harn_vm/value/
error.rs

1use harn_lexer::Span;
2
3use super::{VmDictExt, VmValue};
4
5/// Bound expressing how many arguments a callable accepts. Used in
6/// [`VmError::ArityMismatch`] so error messages can render the exact
7/// signature contract the caller violated.
8#[derive(Debug, Clone, Copy, PartialEq, Eq)]
9pub enum ArityExpect {
10    /// Exactly N parameters, no defaults, no rest.
11    Exact(usize),
12    /// `min..=max`: some params have defaults but the upper bound is fixed.
13    Range { min: usize, max: usize },
14    /// At least N parameters; further args land in a rest list. Used for
15    /// `print` / `log` / variadics.
16    AtLeast(usize),
17}
18
19impl std::fmt::Display for ArityExpect {
20    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
21        match self {
22            ArityExpect::Exact(n) => write!(f, "{n}"),
23            ArityExpect::Range { min, max } => write!(f, "{min}..={max}"),
24            ArityExpect::AtLeast(n) => write!(f, "at least {n}"),
25        }
26    }
27}
28
29#[derive(Debug, Clone)]
30pub struct ArityMismatchError {
31    pub callee: String,
32    pub expected: ArityExpect,
33    pub got: usize,
34    pub span: Option<Span>,
35}
36
37#[derive(Debug, Clone, Copy, PartialEq, Eq)]
38pub enum DeadlockDiagnostic {
39    SelfDeadlock,
40    WaitForGraph,
41}
42
43impl DeadlockDiagnostic {
44    fn code(self) -> &'static str {
45        match self {
46            Self::SelfDeadlock => "HARN-ORC-011",
47            Self::WaitForGraph => "HARN-ORC-012",
48        }
49    }
50}
51
52/// Payload for [`VmError::Deadlock`]. `kind` is the primitive kind
53/// (`"mutex"`, `"channel"`) or `"task"`; `key` is the primitive key or task
54/// id; `detail` names the specific footgun.
55#[derive(Debug, Clone)]
56pub struct DeadlockError {
57    pub diagnostic: DeadlockDiagnostic,
58    pub kind: String,
59    pub key: String,
60    pub detail: String,
61}
62
63impl DeadlockError {
64    pub(crate) fn self_deadlock(
65        kind: impl Into<String>,
66        key: impl Into<String>,
67        detail: impl Into<String>,
68    ) -> Self {
69        Self {
70            diagnostic: DeadlockDiagnostic::SelfDeadlock,
71            kind: kind.into(),
72            key: key.into(),
73            detail: detail.into(),
74        }
75    }
76
77    pub(crate) fn wait_for_graph(
78        kind: impl Into<String>,
79        key: impl Into<String>,
80        detail: impl Into<String>,
81    ) -> Self {
82        Self {
83            diagnostic: DeadlockDiagnostic::WaitForGraph,
84            kind: kind.into(),
85            key: key.into(),
86            detail: detail.into(),
87        }
88    }
89}
90
91#[derive(Debug, Clone)]
92pub struct ArgTypeMismatchError {
93    pub callee: String,
94    pub param: String,
95    pub expected: String,
96    pub got: &'static str,
97    pub span: Option<Span>,
98}
99
100#[derive(Debug, Clone)]
101pub enum VmError {
102    StackUnderflow,
103    StackOverflow,
104    UndefinedVariable(String),
105    UndefinedBuiltin(String),
106    ImmutableAssignment(String),
107    TypeError(String),
108    Runtime(String),
109    DivisionByZero,
110    /// A host-imposed deadline expired while executing the VM. Unlike a Harn
111    /// `deadline` block, this control-plane stop cannot be caught by user code.
112    ExecutionDeadlineExceeded,
113    /// A Harn program requested that its embedding process terminate with this
114    /// status code. Like a host deadline, this is control flow rather than a
115    /// catchable Harn error; the embedding boundary owns the final cleanup and
116    /// process exit.
117    ProcessExit(i32),
118    /// A host dropped a polled top-level execution future. Interpreter state is
119    /// intentionally not resumed after arbitrary async cancellation. Discard
120    /// this VM; see [`crate::Vm::execute_with_timeout`] for ambient-state
121    /// cleanup requirements.
122    AbandonedExecution,
123    Thrown(VmValue),
124    /// Thrown with error category for structured error handling.
125    CategorizedError {
126        message: String,
127        category: ErrorCategory,
128    },
129    /// A provider stream failed before its protocol supplied a terminal
130    /// sentinel. Carries transport phase and deadline provenance structurally
131    /// so retry, transcript, and host projections never need to reclassify
132    /// rendered prose.
