pmd / pmd / 197

Committed 19 Oct 2025 09:43PM UTC coverage: 78.676% (+0.03%) from 78.642%

Build # 197

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github

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oowekyala

Commit Message

Fix reviow comments on #6116

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93.52

/pmd-java/src/main/java/net/sourceforge/pmd/lang/java/rule/codestyle/UselessParenthesesRule.java

/*
 * BSD-style license; for more info see http://pmd.sourceforge.net/license.html
 */

package net.sourceforge.pmd.lang.java.rule.codestyle;

import static net.sourceforge.pmd.lang.java.rule.codestyle.UselessParenthesesRule.Necessity.ALWAYS;
import static net.sourceforge.pmd.lang.java.rule.codestyle.UselessParenthesesRule.Necessity.BALANCING;
import static net.sourceforge.pmd.lang.java.rule.codestyle.UselessParenthesesRule.Necessity.CLARIFYING;
import static net.sourceforge.pmd.lang.java.rule.codestyle.UselessParenthesesRule.Necessity.NEVER;
import static net.sourceforge.pmd.lang.java.rule.codestyle.UselessParenthesesRule.Necessity.definitely;
import static net.sourceforge.pmd.lang.java.rule.codestyle.UselessParenthesesRule.Necessity.necessaryIf;

import net.sourceforge.pmd.lang.java.ast.ASTAssignmentExpression;
import net.sourceforge.pmd.lang.java.ast.ASTCastExpression;
import net.sourceforge.pmd.lang.java.ast.ASTConditionalExpression;
import net.sourceforge.pmd.lang.java.ast.ASTExpression;
import net.sourceforge.pmd.lang.java.ast.ASTInfixExpression;
import net.sourceforge.pmd.lang.java.ast.ASTLambdaExpression;
import net.sourceforge.pmd.lang.java.ast.ASTPrimaryExpression;
import net.sourceforge.pmd.lang.java.ast.ASTSwitchExpression;
import net.sourceforge.pmd.lang.java.ast.ASTUnaryExpression;
import net.sourceforge.pmd.lang.java.ast.BinaryOp;
import net.sourceforge.pmd.lang.java.ast.JavaNode;
import net.sourceforge.pmd.lang.java.ast.internal.PrettyPrintingUtil;
import net.sourceforge.pmd.lang.java.rule.AbstractJavaRulechainRule;
import net.sourceforge.pmd.properties.PropertyDescriptor;
import net.sourceforge.pmd.properties.PropertyFactory;
import net.sourceforge.pmd.util.AssertionUtil;


public final class UselessParenthesesRule extends AbstractJavaRulechainRule {
    // todo rename to UnnecessaryParentheses

    private static final PropertyDescriptor<Boolean> IGNORE_CLARIFYING =
        PropertyFactory.booleanProperty("ignoreClarifying")
                       .defaultValue(true)
                       .desc("Ignore parentheses that separate expressions of difference precedence,"
                                 + " like in `(a % 2 == 0) ? x : -x`")
                       .build();

    private static final PropertyDescriptor<Boolean> IGNORE_BALANCING =
        PropertyFactory.booleanProperty("ignoreBalancing")
                       .defaultValue(true)
                       .desc("Ignore unnecessary parentheses that appear balanced around an equality "
                                 + "operator, because the other operand requires parentheses."
                                 + "For example, in `(a == null) == (b == null)`, only the second pair "
                                 + "of parentheses is necessary, but the expression is clearer that way.")
                       .build();
    private static final int MAX_SNIPPET_LENGTH = 50;

    public UselessParenthesesRule() {
        super(ASTExpression.class);
        definePropertyDescriptor(IGNORE_CLARIFYING);
        definePropertyDescriptor(IGNORE_BALANCING);
    }

    private boolean reportClarifying() {
        return !getProperty(IGNORE_CLARIFYING);
    }

    private boolean reportBalancing() {
        return !getProperty(IGNORE_BALANCING);
    }


    @Override
    public Object visitJavaNode(JavaNode node, Object data) {
        if (node instanceof ASTExpression) {
            checkExpr((ASTExpression) node, data);
        } else {
            throw new IllegalArgumentException("Expected an expression, got " + node);
        }
        return null;
    }

    private void checkExpr(ASTExpression e, Object data) {
        if (!e.isParenthesized()) {
            return;
        }

