perf: reduce IO

crates/erg_common/env.rs

@@ -3,7 +3,7 @@ use std::path::{Path, PathBuf};
 use std::sync::OnceLock;
 
 use crate::normalize_path;
-use crate::python_util::get_sys_path;
+use crate::python_util::{_opt_which_python, get_sys_path};
 use crate::style::colors::*;
 use crate::style::RESET;
 
@@ -115,6 +115,7 @@ pub static ERG_PYSTD_PATH: OnceLock<PathBuf> = OnceLock::new();
 pub static ERG_PKGS_PATH: OnceLock<PathBuf> = OnceLock::new();
 pub static PYTHON_SYS_PATH: OnceLock<Vec<PathBuf>> = OnceLock::new();
 pub static PYTHON_SITE_PACKAGES: OnceLock<Vec<PathBuf>> = OnceLock::new();
+pub static PYTHON_PATH: OnceLock<Result<String, String>> = OnceLock::new();
 
 /// == `Path::new("~/.erg")` if ERG_PATH is not set
 pub fn erg_path() -> &'static PathBuf {
@@ -154,6 +155,10 @@ pub fn python_site_packages() -> &'static Vec<PathBuf> {
     PYTHON_SITE_PACKAGES.get_or_init(|| _python_site_packages().collect())
 }
 
+pub fn opt_which_python() -> Result<&'static String, &'static String> {
+    PYTHON_PATH.get_or_init(_opt_which_python).as_ref()
+}
+
 pub fn is_std_decl_path(path: &Path) -> bool {
     path.starts_with(erg_pystd_path().as_path())
 }

crates/erg_common/lib.rs

@@ -1,6 +1,6 @@
 //! provides utilities for parser, compiler, and vm crate.
 use std::fmt;
-use std::path::PathBuf;
+use std::path::{Component, Path, PathBuf};
 
 pub mod cache;
 pub mod config;
@@ -192,6 +192,33 @@ pub fn normalize_path(path: PathBuf) -> PathBuf {
     PathBuf::from(lower)
 }
 
+pub fn cheap_canonicalize_path(path: &Path) -> PathBuf {
+    let mut components = path.components().peekable();
+    let mut ret = if let Some(c @ Component::Prefix(..)) = components.peek().cloned() {
+        components.next();
+        PathBuf::from(c.as_os_str())
+    } else {
+        PathBuf::new()
+    };
+
+    for component in components {
+        match component {
+            Component::Prefix(..) => unreachable!(),
+            Component::RootDir => {
+                ret.push(component.as_os_str());
+            }
+            Component::CurDir => {}
+            Component::ParentDir => {
+                ret.pop();
+            }
+            Component::Normal(c) => {
+                ret.push(c);
+            }
+        }
+    }
+    ret
+}
+
 /// ```
 /// use erg_common::trim_eliminate_top_indent;
 /// let code = r#"

crates/erg_common/pathutil.rs

@@ -7,7 +7,8 @@ use std::path::{Component, Path, PathBuf};
 use crate::consts::PYTHON_MODE;
 use crate::env::erg_pkgs_path;
 use crate::traits::Immutable;
-use crate::{normalize_path, Str};
+use crate::vfs::VFS;
+use crate::{cheap_canonicalize_path, normalize_path, Str};
 
 /// Guaranteed equivalence path.
 ///
@@ -59,7 +60,7 @@ impl Deref for NormalizedPathBuf {
 
 impl NormalizedPathBuf {
     pub fn new(path: PathBuf) -> Self {
-        NormalizedPathBuf(normalize_path(path.canonicalize().unwrap_or(path)))
+        NormalizedPathBuf(normalize_path(cheap_canonicalize_path(&path)))
     }
 
     pub fn as_path(&self) -> &Path {
@@ -71,7 +72,7 @@ impl NormalizedPathBuf {
     }
 
     pub fn try_read(&self) -> std::io::Result<String> {
-        std::fs::read_to_string(&self.0)
+        VFS.read(self)
     }
 }
 

crates/erg_common/python_util.rs

@@ -7,6 +7,7 @@ use std::io::Write;
 use std::path::{Path, PathBuf};
 use std::process::{Command, ExitStatus, Stdio};
 
+use crate::env::opt_which_python;
 use crate::fn_name_full;
 use crate::io::Output;
 use crate::pathutil::remove_verbatim;
@@ -608,7 +609,7 @@ fn get_poetry_virtualenv_path() -> Option<String> {
         .then_some(path.trim().to_string())
 }
 