133    ProviderStreamFailure(Box<ProviderStreamFailure>),
134    DaemonQueueFull {
135        daemon_id: String,
136        capacity: usize,
137    },
138    /// A deterministic, provably-unresolvable self-deadlock caught before the
139    /// VM would block forever (Rust's borrow checker prevents data races but
140    /// not deadlocks; this is the Go-runtime "all goroutines asleep" analogue
141    /// for the cases we can prove). Boxed — like [`VmError::ArityMismatch`] —
142    /// so the rare three-`String` payload doesn't enlarge `VmError` on the
143    /// pervasive `Result<VmValue, VmError>` hot path. Carries `HARN-ORC-011`.
144    Deadlock(Box<DeadlockError>),
145    Return(VmValue),
146    InvalidInstruction(u8),
147    /// Wrong number of arguments at a call site. Distinct from
148    /// [`VmError::TypeError`] so the runtime can match-and-recover (and
149    /// so error UX renders `expected 2..=3 got 1` consistently).
150    ArityMismatch(Box<ArityMismatchError>),
151    /// Argument value did not satisfy the declared parameter type.
152    /// `expected` is a pretty-printed type expression; `got` is the value's
153    /// runtime type name (`VmValue::type_name`). Used for both
154    /// user-defined function parameters (with declared types) and
155    /// registry-known builtin parameters.
156    ArgTypeMismatch(Box<ArgTypeMismatchError>),
157}
158
159impl VmError {
160    /// Whether this error is VM control flow that user `catch` blocks and
161    /// error-as-data combinators must propagate unchanged.
162    pub fn is_uncatchable_control_flow(&self) -> bool {
163        matches!(self, Self::ExecutionDeadlineExceeded | Self::ProcessExit(_))
164    }
165
166    /// The requested host-process exit status, when this is an explicit Harn
167    /// `exit(code)` control signal.
168    pub fn process_exit_code(&self) -> Option<i32> {
169        match self {
170            Self::ProcessExit(code) => Some(*code),
171            _ => None,
172        }
173    }
174
175    /// The `VmValue` a `catch` binding (or a `parallel settle` result) observes
176    /// for this error: the raw thrown value for [`VmError::Thrown`] (so a
177    /// structured error — e.g. a `{category, message}` dict from `throw_error` —
178    /// keeps its shape and category), a structured `{category, message}` dict for
179    /// [`VmError::CategorizedError`] (so consumers branch on the typed category
180    /// rather than substring-matching rendered prose), otherwise the rendered
181    /// message.
182    ///
183    /// Single source of truth for VM-error-to-value lowering so every seam that
184    /// surfaces a caught error to Harn (`try`/`catch` via `handle_error`,
185    /// `parallel settle`) exposes identical, structure-preserving values. Before
186    /// this was shared, `parallel settle` stringified errors via `to_string()`,
187    /// so a categorized error thrown in a settle branch lost its category (a
188    /// `cancelled`/`internal` fault that must propagate looked `generic`).
189    ///
190    /// The `category` key uses [`ErrorCategory::as_str`] — a canonical,
191    /// exhaustively-matched snake_case contract — so a new variant added there
192    /// is compiler-forced to name its key. `message` preserves the original
193    /// rendered text, so a `catch` that stringifies the caught value still reads
194    /// sensibly (the dict renders both fields).
195    pub fn thrown_value(&self) -> VmValue {
196        match self {
197            VmError::Thrown(v) => v.clone(),
198            VmError::CategorizedError { message, category } => {
199                let mut dict = std::collections::BTreeMap::new();
200                dict.put_str("category", category.as_str());
201                dict.put_str("message", message);
202                VmValue::dict(dict)
203            }
204            VmError::ProviderStreamFailure(failure) => failure.thrown_value(),
205            other => VmValue::String(arcstr::ArcStr::from(other.to_string())),
206        }
207    }
208
209    pub fn provider_stream_failure(&self) -> Option<&ProviderStreamFailure> {
210        match self {
211            Self::ProviderStreamFailure(failure) => Some(failure),
212            _ => None,
213        }
214    }
215}
216
217#[derive(Debug, Clone, Copy, PartialEq, Eq)]
218pub enum ProviderStreamPhase {
219    AwaitingFirstChunk,
220    Streaming,
221}
222
223impl ProviderStreamPhase {
224    pub fn as_str(self) -> &'static str {
225        match self {
226            Self::AwaitingFirstChunk => "awaiting_first_chunk",
227            Self::Streaming => "streaming",
228        }
229    }
230}
231
232#[derive(Debug, Clone, Copy, PartialEq, Eq)]
233pub enum ProviderStreamFailureReason {
234    Read,
235    PrematureEof,
236    Deadline,
237}
238
239impl ProviderStreamFailureReason {
240    pub fn as_str(self) -> &'static str {
241        match self {
242            Self::Read => "read",
243            Self::PrematureEof => "premature_eof",
