Kotlin compilation error "Unresolved reference" for multi-module project

Question

I have spring boot application with multi-module structure.

first-module:
 - services:
     - interfaces.kt


second-module:
...

Second module have spring boot application

@SpringBootApplication
class Application {
    companion object {
        @JvmStatic
        fun main(args: Array<String>) {
            SpringApplicationBuilder(Application::class.java)
                    .initializers(ConfigServerInitializer.create())
                    .run(*args)
        }
    }
}

And also second-module have interfaces implementation. But when i compile it using maven, i faced with next errors:

[WARNING] Using experimental Kotlin incremental compilation
[INFO] Non-incremental compilation will be performed: No information on previous build
[INFO] Kotlin compile iteration: /Users/slandshow/Project/Test/test-project/src/main/kotlin/org/test/Application.kt, /Users/slandshow/Project/Test/test-project/src/main/kotlin/org/test/template/TemplateService.kt
[INFO] Exit code: COMPILATION_ERROR
.../template/TemplateService.kt: (4, 32) Unresolved reference: models
...

I don't really understand why i have such compilation issues.

Also, i have next pom plugins.

1. first-module

<build>
        <plugins>
            <plugin>
                <artifactId>kotlin-maven-plugin</artifactId>
                <groupId>org.jetbrains.kotlin</groupId>
                <version>${kotlin.version}</version>

                <configuration>
                    <compilerPlugins>
                        <plugin>no-arg</plugin>
                    </compilerPlugins>
                </configuration>

                <dependencies>
                    <dependency>
                        <groupId>org.jetbrains.kotlin</groupId>
                        <artifactId>kotlin-maven-noarg</artifactId>
                        <version>${kotlin.version}</version>
                    </dependency>
                </dependencies>
            </plugin>
        </plugins>
    </build>

2. second-module

<build>
        <plugins>
            <plugin>
                <groupId>org.jetbrains.kotlin</groupId>
                <artifactId>kotlin-maven-plugin</artifactId>
                <version>${kotlin.version}</version>

                <configuration>
                    <compilerPlugins>
                        <plugin>spring</plugin>
                    </compilerPlugins>
                </configuration>

                <executions>
                    <execution>
                        <id>compile</id>
                        <phase>compile</phase>
                        <goals>
                            <goal>compile</goal>
                        </goals>

                        <configuration>
                            <sourceDirs>
                                <sourceDir>${project.basedir}/src/main/kotlin</sourceDir>
                                <sourceDir>${project.basedir}/src/main/java</sourceDir>
                            </sourceDirs>
                        </configuration>
                    </execution>

                    <execution>
                        <id>test-compile</id>
                        <phase>test-compile</phase>
                        <goals>
                            <goal>test-compile</goal>
                        </goals>

                        <configuration>
                            <sourceDirs>
                                <sourceDir>${project.basedir}/src/test/kotlin</sourceDir>
                                <sourceDir>${project.basedir}/src/test/java</sourceDir>
                            </sourceDirs>
                        </configuration>
                    </execution>
                </executions>

                <dependencies>
                    <dependency>
                        <groupId>org.jetbrains.kotlin</groupId>
                        <artifactId>kotlin-maven-allopen</artifactId>
                        <version>${kotlin.version}</version>
                    </dependency>
                </dependencies>
            </plugin>

            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-compiler-plugin</artifactId>

                <executions>
                    <execution>
                        <id>default-compile</id>
                        <phase>none</phase>
                    </execution>

                    <execution>
                        <id>default-testCompile</id>
                        <phase>none</phase>
                    </execution>

                    <execution>
                        <id>java-compile</id>
                        <phase>compile</phase>
                        <goals>
                            <goal>compile</goal>
                        </goals>
                    </execution>
                </executions>
            </plugin>

            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-surefire-plugin</artifactId>
                <version>${maven-surefire-plugin.version}</version>

                <configuration>
                    <includes>
                        <include>**/*IT.*</include>
                        <include>**/*Test.*</include>
                    </includes>
                </configuration>
            </plugin>
        </plugins>
    </build>

3. Common pom

<dependency>
            <groupId>org.jetbrains.kotlin</groupId>
            <artifactId>kotlin-stdlib-common</artifactId>
            <version>${kotlin.version}</version>
        </dependency>

        <dependency>
            <groupId>org.jetbrains.kotlin</groupId>
            <artifactId>kotlin-reflect</artifactId>
            <version>${kotlin.version}</version>
        </dependency>

        <dependency>
            <groupId>org.jetbrains.kotlin</groupId>
            <artifactId>kotlin-maven-allopen</artifactId>
            <version>${kotlin.version}</version>
            <exclusions>
                <exclusion>
                    <groupId>org.jetbrains.kotlin</groupId>
                    <artifactId>kotlin-stdlib</artifactId>
                </exclusion>
            </exclusions>
        </dependency>

        <dependency>
            <groupId>org.jetbrains.kotlin</groupId>
            <artifactId>kotlin-maven-noarg</artifactId>
            <version>${kotlin.version}</version>
            <exclusions>
                <exclusion>
                    <groupId>org.jetbrains.kotlin</groupId>
                    <artifactId>kotlin-stdlib</artifactId>
                </exclusion>
            </exclusions>
        </dependency>
    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-compiler-plugin</artifactId>

                <executions>
                    <execution>
                        <id>default-compile</id>
                        <phase>none</phase>
                    </execution>

                    <execution>
                        <id>default-testCompile</id>
                        <phase>none</phase>
                    </execution>

                    <execution>
                        <id>java-compile</id>
                        <phase>compile</phase>
                        <goals>
                            <goal>compile</goal>
                        </goals>
                    </execution>
                </executions>
            </plugin>
        </plugins>
    </build>

What is wrong here?

Answer 1

I have created multiple projects that use multi-module structure but this one is bit unique; as one of the child only holds the services which were later used by another child module.

Similar scenario is defined in Spring docs for multi module java project .

I have spent some time and created this github-repo which creates your desired multi module structure.

Please take a look and let me know if you have any questions.