refactor: wrap and handle the py ver retrieval

build.rs

@@ -1,7 +1,9 @@
 use erg_common::python_util::{env_magic_number, env_python_version};
 
 fn main() -> std::io::Result<()> {
-    let version = env_python_version();
+    let Some(version) = env_python_version() else {
+        panic!("Failed to get python version");
+    };
     if version.major != 3 {
         panic!("Python 3 is required");
     }

crates/erg_common/config.rs

@@ -376,7 +376,7 @@ impl ErgConfig {
                         .parse::<String>()
                         .expect("the value of `-py-command` is not a valid Python command");
                     cfg.py_magic_num = Some(detect_magic_number(&py_command));
-                    cfg.target_version = Some(get_python_version(&py_command));
+                    cfg.target_version = get_python_version(&py_command);
                     cfg.py_command = Some(Box::leak(py_command.into_boxed_str()));
                 }
                 "--hex-py-magic-num" | "--hex-python-magic-number" => {

crates/erg_common/python_util.rs

@@ -693,7 +693,7 @@ impl std::str::FromStr for PythonVersion {
     }
 }
 
-pub fn get_python_version(py_command: &str) -> PythonVersion {
+pub fn get_python_version(py_command: &str) -> Option<PythonVersion> {
     let out = if cfg!(windows) {
         Command::new("cmd")
             .arg("/C")
@@ -710,19 +710,19 @@ pub fn get_python_version(py_command: &str) -> PythonVersion {
             .expect("cannot get the python version")
     };
     let s_version = String::from_utf8(out.stdout).unwrap();
-    let mut iter = s_version.split(' ');
-    let mut iter = iter.nth(1).unwrap().split('.');
+    let iter = s_version.split(' ').nth(1)?;
+    let mut iter = iter.split('.');
     let major = iter.next().and_then(|i| i.parse().ok()).unwrap_or(3);
     let minor = iter.next().and_then(|i| i.parse().ok());
     let micro = iter.next().and_then(|i| i.trim_end().parse().ok());
-    PythonVersion {
+    Some(PythonVersion {
         major,
         minor,
         micro,
-    }
+    })
 }
 
-pub fn env_python_version() -> PythonVersion {
+pub fn env_python_version() -> Option<PythonVersion> {
     get_python_version(&which_python())
 }
 

crates/erg_compiler/codegen.rs

@@ -228,7 +228,12 @@ pub struct PyCodeGenerator {
 impl PyCodeGenerator {
     pub fn new(cfg: ErgConfig) -> Self {
         Self {
-            py_version: cfg.target_version.unwrap_or_else(env_python_version),
+            py_version: cfg.target_version.unwrap_or_else(|| {
+                let Some(version) = env_python_version() else {
+                    panic!("Failed to get python version");
+                };
+                version
+            }),
             cfg,
             str_cache: CacheSet::new(),
             prelude_loaded: false,

tests/embed.rs

@@ -69,7 +69,7 @@ while! do! c < 7, do!:
 
 #[test]
 fn test_transpiler_embedding3() -> Result<(), ()> {
-    if env_python_version().minor < Some(10) {
+    if env_python_version().unwrap().minor < Some(10) {
         println!("skipped: {}", fn_name!());
         return Ok(());
     }
@@ -96,7 +96,7 @@ print!(i, end:=\"\")
 
 #[test]
 fn test_transpiler_embedding4() -> Result<(), ()> {
-    if env_python_version().minor < Some(10) {
+    if env_python_version().unwrap().minor < Some(10) {
         println!("skipped: {}", fn_name!());
         return Ok(());
     }

tests/test.rs

@@ -172,7 +172,7 @@ fn exec_fib() -> Result<(), ()> {
 #[test]
 fn exec_helloworld() -> Result<(), ()> {
     // HACK: When running the test with Windows, the exit code is 1 (the cause is unknown)
-    if cfg!(windows) && env_python_version().minor >= Some(8) {
+    if cfg!(windows) && env_python_version().unwrap().minor >= Some(8) {
         expect_end_with("examples/helloworld.er", 0, 1)
     } else {
         expect_success("examples/helloworld.er", 0)
@@ -323,7 +323,7 @@ fn exec_pattern() -> Result<(), ()> {
 #[test]
 fn exec_pyimport_test() -> Result<(), ()> {
     // HACK: When running the test with Windows, the exit code is 1 (the cause is unknown)
-    if cfg!(windows) && env_python_version().minor < Some(8) {
+    if cfg!(windows) && env_python_version().unwrap().minor < Some(8) {
         expect_end_with("tests/should_ok/pyimport.er", 2, 1)
     } else {
         expect_success("tests/should_ok/pyimport.er", 2)