remove this useless assignment to local variable sonar fix java

Remove this useless assignment to variable

I am using SimpleDataTables JS Library and their minimal suggested implementation: const dataTable = new DataTable("#myTable");

In SC this throws me an Remove this useless assignment to variable "dataTable". and an Remove the declaration of the unused 'dataTable' variable.

If I remove the assignement SC tells me to Either remove this useless object instantiation of "DataTable" or use it.

In SC, the FIRST approach is considered a code-smell, the second approach is considered a bug. So I prefer to use first approach, but still SC is not fully happy.

With my rather limited knowledge of JS, I would say simply doing new DataTable("#myTable"); is the right approach. Of course, strictly speaking, that library should probably not have sideffects when instantiating the object but rather provide a method (like DataTable->run()), but that is not the case.

Is there some other approach to do it “correctly” other than marking this as a false alarm?

Indeed you are using some lib probably having side-effects on constructor execution. I don’t think we will support this lib (I see from npm downloads it’s not very popular), so it’s up to you to ignore the issues.

I would keep the variable (it seems the recommended way as you might hook some events on it later). So either you could “won’t fix” the issues, or you can set in SC settings to ignore particular files for these rules (Administration → General Settings → Analysis Scope → Ignore Issues on Multiple Criteria).

Understood, I will maybe switch to the official data tables lib by jQuery. I had chosen the current one because it is much lighter, but in the end with modern computers and servers etc this doesn’t matter that much anyway.

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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

Supported Languages

Tags: :  Swift SonarQube Software Development

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"Remove this useless assignment to local variable", but the assignment is not useless

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Michael Gumowski

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Sonar "useless assignment to local variable" workaround?

I am working towards improving my code, and I came across this issue from Sonar:

Fact is, it is not useless, as I am using it just after in the code:

Sonar still tells me that "uiRequest" is useless, why ? It is not, as I don't want it to reach the code if it is null. I tried initializing it ( uiRequest = new UiRequest() ) but it keeps telling me that it is useless.

Anyone got an idea about why Sonar behaves like this / how to correct this ?

Your issue simplifies to:

There are two potential paths through this code:

• a() returns true . x is assigned b() then c(x) is called.
• a() returns false . An exception is thrown and c(x) is not called.

Neither of these paths calls c(x) using the initial assignment of null . So whatever you assigned at first, is redundant.

Note that this would also be an issue if the initial assignment was something other than null. Unless the right-hand-side of the assignment has a side effect , any assignment is wasted. (Sonar analyses for side-effects)

This is suspicious to Sonar:

• Maybe the programmer expected the first assignment to have an effect -- it doesn't, so perhaps it's a bug.
• It's also about code clarity -- a future human reader of the code might waste time wondering what the initial value is for.
• If the right-hand-side had involved computation, but had no side effect, it would be wasted computation.

You can fix this in two ways:

Firstly just removing the = null , leaving Foo x; - Java is clever enough to realise that all routes to c(x) involve an assignment, so this will still compile.

Better yet, move c(x) into the block:

This is logically equivalent, neater, and reduces the scope of x . Reducing scope is a good thing. Of course, if you need x in the wider scope, you can't do this.

One more variation, also logically equivalent:

... which responds well to "extract-method" and "inline" refactorings:

Use whichever communicates your intent best.

You can avoid the warning and perhaps have slightly more readable code by:

What about moving it into the if statement?

Or throw exception in the if statement and just have no else clause. i.e let the normal case be the "happy path".

The assignment is useless because no code can possibly see that assigned value.

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Rubocopエラー「Useless assignment to variable」の解決例

上記エラーを調べると、「使っていないローカル変数の定義がある」というエラーのようで 削除すれば解決するとの事でした。

しかし、今回はちゃんと使っている内容で、書き方の問題のようでした。 以下のように、if文などの後に 明示的に使用している記載が必要 とのことでした。

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Remove this useless assignment to local variable - sonarqube - using try catch

In the following code, sonarqube is complaining for the mentioned error in the question:

How can I re-write this code to resolve this complain from sonarqube?

• 1 Does your catch block rethrow? Can you provide a minimal reproducible example example rather then just commented bits? –  Jon Skeet Commented Nov 25, 2020 at 11:15
• @Jon I have provided the exact code. –  teenup Commented Nov 25, 2020 at 11:17
• 1 Have you tried not having a result at all and doing a return await func() / return default(T) instead? –  Caius Jard Commented Nov 25, 2020 at 11:18
• 2 I could assume that it's complaining about T result = default; but why are you making me guess? –  Damien_The_Unbeliever Commented Nov 25, 2020 at 11:19
• 1 @TimSchmelter: How is it redundant? If func() throws an exception or the task it returns throws an exception, there'd be no value in result . Without the initial assignment, the variable isn't definitely assigned at the return statement. –  Jon Skeet Commented Nov 25, 2020 at 11:19

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False Positive useless assignment to local variable #3115

Dixtosa commented Feb 12, 2020 • edited Loading

andrei-epure-sonarsource commented Feb 12, 2020

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