Migrate examples and test buildpacks to struct layer API (#833)

examples/execd/src/main.rs

@@ -1,18 +1,12 @@
-// This example uses the older trait Layer API. The example will be updated to the newer API
-// before the next libcnb.rs release.
-#![allow(deprecated)]
-
-mod layer;
-
-use crate::layer::ExecDLayer;
 use libcnb::build::{BuildContext, BuildResult, BuildResultBuilder};
 use libcnb::data::layer_name;
 use libcnb::detect::{DetectContext, DetectResult, DetectResultBuilder};
 use libcnb::generic::{GenericError, GenericMetadata, GenericPlatform};
-use libcnb::{buildpack_main, Buildpack};
+use libcnb::{additional_buildpack_binary_path, buildpack_main, Buildpack};
 
 // Suppress warnings due to the `unused_crate_dependencies` lint not handling integration tests well.
 use fastrand as _;
+use libcnb::layer::UncachedLayerDefinition;
 #[cfg(test)]
 use libcnb_test as _;
 
@@ -28,7 +22,19 @@ impl Buildpack for ExecDBuildpack {
     }
 
     fn build(&self, context: BuildContext<Self>) -> libcnb::Result<BuildResult, Self::Error> {
-        context.handle_layer(layer_name!("layer_name"), ExecDLayer)?;
+        let layer_ref = context.uncached_layer(
+            layer_name!("layer_name"),
+            UncachedLayerDefinition {
+                build: false,
+                launch: true,
+            },
+        )?;
+
+        layer_ref.write_exec_d_programs([(
+            "dice_roller",
+            additional_buildpack_binary_path!("dice_roller"),
+        )])?;
+
         BuildResultBuilder::new().build()
     }
 }

test-buildpacks/readonly-layer-files/src/main.rs

@@ -1,15 +1,12 @@
-// This test buildpack uses the older trait Layer API. It will be updated to the newer API
-// before the next libcnb.rs release.
-#![allow(deprecated)]
-
-mod layer;
-
-use crate::layer::TestLayer;
 use libcnb::build::{BuildContext, BuildResult, BuildResultBuilder};
 use libcnb::data::layer_name;
 use libcnb::detect::{DetectContext, DetectResult, DetectResultBuilder};
 use libcnb::generic::{GenericMetadata, GenericPlatform};
+use libcnb::layer::{CachedLayerDefinition, InvalidMetadataAction, RestoredLayerAction};
 use libcnb::{buildpack_main, Buildpack};
+use std::fs;
+use std::fs::Permissions;
+use std::os::unix::fs::PermissionsExt;
 
 // Suppress warnings due to the `unused_crate_dependencies` lint not handling integration tests well.
 #[cfg(test)]
@@ -27,7 +24,27 @@ impl Buildpack for TestBuildpack {
     }
 
     fn build(&self, context: BuildContext<Self>) -> libcnb::Result<BuildResult, Self::Error> {
-        context.handle_layer(layer_name!("test"), TestLayer)?;
+        let layer_ref = context.cached_layer(
+            layer_name!("test"),
+            CachedLayerDefinition {
+                build: true,
+                launch: true,
+                invalid_metadata_action: &|_| InvalidMetadataAction::DeleteLayer,
+                restored_layer_action: &|_: &GenericMetadata, _| RestoredLayerAction::DeleteLayer,
+            },
+        )?;
+
+        let directory = layer_ref.path().join("sub_directory");
+        fs::create_dir_all(&directory).expect("Couldn't create subdirectory");
+
+        fs::write(directory.join("foo.txt"), "hello world!").expect("Couldn't write file");
+
+        // By making the sub-directory read-only, files inside it cannot be deleted. This would
+        // cause issues when libcnb.rs tries to delete a cached layer directory unless libcnb.rs
+        // handles this case explicitly.
+        fs::set_permissions(&directory, Permissions::from_mode(0o555))
+            .expect("Couldn't set permissions to read-only");
+
         BuildResultBuilder::new().build()
     }
 }

