Cannot resolve symbol with AutoValue and IntelliJ

Question

I have been trying to find the correct settings for IntelliJ's annotation processing in order for it to co-exist with Gradle's build process.

Whenever I build from IntelliJ I cannot get it to recognise the generated sources from the gradle-apt-plugin.

My requirements for my project are:

• Building between IntelliJ and Gradle should be seamless and not interfere with the process of each other
• I need to use IntelliJ's Create separate module per source set option
• I need to use IntelliJ's folder based structure
• IntelliJ needs to be able to recognise and autocomplete AutoValue classes

Here are the steps for a MCVE in order to reproduce the issue with IntelliJ 2017.2.4 and Gradle 3.5:

• Create a new Gradle project from IntelliJ
• Check the Create separate module per source set option
• Open build.gradle file:
• Add the following plugins block:

plugins {
    id 'java'
    id 'net.ltgt.apt' version '0.12'
}

• Add the following dependencies block

dependencies {
    compileOnly 'com.google.auto.value:auto-value:1.5'
    apt 'com.google.auto.value:auto-value:1.5'
}

• Go to Settings → Build, Execution, Deployment → Annotation Processors
• Check the Enable Annotation Processing
• Create a class:

@AutoValue
public abstract class GeneratedSourcesTest {

    static GeneratedSourcesTest create(String field) {
        return new AutoValue_GeneratedSourcesTest(field);
    }

    public abstract String field();
}

• On IntelliJ run Build → Build Project
• Open the GeneratedSourcesTest class, on the static factory method, everything compiles fine but I get the error:

cannot resolve symbol ‘AutoValue_GeneratedSourcesTest’

How can I make the AutoValue_GeneratedSourcesTest class accessible from IntelliJ?

Answer 1

After importing your Gradle project under IDEA do the following steps:

1. Set annotation processing configuration as follows:

2. Run menu: Build - Build Project

3. Right click on each new generated folder and select: Mark Directory as - Generated Sources Root so it was marked as follows:

   4. Add /generated to project's .gitignore file

That's a minimal viable configuration which will provide full IDE support for generated classes. The drawback is, whenever Gradle project gets re-imported the generated folders will need be marked as Generated Sources Root again. Perhaps this can be improved with adding these paths as source sets under build.gradle.

Sometimes it happens that IDEA modules lose their compiler output path settings in result of the above. It's sufficient to just set it back to their default folders.