libbpf-cargo: Clean up crate-structure mess

It goes against every Cargo project preconception to have certain
modules be compiled from both lib.rs and main.rs and it leads to
shenanigans such as #[allow(dead_code)] tags scattered all over the
place, which is its own can of worms when done at such a high level. Do
it properly and export necessary functionality from the library, for
consumption by the binary. To prevent any misconceptions of there being
a stable API contract for functionality *only* being used by the binary,
put it into an hidden module.

Signed-off-by: Daniel Müller <deso@posteo.net>

libbpf-cargo/src/build.rs

@@ -279,7 +279,7 @@ fn extract_clang_or_default(clang: Option<&PathBuf>) -> PathBuf {
 }
 
 #[allow(clippy::too_many_arguments)]
-pub(crate) fn build(
+pub fn build(
     debug: bool,
     manifest_path: Option<&PathBuf>,
     clang: Option<&PathBuf>,
@@ -309,7 +309,6 @@ pub(crate) fn build(
 }
 
 // Only used in libbpf-cargo library
-#[allow(dead_code)]
 pub(crate) fn build_single(
     debug: bool,
     source: &Path,

libbpf-cargo/src/gen/btf.rs

@@ -449,7 +449,7 @@ impl StructOps {{
 }
 
 
-pub struct GenBtf<'s> {
+pub(crate) struct GenBtf<'s> {
     btf: Btf<'s>,
     anon_types: AnonTypes,
 }

libbpf-cargo/src/gen/mod.rs

@@ -1,4 +1,4 @@
-pub mod btf;
+mod btf;
 
 use std::borrow::Cow;
 use std::collections::BTreeMap;
@@ -43,8 +43,8 @@ use memmap2::Mmap;
 use crate::metadata;
 use crate::metadata::UnprocessedObj;
 
-use self::btf::GenBtf;
-use self::btf::GenStructOps;
+pub(crate) use self::btf::GenBtf;
+pub(crate) use self::btf::GenStructOps;
 
 
 /// Name of the `.kconfig` map.
@@ -195,9 +195,7 @@ pub(crate) enum OutputDest<'a> {
     Stdout,
     /// Infer a filename and place file in specified directory
     Directory(&'a Path),
-    #[allow(dead_code)]
     /// File to place output in
-    // Only constructed in libbpf-cargo library
     File(&'a Path),
 }
 
@@ -1352,7 +1350,7 @@ fn gen_project(
     Ok(())
 }
 
-pub(crate) fn gen(
+pub fn gen(
     debug: bool,
     manifest_path: Option<&PathBuf>,
     rustfmt_path: Option<&PathBuf>,

libbpf-cargo/src/lib.rs

@@ -77,15 +77,9 @@ use anyhow::Result;
 use tempfile::tempdir;
 use tempfile::TempDir;
 
-// libbpf-cargo binary is the primary consumer of the following modules. As such,
-// we do not use all the symbols. Silence any unused code warnings.
-#[allow(dead_code)]
 mod build;
-#[allow(dead_code)]
 mod gen;
-#[allow(dead_code)]
 mod make;
-#[allow(dead_code)]
 mod metadata;
 
 #[cfg(test)]
@@ -285,3 +279,20 @@ impl SkeletonBuilder {
         Ok(())
     }
 }
+
+
+/// Implementation details shared with the binary.
+///
+/// NOT PART OF PUBLIC API SURFACE!
+#[doc(hidden)]
+pub mod __private {
+    pub mod build {
+        pub use crate::build::build;
+    }
+    pub mod gen {
+        pub use crate::gen::gen;
+    }
+    pub mod make {
+        pub use crate::make::make;
+    }
+}

libbpf-cargo/src/main.rs

@@ -9,11 +9,10 @@ use clap::Args;
 use clap::Parser;
 use clap::Subcommand;
 
-#[doc(hidden)]
-mod build;
-mod gen;
-mod make;
-mod metadata;
+use libbpf_cargo::__private::build;
+use libbpf_cargo::__private::gen;
+use libbpf_cargo::__private::make;
+
 
 #[doc(hidden)]
 #[derive(Debug, Parser)]

libbpf-cargo/src/metadata.rs

@@ -24,7 +24,7 @@ struct PackageMetadata {
 }
 
 #[derive(Debug, Clone)]
-pub struct UnprocessedObj {
+pub(crate) struct UnprocessedObj {
     /// Package the object belongs to
     pub package: String,
     /// Path to .c
@@ -142,7 +142,10 @@ fn get_package(
 }
 
 /// Returns the `target_directory` and a list of objects to compile.
-pub fn get(debug: bool, manifest_path: Option<&PathBuf>) -> Result<(PathBuf, Vec<UnprocessedObj>)> {
+pub(crate) fn get(
+    debug: bool,
+    manifest_path: Option<&PathBuf>,
+) -> Result<(PathBuf, Vec<UnprocessedObj>)> {
     let mut cmd = MetadataCommand::new();
 
     if let Some(path) = manifest_path {

libbpf-cargo/src/test.rs

@@ -20,8 +20,8 @@ use tempfile::NamedTempFile;
 use tempfile::TempDir;
 
 use crate::build::build;
-use crate::gen::btf::GenBtf;
-use crate::gen::btf::GenStructOps;
+use crate::gen::GenBtf;
+use crate::gen::GenStructOps;
 use crate::make::make;
 use crate::SkeletonBuilder;