Gradle Composite Build Demo

This demo shows how to support multiple settings.gradle files for multiple projects building (Sort of like the includeBuild, which is only supported in Gradle 3.+).

Structure of demo project

.
├── app
│   └── build.gradle
├── lib1
│   ├── lib1
│   │   └── build.gradle
│   ├── lib1-sample
│   │   └── build.gradle
│   ├── build.gradle
│   └── settings.gradle
├── lib2
│   ├── lib2
│   │   └── build.gradle
│   ├── lib2-sample
│   │   └── build.gradle
│   ├── build.gradle
│   └── settings.gradle
├── build.gradle
└── settings.gradle

How dose multiple settings.gradle work?

See settings.gradle.

Just apply the sub settings.gradle scripts to mock settings instance.

def includeProject(String path, Closure closure) {
    ...
    
    apply {
        from ...
        to new SettingsProxy(...)
    }
}

class SettingsProxy {
    ...
    
    public getRootProject() { ... }

    public void include(String... paths) { ... }

    public project(String path) { ... }

    private String generateDescendantPath(path) { ... }
}

How to substitute dependencies?

See build.gradle.

...

subprojects {
    ...
    
    configurations.all { configuration ->
        resolutionStrategy.dependencySubstitution.all { DependencySubstitution substitution ->
            final ComponentSelector requested = substitution.requested
            if (requested instanceof ModuleComponentSelector) {
                final Project target = substitutionRules.find(requested.group, requested.module)
                if (target) {
                    println "Substitute: $project.name:$configuration.name '$requested' -> $target"

                    project.evaluationDependsOn("$target.path")
                    substitution.useTarget(target)
                }
            }
        }
    }
}