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Add support to nullable slots in ContentSlotReused #343

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Oct 3, 2024
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Add support to nullable slots in ContentSlotReused #343

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7 changes: 4 additions & 3 deletions rules/common/src/main/kotlin/io/nlopez/compose/core/util/KtCallableDeclarations.kt
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Expand Up @@ -50,6 +50,7 @@ val KnownUnstableCollectionTypesRegex = sequenceOf(
fun KtCallableDeclaration.contentSlots(
treatAsLambdaTypes: Set<String>,
treatAsComposableLambdaTypes: Set<String>,
): List<KtParameter> = valueParameters.filter { parameter ->
parameter.typeReference?.isComposableLambda(treatAsLambdaTypes, treatAsComposableLambdaTypes) == true
}
): Sequence<KtParameter> = valueParameters.asSequence()
.filter { parameter ->
parameter.typeReference?.isComposableLambda(treatAsLambdaTypes, treatAsComposableLambdaTypes) == true
}
9 changes: 9 additions & 0 deletions rules/common/src/main/kotlin/io/nlopez/compose/core/util/KtParameters.kt
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@@ -0,0 +1,9 @@
// Copyright 2024 Nacho Lopez
// SPDX-License-Identifier: Apache-2.0
package io.nlopez.compose.core.util

import org.jetbrains.kotlin.psi.KtNullableType
import org.jetbrains.kotlin.psi.KtParameter

val KtParameter.isTypeNullable: Boolean
get() = typeReference?.typeElement is KtNullableType
92 changes: 23 additions & 69 deletions rules/common/src/main/kotlin/io/nlopez/compose/rules/ContentSlotReused.kt
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Expand Up @@ -10,93 +10,47 @@ import io.nlopez.compose.core.util.composableLambdaTypes
import io.nlopez.compose.core.util.contentSlots
import io.nlopez.compose.core.util.findChildrenByClass
import io.nlopez.compose.core.util.findShadowingRedeclarations
import io.nlopez.compose.core.util.isTypeNullable
import io.nlopez.compose.core.util.lambdaTypes
import io.nlopez.compose.core.util.uniquePairs
import org.jetbrains.kotlin.lexer.KtTokens
import org.jetbrains.kotlin.psi.KtBinaryExpression
import org.jetbrains.kotlin.psi.KtCallExpression
import org.jetbrains.kotlin.psi.KtElement
import org.jetbrains.kotlin.psi.KtFunction
import org.jetbrains.kotlin.psi.KtIfExpression
import org.jetbrains.kotlin.psi.KtWhenExpression
import org.jetbrains.kotlin.psi.psiUtil.parents
import org.jetbrains.kotlin.psi.KtParameter
import org.jetbrains.kotlin.psi.KtSafeQualifiedExpression

class ContentSlotReused : ComposeKtVisitor {
override fun visitComposable(function: KtFunction, emitter: Emitter, config: ComposeKtConfig) {
val lambdaTypes = function.containingKtFile.lambdaTypes(config)
val composableLambdaTypes = function.containingKtFile.composableLambdaTypes(config)

val slots = function.contentSlots(lambdaTypes, composableLambdaTypes)
.filter { it.name?.isNotEmpty() == true }
val slotsWithMultipleUsages = function.contentSlots(lambdaTypes, composableLambdaTypes)
.filter { slot -> function.findNotShadowedUsagesOf(slot).count() >= 2 }

val slotsWithMultipleUsages = slots.filter { it.name != null }
.map { slot -> slot to function.findUsages(slot.name!!) }
.filter { (_, usages) -> usages.count() >= 2 }

// Now that we found some candidates, we need to make sure the slots being reused are in different branches
// in the ast tree. We'll need to search for parent ifs, whens, etc.
val slotsInDifferentBranches = slotsWithMultipleUsages
.filter { (_, usages) -> isSlotUsedInSeparateBranches(usages, function) }
.map { (slot, _) -> slot }

for (slot in slotsInDifferentBranches) {
emitter.report(slot, ContentSlotReusedInDifferentBranches)
for (slot in slotsWithMultipleUsages) {
emitter.report(slot, ContentSlotsShouldNotBeReused)
}
}

private fun KtFunction.findUsages(name: String): Sequence<KtCallExpression> =
findChildrenByClass<KtCallExpression>().filter { it.calleeExpression?.text == name }
// Remove shadowed usages
.filter { it.findShadowingRedeclarations(name, this).count() == 0 }