        Necessity necessity = needsParentheses(e, e.getParent());

        if (necessity == NEVER
            || reportClarifying() && necessity == CLARIFYING
            || reportBalancing() && necessity == BALANCING) {
            String template = e.getParenthesisDepth() > 1 ? "Duplicate parentheses around `{0}`."
                : "Useless parentheses around `{0}`.";
            CharSequence snippet = PrettyPrintingUtil.prettyPrint(e);
            String dots = "...";
            if (snippet.length() > MAX_SNIPPET_LENGTH) {
                snippet = snippet.subSequence(0, MAX_SNIPPET_LENGTH - dots.length()) + dots;
            }
            asCtx(data).addViolationWithMessage(e, template,
                snippet);

        }
    }

    public static Necessity needsParentheses(ASTExpression inner, JavaNode outer) {
        // Note: as of jdk 15, PatternExpression cannot be parenthesized
        // TypeExpression may never be parenthesized either
        assert inner.isParenthesized() : inner + " is not parenthesized";


        if (inner.getParenthesisDepth() > 1
            || !(outer instanceof ASTExpression)) {
            // ((a + b))        unnecessary
            // new int[(2)]     unnecessary
            // return (1 + 2);
            return NEVER;
        }

        if (inner instanceof ASTPrimaryExpression) {
            return NEVER;
        }
        if (inner instanceof ASTSwitchExpression) {
            return outer instanceof ASTPrimaryExpression && inner.getIndexInParent() == 0
                    ? ALWAYS : NEVER;
        }

        if (outer instanceof ASTLambdaExpression) {
            // () -> (a + b)        unnecessary
            // () -> (() -> b)      unnecessary
            // () -> (a ? b : c);   unnecessary unless the parent of the lambda is itself a ternary
            if (inner instanceof ASTLambdaExpression) {
                return NEVER;
            }
            return definitely(inner instanceof ASTConditionalExpression && outer.getParent() instanceof ASTConditionalExpression);
        }

        if (inner instanceof ASTAssignmentExpression) {
            //  a * (b = c)          necessary
            //  a ? (b = c) : d      necessary
            //  a = (b = c)          associative
            //  (a = b) = c          (impossible)
            return outer instanceof ASTAssignmentExpression ? NEVER : ALWAYS;
        }

        if (inner instanceof ASTConditionalExpression) {

            // a ? (b ? c : d) : e    necessary
            // a ? b : (c ? d : e)    associative
            // (a ? b : c) ? d : e    necessary
            if (outer instanceof ASTConditionalExpression) {
                return inner.getIndexInParent() == 2 ? NEVER  // last child
                                                     : ALWAYS;
            } else {
                return necessaryIf(!(outer instanceof ASTAssignmentExpression));
            }
        }

        if (inner instanceof ASTLambdaExpression) {
            // a ? (() -> b) + c : d     invalid, but necessary
            // a ? (() -> b) : d         clarifying
            return outer instanceof ASTConditionalExpression ? CLARIFYING
                                                             : definitely(!(outer instanceof ASTAssignmentExpression));
        }

        if (inner instanceof ASTInfixExpression) {
            if (outer instanceof ASTInfixExpression) {
                BinaryOp inop = ((ASTInfixExpression) inner).getOperator();
                BinaryOp outop = ((ASTInfixExpression) outer).getOperator();
                int comp = outop.comparePrecedence(inop);

                // (a * b) + c       unnecessary
                // a * (b + c)       necessary
                // a + (b + c)       unnecessary
                // (a + b) + c       unnecessary
                // (a - b) + c       clarifying

                if (comp > 0) {
                    return ALWAYS; // outer has greater precedence
                } else if (comp < 0) {
                    return CLARIFYING; // outer has lower precedence, but the operators are different
                }

