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Add a few more examples, including a Kotlin Analysis API usage
Also update dependencies. And format with ktfmt.
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-96
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‎checks/src/main/java/com/example/lint/checks/AvoidDateDetector.kt

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/*
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* Copyright (C) 2024 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package com.example.lint.checks
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import com.android.tools.lint.detector.api.Category
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import com.android.tools.lint.detector.api.Detector
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import com.android.tools.lint.detector.api.Implementation
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import com.android.tools.lint.detector.api.Issue
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import com.android.tools.lint.detector.api.JavaContext
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import com.android.tools.lint.detector.api.Scope
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import com.android.tools.lint.detector.api.Severity
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import com.android.tools.lint.detector.api.SourceCodeScanner
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import com.intellij.psi.PsiMethod
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import org.jetbrains.uast.UCallExpression
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class AvoidDateDetector : Detector(), SourceCodeScanner {
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companion object Issues {
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private val IMPLEMENTATION =
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Implementation(AvoidDateDetector::class.java, Scope.JAVA_FILE_SCOPE)
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@JvmField
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val ISSUE =
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Issue.create(
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id = "OldDate",
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briefDescription = "Avoid Date and Calendar",
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explanation =
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"""
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The `java.util.Date` and `java.util.Calendar` classes should not be used; instead \
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use the `java.time` package, such as `LocalDate` and `LocalTime`.
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""",
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category = Category.CORRECTNESS,
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priority = 6,
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severity = Severity.ERROR,
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androidSpecific = true,
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implementation = IMPLEMENTATION,
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)
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}
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// java.util.Date()
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override fun getApplicableConstructorTypes(): List<String> = listOf("java.util.Date")
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override fun visitConstructor(
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context: JavaContext,
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node: UCallExpression,
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constructor: PsiMethod,
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) {
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context.report(
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ISSUE,
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node,
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context.getLocation(node),
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"Don't use `Date`; use `java.time.*` instead",
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fix()
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.alternatives(
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fix().replace().all().with("java.time.LocalTime.now()").shortenNames().build(),
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fix().replace().all().with("java.time.LocalDate.now()").shortenNames().build(),
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fix().replace().all().with("java.time.LocalDateTime.now()").shortenNames().build(),
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),
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)
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}
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// java.util.Calendar.getInstance()
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override fun getApplicableMethodNames(): List<String> = listOf("getInstance")
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override fun visitMethodCall(context: JavaContext, node: UCallExpression, method: PsiMethod) {
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val evaluator = context.evaluator
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if (!evaluator.isMemberInClass(method, "java.util.Calendar")) {
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return
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}
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context.report(
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ISSUE,
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node,
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context.getLocation(node),
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"Don't use `Calendar.getInstance`; use `java.time.*` instead",
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)
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}
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}

‎checks/src/main/java/com/example/lint/checks/NotNullAssertionDetector.kt

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/*
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* Copyright (C) 2024 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package com.example.lint.checks
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import com.android.tools.lint.client.api.UElementHandler
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import com.android.tools.lint.detector.api.Category
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import com.android.tools.lint.detector.api.Detector
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import com.android.tools.lint.detector.api.Implementation
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import com.android.tools.lint.detector.api.Incident
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import com.android.tools.lint.detector.api.Issue
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import com.android.tools.lint.detector.api.JavaContext
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import com.android.tools.lint.detector.api.Scope
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import com.android.tools.lint.detector.api.Severity
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import com.android.tools.lint.detector.api.SourceCodeScanner
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import org.jetbrains.kotlin.analysis.api.analyze
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import org.jetbrains.kotlin.codegen.optimization.common.analyze
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import org.jetbrains.kotlin.psi.KtExpression
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import org.jetbrains.uast.UElement
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import org.jetbrains.uast.UPostfixExpression
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class NotNullAssertionDetector : Detector(), SourceCodeScanner {
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companion object Issues {
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private val IMPLEMENTATION =
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Implementation(NotNullAssertionDetector::class.java, Scope.JAVA_FILE_SCOPE)
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@JvmField
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val ISSUE =
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Issue.create(
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id = "NotNullAssertion",
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briefDescription = "Avoid `!!`",
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explanation =
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"""
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Do not use the `!!` operator. It can lead to null pointer exceptions. \
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Please use the `?` operator instead, or assign to a local variable with \
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`?:` initialization if necessary.
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""",
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category = Category.CORRECTNESS,
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priority = 6,
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severity = Severity.WARNING,
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implementation = IMPLEMENTATION,
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)
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}
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override fun getApplicableUastTypes(): List<Class<out UElement>>? {
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return listOf(UPostfixExpression::class.java)
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}
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override fun createUastHandler(context: JavaContext): UElementHandler {
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return object : UElementHandler() {
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override fun visitPostfixExpression(node: UPostfixExpression) {
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if (node.operator.text == "!!") {
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var message = "Do not use `!!`"
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// Kotlin Analysis API example
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val sourcePsi = node.operand.sourcePsi
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if (sourcePsi is KtExpression) {
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analyze(sourcePsi) {
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val type = sourcePsi.getKtType()
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if (type != null && !type.canBeNull) {
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message += " -- it's not even needed here"
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}
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}
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}
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val incident = Incident(ISSUE, node, context.getLocation(node), message)
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context.report(incident)
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}
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}
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}
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}
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}

