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//! The single error type returned by the library.
//!
//! Every fallible entry point yields [`AppError`], so an embedder matches on
//! one enum instead of the several error types the internals use. The binary
//! maps the same variants to exit codes.
use std::fmt;
use std::io;
/// Application error. Wraps IO and validation failures encountered by the CLI.
#[derive(Debug)]
pub enum AppError {
/// Underlying IO error (file read, write, etc.) with the path or
/// context label that triggered it. Use the `AppError::io` constructor;
/// the blanket `From<io::Error>` is intentionally absent because losing
/// the path on every `?` is exactly what this variant was reshaped to
/// prevent.
Io {
/// Path or sentinel that identifies *what* failed (e.g.
/// `/tmp/out.json`, `<stdout>`). Embedded in `Display`; the
/// underlying `io::Error` is exposed through `Error::source()`
/// so callers using `anyhow`-style chaining see both layers.
context: String,
/// The failure as reported by the operating system.
source: io::Error,
},
/// `--dir` does not exist or is not a directory
InvalidDirectory(String),
/// `--glob` pattern is malformed or uses an unsupported feature
InvalidGlob(String),
/// CLI date argument is not parseable as YYYY-MM-DD
InvalidDate(String),
/// `--tz` is not a valid IANA timezone
InvalidTimezone(String),
/// `--output` path is unsafe (missing parent, symlink, etc.)
InvalidOutput(String),
/// `--from` and `--to` form an invalid range
DateRange(String),
/// JSON or other serializer reported an error
Serialization(String),
/// Regex compilation failed
Regex(String),
}
impl fmt::Display for AppError {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
// The CLI prepends `error: ` to whatever this returns. Avoid adding a
// second category prefix when the inner `msg` is already a complete
// sentence; for opaque variants (Io / Regex / Serialization /
// InvalidTimezone) keep a short lowercase tag so output stays grepable.
match self {
AppError::Io { context, source } => write!(f, "io: {context}: {source}"),
AppError::InvalidDirectory(msg) => write!(f, "{msg}"),
AppError::InvalidGlob(msg) => write!(f, "{msg}"),
AppError::InvalidDate(msg) => write!(f, "{msg}"),
AppError::InvalidTimezone(tz) => write!(f, "invalid timezone: {tz}"),
AppError::InvalidOutput(msg) => write!(f, "{msg}"),
AppError::DateRange(msg) => write!(f, "{msg}"),
AppError::Serialization(msg) => write!(f, "serialization: {msg}"),
AppError::Regex(msg) => write!(f, "regex: {msg}"),
}
}
}
impl AppError {
/// Process exit code that classifies this error category.
///
/// - `2` -- usage / input-validation failures the user can correct by
/// changing CLI arguments (matches clap's own argument-error exit).
/// - `74` -- IO failures (`EX_IOERR` from `sysexits.h`): unreadable files,
/// write failures.
/// - `70` -- internal software errors (`EX_SOFTWARE`): a regex we built
/// ourselves did not compile, or our own serializer failed.
pub fn exit_code(&self) -> i32 {
match self {
AppError::InvalidDirectory(_)
| AppError::InvalidGlob(_)
| AppError::InvalidDate(_)
| AppError::InvalidTimezone(_)
| AppError::InvalidOutput(_)
| AppError::DateRange(_) => 2,
AppError::Io { .. } => 74,
AppError::Regex(_) | AppError::Serialization(_) => 70,
}
}
/// Construct an `AppError::Io` while preserving the underlying source.
///
/// The `context` is a free-form label printed by `Display`: prefer the
/// real filesystem path when one is available (`p.display()`), fall back
/// to the sentinel `<stdout>` / `<stderr>` for the standard streams.
/// Use this in place of `?` on `io::Error` — the blanket `From` was
/// removed precisely so that no IO failure can sneak through without a
/// caller-supplied location.
pub fn io(context: impl Into<String>, source: io::Error) -> Self {
AppError::Io {
context: context.into(),
source,
}
}
}
impl std::error::Error for AppError {
fn source(&self) -> Option<&(dyn std::error::Error + 'static)> {
// Only Io currently carries a wrapped source. Surfacing it lets
// downstream tooling (anyhow, log formatters) walk the chain and
// print the underlying OS error verbatim — important for diagnosing
// EACCES / ENOSPC / EROFS where the raw errno text is the most
// useful signal.
