ab6d0f08b7
## Review A dedicated reviewer checked the rule description successfully for: - [ ] logical errors and incorrect information - [ ] information gaps and missing content - [ ] text style and tone - [ ] PR summary and labels follow [the guidelines](https://github.com/SonarSource/rspec/#to-modify-an-existing-rule)
150 lines
3.5 KiB
Plaintext
150 lines
3.5 KiB
Plaintext
include::../introduction.adoc[]
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include::../why-is-this-an-issue.adoc[]
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include::../what-is-the-potential-impact.adoc[]
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This rule looks for operands of a boolean expression never changing the result of the expression. It also applies to the https://learn.microsoft.com/en-us/dotnet/csharp/language-reference/operators/null-coalescing-operator[null coalescing operator] when one of the operands always evaluates to `null`.
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[source,csharp]
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----
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string d = null;
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var v1 = d ?? "value"; // Noncompliant
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----
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=== Exceptions
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This rule will not raise an issue in either of these cases:
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* When the condition is a single `const bool`
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+
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[source,csharp]
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----
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const bool debug = false;
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//...
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if (debug) // Compliant
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{
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// Print something
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}
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----
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* When the condition is the literal `true` or `false`.
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In these cases, it is obvious the code is as intended.
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include::../how-to-fix-it.adoc[]
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=== Code examples
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==== Noncompliant code example
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[source,csharp]
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----
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public void Sample(bool b, bool c)
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{
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var a = true;
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if (a) // Noncompliant: "a" is always "true"
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{
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DoSomething();
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}
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if (b && a) // Noncompliant: "a" is always "true"
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{
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DoSomething();
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}
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if (c || !a) // Noncompliant: "!a" is always "false"
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{
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DoSomething();
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}
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string d = null;
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var v1 = d ?? "value"; // Noncompliant: "d" is always null and v1 is always "value".
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var v2 = s ?? d; // Noncompliant: "d" is always null and v2 is always equal to s.
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}
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----
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==== Compliant solution
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The unnecessary operand is updated:
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[source,csharp]
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----
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public void Sample(bool b, bool c, string s)
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{
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var a = IsAllowed();
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if (a) // Compliant
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{
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DoSomething();
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}
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if (b && a) // Compliant
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{
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DoSomething();
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}
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if (c || !a) // Compliant
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{
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DoSomething();
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}
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string d = GetStringData();
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var v1 = d ?? "value"; // Compliant
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var v2 = s ?? d; // Compliant
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}
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----
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The unnecessary operand is removed:
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[source,csharp]
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----
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public void Sample(bool b, bool c, string s)
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{
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DoSomething();
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if (b) // Compliant
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{
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DoSomething();
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}
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if (c) // Compliant
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{
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DoSomething();
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}
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var v1 = "value"; // Compliant
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var v2 = s; // Compliant
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}
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----
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== Resources
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=== Documentation
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* https://cwe.mitre.org/data/definitions/571[MITRE, CWE-571] - Expression is Always True
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* https://cwe.mitre.org/data/definitions/570[MITRE, CWE-570] - Expression is Always False
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* https://learn.microsoft.com/en-us/dotnet/csharp/language-reference/operators/boolean-logical-operators#conditional-logical-and-operator-[Conditional logical AND operator &&]
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* https://learn.microsoft.com/en-us/dotnet/csharp/language-reference/operators/boolean-logical-operators#conditional-logical-or-operator-[Conditional logical OR operator ||]
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* https://learn.microsoft.com/en-us/dotnet/csharp/language-reference/operators/null-coalescing-operator[Null-coalescing operators ?? and ??=]
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ifdef::env-github,rspecator-view[]
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'''
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== Implementation Specification
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(visible only on this page)
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=== Message
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* Change this condition so that it does not always evaluate to "[true|false]".
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* Change this expression which always evaluates to the same result.
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include::../highlighting.adoc[]
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'''
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== Comments And Links
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(visible only on this page)
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include::../comments-and-links.adoc[]
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endif::env-github,rspecator-view[]
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