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Add UnnecessaryNotNullCheck rule #5218

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VirtualParticle
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This adds the UnnecessaryNotNullCheck rule as discussed in #5204. It detects usages of requireNotNull and checkNotNull on non-null values.

@github-actions github-actions bot added the rules label Aug 11, 2022
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github-actions bot commented Aug 11, 2022

Messages
📖 Thanks for adding a new rule to Detekt ❤️

Generated by 🚫 dangerJS against eb2aa3d

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codecov bot commented Aug 11, 2022

Codecov Report

Merging #5218 (5411caf) into main (e0a5774) will increase coverage by 0.00%.
The diff coverage is 90.00%.

Current head 5411caf differs from pull request most recent head eb2aa3d. Consider uploading reports for the commit eb2aa3d to get more accurate results

@@            Coverage Diff            @@
##               main    #5218   +/-   ##
=========================================
  Coverage     84.96%   84.97%           
- Complexity     3640     3647    +7     
=========================================
  Files           502      503    +1     
  Lines         11988    12008   +20     
  Branches       2259     2263    +4     
=========================================
+ Hits          10186    10204   +18     
  Misses          690      690           
- Partials       1112     1114    +2     
Impacted Files Coverage Δ
...bosch/detekt/rules/bugs/UnnecessaryNotNullCheck.kt 89.47% <89.47%> (ø)
...turbosch/detekt/rules/bugs/PotentialBugProvider.kt 100.00% <100.00%> (ø)

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@cortinico cortinico added this to the 1.22.0 milestone Aug 13, 2022
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@chao2zhang chao2zhang left a comment

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💯 on adding this new rule. Thank you for your contribution

if (bindingContext == BindingContext.EMPTY) return

val callName = expression.getCallNameExpression()?.text
if (callName == "requireNotNull" || callName == "checkNotNull") {
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Since we have binding context present here, I would recommend match the full qualified name. You may find UseCheckNotNull as a good example

override val issue = Issue(
"UnnecessaryNotNullCheck",
Severity.Defect,
"Unnecessary not-null check detected.",
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Suggested change
"Unnecessary not-null check detected.",
"Remove unnecessary not-null checks on non-null types.",

I would recommend using a more elaborative description since our description has been historically vague.

@@ -470,6 +470,8 @@ potential-bugs:
active: true
UnconditionalJumpStatementInLoop:
active: false
UnnecessaryNotNullCheck:
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I don't think using UnnecessaryNotNullCheck would be catching error-prone bugs. What do you think about style rules instead of potential-bugs section (Define the rule in :detekt-rules-style instead of `:detekt-rules-errorprone)?

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It looks like similar rules like UnnecessaryNotNullOperator and UnnecessarySafeCall are in potential-bugs as well. I think the reason for that is probably that treating a non-null value as nullable shows a potential misuse of code and while not terribly likely to cause bugs, it still could. For example, consider the following:

fun getSomeValue(id: Int): Int {
    // ...
}

// somewhere else
val value = requireNotNull(getSomeValue(0)) { "Value not found" }

This use of requireNotNull is probably assuming that getSomeValue returns null when it can't find the value, but we can see that isn't the case; it could be returning -1 or even throw an exception. The former might and the latter definitely would cause a bug as the exception wouldn't be handled.

CodeSmell(
issue = issue,
entity = Entity.from(expression),
message = "`${expression.text}` contains an unnecessary `$callName`",
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Nitpick: Could we improve the message by
Using $callNameon non-nullcalleeExpression is unnecessary to make it more clear to user?

}

@Nested
inner class `check valid not null check usage` {
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Do you think it's worth adding one test case in this PR?

  • Platform type - Similar to shouldDetectWhenCallingPrimitiveJavaMethod but on a non-primitive
  • Definitely not null generic type. Doc

If this sounds more expensive, we could definitely follow up.

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I already have the first one with shouldIgnoreWhenCallingObjectJavaMethod, I'll add the second one.

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@BraisGabin BraisGabin left a comment

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Nice one! Thanks

@BraisGabin BraisGabin merged commit 4c67bef into detekt:main Oct 4, 2022
21 checks passed
@VirtualParticle VirtualParticle deleted the add-unnecessary-not-null-check branch October 4, 2022 17:43
@cortinico cortinico added the notable changes Marker for notable changes in the changelog label Oct 4, 2022
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4 participants