Enum ClientError 

#[non_exhaustive]
pub enum ClientError {
    Http(HttpError),
    InvalidHeaderValue(InvalidHeaderValueError),
    AuthFailed(u16),
    Parse(ParseError),
    BlobIntegrityMismatch {
        expected: String,
        actual: String,
    },
    InvalidArgument(String),
    InvalidSession(String),
    MethodNotFound(String),
    MethodError {
        error_type: String,
        description: Option<String>,
    },
    Serialize(SerializeError),
    SseFrameTooLarge {
        limit: usize,
    },
    ResponseTooLarge {
        actual: u64,
        limit: u64,
    },
    WebSocket(WebSocketError),
    UnexpectedResponse(String),
    RateLimited {
        retry_after: UTCDate,
    },
}

Errors produced by the base JMAP client.

Variants cover transport failures (Http, WebSocket), authentication (AuthFailed), JMAP protocol errors (MethodError, UnexpectedResponse), caller bugs (InvalidArgument, InvalidHeaderValue, Serialize), and resource-exhaustion guards (ResponseTooLarge, SseFrameTooLarge).

Marked #[non_exhaustive] so additional variants may be introduced in minor releases. See per-variant documentation for retriability guidance.

Variants (Non-exhaustive)

Non-exhaustive enums could have additional variants added in future. Therefore, when matching against variants of non-exhaustive enums, an extra wildcard arm must be added to account for any future variants.

Http(HttpError)

Network or TLS error from the HTTP layer. May be retriable (transient network failure) or permanent (TLS configuration error). Indicates a network or transport problem, not a JMAP protocol error.

The payload is an opaque HttpError that does not expose any third-party error type — this crate’s HTTP transport can be swapped or its major version bumped without affecting downstream callers. Use HttpError::is_timeout, HttpError::status, etc. to diagnose.

InvalidHeaderValue(InvalidHeaderValueError)

A header value could not be encoded. Indicates a caller bug — the credential string contains characters that are not valid HTTP header value characters. Not retriable.

AuthFailed(u16)

The server returned HTTP 401 (authentication failure) or 403 (authorization failure — credentials present but insufficient). Not retriable without correcting credentials.

Parse(ParseError)

A server response could not be parsed or did not match the expected shape. Indicates the server sent a malformed response. Not retriable without a server fix.

The payload is an opaque ParseError that does not expose the underlying JSON parser’s error type — the variant is insulated from a future parser swap. Construct explicitly: .map_err(ClientError::from_parse) (or .map_err(jmap_base_client::ClientError::from_parse) from outside the crate). Pattern-match via ClientError::Parse(e) => e.line(), e.column(), e.classify() — see ParseError.

BlobIntegrityMismatch

Blob SHA-256 mismatch on upload or download. Indicates in-transit corruption or a misbehaving server. Not retriable without re-fetching metadata.

Field semantics across both call sites (bd:JMAP-6r7c.10)

The same variant is emitted from both upload and download paths and the role of each field is constant across paths:

• expected is the pre-stated digest the client was comparing against — i.e. the value that should hold if the bytes are intact.
• actual is the freshly-observed digest the client just computed or just learned.

The source of each value depends on which call produced the error:

Call site	expected	actual
JmapClient::upload_blob	client’s own SHA-256 of the bytes about to be uploaded	server’s reported SHA-256 in the upload response
JmapClient::download_blob	DownloadBlobParams::expected_sha256 supplied by the caller (typed jmap_cid_types::Sha256, guaranteed canonical lowercase)	client’s SHA-256 of the actually-received bytes

Both digests are canonical 64-character lowercase hex (per draft-atwood-jmap-cid-00 §2 ABNF).

Fields

expected: String

Pre-stated SHA-256 hex digest the client was comparing against. On upload, this is the client’s own pre-upload computation; on download, this is the caller-supplied DownloadBlobParams::expected_sha256 (typed jmap_cid_types::Sha256, guaranteed canonical lowercase).

actual: String

Freshly-observed SHA-256 hex digest. On upload, this is the server-reported digest from the upload response. On download, this is the client’s own digest over the received bytes.

InvalidArgument(String)

A caller-supplied argument violates a precondition (e.g. empty token, colon in BasicAuth username, missing required filter field).

InvalidSession(String)

The JMAP Session object from the server was missing a required field. Indicates a server-side bug or incompatible server. Not retriable.

MethodNotFound(String)

The JMAP API response did not contain the expected method call ID. Indicates a server-side bug or unexpected response shape.

MethodError

The JMAP server returned a method-level error object (RFC 8620 §3.6). Retriability depends on error_type (e.g. serverFail may be retried; invalidArguments is not retriable).

description is None when the server omits the optional description field.

Fields

error_type: String

The type field of the JMAP method-level error object (RFC 8620 §3.6.2), e.g. "invalidArguments", "serverFail", "accountNotFound".

description: Option<String>

Optional human-readable error description (RFC 8620 §3.6.2); None when the server omits this field.

Serialize(SerializeError)

A JMAP request could not be serialized to JSON when sending over WebSocket. Indicates a caller bug — the data structure contains non-serializable values. Not retriable.