-pub fn opt_which_python() -> Result<String, String> {
+pub fn _opt_which_python() -> Result<String, String> {
     if let Some(path) = which_python_from_toml() {
         return Ok(path);
     }
@@ -642,8 +643,8 @@ pub fn opt_which_python() -> Result<String, String> {
     Ok(res)
 }
 
-fn which_python() -> String {
-    opt_which_python().unwrap()
+fn which_python() -> &'static str {
+    opt_which_python().as_ref().unwrap()
 }
 
 pub fn detect_magic_number(py_command: &str) -> u32 {
@@ -672,7 +673,7 @@ pub fn detect_magic_number(py_command: &str) -> u32 {
 }
 
 pub fn env_magic_number() -> u32 {
-    detect_magic_number(&which_python())
+    detect_magic_number(which_python())
 }
 
 pub fn module_exists(py_command: &str, module: &str) -> bool {
@@ -786,7 +787,7 @@ pub fn get_python_version(py_command: &str) -> Option<PythonVersion> {
 }
 
 pub fn env_python_version() -> Option<PythonVersion> {
-    get_python_version(&which_python())
+    get_python_version(which_python())
 }
 
 pub fn get_sys_path(working_dir: Option<&Path>) -> Result<Vec<PathBuf>, std::io::Error> {
@@ -834,9 +835,7 @@ fn exec_pyc_in(
         "import marshal; exec(marshal.loads(open(r\"{}\", \"rb\").read()[16:]))",
         file.as_ref().display()
     );
-    let command = py_command
-        .map(ToString::to_string)
-        .unwrap_or(which_python());
+    let command = py_command.map_or_else(|| which_python().to_string(), ToString::to_string);
     let mut out = if cfg!(windows) {
         Command::new("cmd")
             .arg("/C")
@@ -876,9 +875,7 @@ pub fn exec_pyc(
     if let Some(working_dir) = working_dir {
         return exec_pyc_in(file, py_command, working_dir, args, stdout);
     }
-    let command = py_command
-        .map(ToString::to_string)
-        .unwrap_or_else(which_python);
+    let command = py_command.map_or_else(|| which_python().to_string(), ToString::to_string);
     let mut out = if cfg!(windows) {
         Command::new("cmd")
             .arg("/C")
@@ -902,9 +899,7 @@ pub fn exec_pyc(
 
 /// evaluates over a shell, cause `python` may not exist as an executable file (like pyenv)
 pub fn _eval_pyc<S: Into<String>>(file: S, py_command: Option<&str>) -> String {
-    let command = py_command
-        .map(ToString::to_string)
-        .unwrap_or_else(which_python);
+    let command = py_command.map_or_else(|| which_python().to_string(), ToString::to_string);
     let out = if cfg!(windows) {
         Command::new("cmd")
             .arg("/C")
@@ -966,7 +961,7 @@ pub fn env_spawn_py(code: &str) {
 
 pub fn spawn_py(py_command: Option<&str>, code: &str) {
     if cfg!(windows) {
-        Command::new(py_command.unwrap_or(&which_python()))
+        Command::new(py_command.unwrap_or(which_python()))
             .arg("-c")
             .arg(code)
             .spawn()
@@ -974,7 +969,7 @@ pub fn spawn_py(py_command: Option<&str>, code: &str) {
     } else {
         let exec_command = format!(
             "{} -c \"{}\"",
-            py_command.unwrap_or(&which_python()),
+            py_command.unwrap_or(which_python()),
             escape_py_code(code)
         );
         Command::new("sh")

crates/erg_compiler/build_package.rs

@@ -27,6 +27,7 @@ use erg_common::spawn::spawn_new_thread;
 use erg_common::str::Str;
 use erg_common::traits::{ExitStatus, New, Runnable, Stream};
 
+use erg_common::vfs::VFS;
 use erg_parser::ast::{ClassAttr, Expr, InlineModule, Record, RecordAttrOrIdent, VarName, AST};
 use erg_parser::build_ast::{ASTBuildable, ASTBuilder as DefaultASTBuilder};
 use erg_parser::parse::SimpleParser;
@@ -703,6 +704,7 @@ impl<ASTBuilder: ASTBuildable, HIRBuilder: Buildable>
                 .resolve_decl_path(path, cfg)
                 .or_else(|| cfg.input.resolve_real_path(path, cfg))
         };
+        VFS.cache_path(cfg.input.clone(), path.to_path_buf(), resolved.clone());
         let import_path = match resolved {
             Some(path) => path,
             None if ERG_MODE => {