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Separating ComplexMethod rule into CyclomaticComplexMethod and Cognit…
…iveComplexMethod (#5442) * feature: add rule CognitiveComplexMethod * test: add test for CognitiveComplexMethod rule * move: ComplexMethod -> CyclomaticComplexMethod * fix: remove referencing ComplexMethod * fix: detekt correct * fix: set alias * config: deactivate default cognitive complex method rule * test: add positive and negative test cases * Update detekt-rules-complexity/src/main/kotlin/io/gitlab/arturbosch/detekt/rules/complexity/CyclomaticComplexMethod.kt Co-authored-by: Brais Gabín <braisgabin@gmail.com> * fix: remove conflicting activeByDefault and sync Co-authored-by: Brais Gabín <braisgabin@gmail.com>
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60 changes: 60 additions & 0 deletions
60
...ty/src/main/kotlin/io/gitlab/arturbosch/detekt/rules/complexity/CognitiveComplexMethod.kt
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| Original file line number | Diff line number | Diff line change |
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| @@ -0,0 +1,60 @@ | ||
| package io.gitlab.arturbosch.detekt.rules.complexity | ||
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| import io.github.detekt.metrics.CognitiveComplexity | ||
| import io.gitlab.arturbosch.detekt.api.Config | ||
| import io.gitlab.arturbosch.detekt.api.Debt | ||
| import io.gitlab.arturbosch.detekt.api.Entity | ||
| import io.gitlab.arturbosch.detekt.api.Issue | ||
| import io.gitlab.arturbosch.detekt.api.Metric | ||
| import io.gitlab.arturbosch.detekt.api.Rule | ||
| import io.gitlab.arturbosch.detekt.api.Severity | ||
| import io.gitlab.arturbosch.detekt.api.ThresholdedCodeSmell | ||
| import io.gitlab.arturbosch.detekt.api.config | ||
| import io.gitlab.arturbosch.detekt.api.internal.Configuration | ||
| import org.jetbrains.kotlin.psi.KtNamedFunction | ||
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| /** | ||
| * Complex methods are hard to understand and read. It might not be obvious what side-effects a complex method has. | ||
| * Prefer splitting up complex methods into smaller methods that are in turn easier to understand. | ||
| * Smaller methods can also be named much clearer which leads to improved readability of the code. | ||
| * | ||
| * This rule measures and restricts the complexity of the method through the [Cognitive Complexity metric of Sonasource](https://www.sonarsource.com/docs/CognitiveComplexity.pdf). | ||
| * Which improves McCabe's Cyclomatic Complexity ({@link CyclomaticComplexMethod}) considering the programmer's mental model. | ||
| * | ||
| * Similar to cyclomatic complexity, it is a mathematical model that increases +1 complexity for flow control statements, | ||
| * but increases additional complexity when the statements are deeply nested. | ||
| * | ||
| * The statements that increase the complexity or the nesting level are as follows. | ||
| * - __Complexity Increments__ - `if`, `when`, `for`, `while`, `do while`, `catch`, `labeled break`, `labeled continue`, `labeled return`, `recursion call`, `&&`, `||` | ||
| * - __Nesting Level Increments__ - `if`, `when`, `for`, `while`, `do while`, `catch`, `nested function` | ||
| * - __Additional Complexity Increments by Nesting Level__ - `if`, `when`, `for`, `while`, `do while`, `catch` | ||
| */ | ||
| class CognitiveComplexMethod(config: Config = Config.empty) : Rule(config) { | ||
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| override val issue = Issue( | ||
| "CognitiveComplexMethod", | ||
| Severity.Maintainability, | ||
| "Prefer splitting up complex methods into smaller, easier to understand methods.", | ||
| Debt.TWENTY_MINS | ||
| ) | ||
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| @Configuration("Cognitive Complexity number for a method.") | ||
| private val threshold: Int by config(defaultValue = 15) | ||
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| override fun visitNamedFunction(function: KtNamedFunction) { | ||
| val complexity = CognitiveComplexity.calculate(function) | ||
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| if (complexity >= threshold) { | ||
| report( | ||
| ThresholdedCodeSmell( | ||
| issue, | ||
| Entity.atName(function), | ||
| Metric("CC", complexity, threshold), | ||
| "The function ${function.nameAsSafeName} appears to be too complex " + | ||
| "based on Cognitive Complexity (complexity: $complexity). " + | ||
| "Defined complexity threshold for methods is set to '$threshold'" | ||
| ) | ||
| ) | ||
| } | ||
| } | ||
| } |
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47 changes: 47 additions & 0 deletions
47
...rc/test/kotlin/io/gitlab/arturbosch/detekt/rules/complexity/CognitiveComplexMethodSpec.kt
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| Original file line number | Diff line number | Diff line change |
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| @@ -0,0 +1,47 @@ | ||
| package io.gitlab.arturbosch.detekt.rules.complexity | ||
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| import io.gitlab.arturbosch.detekt.api.SourceLocation | ||
| import io.gitlab.arturbosch.detekt.test.TestConfig | ||
| import io.gitlab.arturbosch.detekt.test.assertThat | ||
| import io.gitlab.arturbosch.detekt.test.compileAndLint | ||
| import io.gitlab.arturbosch.detekt.test.isThresholded | ||
| import org.junit.jupiter.api.Test | ||
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| class CognitiveComplexMethodSpec { | ||
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| private val testConfig = TestConfig("threshold" to "1") | ||
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| @Test | ||
| fun `should report complex function`() { | ||
| val code = """ | ||
| fun sumOfPrimes(max: Int): Int { // total cognitive complexity is 7 | ||
| var total = 0 | ||
| next@ for (i in 1..max) { // +1 | ||
| for (j in 2 until i) { // +1 +1 | ||
| if (i % j == 0) { // +1 +2 | ||
| continue@next // +1 | ||
| } | ||
| } | ||
| println(i) | ||
| total++ | ||
| } | ||
| return total | ||
| } | ||
| """.trimIndent() | ||
| val findings = CognitiveComplexMethod(testConfig).compileAndLint(code) | ||
| assertThat(findings).hasSize(1) | ||
| assertThat(findings).hasStartSourceLocations(SourceLocation(1, 5)) | ||
| assertThat(findings.first()).isThresholded().withValue(7) | ||
| } | ||
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| @Test | ||
| fun `should not report simple function`() { | ||
| val code = """ | ||
| fun add(a: Int, b: Int): Int { // total cognitive complexity is 0 | ||
| return a + b | ||
| } | ||
| """.trimIndent() | ||
| val findings = CognitiveComplexMethod(testConfig).compileAndLint(code) | ||
| assertThat(findings).isEmpty() | ||
| } | ||
| } |
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