author | Simon Sapin <simon.sapin@octobus.net> |
Thu, 14 Jan 2021 13:04:12 +0100 | |
changeset 46462 | d03b0601e0eb |
parent 46443 | 43d63979a75e |
child 46483 | 2845892dd489 |
permissions | -rw-r--r-- |
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use std::fmt; |
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/// Common error cases that can happen in many different APIs |
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#[derive(Debug)] |
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pub enum HgError { |
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IoError { |
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error: std::io::Error, |
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context: IoErrorContext, |
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}, |
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/// A file under `.hg/` normally only written by Mercurial |
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/// |
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/// The given string is a short explanation for users, not intended to be |
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/// machine-readable. |
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CorruptedRepository(String), |
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/// The respository or requested operation involves a feature not |
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/// supported by the Rust implementation. Falling back to the Python |
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/// implementation may or may not work. |
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/// |
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/// The given string is a short explanation for users, not intended to be |
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/// machine-readable. |
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UnsupportedFeature(String), |
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} |
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/// Details about where an I/O error happened |
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#[derive(Debug, derive_more::From)] |
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pub enum IoErrorContext { |
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/// A filesystem operation returned `std::io::Error` |
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#[from] |
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File(std::path::PathBuf), |
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/// `std::env::current_dir` returned `std::io::Error` |
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CurrentDir, |
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} |
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impl HgError { |
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pub fn corrupted(explanation: impl Into<String>) -> Self { |
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// TODO: capture a backtrace here and keep it in the error value |
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// to aid debugging? |
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// https://doc.rust-lang.org/std/backtrace/struct.Backtrace.html |
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HgError::CorruptedRepository(explanation.into()) |
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} |
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pub fn unsupported(explanation: impl Into<String>) -> Self { |
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HgError::UnsupportedFeature(explanation.into()) |
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} |
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} |
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// TODO: use `DisplayBytes` instead to show non-Unicode filenames losslessly? |
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impl fmt::Display for HgError { |
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fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result { |
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match self { |
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HgError::IoError { error, context } => { |
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write!(f, "{}: {}", error, context) |
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} |
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HgError::CorruptedRepository(explanation) => { |
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write!(f, "corrupted repository: {}", explanation) |
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} |
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HgError::UnsupportedFeature(explanation) => { |
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write!(f, "unsupported feature: {}", explanation) |
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} |
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} |
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} |
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} |
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// TODO: use `DisplayBytes` instead to show non-Unicode filenames losslessly? |
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impl fmt::Display for IoErrorContext { |
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fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result { |
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match self { |
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IoErrorContext::File(path) => path.display().fmt(f), |
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IoErrorContext::CurrentDir => f.write_str("current directory"), |
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} |
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} |
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} |
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pub trait IoResultExt<T> { |
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/// Annotate a possible I/O error as related to a file at the given path. |
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/// |
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/// This allows printing something like “File not found: example.txt” |
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/// instead of just “File not found”. |
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/// |
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/// Converts a `Result` with `std::io::Error` into one with `HgError`. |
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fn for_file(self, path: &std::path::Path) -> Result<T, HgError>; |
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} |
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impl<T> IoResultExt<T> for std::io::Result<T> { |
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fn for_file(self, path: &std::path::Path) -> Result<T, HgError> { |
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self.map_err(|error| HgError::IoError { |
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error, |
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context: IoErrorContext::File(path.to_owned()), |
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}) |
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} |
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} |
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pub trait HgResultExt<T> { |
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/// Handle missing files separately from other I/O error cases. |
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/// |
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/// Wraps the `Ok` type in an `Option`: |
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/// |
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/// * `Ok(x)` becomes `Ok(Some(x))` |
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/// * An I/O "not found" error becomes `Ok(None)` |
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/// * Other errors are unchanged |
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fn io_not_found_as_none(self) -> Result<Option<T>, HgError>; |
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} |
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impl<T> HgResultExt<T> for Result<T, HgError> { |
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fn io_not_found_as_none(self) -> Result<Option<T>, HgError> { |
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match self { |
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Ok(x) => Ok(Some(x)), |
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Err(HgError::IoError { error, .. }) |
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if error.kind() == std::io::ErrorKind::NotFound => |
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{ |
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Ok(None) |
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} |
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parents:
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Err(other_error) => Err(other_error), |
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} |
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parents:
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} |
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parents:
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} |