Project: HTTP Client in Scala Native

This project is a simple example of a console application in Scala, compiled into a native executable using Scala Native. The application sends an HTTP GET request, receives, and parses a JSON response.

Project Structure

The project is organized as an sbt multi-project and consists of two main parts:

• Main Application: Located in the root directory and contains the Scala Native application source code.
• Documentation Subproject (docs): Located in the docs/ directory and is used to generate a static website using Laika.

1. Prerequisites

To build and run this project, the following tools are required.

Prerequisite Check Script: prereq.sh

This script will check for all necessary components. If you are on a Debian/Ubuntu-based system, it will... How to use: make it executable (chmod +x prereq.sh) and run it (./prereq.sh).

2. Build and Run

All commands are executed from the project's root folder. bash sbt nativeLink ./target/scala-3.4.2/scala-native-hello-native

3. Debugging Common Errors

Problem 1: Dependency Resolution Error (ResolveException: Not Found)

Symptom: sbt cannot download a library.

Cause: Version incompatibility of the "Golden Trio": Scala Version + Scala Native Version + Library Version.

Solution:

1. Go to Scaladex.
2. Find each library and check which of its versions are compatible with your Scala version (3.x) and Scala Native (0.5).
3. Select a working combination of versions in build.sbt and project/plugins.sbt.
4. Ensure that triple percent signs (%%%) are used for Scala Native dependencies.

Problem 2: Native Compilation/Linking Errors

Symptom: sbt downloaded dependencies, but the build fails with an error from clang or ld.

Cause A: fatal error: 'some/file.h' file not found. This means a dev package of a system library is missing.

Solution: Find the corresponding dev package by file name (curl.h -> libcurl) (e.g., libcurl4-openssl-dev) and install it via the system package manager (sudo apt-get install ...).

Cause B: /usr/bin/ld: cannot find -l.... This means the linker cannot find the system library itself. Often this is a "dependency of a dependency".

Solution: By name (-lidn2 -> libidn2) find the corresponding dev package (libidn2-dev) and install it.

Problem 3: Binary Incompatibility Error (binary-incompatible version of NIR)

Symptom: Deep AssertionError from the Scala Native compiler itself.

Cause: Version conflict between the sbt-scala-native plugin and Scala Native system libraries (nativelib, javalib) brought in by one of the dependencies.

Solution:

1. Look in the error log for which version of the system library it is trying to use (e.g., nativelib version 0.5.8).
2. Update the plugin version in project/plugins.sbt to the same version (0.5.8).
3. If this does not help, perform a full cache cleanup: rm -rf ~/.cache/coursier/.

4. CI/CD - Continuous Integration

This project uses GitHub Actions to automatically build, test, and analyze code on every change. The process consists of two independent workflows:

Main Workflow (.github/workflows/scala.yml)

This workflow is responsible for the main application: 1. Setup Dependencies: Configures Java 17, sbt, and system libraries required for Scala Native (clang, libcurl). 2. Run Tests: Executes sbt test to verify code correctness. 3. Code Quality Analysis: Runs the SonarCloud scanner to find bugs, vulnerabilities, and code smells. Analysis results are available on SonarCloud and directly in Pull Requests. 4. Dependency Graph: Submits project dependency information to GitHub to track vulnerabilities.

Website Workflow (.github/workflows/pages.yml)

This workflow is responsible for building and publishing the GitHub Pages site: 1. Generate Site: Runs cd docs && sbt laikaSite to generate HTML files using the Laika library. 2. Publish: Automatically publishes the generated files to GitHub Pages.