Configuration cache configuration input tracking

Samples to demonstrate some improvements to configuration input tracking that will be included in Gradle 8.1.

FileCollections queried at configuration time are included in fingerprint

File collections that are queried at configuration time are now treated as configuration inputs and included in the configuration cache fingerprint. When the contents of these file collections change, Gradle invalidates the configuration cache entry.

To try this out, use the queryDirInDsl task. The build script queries the contents of file-collections/src/dir at configuration time.

When a new file is added to file-collections/src/dir, the configuration cache entry is invalidated. The console reports that an input of file-collections/build.gradle.kts has changed. The message does not yet say exactly which input has changed. This will be improved in Gradle 8.1 to be more useful.

> ./gradlew queryDirInDsl

# Cache hit
> ./gradlew queryDirInDsl

# Create a new file
> echo dsl > file-collections/src/dir/file2.txt

# Cache miss, reports the correct file names
> ./gradlew queryDirInDsl

Compare this with Gradle 7.6, where the new file is ignored:

> alias gradle76=# an installation of Gradle 7.6 or a recent Gradle 7.x installation
> gradle76 queryDirInDsl

# Create a new file -> cache hit
> echo ignored > file-collections/src/dir/file3.txt

# Incorrect cache hit, reports incorrect file names
> gradle76 queryDirInDsl

Here's another example, where a plugin does the same thing:

> ./gradlew queryDirInPlugin

# Cache hit
> ./gradlew queryDirInPlugin

# Create new a file -> cache miss
> echo plugin > file-collections/src/dir/file4.txt
> ./gradlew queryDirInPlugin

# Create an excluded file -> cache hit
> echo ignored > file-collections/src/dir/file4.java
> ./gradlew queryDirInPlugin

# Create an empty directory -> cache hit
> mkdir file-collections/src/dir/empty
> ./gradlew queryDirInPlugin

You can try other mutations, such as deleting files or directories, adding new files or directories, etc.

Not yet complete