match self {
AppError::Io { source, .. } => Some(source),
_ => None,
}
}
}
impl From<serde_json::Error> for AppError {
fn from(err: serde_json::Error) -> Self {
AppError::Serialization(err.to_string())
}
}
#[cfg(test)]
mod tests {
use super::*;
use std::io::{self, ErrorKind};
#[test]
fn display_invalid_directory() {
let e = AppError::InvalidDirectory("directory does not exist: /no/such".into());
assert_eq!(e.to_string(), "directory does not exist: /no/such");
}
#[test]
fn display_invalid_glob() {
let e = AppError::InvalidGlob("invalid pattern '[': ...".into());
assert_eq!(e.to_string(), "invalid pattern '[': ...");
}
#[test]
fn display_invalid_timezone() {
assert_eq!(
AppError::InvalidTimezone("X".into()).to_string(),
"invalid timezone: X"
);
}
#[test]
fn display_invalid_output() {
assert_eq!(
AppError::InvalidOutput("refusing to overwrite symlink: /tmp/foo".into()).to_string(),
"refusing to overwrite symlink: /tmp/foo"
);
}
#[test]
fn display_date_range() {
assert_eq!(
AppError::DateRange("from > to".into()).to_string(),
"from > to"
);
}
#[test]
fn io_constructor_preserves_context_and_source() {
// `AppError::io` is the only path that produces the Io variant now
// (the blanket From<io::Error> was removed). Both the context label
// and the underlying source must round-trip without loss — context
// in Display and source via std::error::Error::source().
use std::error::Error as _;
let io_err = io::Error::new(ErrorKind::NotFound, "missing");
let e = AppError::io("/tmp/out.json", io_err);
assert!(matches!(e, AppError::Io { .. }));
let msg = e.to_string();
assert!(msg.starts_with("io: "), "got: {msg}");
assert!(msg.contains("/tmp/out.json"), "got: {msg}");
assert!(msg.contains("missing"), "got: {msg}");
let src = e.source().expect("source should be set for Io");
assert!(src.to_string().contains("missing"));
}
#[test]
fn source_returns_none_for_non_io_variants() {
// Only Io currently chains a source. Pin the contract so a future
// refactor that adds source() for other variants doesn't ship
// accidentally — every new chained-source variant deserves a test
// here and a CHANGELOG line.
use std::error::Error as _;
assert!(AppError::InvalidDirectory("x".into()).source().is_none());
assert!(AppError::Regex("x".into()).source().is_none());
assert!(AppError::Serialization("x".into()).source().is_none());
}
#[test]
fn from_serde_json_error_wraps() {
let parsed: Result<serde_json::Value, _> = serde_json::from_str("not json");
let e: AppError = parsed.unwrap_err().into();
assert!(matches!(e, AppError::Serialization(_)));
assert!(e.to_string().starts_with("serialization: "));
}
#[test]
fn errors_are_send_sync() {
// Compile-time check that AppError can flow across threads — matters if
// we ever spawn worker threads (e.g. for parallel walker).
fn is_send_sync<T: Send + Sync>() {}
is_send_sync::<AppError>();
}
#[test]
fn exit_code_usage_errors_return_2() {
assert_eq!(
AppError::InvalidDirectory("x".into()).exit_code(),
2,
"InvalidDirectory is a usage error and must map to exit 2"
);
assert_eq!(AppError::InvalidGlob("x".into()).exit_code(), 2);
assert_eq!(AppError::InvalidDate("x".into()).exit_code(), 2);
assert_eq!(AppError::InvalidTimezone("x".into()).exit_code(), 2);
assert_eq!(AppError::InvalidOutput("x".into()).exit_code(), 2);
assert_eq!(AppError::DateRange("x".into()).exit_code(), 2);
}
#[test]
fn exit_code_io_returns_74() {
let io = io::Error::new(ErrorKind::NotFound, "missing");
assert_eq!(
AppError::io("/tmp/x", io).exit_code(),
74,
"Io maps to EX_IOERR (74) from sysexits.h"
);
}
#[test]
fn exit_code_software_errors_return_70() {
assert_eq!(
AppError::Regex("x".into()).exit_code(),
70,
"Regex compile failure is an internal software error (EX_SOFTWARE = 70)"
);
assert_eq!(AppError::Serialization("x".into()).exit_code(), 70);
}
}