test-buildpacks/sbom/src/main.rs

@@ -1,17 +1,11 @@
-// This test buildpack uses the older trait Layer API. It will be updated to the newer API
-// before the next libcnb.rs release.
-#![allow(deprecated)]
-
-mod test_layer;
-mod test_layer_2;
-
-use crate::test_layer::TestLayer;
-use crate::test_layer_2::TestLayer2;
 use libcnb::build::{BuildContext, BuildResult, BuildResultBuilder};
 use libcnb::data::layer_name;
 use libcnb::data::sbom::SbomFormat;
 use libcnb::detect::{DetectContext, DetectResult, DetectResultBuilder};
 use libcnb::generic::{GenericMetadata, GenericPlatform};
+use libcnb::layer::{
+    CachedLayerDefinition, InvalidMetadataAction, LayerState, RestoredLayerAction,
+};
 use libcnb::sbom::Sbom;
 use libcnb::{buildpack_main, Buildpack};
 
@@ -31,8 +25,64 @@ impl Buildpack for TestBuildpack {
     }
 
     fn build(&self, context: BuildContext<Self>) -> libcnb::Result<BuildResult, Self::Error> {
-        context.handle_layer(layer_name!("test"), TestLayer)?;
-        context.handle_layer(layer_name!("test2"), TestLayer2)?;
+        let first_layer_ref = context.cached_layer(
+            layer_name!("test"),
+            CachedLayerDefinition {
+                build: true,
+                launch: true,
+                invalid_metadata_action: &|_| InvalidMetadataAction::DeleteLayer,
+                restored_layer_action: &|_: &GenericMetadata, _| RestoredLayerAction::KeepLayer,
+            },
+        )?;
+
+        match first_layer_ref.state {
+            LayerState::Restored { .. } => {
+                first_layer_ref.write_sboms(&[])?;
+            }
+            LayerState::Empty { .. } => {
+                first_layer_ref.write_sboms(&[
+                    Sbom::from_bytes(
+                        SbomFormat::CycloneDxJson,
+                        *include_bytes!("../etc/cyclonedx_3.sbom.json"),
+                    ),
+                    Sbom::from_bytes(
+                        SbomFormat::SpdxJson,
+                        *include_bytes!("../etc/spdx_3.sbom.json"),
+                    ),
+                    Sbom::from_bytes(
+                        SbomFormat::SyftJson,
+                        *include_bytes!("../etc/syft_3.sbom.json"),
+                    ),
+                ])?;
+            }
+        }
+
+        let second_layer_ref = context.cached_layer(
+            layer_name!("test2"),
+            CachedLayerDefinition {
+                build: true,
+                launch: true,
+                invalid_metadata_action: &|_| InvalidMetadataAction::DeleteLayer,
+                restored_layer_action: &|_: &GenericMetadata, _| RestoredLayerAction::KeepLayer,
+            },
+        )?;
+
+        if let LayerState::Empty { .. } = second_layer_ref.state {
+            second_layer_ref.write_sboms(&[
+                Sbom::from_bytes(
+                    SbomFormat::CycloneDxJson,
+                    *include_bytes!("../etc/cyclonedx_2.sbom.json"),
+                ),
+                Sbom::from_bytes(
+                    SbomFormat::SpdxJson,
+                    *include_bytes!("../etc/spdx_2.sbom.json"),
+                ),
+                Sbom::from_bytes(
+                    SbomFormat::SyftJson,
+                    *include_bytes!("../etc/syft_2.sbom.json"),
+                ),
+            ])?;
+        }
 
         BuildResultBuilder::new()
             .launch_sbom(Sbom::from_bytes(

test-buildpacks/sbom/tests/integration_test.rs

@@ -113,8 +113,7 @@ fn test() {
 
         context.rebuild(&build_config, |context| {
             context.download_sbom_files(|sbom_files| {
-                // The 'test' layer does not return any SBOM files in its update implementation. This
-                // must result in no SBOM files being used from previous build.
+                // The buildpack removes restored SBOMs from the 'test' layer.
                 assert!(!sbom_files
                     .path_for(
                         &buildpack_id,