Safer Rust (catch panic with catch_unwind())

Crossing boundaries of multiple languages is tricky, but we can do at
least something about this, in particular, use catch_unwind() [1] to
catch possible panic!()s.

  [1]: https://doc.rust-lang.org/std/panic/fn.catch_unwind.html

Signed-off-by: Azat Khuzhin <a.khuzhin@semrush.com>

rust/prql/src/lib.rs

@@ -2,6 +2,7 @@ use prql_compiler::sql::Dialect;
 use prql_compiler::{Options, Target};
 use std::ffi::{c_char, CString};
 use std::slice;
+use std::panic;
 
 fn set_output(result: String, out: *mut *mut u8, out_size: *mut u64) {
     assert!(!out_size.is_null());
@@ -13,8 +14,7 @@ fn set_output(result: String, out: *mut *mut u8, out_size: *mut u64) {
     *out_ptr = CString::new(result).unwrap().into_raw() as *mut u8;
 }
 
-#[no_mangle]
+pub unsafe extern "C" fn prql_to_sql_impl(
-pub unsafe extern "C" fn prql_to_sql(
     query: *const u8,
     size: u64,
     out: *mut *mut u8,
@@ -50,6 +50,23 @@ pub unsafe extern "C" fn prql_to_sql(
     }
 }
 
+#[no_mangle]
+pub unsafe extern "C" fn prql_to_sql(
+    query: *const u8,
+    size: u64,
+    out: *mut *mut u8,
+    out_size: *mut u64,
+) -> i64 {
+    let ret = panic::catch_unwind(|| {
+        return prql_to_sql_impl(query, size, out, out_size);
+    });
+    return match ret {
+        // NOTE: using cxxbridge we can return proper Result<> type.
+        Err(_err) => 1,
+        Ok(res) => res,
+    }
+}
+
 #[no_mangle]
 pub unsafe extern "C" fn prql_free_pointer(ptr_to_free: *mut u8) {
     std::mem::drop(CString::from_raw(ptr_to_free as *mut c_char));

rust/skim/src/lib.rs

@@ -1,6 +1,7 @@
 use skim::prelude::*;
 use term::terminfo::TermInfo;
 use cxx::{CxxString, CxxVector};
+use std::panic;
 
 #[cxx::bridge]
 mod ffi {
@@ -36,7 +37,7 @@ impl SkimItem for Item {
     }
 }
 
-fn skim(prefix: &CxxString, words: &CxxVector<CxxString>) -> Result<String, String> {
+fn skim_impl(prefix: &CxxString, words: &CxxVector<CxxString>) -> Result<String, String> {
     // Let's check is terminal available. To avoid panic.
     if let Err(err) = TermInfo::from_env() {
         return Err(format!("{}", err));
@@ -89,3 +90,22 @@ fn skim(prefix: &CxxString, words: &CxxVector<CxxString>) -> Result<String, Stri
     }
     return Ok(output.selected_items[0].output().to_string());
 }
+
+fn skim(prefix: &CxxString, words: &CxxVector<CxxString>) -> Result<String, String> {
+    let ret = panic::catch_unwind(|| {
+        return skim_impl(prefix, words);
+    });
+    return match ret {
+        Err(err) => {
+            let e = if let Some(s) = err.downcast_ref::<String>() {
+                format!("{}", s)
+            } else if let Some(s) = err.downcast_ref::<&str>() {
+                format!("{}", s)
+            } else {
+                format!("Unknown panic type: {:?}", err.type_id())
+            };
+            Err(format!("Rust panic: {:?}", e))
+        },
+        Ok(res) => res,
+    }
+}