How to use generated sources of one module in another module in a multi-module project?

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I have a multi-module gradle project using proto to generate the DTOs. The root project has two different modules, inventory , and inventory-api . The *-api module is the one that has all the .proto definitions. inventory has a dependency on inventory-api

Here is the root gradle file

plugins {
    id 'io.spring.dependency-management' version '1.0.10.RELEASE'
}

subprojects {
    group = 'com.yasinbee.apifirst'
    version = '0.0.1-SNAPSHOT'

    apply plugin: 'idea'
    apply plugin: 'java'
    apply plugin: 'io.spring.dependency-management'
    apply plugin: 'java-library'

    repositories {
        jcenter()
    }

    dependencyManagement {
        imports {
            mavenBom("org.springframework.boot:spring-boot-dependencies:2.1.9.RELEASE")
        }
    }

    compileJava {
        sourceCompatibility = 11
        targetCompatibility = 11
    }
}

Here is the inventory gradle file

plugins {
    id 'org.springframework.boot' version '2.3.4.RELEASE'
}

dependencies {

    implementation project (':inventory-api')

    implementation "org.springframework.boot:spring-boot-starter-data-jpa"
    implementation "org.springframework.boot:spring-boot-starter-jdbc"
    implementation "org.springframework.boot:spring-boot-starter-web"
    implementation "org.mapstruct:mapstruct:1.4.0.Final"

    annotationProcessor 'org.mapstruct:mapstruct-processor:1.4.0.Final'


    developmentOnly 'org.springframework.boot:spring-boot-devtools'

    runtimeOnly 'com.h2database:h2'

    testImplementation('org.springframework.boot:spring-boot-starter-test') {
        exclude group: 'org.junit.vintage', module: 'junit-vintage-engine'
    }
}

test {
    useJUnitPlatform()
}

And the inventory-api gradle file that has all the proto stuff

apply plugin: 'java'
apply plugin: 'java-library'
apply plugin: 'idea'
apply plugin: 'com.google.protobuf'

dependencies {
    implementation 'com.google.protobuf:protobuf-java:3.11.0'
}

buildscript {
    repositories {
        mavenCentral()
    }
    dependencies {
        classpath 'com.google.protobuf:protobuf-gradle-plugin:0.8.13'
    }
}


protobuf {
    protoc {
        artifact = 'com.google.protobuf:protoc:3.10.1'
    }
}

I am able to use the generated proto files within the inventory-api module. However, when I am trying to access the generated files from the inventory module, I am getting a compilation error.

It seems that the generated proto files are not added to the source sets of the inventory app. How can I add the generated source files of *-api modules into other modules that depend on them?