                // the rest deals with ties in precedence

                if (inner.getIndexInParent() == 1) {
                    // parentheses are on the right
                    // eg a - (b + c)

                    if (associatesRightWith(outop, inop, (ASTInfixExpression) inner, (ASTInfixExpression) outer)) {
                        // a & (b & c)
                        // a | (b | c)
                        // a ^ (b ^ c)
                        // a && (b && c)
                        // a || (b || c)
                        return NEVER;
                    } else {
                        return ALWAYS;
                    }
                } else {
                    // parentheses are on the left
                    // eg (a + b) + c
                    if (outop.hasSamePrecedenceAs(BinaryOp.EQ) // EQ or NE
                        && ((ASTInfixExpression) outer).getRightOperand().isParenthesized()) {
                        // (a == null) == (b == null)
                        return BALANCING;
                    } else if (outop == BinaryOp.ADD
                        && inop.hasSamePrecedenceAs(BinaryOp.ADD) && inner.getTypeMirror().isNumeric()
                        && !((ASTInfixExpression) outer).getTypeMirror().isNumeric()) {
                        return CLARIFYING;
                    }

                    return NEVER;
                }
            } else { // outer !is ASTInfixExpression
                if (outer instanceof ASTConditionalExpression && inner.getIndexInParent() == 0) {
                    // (a == b) ? .. : ..
                    return CLARIFYING;
                }

                return necessaryIf(isUnary(outer) || outer instanceof ASTPrimaryExpression);
            }
        }

        if (isUnary(inner)) {
            return isUnary(outer) ? NEVER : necessaryIf(outer instanceof ASTPrimaryExpression);
        }


        throw AssertionUtil.shouldNotReachHere("Unhandled case inside " + outer);
    }

    private static boolean isUnary(JavaNode expr) {
        return expr instanceof ASTUnaryExpression || expr instanceof ASTCastExpression;
    }

    // Returns true if it is safe to remove parentheses in the expression `A outop (B inop C)`
    // outop and inop have the same precedence class
    private static boolean associatesRightWith(BinaryOp outop, BinaryOp inop, ASTInfixExpression inner, ASTInfixExpression outer) {

        /*
         Notes about associativity:
         - Integer multiplication/addition is associative when the operands are all of the same type.
         - Floating-point multiplication/addition is not associative.
         - The boolean equality operators are associative, but input type != output type in general
         - Bitwise and logical operators are associative
         - The conditional-OR/AND operator is fully associative with respect to both side effects and result value.
         */

        switch (inop) {
        case AND:
        case OR:
        case XOR:
        case CONDITIONAL_AND:
        case CONDITIONAL_OR:
            return true;
        case MUL:
            // a * (b * c)      -- yes
            // a * (b / c)      -- no, could change semantics
            // a * (b % c)      -- no

            // a / (b * c)      -- no
            // a / (b / c)      -- no
            // a / (b % c)      -- no

            // a % (b * c)      -- no
            // a % (b / c)      -- no
            // a % (b % c)      -- no

            return inop == outop; // == MUL
        case SUB:
        case ADD:
            // a + (b + c)      -- yes, unless outop is concatenation and inop is addition, or operands are floats
            // a + (b - c)      -- yes

            // a - (b + c)      -- no
            // a - (b - c)      -- no
            return outop == BinaryOp.ADD
                && outer.getTypeMirror().isPrimitive() == inner.getTypeMirror().isPrimitive()
                && !inner.getTypeMirror().isFloatingPoint();
        default:
            return false;
        }
    }

    public enum Necessity {
        ALWAYS,
        NEVER,
        CLARIFYING,
        BALANCING;

        static Necessity definitely(boolean b) {
            return b ? ALWAYS : NEVER;
        }

        static Necessity necessaryIf(boolean b) {
            return b ? ALWAYS : CLARIFYING;
        }
    }
}

