logging-and-error-reporting

logging-and-error-reporting

Warp has two related ways to surface what happened at runtime:

• log::* (error!/warn!/info!/debug!/trace!) — local diagnostics written to the terminal/log file and, on crash-reporting builds, uploaded to Sentry as breadcrumbs (context attached to the next captured event).
• report_error! — captures a structured Sentry event (an actual issue) for errors worth engineering attention.

How logs reach Sentry (important)

On crash-reporting builds a SentryLogger wraps the logger (warp_logging). The filter:

• Error / Warn / Info → breadcrumb only (not their own Sentry issue).
• Debug / Trace → dropped from Sentry entirely (local-only).
• The Error-level line emitted by report_error! itself → ignored by Sentry (the macro already captured a structured event; the log line would double-report).
• A few noisy targets (wgpu, panic, redraw-frame, the crash-reporting module) are dropped.

Consequences:

• log::error! does NOT create a Sentry issue — it's only a breadcrumb. If a failure should be tracked in Sentry, use report_error!. Only report_error! and panics create Sentry events.
• Breadcrumbs (Info and above) are uploaded, so they must never contain secrets or PII — see "Sensitive data: safe_* macros" below.

Choosing: report_error! vs. log::error! vs. log::warn!

Pick based on whose fault the failure is and what it means for the user, not on how bad it feels. Remember only report_error! reaches Sentry (see above) — the two log levels are local/breadcrumb-only, so choosing between them is about log severity, not about paging anyone.

• report_error! — actionable; an engineer should fix something. Use it when the failure means our code is wrong: an invariant was violated, an assumption that should always hold didn't, or execution reached a state that shouldn't be possible. Also use it when the cause isn't our bug but the user-facing impact is severe enough that we need to build a workaround — this covers failures in a critical subsystem (a core startup/lifecycle path, or a fallback that itself guards a critical path), where even an externally-caused failure is worth an engineer's eyes. One further exception: when we're programming against an external system whose behavior is uncertain — its quirks aren't fully understood, or a failure might actually mean we're using it wrong — prefer report_error! over a plain log, since the "external" failure may be our bug in disguise. This is the only form that becomes a Sentry issue, so reserve it for failures worth an engineer's attention.
• log::error! — a genuine failure that is not our code's fault. The operation we intended couldn't be completed, but the cause is external (the environment or an external system), not a bug we can fix. It's a real failure, so it's error severity — but there's nothing to act on, so it does not page us. (Exception: if it's a critical subsystem, or the external system's behavior is uncertain enough that the failure might be our fault, escalate to report_error! per the bullet above.)
• log::warn! — non-ideal but largely expected. The app can still proceed with the functionality generally intact, perhaps with a degraded experience. Recoverable/handled conditions, fallbacks, retries, and skipped work belong here.

For everything else — lifecycle/state info, expected or handled conditions, and diagnostic "loud logs" (e.g. listing valid options after a lookup miss) — use plain log::* at the level that fits (see "Log levels"). If a function's name/doc says it logs (or it emits a header line plus one entry per item), it should use log::*, not report_error!.

Don't signal the same failure twice. Report it once, at the sink where it stops propagating; log::* breadcrumbs on the way there are useful context (see "Report once, at the sink").

Log levels

The default filter is Info, so debug!/trace! are off unless RUST_LOG enables them.

• error! — a genuine failure whose cause is external, not a bug in our code: the environment or an external system prevented the operation we intended. Nothing for us to fix, so it's not report_error!; still a real failure, so it's error severity. Only a breadcrumb — if it turns out to be actionable, use report_error! instead.
• warn! — non-ideal but largely expected: the app proceeds with the functionality generally intact (possibly degraded). Recoverable/handled paths, retries, fallbacks, skipped work.
• info! — coarse lifecycle/state milestones (startup, connection up/down, feature enabled). On by default and uploaded as breadcrumbs, so keep it low-volume and free of per-item spam.
• debug! — verbose diagnostics for local development; off by default; never sent to Sentry.
• trace! — very fine-grained / hot-path detail; off by default; never sent to Sentry.

Guidance:

• Hot loops, per-frame render paths, and per-message handlers must log at debug!/trace! (never info!+), or they flood the log file and breadcrumb buffer.
• Prefer static, greppable message prefixes with structured key=value detail (e.g. "[Remote codebase indexing] … repo_path={} state={:?}"), matching the surrounding module.
• Use inline format args (log::warn!("… {err:#}")) per the workspace clippy config; format an error chain with {err:#}.