‎checks/src/main/java/com/example/lint/checks/SampleCodeDetector.kt

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@@ -29,64 +29,61 @@ import org.jetbrains.uast.ULiteralExpression
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import org.jetbrains.uast.evaluateString
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/**
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* Sample detector showing how to analyze Kotlin/Java code. This example
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* flags all string literals in the code that contain the word "lint".
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* Sample detector showing how to analyze Kotlin/Java code. This example flags all string literals
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* in the code that contain the word "lint".
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*/
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@Suppress("UnstableApiUsage")
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class SampleCodeDetector : Detector(), UastScanner {
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override fun getApplicableUastTypes(): List<Class<out UElement?>> {
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return listOf(ULiteralExpression::class.java)
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}
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override fun getApplicableUastTypes(): List<Class<out UElement?>> {
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return listOf(ULiteralExpression::class.java)
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}
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41-
override fun createUastHandler(context: JavaContext): UElementHandler {
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// Note: Visiting UAST nodes is a pretty general purpose mechanism;
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// Lint has specialized support to do common things like "visit every class
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// that extends a given super class or implements a given interface", and
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// "visit every call site that calls a method by a given name" etc.
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// Take a careful look at UastScanner and the various existing lint check
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// implementations before doing things the "hard way".
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// Also be aware of context.getJavaEvaluator() which provides a lot of
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// utility functionality.
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return object : UElementHandler() {
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override fun visitLiteralExpression(node: ULiteralExpression) {
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val string = node.evaluateString() ?: return
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if (string.contains("lint") && string.matches(Regex(".*\\blint\\b.*"))) {
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context.report(
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ISSUE, node, context.getLocation(node),
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"This code mentions `lint`: **Congratulations**"
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)
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}
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}
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override fun createUastHandler(context: JavaContext): UElementHandler {
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// Note: Visiting UAST nodes is a pretty general purpose mechanism;
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// Lint has specialized support to do common things like "visit every class
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// that extends a given super class or implements a given interface", and
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// "visit every call site that calls a method by a given name" etc.
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// Take a careful look at UastScanner and the various existing lint check
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// implementations before doing things the "hard way".
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// Also be aware of context.getJavaEvaluator() which provides a lot of
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// utility functionality.
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return object : UElementHandler() {
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override fun visitLiteralExpression(node: ULiteralExpression) {
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val string = node.evaluateString() ?: return
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if (string.contains("lint") && string.matches(Regex(".*\\blint\\b.*"))) {
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context.report(
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ISSUE,
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node,
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context.getLocation(node),
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"This code mentions `lint`: **Congratulations**",
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)
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}
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}
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}
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}
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companion object {
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/**
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* Issue describing the problem and pointing to the detector
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* implementation.
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*/
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@JvmField
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val ISSUE: Issue = Issue.create(
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// ID: used in @SuppressLint warnings etc
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id = "SampleId",
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// Title -- shown in the IDE's preference dialog, as category headers in the
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// Analysis results window, etc
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briefDescription = "Lint Mentions",
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// Full explanation of the issue; you can use some markdown markup such as
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// `monospace`, *italic*, and **bold**.
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explanation = """
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This check highlights string literals in code which mentions the word `lint`. \
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Blah blah blah.
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companion object {
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/** Issue describing the problem and pointing to the detector implementation. */
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@JvmField
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val ISSUE: Issue =
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Issue.create(
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// ID: used in @SuppressLint warnings etc
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id = "SampleId",
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// Title -- shown in the IDE's preference dialog, as category headers in the
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// Analysis results window, etc
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briefDescription = "Lint Mentions",
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// Full explanation of the issue; you can use some markdown markup such as
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// `monospace`, *italic*, and **bold**.
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explanation =
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"""
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This check highlights string literals in code which mentions the word `lint`. \
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Blah blah blah.
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Another paragraph here.
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""", // no need to .trimIndent(), lint does that automatically
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category = Category.CORRECTNESS,
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priority = 6,
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severity = Severity.WARNING,
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implementation = Implementation(
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SampleCodeDetector::class.java,
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Scope.JAVA_FILE_SCOPE
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)
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)
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}
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Another paragraph here.
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""", // no need to .trimIndent(), lint does that automatically
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category = Category.CORRECTNESS,
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priority = 6,
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severity = Severity.WARNING,
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implementation = Implementation(SampleCodeDetector::class.java, Scope.JAVA_FILE_SCOPE),
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)
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}
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}

‎checks/src/main/java/com/example/lint/checks/SampleIssueRegistry.kt

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/*
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* The list of issues that will be checked when running <code>lint</code>.
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*/
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@Suppress("UnstableApiUsage")
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class SampleIssueRegistry : IssueRegistry() {
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override val issues = listOf(SampleCodeDetector.ISSUE)
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override val issues =
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listOf(SampleCodeDetector.ISSUE, AvoidDateDetector.ISSUE, NotNullAssertionDetector.ISSUE)
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override val api: Int
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get() = CURRENT_API
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override val api: Int
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get() = CURRENT_API
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override val minApi: Int
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get() = 8 // works with Studio 4.1 or later; see com.android.tools.lint.detector.api.Api / ApiKt
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override val minApi: Int
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get() = 8 // works with Studio 4.1 or later; see com.android.tools.lint.detector.api.Api / ApiKt
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// Requires lint API 30.0+; if you're still building for something
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// older, just remove this property.
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override val vendor: Vendor = Vendor(
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vendorName = "Android Open Source Project",
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feedbackUrl = "https://github.com/googlesamples/android-custom-lint-rules/issues",
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contact = "https://github.com/googlesamples/android-custom-lint-rules"
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// Requires lint API 30.0+; if you're still building for something
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// older, just remove this property.
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override val vendor: Vendor =
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Vendor(
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vendorName = "Android Open Source Project",
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feedbackUrl = "https://github.com/googlesamples/android-custom-lint-rules/issues",
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contact = "https://github.com/googlesamples/android-custom-lint-rules",
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)
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}

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