1	/*
2	* BSD-style license; for more info see http://pmd.sourceforge.net/license.html
3	*/
4
5	package net.sourceforge.pmd.lang.java.rule.codestyle;
6
7	import static net.sourceforge.pmd.lang.java.rule.codestyle.UselessParenthesesRule.Necessity.ALWAYS;
8	import static net.sourceforge.pmd.lang.java.rule.codestyle.UselessParenthesesRule.Necessity.BALANCING;
9	import static net.sourceforge.pmd.lang.java.rule.codestyle.UselessParenthesesRule.Necessity.CLARIFYING;
10	import static net.sourceforge.pmd.lang.java.rule.codestyle.UselessParenthesesRule.Necessity.NEVER;
11	import static net.sourceforge.pmd.lang.java.rule.codestyle.UselessParenthesesRule.Necessity.definitely;
12	import static net.sourceforge.pmd.lang.java.rule.codestyle.UselessParenthesesRule.Necessity.necessaryIf;
13
14	import net.sourceforge.pmd.lang.java.ast.ASTAssignmentExpression;
15	import net.sourceforge.pmd.lang.java.ast.ASTCastExpression;
16	import net.sourceforge.pmd.lang.java.ast.ASTConditionalExpression;
17	import net.sourceforge.pmd.lang.java.ast.ASTExpression;
18	import net.sourceforge.pmd.lang.java.ast.ASTInfixExpression;
19	import net.sourceforge.pmd.lang.java.ast.ASTLambdaExpression;
20	import net.sourceforge.pmd.lang.java.ast.ASTPrimaryExpression;
21	import net.sourceforge.pmd.lang.java.ast.ASTSwitchExpression;
22	import net.sourceforge.pmd.lang.java.ast.ASTUnaryExpression;
23	import net.sourceforge.pmd.lang.java.ast.BinaryOp;
24	import net.sourceforge.pmd.lang.java.ast.JavaNode;
25	import net.sourceforge.pmd.lang.java.ast.internal.PrettyPrintingUtil;
26	import net.sourceforge.pmd.lang.java.rule.AbstractJavaRulechainRule;
27	import net.sourceforge.pmd.properties.PropertyDescriptor;
28	import net.sourceforge.pmd.properties.PropertyFactory;
29	import net.sourceforge.pmd.util.AssertionUtil;
30
31
32	public final class UselessParenthesesRule extends AbstractJavaRulechainRule {
33	// todo rename to UnnecessaryParentheses
34
35	private static final PropertyDescriptor<Boolean> IGNORE_CLARIFYING =	1✔
36	PropertyFactory.booleanProperty("ignoreClarifying")	1✔
37	.defaultValue(true)	1✔
38	.desc("Ignore parentheses that separate expressions of difference precedence,"	1✔
39	+ " like in `(a % 2 == 0) ? x : -x`")
40	.build();	1✔
41
42	private static final PropertyDescriptor<Boolean> IGNORE_BALANCING =	1✔
43	PropertyFactory.booleanProperty("ignoreBalancing")	1✔
44	.defaultValue(true)	1✔
45	.desc("Ignore unnecessary parentheses that appear balanced around an equality "	1✔
46	+ "operator, because the other operand requires parentheses."
47	+ "For example, in `(a == null) == (b == null)`, only the second pair "
48	+ "of parentheses is necessary, but the expression is clearer that way.")
49	.build();	1✔
50	private static final int MAX_SNIPPET_LENGTH = 50;
51
52	public UselessParenthesesRule() {
53	super(ASTExpression.class);	1✔
54	definePropertyDescriptor(IGNORE_CLARIFYING);	1✔
55	definePropertyDescriptor(IGNORE_BALANCING);	1✔
56	}	1✔
57
58	private boolean reportClarifying() {
59	return !getProperty(IGNORE_CLARIFYING);	1✔
60	}
61
62	private boolean reportBalancing() {
63	return !getProperty(IGNORE_BALANCING);	1!
64	}
65
66
67	@Override
68	public Object visitJavaNode(JavaNode node, Object data) {
69	if (node instanceof ASTExpression) {	1!
70	checkExpr((ASTExpression) node, data);	1✔
71	} else {
72	throw new IllegalArgumentException("Expected an expression, got " + node);	×
73	}
74	return null;	1✔
75	}
76
77	private void checkExpr(ASTExpression e, Object data) {
78	if (!e.isParenthesized()) {	1✔
79	return;	1✔
80	}
81