private fun isSlotUsedInSeparateBranches(slots: Sequence<KtCallExpression>, stopAt: KtFunction): Boolean =
slots.uniquePairs()
.any { (slot1, slot2) ->
findCommonAncestor(slot1, slot2, stopAt).isBranchingElement()
}

private fun findCommonAncestor(slot1: KtCallExpression, slot2: KtCallExpression, stopAt: KtFunction): KtElement {
val height1 = slot1.parents.takeWhile { it != stopAt }.count()
val height2 = slot2.parents.takeWhile { it != stopAt }.count()

var current1: KtElement = slot1
var current2: KtElement = slot2

// If the heights are different, we'll need to go up in the one that's deeper until they
when {
height1 > height2 -> {
repeat(height1 - height2) { current1 = current1.parent as KtElement }
}

height1 < height2 -> {
repeat(height2 - height1) { current2 = current2.parent as KtElement }
}
}

// Traverse up until they are at the same level
while (current1 != current2) {
current1 = current1.parent as KtElement
current2 = current2.parent as KtElement
private fun KtFunction.findNotShadowedUsagesOf(slot: KtParameter): Sequence<KtCallExpression> {
val slotName = slot.name?.takeIf { it.isNotEmpty() } ?: return emptySequence()
val slots = when {
// content?.invoke()
slot.isTypeNullable -> findChildrenByClass<KtSafeQualifiedExpression>()
.filter { it.receiverExpression.text == slotName }
.mapNotNull { it.selectorExpression as? KtCallExpression }
.filter { it.calleeExpression?.text == "invoke" }

// content()
else -> findChildrenByClass<KtCallExpression>().filter { it.calleeExpression?.text == slotName }
}

return current1
}

private fun KtElement.isBranchingElement(): Boolean = when (val current = this) {
// Always true, if not, the ancestor would have been found in then or in else expressions
is KtIfExpression -> true
// Always true, if not, the ancestor would have been found in a when entry
is KtWhenExpression -> true
// Only branching if it's an elvis operator
is KtBinaryExpression -> current.operationToken == KtTokens.ELVIS
else -> false
// Return and remove shadowed usages
return slots.filter { it.findShadowingRedeclarations(parameterName = slotName, stopAt = this).count() == 0 }
}

companion object {
val ContentSlotReusedInDifferentBranches = """
Content slots should not be reused in different code branches of a composable function (e.g. if/when/elvis).
val ContentSlotsShouldNotBeReused = """
Content slots should not be reused in different code branches/scopes of a composable function, to preserve the slot internal state.

You can wrap the usages in a remember { movableContentOf { ... }} block to make sure their internal state is preserved correctly.
You can wrap the slot in a remember { movableContentOf { ... }} block to make sure their internal state is preserved correctly.

See https://mrmans0n.github.io/compose-rules/rules/#content-slots-should-not-be-reused-in-branching-code for more information.
""".trimIndent()
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2 changes: 1 addition & 1 deletion rules/detekt/src/main/kotlin/io/nlopez/compose/rules/detekt/ContentSlotReusedCheck.kt
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Expand Up @@ -16,7 +16,7 @@ class ContentSlotReusedCheck(config: Config) :
override val issue: Issue = Issue(
id = "ContentSlotReused",
severity = Severity.Defect,
description = ContentSlotReused.ContentSlotReusedInDifferentBranches,
description = ContentSlotReused.ContentSlotsShouldNotBeReused,
debt = Debt.TEN_MINS,
)
}
45 changes: 43 additions & 2 deletions rules/detekt/src/test/kotlin/io/nlopez/compose/rules/detekt/ContentSlotReusedCheckTest.kt
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Expand Up @@ -19,7 +19,7 @@ class ContentSlotReusedCheckTest {
private val rule = ContentSlotReusedCheck(testConfig)

@Test
fun `errors when there is a slot being reused in different branches`() {
fun `errors when there is a slot being reused`() {
@Language("kotlin")
val code =
"""
Expand All @@ -42,6 +42,11 @@ class ContentSlotReusedCheckTest {
fun D(text: String, content: Potato) {
potato?.let { content() } ?: content()
}
@Composable
fun E(text: String, content: @Composable () -> Unit) {
val content1 = remember { movableContentOf { content() } }
val content2 = remember { movableContentOf { content() } }
}
""".trimIndent()

val errors = rule.lint(code)
Expand All @@ -51,9 +56,45 @@ class ContentSlotReusedCheckTest {
SourceLocation(6, 21),
SourceLocation(13, 21),
SourceLocation(17, 21),
SourceLocation(21, 21),
)
for (error in errors) {
assertThat(error).hasMessage(ContentSlotReused.ContentSlotsShouldNotBeReused)
}
}

