Add sample for Studio 4.0

android-studio-4/README.md

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+# Sample Lint Checks
+
+This project shows how Android Studio 4 handles packaging of lint rules.
+
+## Lint Check Jar Library
+
+First, there's the lint check implementation itself. That's done in the
+"checks" project, which just applies the Gradle "java" plugin, and
+that project produces a jar. Note that the dependencies for the lint
+check project (other than its testing dependencies) must all be "compileOnly":
+
+    dependencies {
+        compileOnly "com.android.tools.lint:lint-api:$lintVersion"
+        compileOnly "com.android.tools.lint:lint-checks:$lintVersion"
+		...
+
+## Lint Check AAR Library
+
+Next, there's a separate Android library project, called "library". This
+library doesn't have any code on its own (though it could). However,
+in its build.gradle, it specifies this:
+
+    dependencies {
+        lintPublish project(':checks')
+    }
+
+This tells the Gradle plugin to take the output from the "checks" project
+and package that as a "lint.jar" payload inside this library's AAR file.
+When that's done, any other projects that depends on this library will
+automatically be using the lint checks.
+
+## App Modules
+
+Note that you don't have to go through the extra "library indirection"
+if you have a lint check that you only want to apply to one or more
+app modules. You can simply include the `lintChecks` dependency as shown
+above there as well, and then lint will include these rules when analyzing
+the project.
+
+## Lint Version
+
+The lint version of the libraries (specified in this project as the
+`lintVersion` variable in build.gradle) should be the same version
+that is used by the Gradle plugin.
+
+If the Gradle plugin version is *X*.*Y*.*Z*, then the Lint library
+version is *X+23*.*Y*.*Z*.

android-studio-4/build.gradle

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+buildscript {
+    ext {
+        gradlePluginVersion = '4.0.0-alpha08'
+        lintVersion = '27.0.0-alpha08'
+        kotlinVersion = '1.3.61'
+    }
+
+    repositories {
+        google()
+        jcenter()
+    }
+    dependencies {
+        classpath "com.android.tools.build:gradle:$gradlePluginVersion"
+        classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlinVersion"
+    }
+}
+
+allprojects {
+    repositories {
+        google()
+        jcenter()
+    }
+}
+
+task clean(type: Delete) {
+    delete rootProject.buildDir
+}

android-studio-4/checks/.gitignore

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+/build
+lint-report.html
+lint-results.txt

android-studio-4/checks/build.gradle

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+apply plugin: 'java-library'
+apply plugin: 'kotlin'
+apply plugin: 'com.android.lint'
+
+lintOptions {
+    htmlReport true
+    htmlOutput file("lint-report.html")
+    textReport true
+    absolutePaths false
+    ignoreTestSources true
+}
+
+dependencies {
+    // For a description of the below dependencies, see the main project README
+    compileOnly "com.android.tools.lint:lint-api:$lintVersion"
+    compileOnly "com.android.tools.lint:lint-checks:$lintVersion"
+    compileOnly "org.jetbrains.kotlin:kotlin-stdlib-jdk7:$kotlinVersion"
+    testImplementation "junit:junit:4.13"
+    testImplementation "com.android.tools.lint:lint:$lintVersion"
+    testImplementation "com.android.tools.lint:lint-tests:$lintVersion"
+    testImplementation "com.android.tools:testutils:$lintVersion"
+}
+
+sourceCompatibility = "1.8"
+targetCompatibility = "1.8"

android-studio-4/checks/src/main/java/com/example/lint/checks/SampleCodeDetector.kt

