Implement standalone executable compilation (#140)

Cargo.toml

@@ -110,7 +110,6 @@ tokio-tungstenite = { version = "0.20", features = ["rustls-tls-webpki-roots"] }
 ### DATETIME
 chrono = "0.4"
 chrono_lc = "0.1"
-num-traits = "0.2"
 
 ### CLI
 

src/cli/build.rs

@@ -0,0 +1,64 @@
+use std::{env, path::Path, process::ExitCode};
+
+use anyhow::Result;
+use console::style;
+use mlua::Compiler as LuaCompiler;
+use tokio::{fs, io::AsyncWriteExt as _};
+
+use crate::executor::MetaChunk;
+
+/**
+    Compiles and embeds the bytecode of a given lua file to form a standalone
+    binary, then writes it to an output file, with the required permissions.
+*/
+#[allow(clippy::similar_names)]
+pub async fn build_standalone(
+    input_path: impl AsRef<Path>,
+    output_path: impl AsRef<Path>,
+    source_code: impl AsRef<[u8]>,
+) -> Result<ExitCode> {
+    let input_path_displayed = input_path.as_ref().display();
+    let output_path_displayed = output_path.as_ref().display();
+
+    // First, we read the contents of the lune interpreter as our starting point
+    println!(
+        "Creating standalone binary using {}",
+        style(input_path_displayed).green()
+    );
+    let mut patched_bin = fs::read(env::current_exe()?).await?;
+
+    // Compile luau input into bytecode
+    let bytecode = LuaCompiler::new()
+        .set_optimization_level(2)
+        .set_coverage_level(0)
+        .set_debug_level(1)
+        .compile(source_code);
+
+    // Append the bytecode / metadata to the end
+    let meta = MetaChunk { bytecode };
+    patched_bin.extend_from_slice(&meta.to_bytes());
+
+    // And finally write the patched binary to the output file
+    println!(
+        "Writing standalone binary to {}",
+        style(output_path_displayed).blue()
+    );
+    write_executable_file_to(output_path, patched_bin).await?;
+
+    Ok(ExitCode::SUCCESS)
+}
+
+async fn write_executable_file_to(path: impl AsRef<Path>, bytes: impl AsRef<[u8]>) -> Result<()> {
+    let mut options = fs::OpenOptions::new();
+    options.write(true).create(true).truncate(true);
+
+    #[cfg(unix)]
+    {
+        options.mode(0o755); // Read & execute for all, write for owner
+    }
+
+    let mut file = options.open(path).await?;
+    file.write_all(bytes.as_ref()).await?;
+
+    Ok(())
+}

src/cli/mod.rs

@@ -1,4 +1,4 @@
-use std::{fmt::Write as _, process::ExitCode};
+use std::{env, fmt::Write as _, path::PathBuf, process::ExitCode};
 
 use anyhow::{Context, Result};
 use clap::Parser;
@@ -9,6 +9,7 @@ use tokio::{
     io::{stdin, AsyncReadExt},
 };
 
+pub(crate) mod build;
 pub(crate) mod gen;
 pub(crate) mod repl;
 pub(crate) mod setup;
@@ -20,6 +21,8 @@ use utils::{
     listing::{find_lune_scripts, sort_lune_scripts, write_lune_scripts_list},
 };
 
+use self::build::build_standalone;
+
 /// A Luau script runner
 #[derive(Parser, Debug, Default, Clone)]
 #[command(version, long_about = None)]
@@ -44,6 +47,9 @@ pub struct Cli {
     /// Generate a Lune documentation file for Luau LSP
     #[clap(long, hide = true)]
     generate_docs_file: bool,
+    /// Build a Luau file to an OS-Native standalone executable
+    #[clap(long)]
+    build: bool,
 }
 
