a3s_code_core/
error.rs

1//! Typed error enum for A3S Code Core
2//!
3//! Provides categorized errors that SDK consumers can match on programmatically,
4//! instead of receiving opaque `anyhow::Error` strings.
5//!
6//! ## Migration Strategy
7//!
8//! The `Internal` variant wraps `anyhow::Error` via `#[from]`, allowing
9//! gradual migration: call sites that haven't been updated yet auto-convert
10//! through `?`. Over time, each call site replaces `anyhow::anyhow!(...)`
11//! with a specific variant like `CodeError::Config(...)`.
12
13use thiserror::Error;
14
15/// Async resource whose initialization is part of building a session.
16#[derive(Debug, Clone, Copy, PartialEq, Eq)]
17pub enum SessionBuildResource {
18    MemoryStore,
19    SessionStore,
20    Queue,
21    Mcp,
22    RlTrajectory,
23}
24
25impl std::fmt::Display for SessionBuildResource {
26    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
27        f.write_str(match self {
28            Self::MemoryStore => "memory store",
29            Self::SessionStore => "session store",
30            Self::Queue => "session queue",
31            Self::Mcp => "MCP",
32            Self::RlTrajectory => "RL trajectory recorder",
33        })
34    }
35}
36
37/// Crate-wide result type alias.
38pub type Result<T> = std::result::Result<T, CodeError>;
39
40/// Categorized error type for A3S Code Core.
41///
42/// SDK bindings (Python/Node) can match on the variant to expose typed
43/// exceptions (e.g., `CodeConfigError`, `CodeLlmError`).
44#[derive(Debug, Error)]
45pub enum CodeError {
46    /// Configuration loading or parsing error
47    #[error("Config error: {0}")]
48    Config(String),
49
50    /// LLM provider communication error
51    #[error("LLM error: {0}")]
52    Llm(String),
53
54    /// Tool execution error
55    #[error("Tool error: {tool}: {message}")]
56    Tool { tool: String, message: String },
57
58    /// Session management error
59    #[error("Session error: {0}")]
60    Session(String),
61
62    /// A session option is missing, malformed, or conflicts with another option.
63    #[error("Invalid session configuration for '{field}': {message}")]
64    SessionConfiguration {
65        field: &'static str,
66        message: String,
67    },
68
69    /// A session resource could not be initialized.
70    #[error("Failed to initialize {resource}: {message}")]
71    SessionInitialization {
72        resource: SessionBuildResource,
73        message: String,
74    },
75
76    /// The synchronous compatibility factory was asked to initialize an
77    /// async-only resource. Call `Agent::session_builder(...).build().await`.
78    #[error(
79        "{resource} requires asynchronous session construction; use Agent::session_builder(...).build().await"
80    )]
81    AsyncSessionBuildRequired { resource: SessionBuildResource },
82
83    /// Session has been closed; further operations are rejected.
84    ///
85    /// Returned by `send`/`stream` (and their variants) after
86    /// [`AgentSession::close`](crate::agent_api::AgentSession::close)
87    /// — or [`Agent::close`](crate::agent_api::Agent::close) — has been called.
88    #[error("Session '{session_id}' is closed")]
89    SessionClosed { session_id: String },
90
91    /// Another conversation operation is already active on this session.
92    ///
93    /// Sessions serialize conversation state, so callers must wait for the
94    /// active operation's returned future or stream handle to finish before
95    /// starting another one.
96    #[error("Session '{session_id}' already has an active operation")]
97    SessionBusy { session_id: String },
98
99    /// A host replayed a run id with different immutable session or input
100    /// identity. The existing run is preserved and no work is started.
101    #[error("Run '{run_id}' is already bound to different immutable input")]
102    RunIdentityConflict { run_id: String },
103
104    /// A host-supplied [`BudgetGuard`](crate::budget::BudgetGuard) denied
105    /// the operation. The session is not closed — callers can re-try
106    /// after the host has re-allocated budget.
107    #[error("Budget exhausted on '{resource}': {reason}")]
108    BudgetExhausted { resource: String, reason: String },
109
110    /// Security subsystem error
111    #[error("Security error: {0}")]
112    Security(String),
113
114    /// Context provider or context store error
115    #[error("Context error: {0}")]
116    Context(String),
117
118    /// MCP (Model Context Protocol) error
119    #[error("MCP error: {0}")]
120    Mcp(String),
121
122    /// Queue or lane error
123    #[error("Queue error: {0}")]
124    Queue(String),
125
126    /// I/O error
127    #[error("IO error: {0}")]
128    Io(#[from] std::io::Error),
129
130    /// JSON serialization/deserialization error
131    #[error("Serialization error: {0}")]
132    Serialization(#[from] serde_json::Error),
133
134    /// Catch-all for errors not yet migrated to a specific variant.