244            Self::Deadline => "deadline",
245        }
246    }
247}
248
249#[derive(Debug, Clone, Copy, PartialEq, Eq)]
250pub enum ProviderStreamDeadline {
251    Total,
252    FirstChunk,
253    Idle,
254}
255
256impl ProviderStreamDeadline {
257    pub fn as_str(self) -> &'static str {
258        match self {
259            Self::Total => "total",
260            Self::FirstChunk => "first_chunk",
261            Self::Idle => "idle",
262        }
263    }
264}
265
266#[derive(Debug, Clone, PartialEq, Eq)]
267pub struct ProviderStreamFailure {
268    pub provider: String,
269    pub phase: ProviderStreamPhase,
270    pub reason: ProviderStreamFailureReason,
271    pub deadline: Option<ProviderStreamDeadline>,
272    pub partial: bool,
273    pub detail: String,
274}
275
276impl ProviderStreamFailure {
277    pub fn category(&self) -> ErrorCategory {
278        if self.deadline.is_some() {
279            ErrorCategory::Timeout
280        } else {
281            ErrorCategory::TransientNetwork
282        }
283    }
284
285    fn thrown_value(&self) -> VmValue {
286        let mut dict = std::collections::BTreeMap::new();
287        dict.put_str("category", self.category().as_str());
288        dict.put_str("message", self.to_string());
289        dict.put_str("source", "provider_stream");
290        dict.put_str("phase", self.phase.as_str());
291        dict.put_str("reason", self.reason.as_str());
292        dict.insert(
293            "deadline".to_string(),
294            self.deadline
295                .map(|deadline| VmValue::String(arcstr::ArcStr::from(deadline.as_str())))
296                .unwrap_or(VmValue::Nil),
297        );
298        dict.insert("partial".to_string(), VmValue::Bool(self.partial));
299        VmValue::dict(dict)
300    }
301}
302
303impl std::fmt::Display for ProviderStreamFailure {
304    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
305        write!(
306            f,
307            "{} provider stream failure (phase={}, reason={}",
308            self.provider,
309            self.phase.as_str(),
310            self.reason.as_str()
311        )?;
312        if let Some(deadline) = self.deadline {
313            write!(f, ", deadline={}", deadline.as_str())?;
314        }
315        write!(f, ", partial={}): {}", self.partial, self.detail)
316    }
317}
318
319/// Error categories for structured error handling in agent orchestration.
320#[derive(Debug, Clone, PartialEq, Eq)]
321pub enum ErrorCategory {
322    /// Network/connection timeout
323    Timeout,
324    /// Authentication/authorization failure
325    Auth,
326    /// Rate limit exceeded (HTTP 429 / quota)
327    RateLimit,
328    /// Upstream provider is overloaded (HTTP 503 / 529).
329    /// Distinct from RateLimit: the client hasn't exceeded a quota — the
330    /// provider is shedding load and will recover on its own.
331    Overloaded,
332    /// Provider-side 5xx error (500, 502) that isn't specifically overload.
333    ServerError,
334    /// Network-level transient failure (connection reset, DNS hiccup,
335    /// partial stream) — retryable but not provider-status-coded.
336    TransientNetwork,
337    /// A shared local resource is temporarily unavailable, such as a
338    /// contended database write lock.
339    ResourceBusy,
340    /// LLM output failed schema validation. Retryable via `schema_retries`.
341    SchemaValidation,
342    /// LLM streaming response was aborted mid-stream because the partial
343    /// JSON content could not conceivably satisfy `output_schema`. Surfaced
344    /// by `llm_call` when `schema_stream_abort` is on (the default for
345    /// schema-bearing calls). Consumes one `schema_retries` budget slot;
346    /// the retry replays the prompt with a corrective nudge that cites
347    /// the abort path + reason.
348    SchemaStreamAborted,
349    /// Tool execution failure
350    ToolError,
351    /// Tool was rejected by the host (not permitted / not in allowlist)
352    ToolRejected,
353    /// Outbound network egress was blocked by policy.
354    EgressBlocked,
355    /// Operation was cancelled
356    Cancelled,
357    /// Channel was closed before the operation could complete.
358    ChannelClosed,
359    /// Resource not found
360    NotFound,
361    /// Circuit breaker is open
362    CircuitOpen,
363    /// LLM cost or token budget would be exceeded
364    BudgetExceeded,
365    /// An internal engine/wiring bug — an undefined builtin, corrupt bytecode,
366    /// or another VM invariant violation that no amount of retrying or model
367    /// reasoning can fix. Distinct from `Generic` so callers (notably the agent
368    /// loop) can re-raise it loudly instead of folding it into a tool-error
369    /// observation and marching on to a `done` status. This is the category
370    /// that keeps a mis-wired builtin (e.g. a `#[harn_builtin]` def missing
371    /// from its install array) from shipping silently inert.