Sensitive data: safe_* macros

Never log secrets, tokens, or credentials at any level. For messages whose useful detail is sensitive-ish — file paths, response payloads, user-generated content — that you want locally but must NOT ship in release-channel logs (which get bundled and become breadcrumbs), use the safe_* macros instead of log::*.

safe_error!, safe_warn!, safe_info!, safe_debug! (plus safe_anyhow! to build an anyhow::Error, and safe_eprintln!) each take a safe: and a full: arm. Dogfood builds log full:; release channels log safe::

use warp_core::safe_error;

safe_error!(
    safe: ("Remote server unexpected response for Initialize"),
    full: ("Remote server unexpected response for Initialize: response={other:?}")
);

• The safe: arm must stand on its own and contain no sensitive/verbose detail; put those bits only in full:.

---

Reporting errors with report_error!

report_error! is the explicit way to send an error to Sentry as a structured event. Reserve it for actionable failures — an invariant or always-true assumption was violated, or the code reached a state it shouldn't, i.e. a bug we should FIX — or for cases where the cause isn't our bug but the user-facing impact is severe enough to warrant a workaround. A failure that's merely an external error (nothing to fix) or an expected/degraded condition belongs at log::error! / log::warn! instead (see "Choosing" above).

At runtime it checks err.is_actionable():

• actionable → captured to Sentry AND logged at Error level.
• not actionable (e.g. registered network errors: reqwest connect/5xx/429, tokio JoinError cancelled) → logged at Warn level only, never sent to Sentry.

This classification only works if the typed error reaches the macro. Sentry buckets events into issues by a fingerprint (its grouping key); because these events are stacktrace-less, Sentry derives that fingerprint from the message text. Interpolating instance-specific data (ids, paths, counts, a stringified error) into the message changes the fingerprint on every occurrence, so one logical error fragments into countless separate issues (and burns through quota). Keep the message a static string so the fingerprint stays stable; per-instance data goes in the error chain (via .context()) or a structured extra: block — neither of which affects the fingerprint — never interpolated into the message.

Bad (fragments Sentry grouping into one group per distinct value, and — when it stringifies a typed error — hides it from is_actionable):

report_error!("Failed to read persisted data: {err}");

Good (canonical in-tree example, app/src/persistence/sqlite.rs):

report_error!(anyhow::Error::new(err).context("Failed to read persisted data"));

Prefer typed error enums over anyhow when it makes sense

Don't default to anyhow. The conventional Rust guidance is "anyhow for applications, thiserror for libraries," but the sharper question is: does anything downstream need to tell the failures apart? If yes, define a typed error enum (thiserror), impl ErrorExt, and register_error! it. In Warp that "downstream" includes the Sentry reporting layer, not just calling code — so typed errors pay off more often than the plain app-vs-library rule suggests.

Reach for a typed error enum when these hold:

• A caller branches on the failure — it matches to recover, retry, fall back, render a specific message/state, or map to a status. This is the classic reason and the strongest signal: an anyhow::Error is opaque, so callers can essentially only print it.
• Mixed actionability — some variants are real bugs worth a Sentry issue and others are expected/environmental (network, auth-expired, user-cancelled, not-found). Per-variant is_actionable() reports the bugs and stays silent on the noise; anyhow is all-or-nothing.
• A fixed, known set of failure modes worth naming — it makes a function's failure surface visible in its signature and gives Sentry stable, meaningful groups (one per variant) instead of one catch-all bucket.
• The same failure recurs across many call sites — define the message and classification once on the type, then report once at the sink.

Default to anyhow when these hold:

• The error is only propagated (? / .context("…")) up to a sink that logs/reports/displays it — nobody matches on its kind.
• The failure modes are open-ended or not worth enumerating.
• A static .context("…") string carries enough for a human reading the Sentry event or log.
• It's leaf/glue code, not an API boundary other code depends on.

It's not either/or: a typed enum can keep an anyhow escape hatch for the genuinely-unexpected case (an Unexpected(#[from] anyhow::Error) variant), classifying the known failures precisely while still absorbing the rest. Group variants by failure mode (what went wrong / what the caller does about it), not by which crate produced the error.

Real example (UserAuthenticationError, crates/warp_server_client/src/auth/mod.rs):

#[derive(thiserror::Error, Debug)]
pub enum UserAuthenticationError {
    #[error("Firebase returned a token error when fetching an ID token")]
    DeniedAccessToken(FirebaseError),
    #[error("unexpected error occurred when fetching an ID token: {0:#}")]
    Unexpected(#[from] anyhow::Error),
    // …
}

impl ErrorExt for UserAuthenticationError {
    fn is_actionable(&self) -> bool {
        match self {
            UserAuthenticationError::DeniedAccessToken(_) => false,
            UserAuthenticationError::Unexpected(e) => e.is_actionable(),
            // …
        }
    }
}
register_error!(UserAuthenticationError);

Choosing the form (variable data out of the grouped message)

Never stringify an already-typed error. report_error!(anyhow::anyhow!("{e}")) flattens e to a String, which erases the typed source chain and defeats is_actionable() (so registered non-actionable network errors get over-reported). Reserve anyhow!("…") for values that are genuinely not errors (see rule 4).

