----
<1> The `authoring-tutorial` root project
<2> The `app` subproject
<3> The `app` source code
<4> The `app` build script
<5> The optional settings file
=====

== Step 2. Add another Subproject to the Build
Imagine that our project is growing and requires a custom library to function.

Let's create this imaginary `lib`.
First, create a `lib` folder:

[source,text]
----
mkdir lib
----

[source,text]
----

	}
}

func (s *httpInstance) Close() error {
	if s.server != nil {
		return s.server.Close()
	}
	return nil
}

type httpHandler struct {
	Config
}

// Imagine a pie of different flavors.
// The flavors are the HTTP response codes.
// The chance of a particular flavor is ( slices / sum of slices ).
type codeAndSlices struct {
	httpResponseCode int
	slices           int
}

However, for consumers, strict versions are still considered globally during graph resolution and _may trigger an error_ if the consumer disagrees.

For example, imagine that your project `B` _strictly_ depends on `C:1.0`.
Now, a consumer, `A`, depends on both `B` and `C:1.1`.

A Java library, for example, exposes two variants (API and runtime) which provide the _same capability_.
As a consequence, it is an error to have both the _API_ and _runtime_ of a single component in a dependency graph.

However, imagine that you need the _runtime_ and the _test fixtures runtime_ of a component.
Then it is allowed as long as the _runtime_ and _test fixtures runtime_ variant of the library declare different capabilities.

include("some-logic")
----
=====
[.multi-language-sample]
=====
.settings.gradle
[source,groovy]
----
rootProject.name = 'gradle-project'
include('app')
include('some-logic')
----
=====
====

Let's imagine that the `app` subproject depends on the subproject called `some-logic`, which contains some Java code.
We add this dependency in the `app` build script:

====
[.multi-language-sample]
=====
.app/build.gradle.kts

NOTE: For Linux users, Gradle will discover the tool chain using the system PATH.

[[sec:custom_swift_source_set_paths]]
=== Customizing file and directory locations

Imagine you are migrating a library project that follows the Swift Package Manager layout (e.g. `Sources/__ModuleName___` directory for the production code).

  //
  // TODO(user): Change API to make it impossible to use a Guard with the "wrong" monitor,
  //    by making the monitor implicit, and to eliminate other sources of IMSE.
  //    Imagine:
  //    guard.lock();
  //    try { /* monitor locked and guard satisfied here */ }
  //    finally { guard.unlock(); }
  // Here are Justin's design notes about this:
  //

		p = "y"
	}

	// Parse actual pattern syntax.
	result := true
	bits := uint64(0)
	start := 0
	wid := 1 // 1-bit (binary); sometimes 4-bit (hex)
	for i := 0; i <= len(p); i++ {
		// Imagine a trailing - at the end of the pattern to flush final suffix
		c := byte('-')
		if i < len(p) {
			c = p[i]
		}
		if i == start && wid == 1 && c == 'x' { // leading x for hex
			start = i + 1
			wid = 4

As explained in the <<declaring_dependencies.adoc#sec:resolvable-consumable-configs, configurations chapter>>, this corresponds to a _consumable configuration_.

Let's imagine that the consumer requires _instrumented classes_ from the producer, but that this artifact is _not_ the main one.
The producer can expose its instrumented classes by creating a configuration that will "carry" this artifact:

## Functional design

Let's look at how bytecode interception works on an example of upgrading a JavaBean property to a lazy one.
Configuration cache instrumentation works in the same way.

Imagine we have in Gradle core a task:
```java
abstract class JavaCompile {
    
    private String sourceCompatibility = null;
    
    @Input
    public String getSourceCompatibility() {