82	Necessity necessity = needsParentheses(e, e.getParent());	1✔
83
84	if (necessity == NEVER	1✔
85	\|\| reportClarifying() && necessity == CLARIFYING	1✔
86	\|\| reportBalancing() && necessity == BALANCING) {	1!
87	String template = e.getParenthesisDepth() > 1 ? "Duplicate parentheses around `{0}`."	1✔
88	: "Useless parentheses around `{0}`.";	1✔
89	CharSequence snippet = PrettyPrintingUtil.prettyPrint(e);	1✔
90	String dots = "...";	1✔
91	if (snippet.length() > MAX_SNIPPET_LENGTH) {	1✔
92	snippet = snippet.subSequence(0, MAX_SNIPPET_LENGTH - dots.length()) + dots;	1✔
93	}
94	asCtx(data).addViolationWithMessage(e, template,	1✔
95	snippet);
96
97	}
98	}	1✔
99
100	public static Necessity needsParentheses(ASTExpression inner, JavaNode outer) {
101	// Note: as of jdk 15, PatternExpression cannot be parenthesized
102	// TypeExpression may never be parenthesized either
103	assert inner.isParenthesized() : inner + " is not parenthesized";	1!
104
105
106	if (inner.getParenthesisDepth() > 1	1✔
107	\|\| !(outer instanceof ASTExpression)) {
108	// ((a + b)) unnecessary
109	// new int[(2)] unnecessary
110	// return (1 + 2);
111	return NEVER;	1✔
112	}
113
114	if (inner instanceof ASTPrimaryExpression) {	1✔
115	return NEVER;	1✔
116	}
117	if (inner instanceof ASTSwitchExpression) {	1✔
118	return outer instanceof ASTPrimaryExpression && inner.getIndexInParent() == 0	1✔
119	? ALWAYS : NEVER;	1✔
120	}
121
122	if (outer instanceof ASTLambdaExpression) {	1✔
123	// () -> (a + b) unnecessary
124	// () -> (() -> b) unnecessary
125	// () -> (a ? b : c); unnecessary unless the parent of the lambda is itself a ternary
126	if (inner instanceof ASTLambdaExpression) {	1✔
127	return NEVER;	1✔
128	}
129	return definitely(inner instanceof ASTConditionalExpression && outer.getParent() instanceof ASTConditionalExpression);	1✔
130	}
131
132	if (inner instanceof ASTAssignmentExpression) {	1✔
133	// a * (b = c) necessary
134	// a ? (b = c) : d necessary
135	// a = (b = c) associative
136	// (a = b) = c (impossible)
137	return outer instanceof ASTAssignmentExpression ? NEVER : ALWAYS;	1✔
138	}
139
140	if (inner instanceof ASTConditionalExpression) {	1✔
141
142	// a ? (b ? c : d) : e necessary
143	// a ? b : (c ? d : e) associative
144	// (a ? b : c) ? d : e necessary
145	if (outer instanceof ASTConditionalExpression) {	1✔
146	return inner.getIndexInParent() == 2 ? NEVER // last child	1✔
147	: ALWAYS;	1✔
148	} else {
149	return necessaryIf(!(outer instanceof ASTAssignmentExpression));	1!
150	}
151	}
152
153	if (inner instanceof ASTLambdaExpression) {	1✔
154	// a ? (() -> b) + c : d invalid, but necessary
155	// a ? (() -> b) : d clarifying
156	return outer instanceof ASTConditionalExpression ? CLARIFYING	1✔
157	: definitely(!(outer instanceof ASTAssignmentExpression));	1✔
158	}
159
160	if (inner instanceof ASTInfixExpression) {	1✔
161	if (outer instanceof ASTInfixExpression) {	1✔
162	BinaryOp inop = ((ASTInfixExpression) inner).getOperator();	1✔
163	BinaryOp outop = ((ASTInfixExpression) outer).getOperator();	1✔
164	int comp = outop.comparePrecedence(inop);	1✔
165
166	// (a * b) + c unnecessary
167	// a * (b + c) necessary
168	// a + (b + c) unnecessary
169	// (a + b) + c unnecessary
170	// (a - b) + c clarifying
171
172	if (comp > 0) {	1✔
173	return ALWAYS; // outer has greater precedence	1✔
174	} else if (comp < 0) {	1✔
175	return CLARIFYING; // outer has lower precedence, but the operators are different	1✔
176	}
177
178	// the rest deals with ties in precedence
179
180	if (inner.getIndexInParent() == 1) {	1✔