Rules, in priority order:

1. The error IS the payload — report it as an error, never demote it into extra:. extra: is only for genuinely incidental data (ids, paths, counts, durations).
2. Prefer Result-level .context() whenever a Result is in hand. This is the preferred, most succinct style — reach for it before an anyhow::Error::new(..) / anyhow!(..) wrapper whenever practical. Works for any Result<_, E: std::error::Error> and for anyhow::Result; add use anyhow::Context for the trait method. Don't add an anyhow::Error::new(..) / anyhow!(..) wrapper when .context() on the Result will do. Avoid the UFCS form anyhow::Context::context(result, "msg") — it reads poorly; import the trait, or if you'd rather not import it, restructure to own the error and use the inherent method: if let Err(e) = some_call() { report_error!(e.context("msg")); }.

   let data = some_call().context("Failed to load data")?;
   

3. Wrap a bare error value only when there is no Result to hang .context() on (closure/callback params, match arms that special-case other variants):
   • e is a std::error::Error but not anyhow: report_error!(anyhow::Error::new(e).context("msg")).
   • e is already an anyhow::Error: report_error!(e.context("msg")).
   • e is a registered error (register_error!): pass it directly — report_error!(e) — which keeps it fully typed.
   • Error type differs by feature/config (sometimes anyhow, sometimes StdError): use the Result-level .context() above, or report_error!(anyhow::Error::from(e).context("msg")) which compiles for both (do NOT use Error::from where e is unconditionally anyhow — clippy flags it as a useless conversion; use e.context() there).
4. Non-Error payload — a String/&str message, a const, format_args!, or an opaque value that isn't std::error::Error — has no typed chain to preserve, so anyhow::anyhow!("{value}") (or "static", extra: { .. }) is correct here.
5. The error must be reused or returned, so it can't be consumed — but first treat this as a smell. The sink (where the error stops propagating) should normally be the one reporting, and it should own the error so it can move it into report_error! fully typed and with .context(). Needing to report a borrowed error usually means you're reporting away from the true sink, or reporting an error you also return (see "Report once, at the sink") — prefer restructuring so the owner reports. When you genuinely can't take ownership, report it borrowed, which still keeps it typed:
   • e is an anyhow::Error or a registered error → report_error!(&e) (optionally report_error!(&e, extra: { .. })). Note this drops any static .context("…") message, so &e groups by the error's own message.
   • If the later use is itself a borrow (building a format!/detail string, calling a &e method), reorder so that borrow runs first and then move e into the report last — report_error!(anyhow::Error::new(e).context("msg")) (StdError) or report_error!(e.context("msg")) (anyhow). This keeps the typed chain AND the static context.
   • inspect_err(|e| report_error!(..)) only hands you &e (a borrow), which forces the stringified anyhow!("{e}") form. When you're reporting-and-swallowing (.ok() / .ok()?) or otherwise discarding the error, switch to map_err(|e| report_error!(anyhow::Error::new(e).context("msg"))) so e is owned and stays typed — the closure returns (), which composes with a trailing .ok()/?. (Clippy's manual_inspect only fires when a map_err closure returns e unchanged; returning () is fine.)
   • Prefer to make the error reportable while typed before falling back to stringify: a Display-only enum or other unregistered concrete error should be upgraded to #[derive(thiserror::Error)] (or register_error!-ed) so you can report_error!(anyhow::Error::new(e).context("msg")) / report_error!(&e). Only when that isn't feasible is report_error!(anyhow::anyhow!("{e}").context("msg")) unavoidable.
6. Non-error bindings (no error object — let ... else, None => arms, count/id mismatches): static message + extra:.
7. If a crate lacks an anyhow dependency, either use the extra: form (needs no anyhow at the call site) or add anyhow.workspace = true — do not dump a real error into extra: just to avoid the dep.

Report once, at the sink

Report a failure where it stops propagating, not at every layer it flows through. If a function returns or propagates the error (?, return Err(..)), don't also report_error! it there — whoever ultimately handles or swallows it reports it. Reporting in both the callee and the sink double-counts the same failure in Sentry.

