Add Android Linting Example

docs/modules/ROOT/nav.adoc

@@ -13,6 +13,7 @@
 ** xref:javalib/build-examples.adoc[]
 ** xref:javalib/web-examples.adoc[]
 ** xref:javalib/android-examples.adoc[]
+** xref:javalib/android-linting.adoc[]
 * xref:scalalib/intro.adoc[]
 ** xref:scalalib/builtin-commands.adoc[]
 ** xref:scalalib/module-config.adoc[]

docs/modules/ROOT/pages/javalib/android-linting.adoc

@@ -0,0 +1,14 @@
+= Linting Android Projects
+:page-aliases: Linting_Android_Projects.adoc
+
+include::partial$gtag-config.adoc[]
+
+This page covers essential practices for maintaining and enforcing code quality
+in Android projects using the Mill build tool. Proper linting helps detect
+and resolve potential issues early, promoting better performance, security,
+and user experience.
+
+
+== Linting with Android cmdline lint tool
+
+include::partial$example/javalib/android/2-linting.adoc[]

example/javalib/android/2-linting/app/AndroidManifest.xml

@@ -0,0 +1,13 @@
+<manifest xmlns:android="http://schemas.android.com/apk/res/android" package="com.helloworld.app">
+    <uses-sdk android:minSdkVersion="9"/>
+    <uses-sdk android:targetSdkVersion="35"/>
+    <application android:label="Hello World" android:debuggable="true">
+        <activity android:name=".MainActivity"
+                android:exported="true">
+            <intent-filter>
+                <action android:name="android.intent.action.MAIN"/>
+                <category android:name="android.intent.category.LAUNCHER"/>
+            </intent-filter>
+        </activity>
+    </application>
+</manifest>

example/javalib/android/2-linting/app/src/main/java/com/helloworld/app/MainActivity.java

@@ -0,0 +1,36 @@
+package com.helloworld.app;
+
+import android.app.Activity;
+import android.os.Bundle;
+import android.view.View;
+import android.widget.TextView;
+import android.view.ViewGroup.LayoutParams;
+import android.view.Gravity;
+
+
+public class MainActivity extends Activity {
+    @Override
+    protected void onCreate(Bundle savedInstanceState) {
+        super.onCreate(savedInstanceState);
+
+        // Create a new TextView
+        TextView textView = new TextView(this);
+
+        // Set the text to "Hello, World!"
+        textView.setText("Hello, World!");
+
+        // Set text size
+        textView.setTextSize(32);
+
+        // Center the text within the view
+        textView.setGravity(Gravity.CENTER);
+
+        // Set layout parameters (width and height)
+        textView.setLayoutParams(new LayoutParams(
+            LayoutParams.MATCH_PARENT,
+            LayoutParams.MATCH_PARENT));
+
+        // Set the content view to display the TextView
+        setContentView(textView);
+    }
+}

example/javalib/android/2-linting/build.mill

@@ -0,0 +1,29 @@
+package build
+
+import mill._
+import mill.javalib.android.{AndroidSdkModule, AndroidLintModule}
+
+// Create and configure an Android SDK module to manage Android SDK paths and tools.
+object androidSdkModule0 extends AndroidSdkModule {
+  def buildToolsVersion = "35.0.0"
+}
+
+// Actual android application
+object app extends AndroidLintModule {
+  def androidSdkModule = mill.define.ModuleRef(androidSdkModule0)
+}
+
+/** See Also: app/AndroidManifest.xml */
+/** See Also: app/src/main/java/com/helloworld/app/MainActivity.java */
+
+/** Usage
+
+> ./mill show app.androidLint  # Display full path to the linting report in HTML
+".../out/app/androidLint.dest/report.html"
+
+*/
+
+// This Mill build configuration includes a linting step, which is essential for ensuring code
+// quality and adhering to best practices in Android development projects. Running the `androidLint` task
+// produces a detailed HTML report identifying potential issues in the code, such as performance,
+// security, and usability warnings. This helps maintain the health and quality of the codebase.

scalalib/src/mill/javalib/android/AndroidAppModule.scala

@@ -254,4 +254,5 @@ trait AndroidAppModule extends JavaModule {
 
     PathRef(keystoreFile)
   }
+
 }

scalalib/src/mill/javalib/android/AndroidLintModule.scala

@@ -0,0 +1,82 @@
+package mill.javalib.android
+
+import mill._
+import mill.api.PathRef
+import mill.scalalib.JavaModule
+import mill.javalib.android.AndroidSdkModule
+
+/**
+ * Android Lint Module for integrating the Android Lint tool in a Mill build.
+ *
+ * This module provides configuration options for executing Android Lint, including setting paths,
+ * specifying lint rules, managing reports, and more.
+ */
+@mill.api.experimental
+trait AndroidLintModule extends AndroidSdkModule with JavaModule {
+
+  /**
+   * Path to the project for which lint should run.
+   */
+  def projectPath: T[PathRef] = Task.Source { millSourcePath }
+
+  /**
+   * Specifies the file format of lint report.
+   */
+  def lintReportFormat: T[String] = Task { "html" }
+
+  /**
+   * Specifies the lint configuration XML file path. This allows setting custom lint rules or modifying existing ones.
+   */
+  def lintConfigPath: T[Option[PathRef]] = Task { None }
+
+  /**
+   * Enable or disable warnings in the lint report.
+   */
+  def warningsAsErrors: T[Boolean] = Task { false }
+
+  /**
+   * Additional options for lint (e.g., enabling/disabling specific checks).
+   */
+  def lintOptions: T[Seq[String]] = Task { Seq("--check", "NewApi,InlinedApi") }
+
+  /**
+   * Runs the Android Lint tool to generate a report on code quality issues.
+   *
+   * This method utilizes Android Lint, a tool provided by the Android SDK,
+   * to analyze the source code for potential bugs, performance issues, and
+   * best practices compliance. It generates an HTML report with the analysis
+   * results for review.
+   *
+   * The lint tool requires the Android SDK's command-line tools to be installed.
+   * The report is saved in the task's destination directory as "report.html".
+   *
+   * For more details on the Android Lint tool, refer to:
+   * [[https://developer.android.com/studio/write/lint]]
+   */
+
+  def androidLint: T[PathRef] = Task {
+
+    val format = lintReportFormat()
+    val lintReport: os.Path = T.dest / s"report.$format"
+
+    // Map the report format to the corresponding lint command flag
+    val lintReportFlag = format match {
+      case "html" => "--html"
+      case "txt" => "--text"
+      case "xml" => "--xml"
+      case _ => throw new Exception(s"Unsupported report format: $format")
+    }
+
+    os.call(
+      Seq(
+        cmdlineToolsPath().path.toString + "/lint",
+        lintReportFlag,
+        lintReport.toString,
+        projectPath.toString
+      )
+    )
+
+    PathRef(lintReport)
+  }
+
+}

scalalib/src/mill/javalib/android/AndroidSdkModule.scala

@@ -52,6 +52,14 @@ trait AndroidSdkModule extends Module {
     PathRef(sdkPath().path / "build-tools" / buildToolsVersion())
   }
 
+  /**
+   * Provides path to the Android cmdline tools for the selected version.
+   */
+  def cmdlineToolsPath: T[PathRef] = Task {
+    installAndroidSdkComponents()
+    PathRef(sdkPath().path / "cmdline-tools" / "latest" / "bin")
+  }
+
   /**
    * Provides path to D8 Dex compiler, used for converting Java bytecode into Dalvik bytecode.
    */