372    Internal,
373    /// A host environment / infrastructure problem that is not the workload's
374    /// code defect: a required developer-toolchain root or cache lies outside
375    /// the sandbox profile, a needed system binary is missing, or another
376    /// machine-provisioning gap. Distinct from `ToolRejected` (the host
377    /// deliberately refused an action) and `Internal` (an engine bug): the fix
378    /// is to widen the sandbox/config or provision the host, not to change the
379    /// agent's code. Callers (and embedders) branch on this to avoid blaming
380    /// the model for an environment gap.
381    Environment,
382    /// Generic/unclassified error
383    Generic,
384}
385
386impl ErrorCategory {
387    /// Every category, in declaration order.
388    ///
389    /// Sibling taxonomies (`ToolCallErrorCategory::ALL`,
390    /// `AgentTerminalKind::ALL`) already publish theirs, and code that has to
391    /// decide something for EVERY category — a wire projection, a docs table,
392    /// a round-trip guard — needs to enumerate them. While this list lived in
393    /// one module's test scope, the tool-call wire projection could not consult
394    /// it, and a category with no decided wire bucket went unnoticed (#5537).
395    pub const ALL: [Self; 20] = [
396        Self::Timeout,
397        Self::Auth,
398        Self::RateLimit,
399        Self::Overloaded,
400        Self::ServerError,
401        Self::TransientNetwork,
402        Self::ResourceBusy,
403        Self::SchemaValidation,
404        Self::SchemaStreamAborted,
405        Self::ToolError,
406        Self::ToolRejected,
407        Self::EgressBlocked,
408        Self::Cancelled,
409        Self::ChannelClosed,
410        Self::NotFound,
411        Self::CircuitOpen,
412        Self::BudgetExceeded,
413        Self::Internal,
414        Self::Environment,
415        Self::Generic,
416    ];
417
418    pub fn as_str(&self) -> &'static str {
419        match self {
420            ErrorCategory::Timeout => "timeout",
421            ErrorCategory::Auth => "auth",
422            ErrorCategory::RateLimit => "rate_limit",
423            ErrorCategory::Overloaded => "overloaded",
424            ErrorCategory::ServerError => "server_error",
425            ErrorCategory::TransientNetwork => "transient_network",
426            ErrorCategory::ResourceBusy => "resource_busy",
427            ErrorCategory::SchemaValidation => "schema_validation",
428            ErrorCategory::SchemaStreamAborted => "schema_stream_aborted",
429            ErrorCategory::ToolError => "tool_error",
430            ErrorCategory::ToolRejected => "tool_rejected",
431            ErrorCategory::EgressBlocked => "egress_blocked",
432            ErrorCategory::Cancelled => "cancelled",
433            ErrorCategory::ChannelClosed => "channel_closed",
434            ErrorCategory::NotFound => "not_found",
435            ErrorCategory::CircuitOpen => "circuit_open",
436            ErrorCategory::BudgetExceeded => "budget_exceeded",
437            ErrorCategory::Internal => "internal",
438            ErrorCategory::Environment => "environment",
439            ErrorCategory::Generic => "generic",
440        }
441    }
442
443    pub fn parse(s: &str) -> Self {
444        match s {
445            "timeout" => ErrorCategory::Timeout,
446            "auth" => ErrorCategory::Auth,
447            "rate_limit" => ErrorCategory::RateLimit,
448            "overloaded" => ErrorCategory::Overloaded,
449            "server_error" => ErrorCategory::ServerError,
450            "transient_network" => ErrorCategory::TransientNetwork,
451            "resource_busy" => ErrorCategory::ResourceBusy,
452            "schema_validation" => ErrorCategory::SchemaValidation,
453            "schema_stream_aborted" => ErrorCategory::SchemaStreamAborted,
454            "tool_error" => ErrorCategory::ToolError,
455            "tool_rejected" => ErrorCategory::ToolRejected,
456            "egress_blocked" => ErrorCategory::EgressBlocked,
457            "cancelled" => ErrorCategory::Cancelled,
458            "channel_closed" => ErrorCategory::ChannelClosed,
459            "not_found" => ErrorCategory::NotFound,
460            "circuit_open" => ErrorCategory::CircuitOpen,
461            "budget_exceeded" => ErrorCategory::BudgetExceeded,
462            "internal" => ErrorCategory::Internal,
463            "environment" => ErrorCategory::Environment,
464            _ => ErrorCategory::Generic,
465        }
466    }
467
468    /// Whether this category represents an internal engine/wiring bug that must
469    /// be surfaced rather than retried or swallowed as a recoverable failure.
470    pub fn is_internal(&self) -> bool {
471        matches!(self, ErrorCategory::Internal)
472    }
473
474    /// Whether an error of this category is worth retrying because the
475    /// underlying condition is transient. Agent loops consult this to decide
476    /// whether to back off and retry vs surface the error to the user.