135    ///
136    /// The `#[from] anyhow::Error` conversion enables gradual migration:
137    /// any function returning `anyhow::Result` can be called with `?` from
138    /// a function returning `crate::error::Result` without changes.
139    #[error("{0:#}")]
140    Internal(#[from] anyhow::Error),
141}
142
143impl CodeError {
144    /// Stable machine-readable code for SDK and service boundaries.
145    pub const fn code(&self) -> &'static str {
146        match self {
147            Self::Config(_) => "CONFIG_ERROR",
148            Self::Llm(_) => "LLM_ERROR",
149            Self::Tool { .. } => "TOOL_ERROR",
150            Self::Session(_) => "SESSION_ERROR",
151            Self::SessionConfiguration { .. } => "SESSION_CONFIGURATION_ERROR",
152            Self::SessionInitialization { .. } => "SESSION_INITIALIZATION_ERROR",
153            Self::AsyncSessionBuildRequired { .. } => "ASYNC_SESSION_BUILD_REQUIRED",
154            Self::SessionClosed { .. } => "SESSION_CLOSED",
155            Self::SessionBusy { .. } => "SESSION_BUSY",
156            Self::RunIdentityConflict { .. } => "RUN_IDENTITY_CONFLICT",
157            Self::BudgetExhausted { .. } => "BUDGET_EXHAUSTED",
158            Self::Security(_) => "SECURITY_ERROR",
159            Self::Context(_) => "CONTEXT_ERROR",
160            Self::Mcp(_) => "MCP_ERROR",
161            Self::Queue(_) => "QUEUE_ERROR",
162            Self::Io(_) => "IO_ERROR",
163            Self::Serialization(_) => "SERIALIZATION_ERROR",
164            Self::Internal(_) => "INTERNAL_ERROR",
165        }
166    }
167}
168
169// ============================================================================
170// Lock Poisoning Helpers (Phase 3b)
171// ============================================================================
172
173/// Acquire a read guard, recovering from poison if the lock was poisoned.
174///
175/// Non-security code should never panic on a poisoned lock. The data may
176/// be in an inconsistent state, but crashing the entire process is worse
177/// than serving stale data in a coding agent context.
178pub(crate) fn read_or_recover<T>(lock: &std::sync::RwLock<T>) -> std::sync::RwLockReadGuard<'_, T> {
179    lock.read().unwrap_or_else(|p| p.into_inner())
180}
181
182/// Acquire a write guard, recovering from poison if the lock was poisoned.
183///
184/// See [`read_or_recover`] for rationale.
185pub(crate) fn write_or_recover<T>(
186    lock: &std::sync::RwLock<T>,
187) -> std::sync::RwLockWriteGuard<'_, T> {
188    lock.write().unwrap_or_else(|p| p.into_inner())
189}
190
191#[cfg(test)]
192mod tests {
193    use super::*;
194
195    #[test]
196    fn test_code_error_config() {
197        let err = CodeError::Config("missing API key".to_string());
198        assert!(err.to_string().contains("Config error"));
199        assert!(err.to_string().contains("missing API key"));
200    }
201
202    #[test]
203    fn test_code_error_llm() {
204        let err = CodeError::Llm("rate limited".to_string());
205        assert!(err.to_string().contains("LLM error"));
206    }
207
208    #[test]
209    fn test_code_error_tool() {
210        let err = CodeError::Tool {
211            tool: "bash".to_string(),
212            message: "command not found".to_string(),
213        };
214        let msg = err.to_string();
215        assert!(msg.contains("bash"));
216        assert!(msg.contains("command not found"));
217    }
218
219    #[test]
220    fn test_code_error_session() {
221        let err = CodeError::Session("not found".to_string());
222        assert!(err.to_string().contains("Session error"));
223    }
224
225    #[test]
226    fn test_code_error_session_configuration_keeps_field_identity() {
227        let err = CodeError::SessionConfiguration {
228            field: "session_id",
229            message: "must not be empty".to_string(),
230        };
231        assert!(err.to_string().contains("session_id"));
232        assert!(err.to_string().contains("must not be empty"));
233    }
234
235    #[test]
236    fn test_code_error_session_busy() {
237        let err = CodeError::SessionBusy {
238            session_id: "session-1".to_string(),
239        };
240        assert!(err.to_string().contains("session-1"));
241        assert!(err.to_string().contains("active operation"));
242    }
243
244    #[test]
245    fn test_code_error_security() {
246        let err = CodeError::Security("taint detected".to_string());
247        assert!(err.to_string().contains("Security error"));