• A callee that wants a local breadcrumb while still returning the error should use log::warn!/log::error!, and leave the report_error! to the sink.
• inspect_err(|e| report_error!(..)).ok() (report-and-swallow) is a legitimate terminal decision — the error is consumed there, not returned.
• For a registered error surfaced through many internal failure points, implement is_actionable on the type and report_error! it once at the top-level sink (e.g. a driver's run), instead of reporting at each internal Err.

report_if_error! for report-and-continue

When you have a Result and simply want to report_error! it if it's Err and otherwise carry on — without binding the error yourself — reach for report_if_error!(<expr returning a Result>). It's the succinct form of if let Err(e) = expr { report_error!(e); }, so prefer it whenever you'd otherwise hand-write that pattern at a sink. It's underused; keep it in mind to make error handling more concise. Pair it with a Result-level .context("…") to attach a static grouping message:

report_if_error!(some_fallible_call().context("Failed to do the thing"));

It reports (and logs) an actionable error and is a no-op on Ok, so it fits "report once, at the sink" for a call whose error you don't otherwise need to bind.

extra: syntax

Attach incidental data as a structured Sentry "details" context block. % forces Display, ? forces Debug, a bare expr defaults to Display:

report_error!(
    "Could not find data for pane",
    extra: { "pane_id" => ?pane_id, "count" => %count }
);

Combine a real error with incidental data:

report_error!(
    anyhow::Error::new(e).context("Failed to write attachment"),
    extra: { "path" => %path.display() }
);

Throttling with ReportErrorLogMode::OncePerRun

Sites that can fire repeatedly (hot loops, per-frame paths, enum-fallback conversions from GraphQL/protobuf) should report only once per app run so they don't flood Sentry. Default is EveryTime.

use warp_errors::ReportErrorLogMode;

report_error!(err, ReportErrorLogMode::OncePerRun);
// with a static message + incidental data:
report_error!(
    "Invalid LlmProvider; update client GraphQL types",
    extra: { "provider" => %value },
    ReportErrorLogMode::OncePerRun
);

No secrets or PII

This applies to report_error! messages/extra: AND to log::* at Info and above (both are uploaded to Sentry — the report as an event, the log as a breadcrumb). Never place secrets, tokens, credentials, or user-generated content (file contents, prompts, command text, personal data) in any of them — Sentry retains everything sent. Limit reported/logged data to non-sensitive diagnostics: ids, paths, counts, durations, and error types. When the useful detail is sensitive but helpful locally, use the safe_* macros (see "Sensitive data" above) so it only appears in dogfood logs.

Best practices

• Static, descriptive grouping message; variable data via .context() or extra:.
• When the grouping message is static, put the inputs that explain why this instance fired in extra: — the offending values, not just identifiers (e.g. an invalid-geometry report carries the sizes/offsets that produced it; a bounds violation carries the actual min/max). A static message with no diagnostic extra: is hard to act on.
• Preserve the typed error chain (.context() / anyhow::Error::new) so is_actionable() can suppress registered non-actionable (network) errors — stringifying with anyhow!("{e}") defeats this.
• Prefer Result-level .context() at the sink over an anyhow::Error::new(e).context(..) wrapper whenever a Result is in hand — it's the most succinct, idiomatic form (see "Choosing the form" rule 2). Reach for report_if_error! when you'd otherwise write if let Err(e) = expr { report_error!(e); }.
• Prefer a typed, registered error enum (thiserror + ErrorExt + register_error!) over anyhow when a caller or the Sentry layer needs to tell failures apart (branching, or mixed actionability); reserve anyhow for errors that are only propagated and reported (see "Prefer typed error enums over anyhow when it makes sense").
• Match log level to volume and audience: hot paths at debug!/trace!, milestones at info!, and reserve report_error! for Sentry-worthy failures.

Anti-patterns

// Interpolates variable data into the grouped message.
report_error!("Failed for user {user_id}: {e}");

// Stringifies an owned, typed error — erases the source chain and defeats
// is_actionable(). Use anyhow::Error::new(e).context("msg") instead.
report_error!(anyhow::anyhow!("{e:#}").context("msg"));

// Demotes a real, typed error into extra: (loses is_actionable classification).
report_error!("Request failed", extra: { "error" => %e });

// UFCS .context() reads poorly — import anyhow::Context, or `if let Err(e)` and
// report e.context("msg").
report_error!(anyhow::Context::context(some_call(), "msg").unwrap_err());

// Redundant wrapper when a Result is in hand — use .context() on the Result.
report_error!(anyhow::Error::new(some_call().unwrap_err()).context("msg"));

// log::error! for a Sentry-worthy failure — this is only a breadcrumb, not an
// issue. Use report_error! if it should be tracked in Sentry.
log::error!("Failed to sync: {e:#}");

// Sensitive detail logged unconditionally — ships to release-channel logs and
// breadcrumbs. Use safe_error!(safe: (..), full: (..)) instead.
log::warn!("Bad response body={body:?}");

// info! (or higher) in a hot/per-frame path — floods logs and breadcrumbs.
// Use debug!/trace! for high-frequency diagnostics.
log::info!("rendered frame {n}");