 #[allow(dead_code)]
@@ -116,6 +122,7 @@ impl Cli {
 
             return Ok(ExitCode::SUCCESS);
         }
+
         // Generate (save) definition files, if wanted
         let generate_file_requested = self.setup
             || self.generate_luau_types
@@ -143,14 +150,17 @@ impl Cli {
             if generate_file_requested {
                 return Ok(ExitCode::SUCCESS);
             }
-            // If we did not generate any typedefs we know that the user did not
-            // provide any other options, and in that case we should enter the REPL
+
+            // If not in a standalone context and we don't have any arguments
+            // display the interactive REPL interface
             return repl::show_interface().await;
         }
+
         // Figure out if we should read from stdin or from a file,
         // reading from stdin is marked by passing a single "-"
         // (dash) as the script name to run to the cli
         let script_path = self.script_path.unwrap();
+
         let (script_display_name, script_contents) = if script_path == "-" {
             let mut stdin_contents = Vec::new();
             stdin()
@@ -165,6 +175,22 @@ impl Cli {
             let file_display_name = file_path.with_extension("").display().to_string();
             (file_display_name, file_contents)
         };
+
+        if self.build {
+            let output_path =
+                PathBuf::from(script_path.clone()).with_extension(env::consts::EXE_EXTENSION);
+
+            return Ok(
+                match build_standalone(script_path, output_path, script_contents).await {
+                    Ok(exitcode) => exitcode,
+                    Err(err) => {
+                        eprintln!("{err}");
+                        ExitCode::FAILURE
+                    }
+                },
+            );
+        }
+
         // Create a new lune object with all globals & run the script
         let result = Lune::new()
             .with_args(self.script_args)

src/executor.rs

@@ -0,0 +1,83 @@
+use std::{env, process::ExitCode};
+
+use lune::Lune;
+
+use anyhow::{bail, Result};
+use tokio::fs;
+
+const MAGIC: &[u8; 8] = b"cr3sc3nt";
+
+/**
+    Metadata for a standalone Lune executable. Can be used to
+    discover and load the bytecode contained in a standalone binary.
+*/
+#[derive(Debug, Clone)]
+pub struct MetaChunk {
+    pub bytecode: Vec<u8>,
+}
+
+impl MetaChunk {
+    /**
+        Tries to read a standalone binary from the given bytes.
+    */
+    pub fn from_bytes(bytes: impl AsRef<[u8]>) -> Result<Self> {
+        let bytes = bytes.as_ref();
+        if bytes.len() < 16 || !bytes.ends_with(MAGIC) {
+            bail!("not a standalone binary")
+        }
+
+        // Extract bytecode size
+        let bytecode_size_bytes = &bytes[bytes.len() - 16..bytes.len() - 8];
+        let bytecode_size =
+            usize::try_from(u64::from_be_bytes(bytecode_size_bytes.try_into().unwrap()))?;
+
+        // Extract bytecode
+        let bytecode = bytes[bytes.len() - 16 - bytecode_size..].to_vec();
+
+        Ok(Self { bytecode })
+    }
+
+    /**
+        Writes the metadata chunk to a byte vector, to later bet read using `from_bytes`.
+    */
+    pub fn to_bytes(&self) -> Vec<u8> {
+        let mut bytes = Vec::new();
+        bytes.extend_from_slice(&self.bytecode);
+        bytes.extend_from_slice(&(self.bytecode.len() as u64).to_be_bytes());
+        bytes.extend_from_slice(MAGIC);
+        bytes
+    }
+}
+
+/**
+    Returns whether or not the currently executing Lune binary
+    is a standalone binary, and if so, the bytes of the binary.
+*/
+pub async fn check_env() -> (bool, Vec<u8>) {
+    let path = env::current_exe().expect("failed to get path to current running lune executable");
+    let contents = fs::read(path).await.unwrap_or_default();
+    let is_standalone = contents.ends_with(MAGIC);
+    (is_standalone, contents)
+}
+
+/**
+    Discovers, loads and executes the bytecode contained in a standalone binary.
+*/
+pub async fn run_standalone(patched_bin: impl AsRef<[u8]>) -> Result<ExitCode> {
+    // The first argument is the path to the current executable
+    let args = env::args().skip(1).collect::<Vec<_>>();
+    let meta = MetaChunk::from_bytes(patched_bin).expect("must be a standalone binary");
+
+    let result = Lune::new()
+        .with_args(args)
+        .run("STANDALONE", meta.bytecode)
+        .await;
+
+    Ok(match result {
+        Err(err) => {
+            eprintln!("{err}");
+            ExitCode::FAILURE
+        }
+        Ok(code) => code,
+    })
+}

src/main.rs

@@ -13,6 +13,7 @@ use std::process::ExitCode;
 use clap::Parser;
 
 pub(crate) mod cli;
+pub(crate) mod executor;
 
 use cli::Cli;
 use console::style;
@@ -26,6 +27,15 @@ async fn main() -> ExitCode {
         .with_timer(tracing_subscriber::fmt::time::uptime())
         .with_level(true)
         .init();
+
+    let (is_standalone, bin) = executor::check_env().await;
+
+    if is_standalone {
+        // It's fine to unwrap here since we don't want to continue
+        // if something fails
+        return executor::run_standalone(bin).await.unwrap();
+    }
+
     match Cli::parse().run().await {
         Ok(code) => code,
         Err(err) => {