String MSG_KEY_VOID = "return.countVoid";
113
114 /** Stack of method contexts. */
115 private final Deque<Context> contextStack = new ArrayDeque<>();
116
117 /** Specify method names to ignore. */
118 private Pattern format = Pattern.compile("^equals$");
119
120 /** Specify maximum allowed number of return statements in non-void methods/lambdas. */
121 private int max = 2;
122 /** Specify maximum allowed number of return statements in void methods/constructors/lambdas. */
123 private int maxForVoid = 1;
124 /** Current method context. */
125 private Context context;
126
127 @Override
128 public int[] getDefaultTokens() {
129 return new int[] {
130 TokenTypes.CTOR_DEF,
131 TokenTypes.METHOD_DEF,
132 TokenTypes.LAMBDA,
133 TokenTypes.LITERAL_RETURN,
134 };
135 }
136
137 @Override
138 public int[] getRequiredTokens() {
139 return new int[] {TokenTypes.LITERAL_RETURN};
140 }
141
142 @Override
143 public int[] getAcceptableTokens() {
144 return new int[] {
145 TokenTypes.CTOR_DEF,
146 TokenTypes.METHOD_DEF,
147 TokenTypes.LAMBDA,
148 TokenTypes.LITERAL_RETURN,
149 };
150 }
151
152 /**
153 * Setter to specify method names to ignore.
154 *
155 * @param pattern a pattern.
156 * @since 3.4
157 */
158 public void setFormat(Pattern pattern) {
159 format = pattern;
160 }
161
162 /**
163 * Setter to specify maximum allowed number of return statements
164 * in non-void methods/lambdas.
165 *
166 * @param max maximum allowed number of return statements.
167 * @since 3.2
168 */
169 public void setMax(int max) {
170 this.max = max;
171 }
172
173 /**
174 * Setter to specify maximum allowed number of return statements
175 * in void methods/constructors/lambdas.
176 *
177 * @param maxForVoid maximum allowed number of return statements for void methods.
178 * @since 6.19
179 */
180 public void setMaxForVoid(int maxForVoid) {
181 this.maxForVoid = maxForVoid;
182 }
183
184 @Override
185 public void beginTree(DetailAST rootAST) {
186 context = new Context(false);
187 contextStack.clear();
188 }
189
190 @Override
191 public void visitToken(DetailAST ast) {
192 switch (ast.getType()) {
193 case TokenTypes.CTOR_DEF:
194 case TokenTypes.METHOD_DEF:
195 visitMethodDef(ast);
196 break;
197 case TokenTypes.LAMBDA:
198 visitLambda();
199 break;
200 case TokenTypes.LITERAL_RETURN:
201 visitReturn(ast);
202 break;
203 default:
204 throw new IllegalStateException(ast.toString());
205 }
206 }
207
208 @Override
209 public void leaveToken(DetailAST ast) {
210 switch (ast.getType()) {
211 case TokenTypes.CTOR_DEF:
212 case TokenTypes.METHOD_DEF:
213 case TokenTypes.LAMBDA:
214 leave(ast);
215 break;
216 case TokenTypes.LITERAL_RETURN:
217 // Do nothing
218 break;
219 default:
220 throw new IllegalStateException(ast.toString());
221 }
222 }
223
224 /**
225 * Creates new method context and places old one on the stack.
226 *
227 * @param ast method definition for check.
228 */
229 private void visitMethodDef(DetailAST ast) {
230 contextStack.push(context);
231 final DetailAST methodNameAST = ast.findFirstToken(TokenTypes.IDENT);
232 final boolean check = !format.matcher(methodNameAST.getText()).find();
233 context = new Context(check);
234 }
235
236 /**
237 * Checks number of return statements and restore previous context.
238 *
239 * @param ast node to leave.
240 */
241 private void leave(DetailAST ast) {
242 context.checkCount(ast);
243 context = contextStack.pop();
244 }
245
246 /**
247 * Creates new lambda context and places old one on the stack.
248 */
249 private void visitLambda() {
250 contextStack.push(context);
251 context = new Context(true);
252 }
253
254 /**
255 * Examines the return statement and tells context about it.
256 *
257 * @param ast return statement to check.
258 */
259 private void visitReturn(DetailAST ast) {
260 // we can't identify which max to use for lambdas, so we can only assign
261 // after the first return statement is seen
262 if (ast.getFirstChild().getType() == TokenTypes.SEMI) {
263 context.visitLiteralReturn(maxForVoid, Boolean.TRUE);
264 }
265 else {
266 context.visitLiteralReturn(max, Boolean.FALSE);
267 }
268 }
269
270 /**
271 * Class to encapsulate information about one method.
272 */
273 private final class Context {
274
275 /** Whether we should check this method or not. */
276 private final boolean checking;
277 /** Counter for return statements. */
278 private int count;
279 /** Maximum allowed number of return statements. */
280 private Integer maxAllowed;
281 /** Identifies if context is void. */
282 private boolean isVoidContext;
283
284 /**
285 * Creates new method context.
286 *
287 * @param checking should we check this method or not
288 */
289 private Context(boolean checking) {
290 this.checking = checking;
291 }
292
293 /**
294 * Increase the number of return statements and set context return type.
295 *
296 * @param maxAssigned Maximum allowed number of return statements.
297 * @param voidReturn Identifies if context is void.
298 */
299 public void visitLiteralReturn(int maxAssigned, Boolean voidReturn) {
300 isVoidContext = voidReturn;
301 maxAllowed = maxAssigned;
302
303 ++count;
304 }
305
306 /**
307 * Checks if number of return statements in the method are more
308 * than allowed.
309 *
310 * @param ast method def associated with this context.
311 */
312 public void checkCount(DetailAST ast) {
313 if (checking && maxAllowed != null && count > maxAllowed) {
314 if (isVoidContext) {
315 log(ast, MSG_KEY_VOID, count, maxAllowed);
316 }
317 else {
318 log(ast, MSG_KEY, count, maxAllowed);
319 }
320 }
321 }
322
323 }
324
325 }