Fix gitignore to allow llvm source directory to be tracked

Author: ciaranra

.gitignore

@@ -4,7 +4,7 @@ tmp/
 **/.*/settings.local.json
 
 # LLVM (extracted from archive for Windows development)
-llvm/
+/llvm/
 
 # Cargo config with machine-specific LLVM paths
 .cargo/config.toml

crates/pecos-dev/src/llvm/config.rs

@@ -0,0 +1,170 @@
+//! LLVM configuration management for `.cargo/config.toml`
+
+#![allow(clippy::missing_errors_doc)]
+
+use crate::errors::{Error, Result};
+use crate::llvm::{
+    find_cargo_project_root, find_llvm_14, get_repo_root_from_manifest, is_valid_llvm_14,
+};
+use std::fs;
+use std::path::{Path, PathBuf};
+
+/// Automatically configure LLVM for PECOS
+///
+/// This function determines the best LLVM 14 installation to use and writes
+/// it to `.cargo/config.toml` with `force=true`.
+///
+/// Priority order:
+/// 1. `~/.pecos/llvm` (PECOS-managed LLVM)
+/// 2. `LLVM_SYS_140_PREFIX` environment variable
+/// 3. System LLVM 14 (Homebrew, system paths, etc.)
+///
+/// # Errors
+///
+/// Returns an error if no suitable LLVM 14 installation could be found
+pub fn auto_configure_llvm(project_root: Option<PathBuf>) -> Result<PathBuf> {
+    // Priority 1: Check ~/.pecos/ for PECOS-managed LLVM
+    if let Some(home_dir) = dirs::home_dir() {
+        let pecos_dir = home_dir.join(".pecos");
+
+        #[cfg(target_os = "windows")]
+        let pecos_llvm_paths = vec![pecos_dir.join("LLVM-14"), pecos_dir.join("llvm")];
+
+        #[cfg(not(target_os = "windows"))]
+        let pecos_llvm_paths = vec![pecos_dir.join("llvm")];
+
+        for pecos_llvm in pecos_llvm_paths {
+            if is_valid_llvm_14(&pecos_llvm) {
+                let project_root = project_root
+                    .or_else(get_repo_root_from_manifest)
+                    .or_else(find_cargo_project_root)
+                    .ok_or_else(|| Error::Config("Could not find Cargo project root".into()))?;
+
+                write_cargo_config(&project_root, &pecos_llvm, true)?;
+                return Ok(pecos_llvm);
+            }
+        }
+    }
+
+    // Priority 2: Check LLVM_SYS_140_PREFIX
+    if let Ok(sys_prefix) = std::env::var("LLVM_SYS_140_PREFIX") {
+        let path = PathBuf::from(&sys_prefix);
+        if is_valid_llvm_14(&path) {
+            let project_root = project_root
+                .or_else(get_repo_root_from_manifest)
+                .or_else(find_cargo_project_root)
+                .ok_or_else(|| Error::Config("Could not find Cargo project root".into()))?;
+
+            write_cargo_config(&project_root, &path, true)?;
+            return Ok(path);
+        }
+    }
+
+    // Priority 3: Scan system for LLVM 14
+    let repo_root = get_repo_root_from_manifest();
+    if let Some(detected_path) = find_llvm_14(repo_root) {
+        let project_root = project_root
+            .or_else(get_repo_root_from_manifest)
+            .or_else(find_cargo_project_root)
+            .ok_or_else(|| Error::Config("Could not find Cargo project root".into()))?;
+
+        write_cargo_config(&project_root, &detected_path, true)?;
+        return Ok(detected_path);
+    }
+
+    Err(Error::Llvm("No suitable LLVM 14 installation found".into()))
+}
+
+/// Write or update `.cargo/config.toml` with LLVM configuration
+///
+/// # Arguments
+/// * `project_root` - Path to the Cargo project root
+/// * `llvm_path` - Path to the LLVM installation
+/// * `force` - If true, use `force=true` to override shell environment variables
+pub fn write_cargo_config(project_root: &Path, llvm_path: &Path, force: bool) -> Result<()> {
+    let cargo_dir = project_root.join(".cargo");
+    let config_path = cargo_dir.join("config.toml");
+
+    fs::create_dir_all(&cargo_dir)?;
+
+    // Convert path to forward slashes for TOML compatibility
+    let llvm_path_str = llvm_path.to_string_lossy().replace('\\', "/");
+
+    let llvm_line = if force {
+        format!("LLVM_SYS_140_PREFIX = {{ value = \"{llvm_path_str}\", force = true }}")
+    } else {
+        format!("LLVM_SYS_140_PREFIX = \"{llvm_path_str}\"")
+    };
+
+    let existing_content = fs::read_to_string(&config_path).unwrap_or_default();
+
+    // Check if config already has correct LLVM_SYS_140_PREFIX
+    if existing_content.contains("LLVM_SYS_140_PREFIX") {
+        let simple_format = format!("LLVM_SYS_140_PREFIX = \"{llvm_path_str}\"");
+        let force_format =
+            format!("LLVM_SYS_140_PREFIX = {{ value = \"{llvm_path_str}\", force = true }}");
+
+        if (force && existing_content.contains(&force_format))
+            || (!force && existing_content.contains(&simple_format))
+        {
+            return Ok(());
+        }
+
+        // Update existing configuration
+        let lines: Vec<&str> = existing_content.lines().collect();
+        let mut new_lines = Vec::new();
+        let mut in_env_section = false;
+        let mut updated = false;
+        let mut skip_next_lines = 0;
+
+        for (i, line) in lines.iter().enumerate() {
+            if skip_next_lines > 0 {
+                skip_next_lines -= 1;
+                continue;
+            }
+
+            let trimmed = line.trim();
+
+            if trimmed.starts_with('[') {
+                in_env_section = trimmed == "[env]";
+            }
+
+            if in_env_section && trimmed.starts_with("LLVM_SYS_140_PREFIX") {
+                new_lines.push(llvm_line.clone());
+                updated = true;
+
+                if trimmed.contains('{') && !trimmed.contains('}') {
+                    for line in lines.iter().skip(i + 1) {
+                        skip_next_lines += 1;
+                        if line.contains('}') {
+                            break;
+                        }
+                    }
+                }
+            } else {
+                new_lines.push((*line).to_string());
+            }
+        }
+
+        if updated {
+            fs::write(&config_path, new_lines.join("\n"))?;
+            return Ok(());
+        }
+    }
+
+    // No LLVM configuration exists, append it
+    let llvm_config = format!(
+        "\n# LLVM configuration for PECOS\n\
+         [env]\n\
+         {llvm_line}\n"
+    );
+
+    let new_content = if existing_content.is_empty() {
+        llvm_config.trim_start().to_string()
+    } else {
+        format!("{existing_content}{llvm_config}")
+    };
+
+    fs::write(&config_path, new_content)?;
+    Ok(())
+}