Use Result in integration-test's build script

Something of an experiment.

test/integration-test/Cargo.toml

@@ -30,6 +30,7 @@ tokio = { workspace = true, features = ["macros", "rt-multi-thread", "time"] }
 xdpilone = { workspace = true }
 
 [build-dependencies]
+anyhow = { workspace = true }
 aya-build = { path = "../../aya-build" }
 # TODO(https://github.com/rust-lang/cargo/issues/12375): this should be an artifact dependency, but
 # it's not possible to tell cargo to use `-Z build-std` to build it. We cargo-in-cargo in the build

test/integration-test/build.rs

@@ -6,6 +6,7 @@ use std::{
     process::{Child, Command, Output, Stdio},
 };
 
+use anyhow::{anyhow, Context as _, Ok, Result};
 use aya_build::cargo_metadata::{Metadata, MetadataCommand, Package, Target, TargetKind};
 use xtask::{exec, AYA_BUILD_INTEGRATION_BPF, LIBBPF_DIR};
 
@@ -22,26 +23,42 @@ use xtask::{exec, AYA_BUILD_INTEGRATION_BPF, LIBBPF_DIR};
 /// occur on metadata-only actions such as `cargo check` or `cargo clippy` of this crate. This means
 /// that naively attempting to `cargo test --no-run` this crate will produce binaries that fail at
 /// runtime because the stubs are inadequate for actually running the tests.
-fn main() {
-    println!("cargo:rerun-if-env-changed={}", AYA_BUILD_INTEGRATION_BPF);
+fn main() -> Result<()> {
+    println!("cargo:rerun-if-env-changed={AYA_BUILD_INTEGRATION_BPF}");
 
     // TODO(https://github.com/rust-lang/cargo/issues/4001): generalize this and move it to
     // aya-build if we can determine that we're in a check build.
-    let build_integration_bpf = env::var(AYA_BUILD_INTEGRATION_BPF)
-        .as_deref()
-        .map(str::parse)
-        .map(Result::unwrap)
+    let build_integration_bpf = env::var_os(AYA_BUILD_INTEGRATION_BPF)
+        .map(|build_integration_bpf| {
+            let build_integration_bpf = std::str::from_utf8(
+                build_integration_bpf.as_encoded_bytes(),
+            )
+            .with_context(|| format!("{AYA_BUILD_INTEGRATION_BPF}={build_integration_bpf:?}"))?;
+            let build_integration_bpf = build_integration_bpf
+                .parse()
+                .with_context(|| format!("{AYA_BUILD_INTEGRATION_BPF}={build_integration_bpf}"))?;
+            Ok(build_integration_bpf)
+        })
+        .transpose()?
         .unwrap_or_default();
 
-    let Metadata { packages, .. } = MetadataCommand::new().no_deps().exec().unwrap();
+    let Metadata {
+        packages,
+        workspace_root,
+        ..
+    } = MetadataCommand::new()
+        .no_deps()
+        .exec()
+        .context("MetadataCommand::exec")?;
     let integration_ebpf_package = packages
         .into_iter()
         .find(|Package { name, .. }| name == "integration-ebpf")
-        .unwrap();
+        .ok_or_else(|| anyhow!("integration-ebpf package not found"))?;
 
-    let manifest_dir = env::var_os("CARGO_MANIFEST_DIR").unwrap();
+    let manifest_dir =
+        env::var_os("CARGO_MANIFEST_DIR").ok_or(anyhow!("CARGO_MANIFEST_DIR not set"))?;
     let manifest_dir = PathBuf::from(manifest_dir);
-    let out_dir = env::var_os("OUT_DIR").unwrap();
+    let out_dir = env::var_os("OUT_DIR").ok_or(anyhow!("OUT_DIR not set"))?;
     let out_dir = PathBuf::from(out_dir);
 
     const C_BPF: &[(&str, bool)] = &[
@@ -55,22 +72,18 @@ fn main() {
     ];
 
     if build_integration_bpf {
-        let endian = env::var_os("CARGO_CFG_TARGET_ENDIAN").unwrap();
+        let endian = env::var_os("CARGO_CFG_TARGET_ENDIAN")
+            .ok_or(anyhow!("CARGO_CFG_TARGET_ENDIAN not set"))?;
         let target = if endian == "big" {
             "bpfeb"
         } else if endian == "little" {
             "bpfel"
         } else {
-            panic!("unsupported endian={:?}", endian)
+            return Err(anyhow!("unsupported endian={endian:?}"));
         };
 
