ed1c6003b7
Adapts the [rule](https://sonarsource.github.io/rspec/#/rspec/S4524) to LaYC format level 2, for csharp.
114 lines
3.0 KiB
Plaintext
114 lines
3.0 KiB
Plaintext
== Why is this an issue?
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The https://learn.microsoft.com/en-us/dotnet/csharp/language-reference/statements/selection-statements#the-switch-statement[switch statement] is a conditional statement that executes a sequence of instructions based on patterns matching the provided value.
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[source,csharp]
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----
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switch (temperatureInCelsius)
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{
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case < 35.0:
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Console.WriteLine("Hypothermia");
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break;
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case >= 36.5 and <= 37.5:
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Console.WriteLine("Normal");
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break;
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case > 37.5 and <= 40.0:
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Console.WriteLine("Fever or hyperthermia");
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break;
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case > 40.0:
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Console.WriteLine("Hyperpyrexia");
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break;
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}
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----
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The `switch` statement can optionally contain a `default` clause, executed when none of the `case` clauses are executed (or in presence of a `goto default;`).
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[source,csharp]
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----
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switch (gradeLetter)
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{
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case "A+":
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case "A":
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case "A-":
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Console.WriteLine("Excellent");
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break;
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case "B+":
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case "B":
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Console.WriteLine("Very Good");
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break;
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case "B-":
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case "C+":
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Console.WriteLine("Good");
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break;
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case "C":
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Console.WriteLine("Pass");
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break;
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case "F":
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Console.WriteLine("Fail");
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break;
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default:
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Console.WriteLine("Invalid grade letter!");
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break;
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}
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----
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The `default` clause can be defined for various reasons:
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* to handle *unexpected values*, as shown in the example above
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* or to show that all the cases were properly considered, making the function explicitely *total* (as opposed to https://en.wikipedia.org/wiki/Partial_function[partial])
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While C# allows the `default` clause to appear in any place within a `switch` statement, and while its position doesn't alter its behavior, it is recommended to put the `default` clause either at the beginning or at the end of the `switch` statement.
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That improves readability and helps the developer to quickly find the default behavior of a `switch` statement.
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This rule raises an issue if the `default` clause is neither the first nor the last one of the `switch` statement.
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== How to fix it
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=== Code examples
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==== Noncompliant code example
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[source,csharp,diff-id=1,diff-type=noncompliant]
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----
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switch (param)
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{
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case 0:
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DoSomething();
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break;
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default: // Noncompliant: default clause should be the first or last one
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Error();
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break;
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case 1:
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DoSomethingElse();
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break;
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}
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----
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==== Compliant solution
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[source,csharp,diff-id=1,diff-type=compliant]
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----
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switch (param)
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{
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case 0:
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DoSomething();
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break;
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case 1:
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DoSomethingElse();
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break;
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default:
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Error();
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break;
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}
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----
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== Resources
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=== Documentation
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* https://learn.microsoft.com/en-us/dotnet/csharp/language-reference/statements/selection-statements#the-switch-statement[Switch statement]
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* https://en.wikipedia.org/wiki/Partial_function[Partial function]
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include::../rspecator.adoc[]
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