forked from detekt/detekt
/
LibraryCodeMustSpecifyReturnType.kt
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/
LibraryCodeMustSpecifyReturnType.kt
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package io.gitlab.arturbosch.detekt.libraries
import io.gitlab.arturbosch.detekt.api.CodeSmell
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.Rule
import io.gitlab.arturbosch.detekt.api.Severity
import io.gitlab.arturbosch.detekt.api.internal.ActiveByDefault
import io.gitlab.arturbosch.detekt.api.internal.RequiresTypeResolution
import org.jetbrains.kotlin.psi.KtCallableDeclaration
import org.jetbrains.kotlin.psi.KtNamedFunction
import org.jetbrains.kotlin.psi.KtProperty
import org.jetbrains.kotlin.resolve.BindingContext
import org.jetbrains.kotlin.resolve.checkers.ExplicitApiDeclarationChecker
/**
* Functions/properties exposed as public APIs of a library should have an explicit return type.
* Inferred return type can easily be changed by mistake which may lead to breaking changes.
*
* See also: [Kotlin 1.4 Explicit API](https://kotlinlang.org/docs/whatsnew14.html#explicit-api-mode-for-library-authors)
*
* <noncompliant>
* // code from a library
* val strs = listOf("foo, bar")
* fun bar() = 5
* class Parser {
* fun parse() = ...
* }
* </noncompliant>
*
* <compliant>
* // code from a library
* val strs: List<String> = listOf("foo, bar")
* fun bar(): Int = 5
*
* class Parser {
* fun parse(): ParsingResult = ...
* }
* </compliant>
*
*/
@RequiresTypeResolution
@ActiveByDefault(since = "1.2.0")
class LibraryCodeMustSpecifyReturnType(config: Config = Config.empty) : Rule(config) {
override val issue = Issue(
this.javaClass.simpleName,
Severity.Style,
"Library functions/properties should have an explicit return type. " +
"Inferred return types can easily be changed by mistake which may lead to breaking changes.",
Debt.FIVE_MINS
)
override fun visitProperty(property: KtProperty) {
if (property.explicitReturnTypeRequired()) {
report(
CodeSmell(
issue,
Entity.atName(property),
"Library property '${property.nameAsSafeName}' without explicit return type."
)
)
}
super.visitProperty(property)
}
override fun visitNamedFunction(function: KtNamedFunction) {
if (bindingContext == BindingContext.EMPTY) {
return
}
if (function.explicitReturnTypeRequired()) {
report(
CodeSmell(
issue,
Entity.atName(function),
"Library function '${function.nameAsSafeName}' without explicit return type."
)
)
}
super.visitNamedFunction(function)
}
private fun KtCallableDeclaration.explicitReturnTypeRequired(): Boolean =
ExplicitApiDeclarationChecker.returnTypeCheckIsApplicable(this) &&
ExplicitApiDeclarationChecker.returnTypeRequired(
element = this,
descriptor = bindingContext[BindingContext.DECLARATION_TO_DESCRIPTOR, this],
checkForPublicApi = true,
checkForInternal = false,
checkForPrivate = false
)
}