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-supplied [`BudgetGuard`](crate::budget::BudgetGuard) denied
100    /// the operation. The session is not closed — callers can re-try
101    /// after the host has re-allocated budget.
102    #[error("Budget exhausted on '{resource}': {reason}")]
103    BudgetExhausted { resource: String, reason: String },
104
105    /// Security subsystem error
106    #[error("Security error: {0}")]
107    Security(String),
108
109    /// Context provider or context store error
110    #[error("Context error: {0}")]
111    Context(String),
112
113    /// MCP (Model Context Protocol) error
114    #[error("MCP error: {0}")]
115    Mcp(String),
116
117    /// Queue or lane error
118    #[error("Queue error: {0}")]
119    Queue(String),
120
121    /// I/O error
122    #[error("IO error: {0}")]
123    Io(#[from] std::io::Error),
124
125    /// JSON serialization/deserialization error
126    #[error("Serialization error: {0}")]
127    Serialization(#[from] serde_json::Error),
128
129    /// Catch-all for errors not yet migrated to a specific variant.
130    ///
131    /// The `#[from] anyhow::Error` conversion enables gradual migration:
132    /// any function returning `anyhow::Result` can be called with `?` from
133    /// a function returning `crate::error::Result` without changes.
134    #[error("{0:#}")]
135    Internal(#[from] anyhow::Error),
136}
137
138impl CodeError {
139    /// Stable machine-readable code for SDK and service boundaries.
140    pub const fn code(&self) -> &'static str {
141        match self {
142            Self::Config(_) => "CONFIG_ERROR",
143            Self::Llm(_) => "LLM_ERROR",
144            Self::Tool { .. } => "TOOL_ERROR",
145            Self::Session(_) => "SESSION_ERROR",
146            Self::SessionConfiguration { .. } => "SESSION_CONFIGURATION_ERROR",
147            Self::SessionInitialization { .. } => "SESSION_INITIALIZATION_ERROR",
148            Self::AsyncSessionBuildRequired { .. } => "ASYNC_SESSION_BUILD_REQUIRED",
149            Self::SessionClosed { .. } => "SESSION_CLOSED",
150            Self::SessionBusy { .. } => "SESSION_BUSY",
151            Self::BudgetExhausted { .. } => "BUDGET_EXHAUSTED",
152            Self::Security(_) => "SECURITY_ERROR",
153            Self::Context(_) => "CONTEXT_ERROR",
154            Self::Mcp(_) => "MCP_ERROR",
155            Self::Queue(_) => "QUEUE_ERROR",
156            Self::Io(_) => "IO_ERROR",
157            Self::Serialization(_) => "SERIALIZATION_ERROR",
158            Self::Internal(_) => "INTERNAL_ERROR",
159        }
160    }
161}
162
163// ============================================================================
164// Lock Poisoning Helpers (Phase 3b)
165// ============================================================================
166
167/// Acquire a read guard, recovering from poison if the lock was poisoned.
168///
169/// Non-security code should never panic on a poisoned lock. The data may
170/// be in an inconsistent state, but crashing the entire process is worse
171/// than serving stale data in a coding agent context.
172pub(crate) fn read_or_recover<T>(lock: &std::sync::RwLock<T>) -> std::sync::RwLockReadGuard<'_, T> {
173    lock.read().unwrap_or_else(|p| p.into_inner())
174}
175
176/// Acquire a write guard, recovering from poison if the lock was poisoned.
177///
178/// See [`read_or_recover`] for rationale.
