Support for CodeLLDB debugger (#156)

## What Changed?

Adds the option to attach remotely to a CodeLLDB debugging session
directly from within paralegal-flow. It uses the mechanism described
[here](https://github.com/vadimcn/codelldb/blob/v1.10.0/MANUAL.md)

Adds a `--attach-to-debugger` command line option which accepts the name
of a debugger to initiate a session with. Currently only the value
`code-lldb` is accepted. It will attach to a debugger for every analysis
target. Skipped crates (where regular rustc runs) do not attach.

## Why Does It Need To?

Vastly simplifies the process of using a debugger with the tool.

## Checklist

- [x] Above description has been filled out so that upon quash merge we
have a
  good record of what changed.
- [x] New functions, methods, types are documented. Old documentation is
updated
  if necessary
- [ ] Documentation in Notion has been updated
- [ ] Tests for new behaviors are provided
  - [ ] New test suites (if any) ave been added to the CI tests (in
`.github/workflows/rust.yml`) either as compiler test or integration
test.
*Or* justification for their omission from CI has been provided in this
PR
    description.

crates/paralegal-flow/src/args.rs

@@ -53,6 +53,7 @@ impl TryFrom<ClapArgs> for Args {
             marker_control,
             cargo_args,
             trace,
+            attach_to_debugger,
         } = value;
         let mut dump: DumpArgs = dump.into();
         if let Some(from_env) = env_var_expect_unicode("PARALEGAL_DUMP")? {
@@ -102,10 +103,17 @@ impl TryFrom<ClapArgs> for Args {
             build_config,
             marker_control,
             cargo_args,
+            attach_to_debugger,
         })
     }
 }
 
+#[derive(serde::Serialize, serde::Deserialize, clap::ValueEnum, Clone, Copy)]
+pub enum Debugger {
+    /// The CodeLLDB debugger. Learn more at <https://github.com/vadimcn/codelldb/blob/v1.10.0/MANUAL.md>.
+    CodeLldb,
+}
+
 #[derive(serde::Serialize, serde::Deserialize)]
 pub struct Args {
     /// Print additional logging output (up to the "info" level)
@@ -115,10 +123,12 @@ pub struct Args {
     result_path: std::path::PathBuf,
     /// Emit warnings instead of aborting the analysis on sanity checks
     relaxed: bool,
-
+    /// Target a specific package
     target: Option<String>,
     /// Abort the compilation after finishing the analysis
     abort_after_analysis: bool,
+    /// Make the compiler attach to a debugger
+    attach_to_debugger: Option<Debugger>,
     /// Additional arguments on marker assignment and discovery
     marker_control: MarkerControl,
     /// Additional arguments that control the flow analysis specifically
@@ -160,12 +170,15 @@ pub struct ClapArgs {
     /// Emit warnings instead of aborting the analysis on sanity checks
     #[clap(long, env = "PARALEGAL_RELAXED")]
     relaxed: bool,
-
+    /// Run paralegal only on this crate
     #[clap(long, env = "PARALEGAL_TARGET")]
     target: Option<String>,
     /// Abort the compilation after finishing the analysis
     #[clap(long, env)]
     abort_after_analysis: bool,
+    /// Attach to a debugger before running the analyses
+    #[clap(long)]
+    attach_to_debugger: Option<Debugger>,
     /// Additional arguments that control the flow analysis specifically
     #[clap(flatten, next_help_heading = "Flow Analysis")]
     anactrl: ClapAnalysisCtrl,
@@ -347,6 +360,10 @@ impl Args {
     pub fn cargo_args(&self) -> &[String] {
         &self.cargo_args
     }
+
+    pub fn attach_to_debugger(&self) -> Option<Debugger> {
+        self.attach_to_debugger
+    }
 }
 
 #[derive(serde::Serialize, serde::Deserialize, clap::Args)]

crates/paralegal-flow/src/lib.rs

@@ -62,7 +62,7 @@ pub mod rust {
     pub use mir::Location;
 }
 
-use args::{ClapArgs, LogLevelConfig};
+use args::{ClapArgs, Debugger, LogLevelConfig};
 use desc::utils::write_sep;
 use rust::*;
 
@@ -357,6 +357,10 @@ impl rustc_plugin::RustcPlugin for DfppPlugin {
             "-Zcrate-attr=register_tool(paralegal_flow)".into(),
         ]);
 
+        if let Some(dbg) = opts.attach_to_debugger() {
+            dbg.attach()
+        }
+
         debug!(
             "Arguments: {}",
             Print(|f| write_sep(f, " ", &compiler_args, Display::fmt))
@@ -372,3 +376,26 @@ impl rustc_plugin::RustcPlugin for DfppPlugin {
         .run()
     }
 }
+
+impl Debugger {
+    fn attach(self) {
+        use std::process::{id, Command};
+        use std::thread::sleep;
+        use std::time::Duration;
+
+        match self {
+            Debugger::CodeLldb => {
+                let url = format!(
+                    "vscode://vadimcn.vscode-lldb/launch/config?{{'request':'attach','pid':{}}}",
+                    id()
+                );
+                Command::new("code")
+                    .arg("--open-url")
+                    .arg(url)
+                    .output()
+                    .unwrap();
+                sleep(Duration::from_millis(1000));
+            }
+        }
+    }
+}