s1854 remove this useless assignment to local variable

Sonarlint wrong "useless assignment to local variables"

Since the last update of Sonarlint, we now have some obviously wrong issues reported about useless assignments to local variables:

I think this only happens in standalone mode, when connected to Sonar those issues are not shown.

Is this known already and is there a ticket to follow?

Version: SonarLint for Eclipse 5.1.0.17086 org.sonarlint.eclipse.feature.feature.group SonarSource

I can still see it with the version SonarLint for Eclipse 5.2.1.18852 org.sonarlint.eclipse.feature.feature.group SonarSource

Nobody else is affected?

The noise that this is creating is quite annoying.

Hi Phlippe,

Can you share a reproducer? Like a sample project on GitHub having the issue.

Unfortunately I haven’t found a good way to reproduce the issue but now I know a little bit more about it. I have uploaded the example code I used above here: https://github.com/philippecade/sonarlint.bug

• When I only have this project in Eclipse, the issue doesn’t appear. I can only see it when this project is in a workspace with ~30 other projects, some connected to Sonar and some not.
• The issue only happens if the project in question is not connected to a Sonar server.
• It is a regression from version 4.3.0.
• I don’t think that it depends on a particular code construct, the issue is also reported in a simple for loop for example: for (Foo f: list) { f.foo(); } <-- Remove this unused “f” local variable

Not sure if this is enough information for you. I’m willing to help further if you have a debug build or something like that.

Thanks Philippe

I’m still unable to reproduce.

• enable analysis + verbose logs
• clear the SonarLint console
• close/reopen the file LdapUtils
• share the logs

For the record, this is what I get:

This is what I get in the Eclipse that shows the error:

I see your project is configured to use a JRE, not a JDK. Could it be the reason of the difference? Could you try to configure a JDK instead? I will try to reproduce on my side.

I was able to reproduce. This is because you run Eclipse with a JDK 8, but your project is configured to use a Java 11 runtime. We have a ticket on our side to track this issue: https://jira.sonarsource.com/browse/SLE-348 I will update it and try to make its resolution prioritized.

In the meantime, a workaround is to configure Eclipse to run with a more recent JDK.

Great, I’m glad you found it.

I can also confirm that using Java 11 for Eclipse solves the issue.

Thanks for your help!

This topic was automatically closed 7 days after the last reply. New replies are no longer allowed.

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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False positive with s1854.

Product: SolarLint 6.8.0.53188 IDE: VS 2022 CE 17.0.4 Preview 2 Language: C# Rule: S1854 - "Remove this useless assignment to local variable"

I am using the prefix increment operator in code that sends an integer to a method. Here's a MRE:

If there are hundreds of calls to MyMethod2(int i) , making the last and only last " i+1 " is a code smell in itself:

(this would be difficult to spot visually, and adding another line to the end with the prefix operator would introduce a bug).

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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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Useless assignment to local variable ¶

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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 .

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Eclipse SonarLint false positive "Unused assignments should be removed (java:S1854)"

I'm using Eclipse 2020-03 (4.15.0) with Sonarlint for Eclipse 5.1.0.17086 and I get , IMO, false positive S1854 warnings in the following code (taken from the book "Java 8 In Action"). Working with Java OpenJDK 13.0.2. This is not a showstopper since I am merely studying Java 8 techniques. I just want to understand why these lines are flagged...

Did I miss something here? Both "length", "leftTask" and "rightTask" are used several times in the code...

Above class is tested with the following class:

• sonarlint-eclipse

• What are end , start and THRESHOLD ? Please provide a minimal reproducible example . –  howlger Commented May 13, 2020 at 14:37
• Edited to add more code info. –  PaulN Commented May 14, 2020 at 8:51

2 Answers 2

I did a brief survey about Warning S1854 on Sonar and saw several issues created on Github and on the Sonar website itself, apparently it was fixed in February/2020. Check if your Sonar is up to date, and if it is, the error probably hasn't been fixed :(

https://jira.sonarsource.com/browse/SONARJAVA-3281

• Thanks for your survey. I checked in Eclipse for SonarLint updates. There were none. I also checked your link. It handles false positives in lambda code, which is not the case in my code. We'll see... –  PaulN Commented May 13, 2020 at 11:52

I finally solved the problem, I was set on the right track by a post on the sonarlint forum ( https://community.sonarsource.com/t/java-s2166-rule-not-working/22943/15 ). My projects were working with Java 13 while my Windows cmd "Java -version" returned Java 1.8 as the running Java version. This mismatch (Eclipse starting up with Java 1.8 and the project working with Java 13) caused the SonarLint FP's.

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