179pub(crate) fn write_or_recover<T>(
180    lock: &std::sync::RwLock<T>,
181) -> std::sync::RwLockWriteGuard<'_, T> {
182    lock.write().unwrap_or_else(|p| p.into_inner())
183}
184
185#[cfg(test)]
186mod tests {
187    use super::*;
188
189    #[test]
190    fn test_code_error_config() {
191        let err = CodeError::Config("missing API key".to_string());
192        assert!(err.to_string().contains("Config error"));
193        assert!(err.to_string().contains("missing API key"));
194    }
195
196    #[test]
197    fn test_code_error_llm() {
198        let err = CodeError::Llm("rate limited".to_string());
199        assert!(err.to_string().contains("LLM error"));
200    }
201
202    #[test]
203    fn test_code_error_tool() {
204        let err = CodeError::Tool {
205            tool: "bash".to_string(),
206            message: "command not found".to_string(),
207        };
208        let msg = err.to_string();
209        assert!(msg.contains("bash"));
210        assert!(msg.contains("command not found"));
211    }
212
213    #[test]
214    fn test_code_error_session() {
215        let err = CodeError::Session("not found".to_string());
216        assert!(err.to_string().contains("Session error"));
217    }
218
219    #[test]
220    fn test_code_error_session_configuration_keeps_field_identity() {
221        let err = CodeError::SessionConfiguration {
222            field: "session_id",
223            message: "must not be empty".to_string(),
224        };
225        assert!(err.to_string().contains("session_id"));
226        assert!(err.to_string().contains("must not be empty"));
227    }
228
229    #[test]
230    fn test_code_error_session_busy() {
231        let err = CodeError::SessionBusy {
232            session_id: "session-1".to_string(),
233        };
234        assert!(err.to_string().contains("session-1"));
235        assert!(err.to_string().contains("active operation"));
236    }
237
238    #[test]
239    fn test_code_error_security() {
240        let err = CodeError::Security("taint detected".to_string());
241        assert!(err.to_string().contains("Security error"));
242    }
243
244    #[test]
245    fn test_code_error_context() {
246        let err = CodeError::Context("provider failed".to_string());
247        assert!(err.to_string().contains("Context error"));
248    }
249
250    #[test]
251    fn test_code_error_mcp() {
252        let err = CodeError::Mcp("connection refused".to_string());
253        assert!(err.to_string().contains("MCP error"));
254    }
255
256    #[test]
257    fn test_code_error_queue() {
258        let err = CodeError::Queue("lane full".to_string());
259        assert!(err.to_string().contains("Queue error"));
260    }
261
262    #[test]
263    fn test_code_error_from_io() {
264        let io_err = std::io::Error::new(std::io::ErrorKind::NotFound, "file missing");
265        let err: CodeError = io_err.into();
266        assert!(matches!(err, CodeError::Io(_)));
267        assert!(err.to_string().contains("file missing"));
268    }
269
270    #[test]
271    fn test_code_error_from_serde_json() {
272        let json_err = serde_json::from_str::<serde_json::Value>("invalid").unwrap_err();
273        let err: CodeError = json_err.into();
274        assert!(matches!(err, CodeError::Serialization(_)));
275    }
276
277    #[test]
278    fn test_code_error_from_anyhow() {
279        let anyhow_err = anyhow::anyhow!("something went wrong");
280        let err: CodeError = anyhow_err.into();
281        assert!(matches!(err, CodeError::Internal(_)));
282        assert!(err.to_string().contains("something went wrong"));
283    }
284
285    #[test]
286    fn stable_error_codes_cover_control_flow_variants() {
287        assert_eq!(
288            CodeError::SessionBusy {
289                session_id: "session-1".to_string(),
290            }
291            .code(),
292            "SESSION_BUSY"
293        );
294        assert_eq!(
295            CodeError::SessionClosed {
296                session_id: "session-1".to_string(),
297            }
298            .code(),
299            "SESSION_CLOSED"
300        );
301        assert_eq!(
302            CodeError::BudgetExhausted {
303                resource: "tokens".to_string(),
304                reason: "limit".to_string(),
305            }
306            .code(),
307            "BUDGET_EXHAUSTED"
308        );
309    }
310
311    #[test]
312    fn test_code_error_question_mark_from_anyhow() {
313        fn inner() -> anyhow::Result<()> {
314            anyhow::bail!("inner error")
315        }
316
317        fn outer() -> Result<()> {
318            inner()?; // anyhow::Error -> CodeError::Internal via #[from]
319            Ok(())
320        }
321
322        let result = outer();
323        assert!(result.is_err());
324        let err = result.unwrap_err();
325        assert!(matches!(err, CodeError::Internal(_)));
326    }
327
328    #[test]
329    fn test_read_or_recover_normal() {
330        let lock = std::sync::RwLock::new(42);
331        let guard = read_or_recover(&lock);
332        assert_eq!(*guard, 42);
333    }
334
335    #[test]
336    fn test_write_or_recover_normal() {
337        let lock = std::sync::RwLock::new(42);
338        let mut guard = write_or_recover(&lock);
339        *guard = 99;
340        drop(guard);
341        assert_eq!(*read_or_recover(&lock), 99);
342    }
343
344    #[test]
345    fn test_read_or_recover_poisoned() {
346        let lock = std::sync::RwLock::new(42);
347        // Poison the lock by panicking while holding a write guard
348        let _ = std::panic::catch_unwind(std::panic::AssertUnwindSafe(|| {
349            let _guard = lock.write().unwrap();
350            panic!("intentional poison");
351        }));
352        // Should recover without panicking
353        let guard = read_or_recover(&lock);
354        assert_eq!(*guard, 42);
355    }
356
357    #[test]
358    fn test_write_or_recover_poisoned() {
359        let lock = std::sync::RwLock::new(42);
360        let _ = std::panic::catch_unwind(std::panic::AssertUnwindSafe(|| {
361            let _guard = lock.write().unwrap();
362            panic!("intentional poison");
363        }));
364        let mut guard = write_or_recover(&lock);
365        *guard = 100;
366        assert_eq!(*guard, 100);
367    }
368}
a3s_code_core/error.rs

a3s_code_core/
error.rs