181	// parentheses are on the right
182	// eg a - (b + c)
183
184	if (associatesRightWith(outop, inop, (ASTInfixExpression) inner, (ASTInfixExpression) outer)) {	1✔
185	// a & (b & c)
186	// a \| (b \| c)
187	// a ^ (b ^ c)
188	// a && (b && c)
189	// a \|\| (b \|\| c)
190	return NEVER;	1✔
191	} else {
192	return ALWAYS;	1✔
193	}
194	} else {
195	// parentheses are on the left
196	// eg (a + b) + c
197	if (outop.hasSamePrecedenceAs(BinaryOp.EQ) // EQ or NE	1✔
198	&& ((ASTInfixExpression) outer).getRightOperand().isParenthesized()) {	1✔
199	// (a == null) == (b == null)
200	return BALANCING;	1✔
201	} else if (outop == BinaryOp.ADD	1✔
202	&& inop.hasSamePrecedenceAs(BinaryOp.ADD) && inner.getTypeMirror().isNumeric()	1!
203	&& !((ASTInfixExpression) outer).getTypeMirror().isNumeric()) {	1✔
204	return CLARIFYING;	1✔
205	}
206
207	return NEVER;	1✔
208	}
209	} else { // outer !is ASTInfixExpression
210	if (outer instanceof ASTConditionalExpression && inner.getIndexInParent() == 0) {	1!
211	// (a == b) ? .. : ..
212	return CLARIFYING;	1✔
213	}
214
215	return necessaryIf(isUnary(outer) \|\| outer instanceof ASTPrimaryExpression);	1!
216	}
217	}
218
219	if (isUnary(inner)) {	1!
220	return isUnary(outer) ? NEVER : necessaryIf(outer instanceof ASTPrimaryExpression);	1✔
221	}
222
223
UNCOV 224	throw AssertionUtil.shouldNotReachHere("Unhandled case inside " + outer);	×
225	}
226
227	private static boolean isUnary(JavaNode expr) {
228	return expr instanceof ASTUnaryExpression \|\| expr instanceof ASTCastExpression;	1✔
229	}
230
231	// Returns true if it is safe to remove parentheses in the expression `A outop (B inop C)`
232	// outop and inop have the same precedence class
233	private static boolean associatesRightWith(BinaryOp outop, BinaryOp inop, ASTInfixExpression inner, ASTInfixExpression outer) {
234
235	/*
236	Notes about associativity:
237	- Integer multiplication/addition is associative when the operands are all of the same type.
238	- Floating-point multiplication/addition is not associative.
239	- The boolean equality operators are associative, but input type != output type in general
240	- Bitwise and logical operators are associative
241	- The conditional-OR/AND operator is fully associative with respect to both side effects and result value.
242	*/
243
244	switch (inop) {	1✔
245	case AND:
246	case OR:
247	case XOR:
248	case CONDITIONAL_AND:
249	case CONDITIONAL_OR:
250	return true;	1✔
251	case MUL:
252	// a * (b * c) -- yes
253	// a * (b / c) -- no, could change semantics
254	// a * (b % c) -- no
255
256	// a / (b * c) -- no
257	// a / (b / c) -- no
258	// a / (b % c) -- no
259
260	// a % (b * c) -- no
261	// a % (b / c) -- no
262	// a % (b % c) -- no
263
264	return inop == outop; // == MUL	1✔
265	case SUB:
266	case ADD:
267	// a + (b + c) -- yes, unless outop is concatenation and inop is addition, or operands are floats
268	// a + (b - c) -- yes
269
270	// a - (b + c) -- no
271	// a - (b - c) -- no
272	return outop == BinaryOp.ADD	1✔
273	&& outer.getTypeMirror().isPrimitive() == inner.getTypeMirror().isPrimitive()	1✔
274	&& !inner.getTypeMirror().isFloatingPoint();	1✔
275	default:
276	return false;	1✔
277	}
278	}
279
280	public enum Necessity {	1✔
281	ALWAYS,	1✔
282	NEVER,	1✔
283	CLARIFYING,	1✔
284	BALANCING;	1✔
285
286	static Necessity definitely(boolean b) {
287	return b ? ALWAYS : NEVER;	1✔
288	}
289
290	static Necessity necessaryIf(boolean b) {
291	return b ? ALWAYS : CLARIFYING;	1✔
292	}
293	}
294	}

pmd / pmd / 197

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