248    }
249
250    #[test]
251    fn test_code_error_context() {
252        let err = CodeError::Context("provider failed".to_string());
253        assert!(err.to_string().contains("Context error"));
254    }
255
256    #[test]
257    fn test_code_error_mcp() {
258        let err = CodeError::Mcp("connection refused".to_string());
259        assert!(err.to_string().contains("MCP error"));
260    }
261
262    #[test]
263    fn test_code_error_queue() {
264        let err = CodeError::Queue("lane full".to_string());
265        assert!(err.to_string().contains("Queue error"));
266    }
267
268    #[test]
269    fn test_code_error_from_io() {
270        let io_err = std::io::Error::new(std::io::ErrorKind::NotFound, "file missing");
271        let err: CodeError = io_err.into();
272        assert!(matches!(err, CodeError::Io(_)));
273        assert!(err.to_string().contains("file missing"));
274    }
275
276    #[test]
277    fn test_code_error_from_serde_json() {
278        let json_err = serde_json::from_str::<serde_json::Value>("invalid").unwrap_err();
279        let err: CodeError = json_err.into();
280        assert!(matches!(err, CodeError::Serialization(_)));
281    }
282
283    #[test]
284    fn test_code_error_from_anyhow() {
285        let anyhow_err = anyhow::anyhow!("something went wrong");
286        let err: CodeError = anyhow_err.into();
287        assert!(matches!(err, CodeError::Internal(_)));
288        assert!(err.to_string().contains("something went wrong"));
289    }
290
291    #[test]
292    fn stable_error_codes_cover_control_flow_variants() {
293        assert_eq!(
294            CodeError::SessionBusy {
295                session_id: "session-1".to_string(),
296            }
297            .code(),
298            "SESSION_BUSY"
299        );
300        assert_eq!(
301            CodeError::SessionClosed {
302                session_id: "session-1".to_string(),
303            }
304            .code(),
305            "SESSION_CLOSED"
306        );
307        assert_eq!(
308            CodeError::RunIdentityConflict {
309                run_id: "run-1".to_string(),
310            }
311            .code(),
312            "RUN_IDENTITY_CONFLICT"
313        );
314        assert_eq!(
315            CodeError::BudgetExhausted {
316                resource: "tokens".to_string(),
317                reason: "limit".to_string(),
318            }
319            .code(),
320            "BUDGET_EXHAUSTED"
321        );
322    }
323
324    #[test]
325    fn test_code_error_question_mark_from_anyhow() {
326        fn inner() -> anyhow::Result<()> {
327            anyhow::bail!("inner error")
328        }
329
330        fn outer() -> Result<()> {
331            inner()?; // anyhow::Error -> CodeError::Internal via #[from]
332            Ok(())
333        }
334
335        let result = outer();
336        assert!(result.is_err());
337        let err = result.unwrap_err();
338        assert!(matches!(err, CodeError::Internal(_)));
339    }
340
341    #[test]
342    fn test_read_or_recover_normal() {
343        let lock = std::sync::RwLock::new(42);
344        let guard = read_or_recover(&lock);
345        assert_eq!(*guard, 42);
346    }
347
348    #[test]
349    fn test_write_or_recover_normal() {
350        let lock = std::sync::RwLock::new(42);
351        let mut guard = write_or_recover(&lock);
352        *guard = 99;
353        drop(guard);
354        assert_eq!(*read_or_recover(&lock), 99);
355    }
356
357    #[test]
358    fn test_read_or_recover_poisoned() {
359        let lock = std::sync::RwLock::new(42);
360        // Poison the lock by panicking while holding a write guard
361        let _ = std::panic::catch_unwind(std::panic::AssertUnwindSafe(|| {
362            let _guard = lock.write().unwrap();
363            panic!("intentional poison");
364        }));
365        // Should recover without panicking
366        let guard = read_or_recover(&lock);
367        assert_eq!(*guard, 42);
368    }
369
370    #[test]
371    fn test_write_or_recover_poisoned() {
372        let lock = std::sync::RwLock::new(42);
373        let _ = std::panic::catch_unwind(std::panic::AssertUnwindSafe(|| {
374            let _guard = lock.write().unwrap();
375            panic!("intentional poison");
376        }));
377        let mut guard = write_or_recover(&lock);
378        *guard = 100;
379        assert_eq!(*guard, 100);
380    }
381}
a3s_code_core/error.rs

a3s_code_core/
error.rs