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+/*
+ * Copyright (C) 2020 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package com.example.lint.checks
+
+import com.android.tools.lint.client.api.UElementHandler
+import com.android.tools.lint.detector.api.*
+import com.android.tools.lint.detector.api.Detector.UastScanner
+import org.jetbrains.uast.UElement
+import org.jetbrains.uast.ULiteralExpression
+import org.jetbrains.uast.evaluateString
+
+/**
+ * Sample detector showing how to analyze Kotlin/Java code.
+ * This example flags all string literals in the code that contain
+ * the word "lint".
+ */
+@Suppress("UnstableApiUsage")
+class SampleCodeDetector : Detector(), UastScanner {
+    override fun getApplicableUastTypes(): List<Class<out UElement?>>? {
+        return listOf(ULiteralExpression::class.java)
+    }
+
+    override fun createUastHandler(context: JavaContext): UElementHandler? {
+        // Note: Visiting UAST nodes is a pretty general purpose mechanism;
+        // Lint has specialized support to do common things like "visit every class
+        // that extends a given super class or implements a given interface", and
+        // "visit every call site that calls a method by a given name" etc.
+        // Take a careful look at UastScanner and the various existing lint check
+        // implementations before doing things the "hard way".
+        // Also be aware of context.getJavaEvaluator() which provides a lot of
+        // utility functionality.
+        return object : UElementHandler() {
+            override fun visitLiteralExpression(node: ULiteralExpression) {
+                val string = node.evaluateString() ?: return
+                if (string.contains("lint") && string.matches(Regex(".*\\blint\\b.*"))) {
+                    context.report(ISSUE, node, context.getLocation(node),
+                            "This code mentions `lint`: **Congratulations**")
+                }
+            }
+        }
+    }
+
+    companion object {
+        /** Issue describing the problem and pointing to the detector implementation */
+        @JvmField
+        val ISSUE: Issue = Issue.create(
+                // ID: used in @SuppressLint warnings etc
+                id = "ShortUniqueId",
+                // Title -- shown in the IDE's preference dialog, as category headers in the
+                // Analysis results window, etc
+                briefDescription = "Lint Mentions",
+                // Full explanation of the issue; you can use some markdown markup such as
+                // `monospace`, *italic*, and **bold**.
+                explanation = """
+                    This check highlights string literals in code which mentions the word `lint`. \
+                    Blah blah blah.
+
+                    Another paragraph here.
+                    """, // no need to .trimIndent(), lint does that automatically
+                category = Category.CORRECTNESS,
+                priority = 6,
+                severity = Severity.WARNING,
+                implementation = Implementation(
+                        SampleCodeDetector::class.java,
+                        Scope.JAVA_FILE_SCOPE))
+    }
+}

android-studio-4/checks/src/main/java/com/example/lint/checks/SampleIssueRegistry.kt

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+/*
+ * Copyright (C) 2017 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package com.example.lint.checks
+
+import com.android.tools.lint.client.api.IssueRegistry
+import com.android.tools.lint.detector.api.CURRENT_API
+
+/*
+ * The list of issues that will be checked when running <code>lint</code>.
+ */
+@Suppress("UnstableApiUsage")
+class SampleIssueRegistry : IssueRegistry() {
+    override val issues = listOf(SampleCodeDetector.ISSUE)
+
+    override val api: Int
+        get() = CURRENT_API
+}

android-studio-4/checks/src/main/resources/META-INF/services/com.android.tools.lint.client.api.IssueRegistry

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+com.example.lint.checks.SampleIssueRegistry

android-studio-4/checks/src/test/java/com/example/lint/checks/SampleCodeDetectorTest.kt

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+/*
+ * Copyright (C) 2017 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package com.example.lint.checks
+
+import com.android.tools.lint.checks.infrastructure.LintDetectorTest
+import com.android.tools.lint.detector.api.Detector
+import com.android.tools.lint.detector.api.Issue
+
+@Suppress("UnstableApiUsage")
+class SampleCodeDetectorTest : LintDetectorTest() {
+    fun testBasic() {
+        lint().files(
+                java("""
+                    package test.pkg;
+                    public class TestClass1 {
+                        // In a comment, mentioning "lint" has no effect
+                        private static String s1 = "Ignore non-word usages: linting";
+                        private static String s2 = "Let's say it: lint";
+                    }
+                    """
+                ).indented())
+                .run()
+                .expect("""
+                    src/test/pkg/TestClass1.java:5: Warning: This code mentions lint: Congratulations [ShortUniqueId]
+                        private static String s2 = "Let's say it: lint";
+                                                   ~~~~~~~~~~~~~~~~~~~~
+                    0 errors, 1 warnings
+                    """
+                )
+    }
+
+    override fun getDetector(): Detector {
+        return SampleCodeDetector()
+    }
+
+    override fun getIssues(): List<Issue> {
+        return listOf(SampleCodeDetector.ISSUE)
+    }
+}

android-studio-4/gradle.properties

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+# Project-wide Gradle settings.
+
+# IDE (e.g. Android Studio) users:
+# Gradle settings configured through the IDE *will override*
+# any settings specified in this file.
+
+# For more details on how to configure your build environment visit
+# http://www.gradle.org/docs/current/userguide/build_environment.html
+
+# Specifies the JVM arguments used for the daemon process.
+# The setting is particularly useful for tweaking memory settings.
+org.gradle.jvmargs=-Xmx1536m
+
+# When configured, Gradle will run in incubating parallel mode.
+# This option should only be used with decoupled projects. More details, visit
+# http://www.gradle.org/docs/current/userguide/multi_project_builds.html#sec:decoupled_projects
+# org.gradle.parallel=true

android-studio-4/gradle/wrapper/gradle-wrapper.properties

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+#Fri Sep 01 06:52:38 PDT 2017
+distributionBase=GRADLE_USER_HOME
+distributionPath=wrapper/dists
+zipStoreBase=GRADLE_USER_HOME
+zipStorePath=wrapper/dists
+distributionUrl=https\://services.gradle.org/distributions/gradle-6.1-rc-1-all.zip