477    pub fn is_transient(&self) -> bool {
478        matches!(
479            self,
480            ErrorCategory::Timeout
481                | ErrorCategory::RateLimit
482                | ErrorCategory::Overloaded
483                | ErrorCategory::ServerError
484                | ErrorCategory::TransientNetwork
485                | ErrorCategory::ResourceBusy
486        )
487    }
488}
489
490/// Create a categorized error conveniently.
491pub fn categorized_error(message: impl Into<String>, category: ErrorCategory) -> VmError {
492    VmError::CategorizedError {
493        message: message.into(),
494        category,
495    }
496}
497
498/// Extract error category from a VmError.
499///
500/// Classification priority:
501/// 1. Explicit CategorizedError variant (set by throw_error or internal code)
502/// 2. Thrown dict with a "category" field (user-created structured errors)
503/// 3. HTTP status code extraction (standard, unambiguous)
504/// 4. Deadline exceeded (VM-internal)
505/// 5. Fallback to Generic
506pub fn error_to_category(err: &VmError) -> ErrorCategory {
507    match err {
508        VmError::ExecutionDeadlineExceeded => ErrorCategory::Timeout,
509        // ProcessExit is uncatchable control flow rather than an agent-facing
510        // failure. Keep this fallback total for callers that classify an
511        // arbitrary VmError without treating the request as retryable.
512        VmError::ProcessExit(_) => ErrorCategory::Generic,
513        VmError::AbandonedExecution => ErrorCategory::Cancelled,
514        VmError::CategorizedError { category, .. } => category.clone(),
515        VmError::ProviderStreamFailure(failure) => failure.category(),
516        VmError::Thrown(VmValue::Dict(d)) => d
517            .get("category")
518            .map(|v| ErrorCategory::parse(&v.display()))
519            .unwrap_or(ErrorCategory::Generic),
520        VmError::Thrown(VmValue::String(s)) => classify_error_message(s),
521        VmError::Runtime(msg) => classify_error_message(msg),
522        // Engine/wiring bugs: an undefined builtin (declared but not installed,
523        // or a typo in stdlib/host code) or corrupt bytecode. No retry or model
524        // reasoning fixes these, so they get their own category the agent loop
525        // re-raises instead of swallowing.
526        VmError::UndefinedBuiltin(_) | VmError::InvalidInstruction(_) => ErrorCategory::Internal,
527        // A deadlock is permanently non-retryable and not provider-related —
528        // `Generic` is the correct "surface it, don't back off" bucket.
529        VmError::Deadlock(_) => ErrorCategory::Generic,
530        _ => ErrorCategory::Generic,
531    }
532}
533
534/// Classify an error message using HTTP status codes and well-known patterns.
535/// Prefers unambiguous signals (status codes) over substring heuristics.
536pub fn classify_error_message(msg: &str) -> ErrorCategory {
537    // 1. HTTP status codes — most reliable signal
538    if let Some(cat) = classify_by_http_status(msg) {
539        return cat;
540    }
541    // 2. Internal engine/wiring bug surfaced as a plain message. Some call
542    //    sites build `Runtime("Undefined builtin: …")` strings instead of the
543    //    structured `VmError::UndefinedBuiltin` variant; classify both the same
544    //    so the agent loop re-raises rather than swallows.
545    if msg.contains("Undefined builtin") {
546        return ErrorCategory::Internal;
547    }
548    // 3. Well-known error identifiers from major APIs
549    //    (Anthropic, OpenAI, and standard HTTP patterns)
550    let lower = msg.to_lowercase();
551    if lower.contains("cancelled") || lower.contains("canceled") {
552        return ErrorCategory::Cancelled;
553    }
554    if msg.contains("ChannelClosed") || lower.contains("channel closed") {
555        return ErrorCategory::ChannelClosed;
556    }
557    if msg.contains("Deadline exceeded") || msg.contains("context deadline exceeded") {
558        return ErrorCategory::Timeout;
559    }
560    if msg.contains("overloaded_error") {
561        // Anthropic overloaded_error surfaces as HTTP 529.
562        return ErrorCategory::Overloaded;
563    }
564    if msg.contains("api_error") {
565        // Anthropic catch-all server-side error.
566        return ErrorCategory::ServerError;
567    }
568    if msg.contains("insufficient_quota") || msg.contains("billing_hard_limit_reached") {
569        // OpenAI-specific quota error types.
570        return ErrorCategory::RateLimit;
571    }
572    if msg.contains("invalid_api_key") || msg.contains("authentication_error") {
573        return ErrorCategory::Auth;
574    }
575    if msg.contains("not_found_error") || msg.contains("model_not_found") {
576        return ErrorCategory::NotFound;
577    }
578    // OpenRouter reports an unknown model as HTTP 400 with the body
579    // "<id> is not a valid model ID" — no status-code or typed-error signal
580    // that `classify_by_http_status` / the checks above can latch onto. Map
581    // the prose to NotFound so it lines up with Cerebras's 404 path (and with
582    // `errors::is_model_unavailable`'s reason taxonomy).
