specify erl path from cli

Summary:
in buck env everything should be hermetic, so we can't rely on erl in the path.
this diff adds an option to specify path to `erl` binary for any command.
If the option is not specified `elp` will use `erl` from `$PATH`

this option will be used in D55965578

Reviewed By: alanz

Differential Revision: D56197691

fbshipit-source-id: 51f735d25e5006c558b7abdb80a0a53b7a0ea256

crates/elp/src/bin/args.rs

@@ -326,6 +326,8 @@ pub enum Command {
 pub struct Args {
     #[bpaf(argument("LOG_FILE"))]
     pub log_file: Option<PathBuf>,
+    #[bpaf(argument("ERL"))]
+    pub erl: Option<PathBuf>,
     pub no_log_buffering: bool,
     #[bpaf(external(command))]
     pub command: Command,

crates/elp/src/bin/main.rs

@@ -23,6 +23,7 @@ use elp_log::timeit;
 use elp_log::FileLogger;
 use elp_log::Logger;
 use elp_project_model::eqwalizer_support;
+use elp_project_model::otp::ERL;
 use include_dir::include_dir;
 use include_dir::Dir;
 use lsp_server::Connection;
@@ -75,12 +76,24 @@ fn handle_res(result: Result<()>, stderr: &mut dyn Write) -> i32 {
     }
 }
 
-fn try_main(cli: &mut dyn Cli, args: Args) -> Result<()> {
-    let logger = setup_logging(args.log_file, args.no_log_buffering)?;
+fn setup_static(args: &Args) {
     if let Err(err) = eqwalizer_support::setup_eqwalizer_support(&EQWALIZER_SUPPORT_DIR) {
         log::warn!("Failed to setup eqwalizer_support: {}", err);
     }
-    INIT.call_once(setup_thread_pool);
+    if let Some(erl) = &args.erl {
+        let path = fs::canonicalize(erl).expect("erl path should be valid");
+        let mut erl = ERL.write().unwrap();
+        *erl = path.to_string_lossy().to_string();
+    }
+}
+
+fn try_main(cli: &mut dyn Cli, args: Args) -> Result<()> {
+    let logger = setup_logging(&args.log_file, args.no_log_buffering)?;
+
+    INIT.call_once(|| {
+        setup_static(&args);
+        setup_thread_pool();
+    });
     match args.command {
         args::Command::RunServer(_) => run_server(logger)?,
         args::Command::ParseAll(args) => erlang_service_cli::parse_all(&args, cli)?,
@@ -113,7 +126,7 @@ fn try_main(cli: &mut dyn Cli, args: Args) -> Result<()> {
     Ok(())
 }
 
-fn setup_logging(log_file: Option<PathBuf>, no_buffering: bool) -> Result<Logger> {
+fn setup_logging(log_file: &Option<PathBuf>, no_buffering: bool) -> Result<Logger> {
     env::set_var("RUST_BACKTRACE", "short");
 
     let log_file = match log_file {

crates/elp/src/resources/test/help.stdout

@@ -1,7 +1,8 @@
-Usage: [--log-file LOG_FILE] [--no-log-buffering] [COMMAND ...]
+Usage: [--log-file LOG_FILE] [--erl ERL] [--no-log-buffering] [COMMAND ...]
 
 Available options:
         --log-file <LOG_FILE>
+        --erl <ERL>
         --no-log-buffering
     -h, --help                 Prints help information
 

crates/project_model/src/otp.rs

@@ -11,10 +11,12 @@ use std::fs;
 use std::path::Path;
 use std::path::PathBuf;
 use std::process::Command;
+use std::sync::RwLock;
 
 use anyhow::bail;
 use anyhow::Result;
 use elp_log::timeit;
+use lazy_static::lazy_static;
 use paths::AbsPathBuf;
 
 use crate::ProjectAppData;
@@ -24,10 +26,15 @@ pub struct Otp {
     pub lib_dir: AbsPathBuf,
 }
 
+lazy_static! {
+    pub static ref ERL: RwLock<String> = RwLock::new("erl".to_string());
+}
+
 impl Otp {
     pub fn find_otp() -> Result<PathBuf> {
         let _timer = timeit!("find otp");
-        let output = Command::new("erl")
+        let erl = ERL.read().unwrap();
+        let output = Command::new(&*erl)
             .arg("-noshell")
             .arg("-eval")
             .arg("io:format('~s', [code:root_dir()])")