code smell remove this useless assignment to local variable

Solving Sonar's 'Remove Useless Assignment of Local Variable' Error in Swift

Abstract: Learn how to resolve SonarQube's 'Remove Useless Assignment of Local Variable' error in Swift by understanding its cause and using different workarounds.

Solving Sonar's "Remove Useless Assignment to Local Variable" Error in Swift

Sonar is a popular tool used for code analysis and review. It helps developers identify and fix issues in their code, making it more readable, maintainable, and secure. One common issue that Sonar flags is the "Remove Useless Assignment to Local Variable" error in Swift. This error occurs when a local variable is assigned a value that is not used in the code. In this article, we will discuss how to solve this error in Swift.

Understanding the Error

To understand the error, let's consider an example:

In this example, we declare two local variables, x and y. We assign the value 5 to x and then calculate the value of y by multiplying x by 2. However, we never use the value of x again in the code. Therefore, Sonar flags the assignment of x as a useless assignment.

Solving the Error

To solve the error, we need to ensure that every local variable is used in the code. We can do this by either using the variable or removing its declaration. In the above example, we can remove the declaration of x, as it is not used in the code:

Alternatively, we can use the value of x in the code:

In this example, we print the value of x to the console, ensuring that it is used in the code.

Using Sonar to Identify Useless Assignments

Sonar can help us identify useless assignments in our code. To do this, we need to configure Sonar to analyze our Swift code. We can do this by installing the SonarSwift plugin and configuring it to analyze our project. Once we have done this, Sonar will flag any useless assignments in our code, allowing us to fix them.

The "Remove Useless Assignment to Local Variable" error in Swift is a common issue that Sonar flags. To solve this error, we need to ensure that every local variable is used in the code. We can do this by either using the variable or removing its declaration. Sonar can help us identify useless assignments in our code, allowing us to fix them and improve the quality of our code.

Remove Useless Assignment to Local Variable

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Tags: :  Swift SonarQube Software Development

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SonarQube displaying to 'remove this useless assignment to local variable'

Why is SonarQube giving this error? How should I fix it? Their rule page does not specify the solution,

Remove this useless assignment to local variable validateAddressRequest.

 Answers

This site says that the error occurs when:

A value is assigned to a variable or property, but either that location is never read later on, or its value is always overwritten before being read. This means that the original assignment has no effect, and could indicate a logic error or incomplete code.

On the first line of the if block, you assign to validateAddressRequest , but then on the third line of the if block, you overwrite validateAddressRequest without having read the previously assigned variable. So the first line is useless.

Declare validateAddressRequest only when calling convertToValidateRequest instead.

Note that you almost certainly don't need the type annotation - if Typescript knows that convertToValidateRequest returns a ValidateAddressRequest already, there's no need to do so again with the new variable. You can do so if you think it's unclear otherwise, or if you don't have type Intellisense, but it may just be noise.

If you were declaring the variable with let so as to enable assignment to it in the future, keep in mind that it's best to avoid reassignment whenever possible, and it's almost always possible to avoid reassignment. If you need another variable that contains a ValidateAddressRequest , give it a different variable name so that you can use const to declare both variables; that makes the code more understandable at a glance, when a reader can be sure that a particular variable reference isn't ever going to be reassigned.

freddiejarretk

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If a buffer contains sensitive data, such as passwords or access tokens, it is good practice to overwrite the buffer before releasing the memory. This ensures that the sensitive data is not available when that memory is reallocated. The memset function is commonly used for this purpose.

Why is this an issue?

How can i fix it.

The C language specification allows the compiler to remove unnecessary code during the optimization phase. For example, when a memory buffer is about to be destroyed, any writes to that buffer may be seen as unnecessary to the operation of the program. The compiler may choose to remove these write operations.

When the memset function is used to clear sensitive data from memory and that memory is destroyed immediately afterward, the compiler may see the memset call as unnecessary and remove it. The sensitive data will, therefore, remain in memory.

This rule raises an issue when a call to memset is followed by the destruction of the buffer.