@Test
fun `errors when there is a nullable slot being reused`() {
@Language("kotlin")
val code =
"""
@Composable
fun A(text: String, content: (@Composable () -> Unit)? = null) {
if (x) content?.invoke() else content?.invoke()
}
@Composable
fun B(text: String, content: (@Composable () -> Unit)? = null) {
when {
x -> content?.invoke()
else -> content?.invoke()
}
}
@Composable
fun C(text: String, content: (@Composable () -> Unit)? = null) {
val content1 = remember { movableContentOf { content?.invoke() } }
val content2 = remember { movableContentOf { content?.invoke() } }
}
""".trimIndent()

val errors = rule.lint(code)
assertThat(errors)
.hasStartSourceLocations(
SourceLocation(2, 21),
SourceLocation(6, 21),
SourceLocation(13, 21),
)
for (error in errors) {
assertThat(error).hasMessage(ContentSlotReused.ContentSlotReusedInDifferentBranches)
assertThat(error).hasMessage(ContentSlotReused.ContentSlotsShouldNotBeReused)
}
}

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63 changes: 58 additions & 5 deletions rules/ktlint/src/test/kotlin/io/nlopez/compose/rules/ktlint/ContentSlotReusedCheckTest.kt
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Expand Up @@ -13,7 +13,7 @@ class ContentSlotReusedCheckTest {
private val ruleAssertThat = assertThatRule { ContentSlotReusedCheck() }

@Test
fun `errors when there is a slot being reused in different branches`() {
fun `errors when there is a slot being reused`() {
@Language("kotlin")
val code =
"""
Expand All @@ -36,6 +36,11 @@ class ContentSlotReusedCheckTest {
fun D(text: String, content: Potato) {
potato?.let { content() } ?: content()
}
@Composable
fun E(text: String, content: @Composable () -> Unit) {
val content1 = remember { movableContentOf { content() } }
val content2 = remember { movableContentOf { content() } }
}
""".trimIndent()

ruleAssertThat(code)
Expand All @@ -44,22 +49,70 @@ class ContentSlotReusedCheckTest {
LintViolation(
line = 2,
col = 21,
detail = ContentSlotReused.ContentSlotReusedInDifferentBranches,
detail = ContentSlotReused.ContentSlotsShouldNotBeReused,
),
LintViolation(
line = 6,
col = 21,
detail = ContentSlotReused.ContentSlotReusedInDifferentBranches,
detail = ContentSlotReused.ContentSlotsShouldNotBeReused,
),
LintViolation(
line = 13,
col = 21,
detail = ContentSlotReused.ContentSlotReusedInDifferentBranches,
detail = ContentSlotReused.ContentSlotsShouldNotBeReused,
),
LintViolation(
line = 17,
col = 21,
detail = ContentSlotReused.ContentSlotReusedInDifferentBranches,
detail = ContentSlotReused.ContentSlotsShouldNotBeReused,
),
LintViolation(
line = 21,
col = 21,
detail = ContentSlotReused.ContentSlotsShouldNotBeReused,
),
)
}

@Test
fun `errors when there is a nullable slot being reused`() {
@Language("kotlin")
val code =
"""
@Composable
fun A(text: String, content: (@Composable () -> Unit)? = null) {
if (x) content?.invoke() else content?.invoke()
}
@Composable
fun B(text: String, content: (@Composable () -> Unit)? = null) {
when {
x -> content?.invoke()
else -> content?.invoke()
}
}
@Composable
fun C(text: String, content: (@Composable () -> Unit)? = null) {
val content1 = remember { movableContentOf { content?.invoke() } }
val content2 = remember { movableContentOf { content?.invoke() } }
}
""".trimIndent()

ruleAssertThat(code)
.hasLintViolationsWithoutAutoCorrect(
LintViolation(
line = 2,
col = 21,
detail = ContentSlotReused.ContentSlotsShouldNotBeReused,
),
LintViolation(
line = 6,
col = 21,
detail = ContentSlotReused.ContentSlotsShouldNotBeReused,
),
LintViolation(
line = 13,
col = 21,
detail = ContentSlotReused.ContentSlotsShouldNotBeReused,
),
)
}
Expand Down