583    if lower.contains("is not a valid model id") || lower.contains("invalid model id") {
584        return ErrorCategory::NotFound;
585    }
586    if msg.contains("circuit_open") {
587        return ErrorCategory::CircuitOpen;
588    }
589    // Network-level transient patterns (pre-HTTP-status, pre-provider-framing).
590    if lower.contains("connection reset")
591        || lower.contains("connection refused")
592        || lower.contains("connection closed")
593        || lower.contains("broken pipe")
594        || lower.contains("dns error")
595        || lower.contains("stream error")
596        || lower.contains("unexpected eof")
597    {
598        return ErrorCategory::TransientNetwork;
599    }
600    ErrorCategory::Generic
601}
602
603/// Classify errors by HTTP status code if one appears in the message.
604/// This is the most reliable classification method since status codes
605/// are standardized (RFC 9110) and unambiguous.
606fn classify_by_http_status(msg: &str) -> Option<ErrorCategory> {
607    // Extract 3-digit HTTP status codes from common patterns:
608    // "HTTP 429", "status 429", "429 Too Many", "error: 401"
609    for code in extract_http_status_codes(msg) {
610        return Some(match code {
611            401 | 403 => ErrorCategory::Auth,
612            404 | 410 => ErrorCategory::NotFound,
613            408 | 504 | 522 | 524 => ErrorCategory::Timeout,
614            429 => ErrorCategory::RateLimit,
615            503 | 529 => ErrorCategory::Overloaded,
616            500 | 502 => ErrorCategory::ServerError,
617            _ => continue,
618        });
619    }
620    None
621}
622
623/// Extract plausible HTTP status codes from an error message.
624fn extract_http_status_codes(msg: &str) -> Vec<u16> {
625    let mut codes = Vec::new();
626    let bytes = msg.as_bytes();
627    for i in 0..bytes.len().saturating_sub(2) {
628        // Look for 3-digit sequences in the 100-599 range
629        if bytes[i].is_ascii_digit()
630            && bytes[i + 1].is_ascii_digit()
631            && bytes[i + 2].is_ascii_digit()
632        {
633            // Ensure it's not part of a longer number
634            let before_ok = i == 0 || !bytes[i - 1].is_ascii_digit();
635            let after_ok = i + 3 >= bytes.len() || !bytes[i + 3].is_ascii_digit();
636            if before_ok && after_ok {
637                if let Ok(code) = msg[i..i + 3].parse::<u16>() {
638                    if (400..=599).contains(&code) {
639                        codes.push(code);
640                    }
641                }
642            }
643        }
644    }
645    codes
646}
647
648impl std::fmt::Display for VmError {
649    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
650        match self {
651            VmError::StackUnderflow => write!(f, "Stack underflow"),
652            VmError::StackOverflow => write!(f, "Stack overflow: too many nested calls"),
653            VmError::UndefinedVariable(n) => write!(f, "Undefined variable: {n}"),
654            VmError::UndefinedBuiltin(n) => write!(f, "Undefined builtin: {n}"),
655            VmError::ImmutableAssignment(n) => {
656                write!(f, "Cannot assign to immutable binding: {n}")
657            }
658            VmError::TypeError(msg) => write!(f, "Type error: {msg}"),
659            VmError::Runtime(msg) => write!(f, "Runtime error: {msg}"),
660            VmError::DivisionByZero => write!(f, "Division by zero"),
661            VmError::ExecutionDeadlineExceeded => write!(f, "Execution deadline exceeded"),
662            VmError::ProcessExit(code) => write!(f, "Process exit requested: {code}"),
663            VmError::AbandonedExecution => write!(
664                f,
665                "Execution future was abandoned; discard this VM and reset its exclusively owned execution context"
666            ),
667            VmError::Thrown(v) => write!(f, "Thrown: {}", v.display()),
668            VmError::CategorizedError { message, category } => {
669                write!(f, "Error [{}]: {}", category.as_str(), message)
670            }
671            VmError::ProviderStreamFailure(failure) => failure.fmt(f),
672            VmError::DaemonQueueFull {
673                daemon_id,
674                capacity,
675            } => write!(
676                f,
677                "Daemon queue full: daemon '{daemon_id}' reached its event_queue_capacity of {capacity}"
678            ),
679            VmError::Deadlock(err) => match err.diagnostic {
680                DeadlockDiagnostic::SelfDeadlock => write!(
681                    f,
682                    "{}: deadlock detected: {} ({} '{}') — this wait can never complete and would block forever",
683                    err.diagnostic.code(),
684                    err.detail,
685                    err.kind,
686                    err.key
687                ),
688                DeadlockDiagnostic::WaitForGraph => write!(
689                    f,
690                    "{}: wait-for deadlock detected: {} ({} '{}') — no active task can make progress",
691                    err.diagnostic.code(),
692                    err.detail,
693                    err.kind,
694                    err.key
695                ),
696            },
697            VmError::Return(_) => write!(f, "Return from function"),
