libcnb-package: Only expose functions/types publicly if they are actu…

…ally used (#750)

In order to:
- make the implementation of `libcnb-package` easier to reason about/refactor
- reduce the number of APIs visible to consumers of `libcnb-package`, so it's
  easier for them to see which APIs they should be using

In the case of `calculate_dir_size`, I've moved it back to `libcnb-cargo`
(where it was originally), since it's only used there.

I've checked that none of these APIs are used by our release automation:
https://github.com/search?q=repo%3Aheroku%2Flanguages-github-actions+libcnb_package+language%3ARust&type=code&l=Rust
(And longer term we should switch to having that automation call
a new `libcnb-cargo` subcommand rather than use `libcnb-package`
directly.)

I've not added a changelog entry, since we document `libcnb-package` as being
for internal use only and having no stability guarantees:
https://github.com/heroku/libcnb.rs/blob/main/libcnb-package/README.md

GUS-W-14512388.

libcnb-cargo/src/package/command.rs

@@ -5,7 +5,7 @@ use libcnb_package::buildpack_dependency_graph::build_libcnb_buildpacks_dependen
 use libcnb_package::cross_compile::{cross_compile_assistance, CrossCompileAssistance};
 use libcnb_package::dependency_graph::get_dependencies;
 use libcnb_package::output::create_packaged_buildpack_dir_resolver;
-use libcnb_package::util::{absolutize_path, calculate_dir_size};
+use libcnb_package::util::absolutize_path;
 use libcnb_package::{find_cargo_workspace_root_dir, CargoProfile};
 use std::collections::BTreeMap;
 use std::fs;
@@ -170,3 +170,24 @@ fn eprint_compiled_buildpack_success(current_dir: &Path, target_dir: &Path) {
         relative_output_path.to_string_lossy(),
     );
 }
+
+/// Recursively calculate the size of a directory and its contents in bytes.
+fn calculate_dir_size(path: impl AsRef<Path>) -> std::io::Result<u64> {
+    let mut size_in_bytes = 0;
+
+    // The size of the directory entry (ie: its metadata only, not the directory contents).
+    size_in_bytes += path.as_ref().metadata()?.len();
+
+    for entry in std::fs::read_dir(&path)? {
+        let entry = entry?;
+        let metadata = entry.metadata()?;
+
+        if metadata.is_dir() {
+            size_in_bytes += calculate_dir_size(entry.path())?;
+        } else {
+            size_in_bytes += metadata.len();
+        }
+    }
+
+    Ok(size_in_bytes)
+}

libcnb-package/src/build.rs

@@ -20,7 +20,7 @@ use std::process::{Command, ExitStatus};
 ///
 /// Will return `Err` if any build did not finish successfully, the configuration can't be
 /// read or the configured main buildpack binary does not exist.
-pub fn build_buildpack_binaries(
+pub(crate) fn build_buildpack_binaries(
     project_path: impl AsRef<Path>,
     cargo_metadata: &Metadata,
     cargo_profile: CargoProfile,
@@ -95,7 +95,7 @@ pub fn build_buildpack_binaries(
 /// # Errors
 ///
 /// Will return `Err` if the build did not finish successfully.
-pub fn build_binary(
+fn build_binary(
     project_path: impl AsRef<Path>,
     cargo_metadata: &Metadata,
     cargo_profile: CargoProfile,
@@ -158,11 +158,11 @@ pub fn build_binary(
 }
 
 #[derive(Debug)]
-pub struct BuildpackBinaries {
+pub(crate) struct BuildpackBinaries {
     /// The path to the main buildpack binary
-    pub buildpack_target_binary_path: PathBuf,
+    pub(crate) buildpack_target_binary_path: PathBuf,
     /// Paths to additional binaries from the buildpack
-    pub additional_target_binary_paths: HashMap<String, PathBuf>,
+    pub(crate) additional_target_binary_paths: HashMap<String, PathBuf>,
 }
 
 #[derive(thiserror::Error, Debug)]

libcnb-package/src/buildpack_kind.rs

@@ -3,7 +3,7 @@ use libcnb_data::buildpack::BuildpackDescriptor;
 use std::path::Path;
 