Error 'unused local variables should be removed' issue in consumer interface

I used the foreach method of list,I defined a variable in it and used it.But sonarqube analyzed it as an issue -'unused local variables should be removed '.

After that, I changed the code to an enhanced loop, and the issue didn’t appear,

I didn’t find this problem when I used the previous version.

And I think it’s just a sonarqube issue, not a sonarlint issue.

Hello @muii , thanks for the feedback.

Indeed, it looks like a wrong behavior of the rule, it seems to be related to this problem , and I’m glad to say that we tackled it two days ago .

You should not face this issue anymore with (soon to be released) SonarJava 6.1.

Hope this helps, Quentin

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Remove unnecessary value assignment (IDE0059)

• 4 contributors

This rule flags unnecessary value assignments. For example:

You can take one of the following actions to fix this violation:

If the expression on the right side of the assignment has no side effects, remove the expression or the entire assignment statement. This improves performance by avoiding unnecessary computation.

If the expression on the right side of the assignment has side effects, replace the left side of the assignment with a discard (C# only) or a local variable that's never used. Discards improve code clarity by explicitly showing the intent to discard an unused value.

The options for this specify whether to prefer the use of a discard or an unused local variable:

• C# - csharp_style_unused_value_assignment_preference
• Visual Basic - visual_basic_style_unused_value_assignment_preference

For information about configuring options, see Option format .

csharp_style_unused_value_assignment_preference

Visual_basic_style_unused_value_assignment_preference, suppress a warning.

If you want to suppress only a single violation, add preprocessor directives to your source file to disable and then re-enable the rule.

To disable the rule for a file, folder, or project, set its severity to none in the configuration file .

To disable all of the code-style rules, set the severity for the category Style to none in the configuration file .

For more information, see How to suppress code analysis warnings .

This rule flags unnecessary value assignments. For example, answer is unused in the following snippet:

• Remove unused expression value (IDE0058)
• Code style rules reference

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Additional resources

• CodeQL overview
• Writing CodeQL queries
• CodeQL query help documentation »
• CodeQL query help for Go »

Useless assignment to local variable ¶

Click to see the query in the CodeQL repository

A value is assigned to a variable, but either it is never read, or its value is always overwritten before being read. This means that the original assignment has no effect, and could indicate a logic error or incomplete code.

Recommendation ¶

Remove assignments to variables that are immediately overwritten, or use the blank identifier _ as a placeholder for return values that are never used.

In the following example, a value is assigned to a , but then immediately overwritten, a value is assigned to b and never used, and finally, the results of a call to fmt.Println are assigned to two temporary variables, which are then immediately overwritten by a call to function .

The result of calculateValue is never used, and if calculateValue is a side-effect free function, those assignments can be removed. To ignore all the return values of fmt.Println , you can simply not assign it to any variables. To ignore only certain return values, use _ .

References ¶

Wikipedia: Dead store .

The Go Programming Language Specification: Blank identifier .

Common Weakness Enumeration: CWE-563 .

no-useless-assignment

Disallow variable assignments when the value is not used

Wikipedia describes a “dead store” as follows:

In computer programming, a local variable that is assigned a value but is not read by any subsequent instruction is referred to as a dead store .

“Dead stores” waste processing and memory, so it is better to remove unnecessary assignments to variables.

Also, if the author intended the variable to be used, there is likely a mistake around the dead store. For example,

• you should have used a stored value but forgot to do so.
• you made a mistake in the name of the variable to be stored.

Rule Details

This rule aims to report variable assignments when the value is not used.

Examples of incorrect code for this rule:

Examples of correct code for this rule:

This rule will not report variables that are never read. Because it’s clearly an unused variable. If you want it reported, please enable the no-unused-vars rule.

When Not To Use It

If you don’t want to be notified about values that are never read, you can safely disable this rule.

Related Rules

• no-unused-vars

This rule was introduced in ESLint v9.0.0-alpha.1.

Further Reading

• Rule source
• Tests source