698            VmError::InvalidInstruction(op) => write!(f, "Invalid instruction: 0x{op:02x}"),
699            VmError::ArityMismatch(err) => {
700                let arg_word = match err.expected {
701                    ArityExpect::Exact(1) | ArityExpect::AtLeast(1) => "argument",
702                    _ => "arguments",
703                };
704                write!(
705                    f,
706                    "Arity mismatch: '{}' expects {} {}, got {}{}",
707                    err.callee,
708                    err.expected,
709                    arg_word,
710                    err.got,
711                    fmt_span_suffix(&err.span)
712                )
713            }
714            VmError::ArgTypeMismatch(err) => {
715                write!(
716                    f,
717                    "Type error: '{}' parameter `{}` expects {}, got {}{}",
718                    err.callee,
719                    err.param,
720                    err.expected,
721                    err.got,
722                    fmt_span_suffix(&err.span)
723                )
724            }
725        }
726    }
727}
728
729fn fmt_span_suffix(span: &Option<Span>) -> String {
730    match span {
731        Some(s) => format!(" (at byte {}..{})", s.start, s.end),
732        None => String::new(),
733    }
734}
735
736impl std::error::Error for VmError {}
737
738#[cfg(test)]
739mod tests {
740    use super::*;
741
742    /// A new variant must be added to [`ErrorCategory::ALL`], or the guards below
743    /// silently stop covering it. This match is the tripwire: it fails to
744    /// compile until the variant is named, and the arm points at the list.
745    #[test]
746    fn all_categories_is_exhaustive() {
747        for category in &ErrorCategory::ALL {
748            match category {
749                ErrorCategory::Timeout
750                | ErrorCategory::Auth
751                | ErrorCategory::RateLimit
752                | ErrorCategory::Overloaded
753                | ErrorCategory::ServerError
754                | ErrorCategory::TransientNetwork
755                | ErrorCategory::ResourceBusy
756                | ErrorCategory::SchemaValidation
757                | ErrorCategory::SchemaStreamAborted
758                | ErrorCategory::ToolError
759                | ErrorCategory::ToolRejected
760                | ErrorCategory::EgressBlocked
761                | ErrorCategory::Cancelled
762                | ErrorCategory::ChannelClosed
763                | ErrorCategory::NotFound
764                | ErrorCategory::CircuitOpen
765                | ErrorCategory::BudgetExceeded
766                | ErrorCategory::Internal
767                | ErrorCategory::Environment
768                | ErrorCategory::Generic => {}
769            }
770        }
771        assert_eq!(
772            ErrorCategory::ALL.len(),
773            20,
774            "a category was added or removed — update `ErrorCategory::ALL` and the \
775             `Error categories` table in docs/src/builtins.md"
776        );
777    }
778
779    #[test]
780    fn every_category_round_trips_through_parse() {
781        for category in &ErrorCategory::ALL {
782            assert_eq!(
783                &ErrorCategory::parse(category.as_str()),
784                category,
785                "`{}` does not round-trip — `parse` is missing an arm, so a \
786                 host handing this category back to Harn silently gets \
787                 `generic`",
788                category.as_str()
789            );
790        }
791    }
792
793    /// Scripts branch on these strings, so an undocumented category is a
794    /// caller writing a match that cannot handle a value the runtime emits.
795    /// `error_category()` used to advertise 10 of the full category set — a dead-port probe
796    /// returning `transient_network` fell outside its own documented list.
797    #[test]
798    fn every_category_is_documented_in_builtins_md() {
799        let path = concat!(env!("CARGO_MANIFEST_DIR"), "/../../docs/src/builtins.md");
800        let doc =
801            std::fs::read_to_string(path).unwrap_or_else(|err| panic!("cannot read {path}: {err}"));
802        let table = doc
803            .split_once("### Error categories")
804            .unwrap_or_else(|| {
805                panic!("docs/src/builtins.md lost its `### Error categories` section")
806            })
807            .1;
808        let table = table.split_once("\n## ").map_or(table, |(head, _)| head);
809        for category in &ErrorCategory::ALL {
810            let row = format!("| `{}` |", category.as_str());
811            assert!(
812                table.contains(&row),
813                "`{}` is missing from the `Error categories` table in \
814                 docs/src/builtins.md",
815                category.as_str()
816            );
817        }
818    }
819
820    #[test]
821    fn classifies_cancelled_messages() {
822        assert_eq!(
823            classify_error_message("Bridge: operation cancelled"),
824            ErrorCategory::Cancelled
825        );
826        assert_eq!(
827            classify_error_message("operation canceled by host"),
828            ErrorCategory::Cancelled
829        );
830    }
831
832    #[test]
833    fn classifies_undefined_builtin_as_internal() {
834        // Structured variant (dispatch table miss / uninstalled builtin).