-        let libbpf_dir = manifest_dir
-            .parent()
-            .unwrap()
-            .parent()
-            .unwrap()
-            .join(LIBBPF_DIR);
-        println!("cargo:rerun-if-changed={}", libbpf_dir.to_str().unwrap());
+        let libbpf_dir = workspace_root.join(LIBBPF_DIR);
+        println!("cargo:rerun-if-changed={libbpf_dir}");
 
         let libbpf_headers_dir = out_dir.join("libbpf_headers");
 
@@ -84,15 +97,15 @@ fn main() {
                 .arg(libbpf_dir.join("src"))
                 .arg(includedir)
                 .arg("install_headers"),
-        )
-        .unwrap();
+        )?;
 
         let bpf_dir = manifest_dir.join("bpf");
 
         let mut target_arch = OsString::new();
         target_arch.push("-D__TARGET_ARCH_");
 
-        let arch = env::var_os("CARGO_CFG_TARGET_ARCH").unwrap();
+        let arch =
+            env::var_os("CARGO_CFG_TARGET_ARCH").ok_or(anyhow!("CARGO_CFG_TARGET_ARCH not set"))?;
         if arch == "x86_64" {
             target_arch.push("x86");
         } else if arch == "aarch64" {
@@ -125,9 +138,12 @@ fn main() {
         for (src, build_btf) in C_BPF {
             let dst = out_dir.join(src).with_extension("o");
             let src = bpf_dir.join(src);
-            println!("cargo:rerun-if-changed={}", src.to_str().unwrap());
+            {
+                let src = src.to_str().with_context(|| format!("{src:?}"))?;
+                println!("cargo:rerun-if-changed={src}");
+            }
 
-            exec(clang().arg(&src).arg("-o").arg(&dst)).unwrap();
+            exec(clang().arg(&src).arg("-o").arg(&dst))?;
 
             if *build_btf {
                 let mut cmd = clang();
@@ -137,10 +153,10 @@ fn main() {
                     .args(["-o", "-"])
                     .stdout(Stdio::piped())
                     .spawn()
-                    .unwrap_or_else(|err| panic!("failed to spawn {cmd:?}: {err}"));
+                    .with_context(|| format!("failed to spawn {cmd:?}"))?;
 
                 let Child { stdout, .. } = &mut child;
-                let stdout = stdout.take().unwrap();
+                let stdout = stdout.take().expect("stdout");
 
                 let dst = dst.with_extension("target.o");
 
@@ -154,25 +170,26 @@ fn main() {
                         .arg(output)
                         .arg("-")
                         .stdin(stdout),
-                )
-                .unwrap();
+                )?;
 
                 let output = child
                     .wait_with_output()
-                    .unwrap_or_else(|err| panic!("failed to wait for {cmd:?}: {err}"));
+                    .with_context(|| format!("failed to wait for {cmd:?}"))?;
                 let Output { status, .. } = &output;
-                assert_eq!(status.code(), Some(0), "{cmd:?} failed: {output:?}");
+                if !status.success() {
+                    return Err(anyhow!("{cmd:?} failed: {status:?}"));
+                }
             }
         }
 
-        aya_build::build_ebpf([integration_ebpf_package]).unwrap();
+        aya_build::build_ebpf([integration_ebpf_package])?;
     } else {
         for (src, build_btf) in C_BPF {
             let dst = out_dir.join(src).with_extension("o");
-            fs::write(&dst, []).unwrap_or_else(|err| panic!("failed to create {dst:?}: {err}"));
+            fs::write(&dst, []).with_context(|| format!("failed to create {dst:?}"))?;
             if *build_btf {
                 let dst = dst.with_extension("target.o");
-                fs::write(&dst, []).unwrap_or_else(|err| panic!("failed to create {dst:?}: {err}"));
+                fs::write(&dst, []).with_context(|| format!("failed to create {dst:?}"))?;
             }
         }
 
@@ -182,7 +199,8 @@ fn main() {
                 continue;
             }
             let dst = out_dir.join(name);
-            fs::write(&dst, []).unwrap_or_else(|err| panic!("failed to create {dst:?}: {err}"));
+            fs::write(&dst, []).with_context(|| format!("failed to create {dst:?}"))?;
         }
     }
+    Ok(())
 }