For #17917 - Add a Kotlin synthetics Lint detector

This would help ease the current refactoring effort by ensuring no new
synthetics usages.

mozilla-lint-rules/src/main/java/org/mozilla/fenix/lintrules/KotlinSyntheticsDetector.kt

@@ -0,0 +1,62 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+@file:Suppress("UnstableApiUsage")
+
+package org.mozilla.fenix.lintrules
+
+import com.android.tools.lint.client.api.UElementHandler
+import com.android.tools.lint.detector.api.Category
+import com.android.tools.lint.detector.api.Detector
+import com.android.tools.lint.detector.api.Implementation
+import com.android.tools.lint.detector.api.Issue
+import com.android.tools.lint.detector.api.JavaContext
+import com.android.tools.lint.detector.api.Scope
+import com.android.tools.lint.detector.api.Severity
+import com.android.tools.lint.detector.api.SourceCodeScanner
+import org.jetbrains.uast.UElement
+import org.jetbrains.uast.UImportStatement
+
+/**
+ * Custom Lint detector that checks for deprecated "kotlinx.android.synthetic" imports.
+ */
+class KotlinSyntheticsDetector : Detector(), SourceCodeScanner {
+
+    override fun createUastHandler(context: JavaContext) = object : UElementHandler() {
+        override fun visitImportStatement(node: UImportStatement) {
+            node.importReference?.asSourceString()?.let { import ->
+                if (import.startsWith(SYNTHETIC_IMPORT_PATTERN)) {
+                    context.report(
+                        DEPRECATED_KOTLIN_SYNTHETICS_ISSUE,
+                        node,
+                        context.getLocation(node),
+                        DEPRECATED_KOTLIN_SYNTHETICS_MESSAGE
+                    )
+                }
+            }
+        }
+    }
+
+    override fun getApplicableUastTypes(): List<Class<out UElement>> {
+        return listOf(UImportStatement::class.java)
+    }
+
+    companion object {
+        private const val DEPRECATED_KOTLIN_SYNTHETICS_MESSAGE = "Kotlin synthetics are to be replaced with Jetpack View Binding. " +
+            "Please refer to https://github.com/mozilla-mobile/fenix/issues/17917 for more details."
+        private const val SYNTHETIC_IMPORT_PATTERN = "kotlinx.android.synthetic"
+
+        val DEPRECATED_KOTLIN_SYNTHETICS_ISSUE = Issue.create(
+            "KotlinSyntheticsDeprecation",
+            briefDescription = "Kotlin synthetics are deprecated and actively refactored out",
+            explanation = "The 'kotlin-android-extensions' Gradle plugin is deprecated and " +
+                "will be removed in a future Kotlin release in (or after) September 2021. " +
+                "We are to migrate to Jetpack View Binding. " +
+                "Please refer to https://github.com/mozilla-mobile/fenix/issues/17917",
+            category = Category.PRODUCTIVITY,
+            severity = Severity.ERROR,
+            implementation = Implementation(KotlinSyntheticsDetector::class.java, Scope.JAVA_FILE_SCOPE)
+        )
+    }
+}

mozilla-lint-rules/src/main/java/org/mozilla/fenix/lintrules/LintIssueRegistry.kt

@@ -21,7 +21,8 @@ class LintIssueRegistry : IssueRegistry() {
         TextViewAndroidSrcXmlDetector.ISSUE_XML_SRC_USAGE,
         ImageViewAndroidTintXmlDetector.ISSUE_XML_SRC_USAGE,
         LicenseDetector.ISSUE_MISSING_LICENSE,
-        LicenseDetector.ISSUE_INVALID_LICENSE_FORMAT
+        LicenseDetector.ISSUE_INVALID_LICENSE_FORMAT,
+        KotlinSyntheticsDetector.DEPRECATED_KOTLIN_SYNTHETICS_ISSUE
     ) + ConstraintLayoutPerfDetector.ISSUES + ContextCompatDetector.ISSUES
     override val vendor: Vendor = Vendor(
         vendorName = "Mozilla",

mozilla-lint-rules/src/test/java/org/mozilla/fenix/lintrules/KotlinSyntheticsDetectorTest.kt

@@ -0,0 +1,71 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+@file:Suppress("UnstableApiUsage")
+
+package org.mozilla.fenix.lintrules
+
+import com.android.tools.lint.checks.infrastructure.LintDetectorTest
+import com.android.tools.lint.checks.infrastructure.TestFiles
+import com.android.tools.lint.detector.api.Detector
+import com.android.tools.lint.detector.api.Issue
+import org.junit.Test
+import org.junit.runner.RunWith
+import org.junit.runners.JUnit4
+import org.mozilla.fenix.lintrules.KotlinSyntheticsDetector.Companion.DEPRECATED_KOTLIN_SYNTHETICS_ISSUE
+
+@RunWith(JUnit4::class)
+class KotlinSyntheticsDetectorTest : LintDetectorTest() {
+
+    override fun getIssues(): MutableList<Issue> = mutableListOf(DEPRECATED_KOTLIN_SYNTHETICS_ISSUE)
+
+    override fun getDetector(): Detector = KotlinSyntheticsDetector()
+
+    @Test
+    fun `GIVEN no kotlin synthetics import WHEN KotlinSyntheticsDetector runs THEN there are no errors or exceptions`() {
+        val code = """
+            |package example
+            |
+            |import org.mozilla.fenix.databinding.OnboardingTrackingProtectionBinding
+            |
+            |class SomeExample {
+            |   fun hello() {
+            |       println("World")
+            |   }
+            |}""".trimMargin()
+
+        lint()
+            .files(TestFiles.kt(code))
+            .allowCompilationErrors()
+            .allowMissingSdk(true)
+            .run()
+            .expectClean()
+    }
+
+    @Test
+    fun `GIVEN a kotlin synthetics import WHEN KotlinSyntheticsDetector runs THEN there are no errors or exceptions`() {
+        val code = """
+            |package example
+            |
+            |import kotlinx.android.synthetic.main.layout
+            |
+            |class SomeExample {
+            |   fun hello() {
+            |       println("World")
+            |   }
+            |}""".trimMargin()
+
+        val expectedReport = """
+            |src/example/SomeExample.kt:3: Error: Kotlin synthetics are to be replaced with Jetpack View Binding. Please refer to https://github.com/mozilla-mobile/fenix/issues/17917 for more details. [KotlinSyntheticsDeprecation]
+            |import kotlinx.android.synthetic.main.layout
+            |~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+            |1 errors, 0 warnings""".trimMargin()
+
+        lint()
+            .files(TestFiles.kt(code))
+            .allowMissingSdk(true)
+            .run()
+            .expect(expectedReport)
+    }
+}