835        assert_eq!(
836            error_to_category(&VmError::UndefinedBuiltin("__host_agent_foo".into())),
837            ErrorCategory::Internal
838        );
839        // Corrupt bytecode / compiler-VM opcode drift.
840        assert_eq!(
841            error_to_category(&VmError::InvalidInstruction(200)),
842            ErrorCategory::Internal
843        );
844        // Stringly form: some call sites build a `Runtime("Undefined builtin: …")`
845        // message instead of the structured variant — both must classify the same.
846        assert_eq!(
847            error_to_category(&VmError::Runtime(
848                "Undefined builtin: __host_agent_foo (did you mean `bar`?)".into()
849            )),
850            ErrorCategory::Internal
851        );
852        assert_eq!(
853            classify_error_message("Undefined builtin: __host_agent_foo"),
854            ErrorCategory::Internal
855        );
856        // Internal errors are never treated as transient/retryable.
857        assert!(!ErrorCategory::Internal.is_transient());
858        assert!(ErrorCategory::Internal.is_internal());
859        // Round-trips through the string form the agent loop compares against.
860        assert_eq!(ErrorCategory::Internal.as_str(), "internal");
861        assert_eq!(ErrorCategory::parse("internal"), ErrorCategory::Internal);
862    }
863
864    #[test]
865    fn classifies_openrouter_invalid_model_id_as_not_found() {
866        // OpenRouter reports an unknown model as HTTP 400 + prose. The 400 is
867        // not classified by status, so the prose substring must lift it to
868        // NotFound to match Cerebras's 404 path.
869        assert_eq!(
870            classify_error_message(
871                "openrouter API error: qwen/qwen3-coder-bogus is not a valid model ID"
872            ),
873            ErrorCategory::NotFound
874        );
875        assert_eq!(
876            classify_error_message("invalid model id supplied"),
877            ErrorCategory::NotFound
878        );
879    }
880
881    #[test]
882    fn categorized_error_lowers_to_structured_dict() {
883        // A caught `CategorizedError` must surface as a `{category, message}`
884        // dict so `.harn` consumers branch on the typed category instead of
885        // substring-matching the rendered prose (issue #4420).
886        let err = categorized_error(
887            "sandbox violation: /etc/passwd",
888            ErrorCategory::ToolRejected,
889        );
890        let VmValue::Dict(dict) = err.thrown_value() else {
891            panic!(
892                "categorized error must lower to a dict, got {:?}",
893                err.thrown_value()
894            );
895        };
896        assert_eq!(
897            dict.get("category").map(|v| v.display()).as_deref(),
898            Some("tool_rejected"),
899        );
900        assert_eq!(
901            dict.get("message").map(|v| v.display()).as_deref(),
902            Some("sandbox violation: /etc/passwd"),
903        );
904        // The key is the canonical, exhaustively-matched `ErrorCategory::as_str`
905        // contract — not the Display prose. A stringified catch still renders the
906        // message + category (so generic catch-and-log stays sensible).
907        let rendered = categorized_error("boom", ErrorCategory::Cancelled)
908            .thrown_value()
909            .display();
910        assert!(rendered.contains("cancelled"), "rendered dict: {rendered}");
911        assert!(rendered.contains("boom"), "rendered dict: {rendered}");
912    }
913
914    #[test]
915    fn thrown_value_passes_structured_thrown_through_unchanged() {
916        // A user `throw` of a structured value keeps its exact shape — the
917        // lowering seam must not stringify or re-wrap it.
918        let original = VmValue::dict(std::collections::BTreeMap::from([(
919            "code".to_string(),
920            VmValue::Int(7),
921        )]));
922        let VmValue::Dict(dict) = VmError::Thrown(original).thrown_value() else {
923            panic!("thrown dict must pass through as a dict");
924        };
925        assert!(matches!(dict.get("code"), Some(VmValue::Int(7))));
926    }
927
928    #[test]
929    fn deadlock_renders_with_stable_code() {
930        let err = VmError::Deadlock(Box::new(DeadlockError::self_deadlock(
931            "mutex",
932            "__default__",
933            "re-entrant acquire",
934        )));
935        assert!(
936            err.to_string().starts_with("HARN-ORC-011"),
937            "deadlock Display must carry the stable code: {err}"
938        );
939    }
940
941    #[test]
942    fn deadlock_maps_to_generic_category() {
943        let err = VmError::Deadlock(Box::new(DeadlockError::self_deadlock(
944            "task",
945            "task_1",
946            "self-join",
947        )));
948        let category = error_to_category(&err);
949        assert_eq!(category, ErrorCategory::Generic);
950        assert!(
951            !category.is_transient(),
952            "a deadlock must not be treated as a retryable transient error"
953        );
954    }
955}
harn_vm/value/error.rs

harn_vm/value/
error.rs
