Support Heroku-24 and ARM architecture

Heroku 24 stack image supports both arm64 and amd64. The Ruby binaries are available on heroku-24 compiled to these two stacks heroku/docker-heroku-ruby-builder#38. The buildpack adds support by:

- Updating the `buildpackl.toml` to include ARM architecture
- Using architecture information to build the URL for Ubuntu 24.04 (heroku-24)
- Integration testing on all supported Ubuntu versions

buildpacks/ruby/buildpack.toml

@@ -28,5 +28,17 @@ version = "20.04"
 name = "ubuntu"
 version = "22.04"
 
+[[targets.distros]]
+name = "ubuntu"
+version = "24.04"
+
+[[targets]]
+os = "linux"
+arch = "arm64"
+
+[[targets.distros]]
+name = "ubuntu"
+version = "24.04"
+
 [metadata.release]
 image = { repository = "docker.io/heroku/buildpack-ruby" }

buildpacks/ruby/src/layers/ruby_install_layer.rs

@@ -236,11 +236,18 @@ fn download_url(
     let filename = format!("ruby-{version}.tgz");
     let base = "https://heroku-buildpack-ruby.s3.us-east-1.amazonaws.com";
     let mut url = Url::parse(base).map_err(RubyInstallError::UrlParseError)?;
+    {
+        let mut segments = url
+            .path_segments_mut()
+            .map_err(|()| RubyInstallError::InvalidBaseUrl(String::from(base)))?;
+
+        segments.push(&target.stack_name().map_err(RubyInstallError::TargetError)?);
+        if target.is_arch_aware() {
+            segments.push(&target.cpu_architecture);
+        }
+        segments.push(&filename);
+    }
 
-    url.path_segments_mut()
-        .map_err(|()| RubyInstallError::InvalidBaseUrl(String::from(base)))?
-        .push(&target.stack_name().map_err(RubyInstallError::TargetError)?)
-        .push(&filename);
     Ok(url)
 }
 

buildpacks/ruby/src/target_id.rs

@@ -1,28 +1,30 @@
-use serde::{Deserialize, Serialize};
-
-#[derive(Deserialize, Serialize, Debug, Clone, PartialEq, Eq)]
-#[serde(deny_unknown_fields)]
+#[derive(Debug, Clone, PartialEq, Eq)]
 pub(crate) struct TargetId {
     pub(crate) distro_name: String,
     pub(crate) distro_version: String,
     pub(crate) cpu_architecture: String,
 }
-
+const ARCH_AWARE_VERSIONS: &[&str] = &["24.04"];
 const DISTRO_VERSION_STACK: &[(&str, &str, &str)] = &[
     ("ubuntu", "20.04", "heroku-20"),
     ("ubuntu", "22.04", "heroku-22"),
+    ("ubuntu", "24.04", "heroku-24"),
 ];
 
 #[derive(Debug, thiserror::Error)]
 pub(crate) enum TargetIdError {
-    #[error("Distro name and version {0}-{1} is not supported. Must be one of: {}", DISTRO_VERSION_STACK.iter().map(|&(name, version, _)| format!("{name}-{version}")).collect::<Vec<_>>().join(", "))]
+    #[error("Distro name and version '{0}-{1}' is not supported. Must be one of: {}", DISTRO_VERSION_STACK.iter().map(|&(name, version, _)| format!("'{name}-{version}'")).collect::<Vec<_>>().join(", "))]
     UnknownDistroNameVersionCombo(String, String),
 
-    #[error("Cannot convert stack name {0} into a target OS. Must be one of: {}", DISTRO_VERSION_STACK.iter().map(|&(_, _, stack)| String::from(stack)).collect::<Vec<_>>().join(", "))]
+    #[error("Cannot convert stack name '{0}' into a target OS. Must be one of: {}", DISTRO_VERSION_STACK.iter().map(|&(_, _, stack)| format!("'{stack}'")).collect::<Vec<_>>().join(", "))]
     UnknownStack(String),
 }
 
 impl TargetId {
+    pub(crate) fn is_arch_aware(&self) -> bool {
+        ARCH_AWARE_VERSIONS.contains(&self.distro_version.as_str())
+    }
+
     pub(crate) fn stack_name(&self) -> Result<String, TargetIdError> {
         DISTRO_VERSION_STACK
             .iter()
@@ -53,6 +55,13 @@ impl TargetId {
 mod test {
     use super::*;
 
+    #[test]
+    fn test_arch_aware_versions_are_also_known_as_a_stack() {
+        for version in ARCH_AWARE_VERSIONS {
+            assert!(DISTRO_VERSION_STACK.iter().any(|&(_, v, _)| &v == version));
+        }
+    }
+
     #[test]
     fn test_stack_name() {
         assert_eq!(

buildpacks/ruby/tests/integration_test.rs

@@ -16,6 +16,11 @@ use ureq::Response;
 #[test]
 #[ignore = "integration test"]
 fn test_migrating_metadata() {
+    // This test is a placeholder for when a change modifies metadata structures.
+    // Remove the return and update the `buildpack-ruby` reference to the latest version.
+    #![allow(unreachable_code)]
+    return;
+
     let builder = "heroku/builder:22";
     let app_dir = "tests/fixtures/default_ruby";
 
@@ -57,9 +62,26 @@ fn test_default_app_ubuntu20() {
 
 #[test]
 #[ignore = "integration test"]
-fn test_default_app_latest_distro() {
+fn test_default_app_ubuntu22() {
     TestRunner::default().build(
         BuildConfig::new("heroku/builder:22", "tests/fixtures/default_ruby"),
+        |context| {
+            println!("{}", context.pack_stdout);
+            assert_contains!(context.pack_stdout, "# Heroku Ruby Buildpack");
+            assert_contains!(
+                context.pack_stdout,
+                r#"`BUNDLE_BIN="/layers/heroku_ruby/gems/bin" BUNDLE_CLEAN="1" BUNDLE_DEPLOYMENT="1" BUNDLE_GEMFILE="/workspace/Gemfile" BUNDLE_PATH="/layers/heroku_ruby/gems" BUNDLE_WITHOUT="development:test" bundle install`"#);
+
+            assert_contains!(context.pack_stdout, "Installing webrick");
+        },
+    );
+}
+
+#[test]
+#[ignore = "integration test"]
+fn test_default_app_latest_distro() {
+    TestRunner::default().build(
+        BuildConfig::new("heroku/builder:24", "tests/fixtures/default_ruby"),
         |context| {
             println!("{}", context.pack_stdout);
             assert_contains!(context.pack_stdout, "# Heroku Ruby Buildpack");