This error is only returned by WsSession::send_request; the HTTP call() path delegates serialization to reqwest, which surfaces serialization failures as ClientError::Http.

The payload is an opaque SerializeError that does not expose the underlying JSON serializer’s error type. Construct explicitly: .map_err(ClientError::from_serialize). Pattern-match via ClientError::Serialize(e) => e.line(), e.column(), e.classify() — see SerializeError.

SseFrameTooLarge

An SSE frame exceeded the configured buffer limit (ClientConfig::max_sse_frame). The stream is terminated after this error. Indicates a misbehaving or hostile server.

Fields

limit: usize

The configured per-frame buffer cap (in bytes) that was exceeded.

ResponseTooLarge

A server response body exceeded the enforced size limit. Protects against unbounded memory allocation from malicious or buggy servers. actual is in bytes (from Content-Length or actual read size).

Fields

actual: u64

Observed response size in bytes (from Content-Length or the running total of bytes read so far when streaming).

limit: u64

Configured maximum response size in bytes.

WebSocket(WebSocketError)

A WebSocket transport error (connection, framing, or TLS). May be retriable (transient network failure) or permanent (TLS config error).

The payload is an opaque WebSocketError that does not expose any third-party error type — see HttpError for the same SemVer rationale. Use WebSocketError::is_io, WebSocketError::is_protocol, etc. to diagnose.

UnexpectedResponse(String)

The server returned a response that violates the JMAP protocol (outside the Session fetch path). Examples: wrong Content-Type on an SSE connection, unexpected response shape on a non-session endpoint.

Distinct from ClientError::InvalidSession, which indicates a problem with the Session document itself. Not retriable without a server fix.

RateLimited

Server rate-limited the request. retry_after indicates when to retry.

⚠ Not currently produced by this crate (bd:JMAP-6lsm.3, bd:JMAP-6r7c.33)

HTTP 429 responses fall through reqwest::error_for_status() and surface as ClientError::Http today, NOT as ClientError::RateLimited. A caller that matches only on this variant will miss every actual 429 from the base crate. Until bd:JMAP-6lsm.3 lands the native 429 → RateLimited conversion, callers MUST handle both cases:

match err {
    ClientError::RateLimited { retry_after } => {
        // Eventually the only path; today only produced by extension
        // crates that wrap this crate's error conversion.
        sleep_until(retry_after).await;
    }
    ClientError::Http(http) if http.status() == Some(429) => {
        // Base-crate path today (bd:JMAP-6lsm.3 will collapse this
        // into the RateLimited arm above).
        sleep(Duration::from_secs(30)).await; // or parse Retry-After
    }
    other => { /* propagate */ }
}

Why the variant ships anyway

The variant is part of the public contract so:

1. Extension crates that wrap or replace this crate’s transport may detect 429 + parse Retry-After themselves and produce RateLimited from their own error-conversion code.
2. Callers that want to handle rate limiting via this typed variant have a stable target to match on, even before the conversion logic lands here (tracked under bd:JMAP-6lsm.3).

The variant shape will not change in a backward-incompatible way when 429 → RateLimited conversion lands — it is part of a #[non_exhaustive] enum and the struct payload is itself stable, so callers writing the dual-match pattern above today will not need to adjust when the migration completes.

Fields

retry_after: UTCDate

Absolute UTC instant the client should wait until before retrying, parsed from the Retry-After HTTP header (RFC 9110 §10.2.3).

Implementations

impl ClientError

pub fn from_parse(e: Error) -> ClientError

Convert a serde_json::Error from a deserialize / parse step into a ClientError::Parse variant carrying an opaque ParseError payload (bd:JMAP-6r7c.26).

Public because extension client crates (jmap-mail-client, jmap-chat-client, etc.) need to surface their own JSON parse failures as ClientError::Parse. Use in .map_err:

let val: T = serde_json::from_slice(&bytes)
    .map_err(jmap_base_client::ClientError::from_parse)?;

A future JSON-parser swap would deprecate this constructor in favor of an analogous one for the new parser; the variant payload type (ParseError) stays stable.

pub fn from_serialize(e: Error) -> ClientError

Convert a serde_json::Error from a serialize step into a ClientError::Serialize variant carrying an opaque SerializeError payload (bd:JMAP-6r7c.26).

Public for the same reason as from_parse.

Trait Implementations

impl Debug for ClientError

fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error>

Formats the value using the given formatter.

impl Display for ClientError

fn fmt(&self, __formatter: &mut Formatter<'_>) -> Result<(), Error>

Formats the value using the given formatter.

impl Error for ClientError

fn source(&self) -> Option<&(dyn Error + 'static)>

Returns the lower-level source of this error, if any.

fn description(&self) -> &str

👎Deprecated since 1.42.0:

use the Display impl or to_string()

fn cause(&self) -> Option<&dyn Error>

👎Deprecated since 1.33.0:

replaced by Error::source, which can support downcasting

fn provide<'a>(&'a self, request: &mut Request<'a>)

🔬This is a nightly-only experimental API. (error_generic_member_access)

Provides type-based access to context intended for error reports.