 #[must_use]
-pub fn determine_buildpack_kind(buildpack_dir: &Path) -> Option<BuildpackKind> {
+pub(crate) fn determine_buildpack_kind(buildpack_dir: &Path) -> Option<BuildpackKind> {
     read_toml_file::<BuildpackDescriptor>(buildpack_dir.join("buildpack.toml"))
         .ok()
         .map(|buildpack_descriptor| match buildpack_descriptor {
@@ -18,7 +18,7 @@ pub fn determine_buildpack_kind(buildpack_dir: &Path) -> Option<BuildpackKind> {
         })
 }
 
-pub enum BuildpackKind {
+pub(crate) enum BuildpackKind {
     Composite,
     LibCnbRs,
     Other,

libcnb-package/src/dependency_graph.rs

@@ -3,8 +3,6 @@ use petgraph::Graph;
 use std::error::Error;
 
 /// A node of a dependency graph.
-///
-/// See: [`create_dependency_graph`]
 pub trait DependencyNode<T, E>
 where
     T: PartialEq,
@@ -25,7 +23,7 @@ where
 ///
 /// Will return an `Err` if the graph contains references to missing dependencies or the
 /// dependencies of a [`DependencyNode`] couldn't be gathered.
-pub fn create_dependency_graph<T, I, E>(
+pub(crate) fn create_dependency_graph<T, I, E>(
     nodes: Vec<T>,
 ) -> Result<Graph<T, ()>, CreateDependencyGraphError<I, E>>
 where
@@ -59,7 +57,7 @@ where
     Ok(graph)
 }
 
-/// An error from [`create_dependency_graph`]
+/// An error that occurred while creating the dependency graph.
 #[derive(thiserror::Error, Debug)]
 pub enum CreateDependencyGraphError<I, E: Error> {
     #[error("Error while determining dependencies of a node: {0}")]

libcnb-package/src/lib.rs

@@ -39,7 +39,7 @@ pub enum CargoProfile {
 /// # Errors
 ///
 /// Will return `Err` if the buildpack directory couldn't be assembled.
-pub fn assemble_buildpack_directory(
+fn assemble_buildpack_directory(
     destination_path: impl AsRef<Path>,
     buildpack_descriptor_path: impl AsRef<Path>,
     buildpack_binaries: &BuildpackBinaries,

libcnb-package/src/package.rs

@@ -56,7 +56,7 @@ pub enum PackageBuildpackError {
 /// # Errors
 ///
 /// Returns `Err` if compilation or packaging failed.
-pub fn package_libcnb_buildpack(
+fn package_libcnb_buildpack(
     buildpack_directory: &Path,
     cargo_profile: CargoProfile,
     target_triple: &str,

libcnb-package/src/util.rs

@@ -1,30 +1,5 @@
 use std::path::{Component, Path, PathBuf};
 
-/// Recursively calculate the size of a directory and its contents in bytes.
-///
-/// # Errors
-///
-/// Returns `Err` if an I/O error occurred during the size calculation.
-pub fn calculate_dir_size(path: impl AsRef<Path>) -> std::io::Result<u64> {
-    let mut size_in_bytes = 0;
-
-    // The size of the directory entry (ie: its metadata only, not the directory contents).
-    size_in_bytes += path.as_ref().metadata()?.len();
-
-    for entry in std::fs::read_dir(&path)? {
-        let entry = entry?;
-        let metadata = entry.metadata()?;
-
-        if metadata.is_dir() {
-            size_in_bytes += calculate_dir_size(entry.path())?;
-        } else {
-            size_in_bytes += metadata.len();
-        }
-    }
-
-    Ok(size_in_bytes)
-}
-
 #[must_use]
 pub fn absolutize_path(path: &Path, parent: &Path) -> PathBuf {
     if path.is_relative() {
@@ -40,7 +15,7 @@ pub fn absolutize_path(path: &Path, parent: &Path) -> PathBuf {
 /// symbolic links will not be resolved. In return, it can be used before creating a path on the
 /// file system.
 #[must_use]
-pub fn normalize_path(path: &Path) -> PathBuf {
+fn normalize_path(path: &Path) -> PathBuf {
     let mut components = path.components().peekable();
 
     let mut result = if let Some(component @ Component::Prefix(..)) = components.peek().copied() {