support NixErr::Recoverable

nixide/src/errors/context.rs

@@ -118,6 +118,8 @@ impl Into<NixideResult<()>> for &ErrorContext {
                     .unwrap_or_else(|| panic_issue_call_failed!()),
             },
 
+            // XXX: WARNING: Recoverable only exists in later version of Nix
+            sys::NixErr::Recoverable => NixError::Recoverable,
             sys::NixErr::Unknown => NixError::Unknown,
         };
 

nixide/src/errors/nix_error.rs

@@ -6,6 +6,22 @@ use crate::sys;
 /// produced by the libnix C API.
 #[derive(Debug, Clone)]
 pub enum NixError {
+    /// A recoverable error occurred.
+    ///
+    /// # Reason
+    ///
+    /// This is used primarily by C API *consumers* to communicate that a failed
+    /// primop call should be retried on the next evaluation attempt.
+    ///
+    /// # Nix C++ API Internals
+    ///
+    /// ```cpp
+    /// // `NIX_ERR_NIX_ERROR` variant of the `nix_err` enum type
+    /// NIX_ERR_RECOVERABLE = -4
+    /// ```
+    ///
+    Recoverable,
+
     /// A generic Nix error occurred.
     ///
     /// # Reason
@@ -19,6 +35,7 @@ pub enum NixError {
     /// // `NIX_ERR_NIX_ERROR` variant of the `nix_err` enum type
     /// NIX_ERR_NIX_ERROR = -4
     /// ```
+    ///
     ExprEval { name: String, info_msg: String },
 
     /// A key/index access error occurred in C API functions.
@@ -47,6 +64,7 @@ pub enum NixError {
     /// // `NIX_ERR_KEY` variant of the `nix_err` enum type
     /// NIX_ERR_KEY = -3
     /// ```
+    ///
     KeyNotFound(Option<String>),
 
     /// An overflow error occurred.
@@ -62,6 +80,7 @@ pub enum NixError {
     /// // `NIX_ERR_OVERFLOW` variant of the `nix_err` enum type
     /// NIX_ERR_OVERFLOW = -2
     /// ```
+    ///
     Overflow,
 
     /// An unknown error occurred.
@@ -77,6 +96,7 @@ pub enum NixError {
     /// // `NIX_ERR_OVERFLOW` variant of the `nix_err` enum type
     /// NIX_ERR_UNKNOWN = -1
     /// ```
+    ///
     Unknown,
 
     ///
@@ -95,12 +115,14 @@ pub enum NixError {
     /// This is solely a language difference between C++ and Rust, since
     /// [sys::NixErr] is defined over the *"continuous" (not realy)*
     /// type [::core::ffi::c_int].
+    ///
     Undocumented(sys::NixErr),
 }
 
 impl Display for NixError {
     fn fmt(&self, f: &mut Formatter<'_>) -> FmtResult {
         match self {
+            NixError::Recoverable => write!(f, "[libnix] Recoverable error occurred"),
             NixError::ExprEval { name, info_msg } => write!(
                 f,
                 "[libnix] NixExpr evaluation failed [name=\"{name}\", info_msg=\"{info_msg}\"]"
@@ -120,12 +142,13 @@ impl Display for NixError {
 impl NixError {
     pub fn err_code(&self) -> sys::NixErr {
         match self {
-            NixError::Overflow => sys::NixErr::Overflow,
+            NixError::Recoverable => sys::NixErr::Recoverable,
-            NixError::KeyNotFound(_) => sys::NixErr::Key,
             NixError::ExprEval {
                 name: _,
                 info_msg: _,
             } => sys::NixErr::NixError,
+            NixError::KeyNotFound(_) => sys::NixErr::Key,
+            NixError::Overflow => sys::NixErr::Overflow,
             NixError::Unknown => sys::NixErr::NixError,
             NixError::Undocumented(err) => err.clone(),
         }