gRPC code not being generated from proto file

I followed this guide to add gRPC to my Android project, but the proto file does not seem to generate code.

I placed book.proto under app\src\main\java\com\example\android together with my Kotlin code.

That's my project's build.gradle:

// Top-level build file where you can add configuration options common to all sub-projects/modules.
buildscript {
    ext.kotlin_version = "1.3.72"
    repositories {
        google()
        jcenter()
    }
    dependencies {
        classpath "com.android.tools.build:gradle:4.1.2"
        classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version"

        // Tar's:
        classpath 'com.google.protobuf:protobuf-gradle-plugin:0.8.15' // gRPC

        // NOTE: Do not place your application dependencies here; they belong
        // in the individual module build.gradle files
    }
}

allprojects {
    repositories {
        google()
        jcenter()
    }
}

task clean(type: Delete) {
    delete rootProject.buildDir
}

That's my module build.gradle:

plugins {
    id 'com.android.application'
    id 'com.google.protobuf' // Tar's: gRPC
    id 'kotlin-android'
}

android {
    compileSdkVersion 30
    buildToolsVersion "30.0.3"

    defaultConfig {
        applicationId "com.example.android"
        minSdkVersion 28
        targetSdkVersion 30
        versionCode 1
        versionName "1.0"

        testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
    }

    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
        }
    }
    compileOptions {
        sourceCompatibility JavaVersion.VERSION_1_8
        targetCompatibility JavaVersion.VERSION_1_8
    }
    kotlinOptions {
        jvmTarget = '1.8'
    }

    buildFeatures { // Tar: for using ObservableList, which is part of the Data Binding Library - see https://stackoverflow.com/questions/66352403/observablelist-is-missing-in-android-studio and https://developer.android.com/topic/libraries/data-binding/start
        dataBinding true
    }
}

// Tar's: gRPC {
protobuf {
    protoc { artifact = 'com.google.protobuf:protoc:3.10.0' }
    plugins {
        javalite { artifact = "com.google.protobuf:protoc-gen-javalite:3.0.0" }
        grpc { artifact = 'io.grpc:protoc-gen-grpc-java:1.25.0' // CURRENT_GRPC_VERSION
        }
    }
    generateProtoTasks {
        all().each { task ->
            task.plugins {
                javalite {}
                grpc { // Options added to --grpc_out
                    option 'lite' }
            }
        }
    }
}
// }

dependencies {

    implementation "org.jetbrains.kotlin:kotlin-stdlib:$kotlin_version"
    implementation 'androidx.core:core-ktx:1.3.2'
    implementation 'androidx.appcompat:appcompat:1.2.0'
    implementation 'com.google.android.material:material:1.2.1'
    implementation 'androidx.constraintlayout:constraintlayout:2.0.4'
    implementation 'androidx.gridlayout:gridlayout:1.0.0'
    testImplementation 'junit:junit:4.+'
    androidTestImplementation 'androidx.test.ext:junit:1.1.2'
    androidTestImplementation 'androidx.test.espresso:espresso-core:3.3.0'
    // Tar's:
    implementation "org.java-websocket:Java-WebSocket:1.5.1" // Webscokets
    //implementation "org.jetbrains.kotlinx:kotlinx-serialization-json:1.1.0" // Tar: for JSON: https://github.com/Kotlin/kotlinx.serialization
    // Tar's - gRPC: {
    implementation 'com.google.protobuf:protobuf-lite:3.0.1'
    implementation 'io.grpc:grpc-okhttp:1.25.0' // CURRENT_GRPC_VERSION
    implementation 'io.grpc:grpc-protobuf-lite:1.25.0' // CURRENT_GRPC_VERSION
    implementation 'io.grpc:grpc-stub:1.25.0' // CURRENT_GRPC_VERSION
    implementation 'javax.annotation:javax.annotation-api:1.3.2'
    // }
}

What could be the problem?

Looks like the path of proto file is not correctly set. Try to move proto files to src/main/resouces/proto or set path in protobuf plugin configuration.

This works well with Kotlin DSL.

import com.google.protobuf.gradle.*

plugins {
    java
    idea
    application
    id("com.google.protobuf") version "0.8.14"
    id("io.freefair.lombok") version "5.3.0"
}

repositories {
    mavenCentral()
    jcenter()
}


val grpcVersion = "1.34.1"
val protocVersion = "3.12.0"
val slf4jVersion = "1.7.25"

dependencies {
    implementation("io.grpc:grpc-netty:${grpcVersion}")
    implementation("io.grpc:grpc-protobuf:${grpcVersion}")
    implementation("io.grpc:grpc-stub:${grpcVersion}")
    implementation("org.slf4j:slf4j-api:${slf4jVersion}")
    implementation("org.slf4j:slf4j-simple:${slf4jVersion}")

    testImplementation("junit:junit:4.13")
}

// Look here for set path
sourceSets {
    main {
        proto {
            srcDir("src/main/resources/proto")
        }
    }
}

protobuf {
    protoc { artifact = "com.google.protobuf:protoc:${protocVersion}" }
    plugins {
        id("grpc") {
            artifact = "io.grpc:protoc-gen-grpc-java:${grpcVersion}"
        }
    }
    generateProtoTasks {
        ofSourceSet("main").forEach {
            it.plugins {
                id("grpc")
            }
        }
    }
}