view rust/hg-core/src/errors.rs @ 46472:98e39f04d60e

upgrade: implement partial upgrade for upgrading persistent-nodemap

Upgrading repositories to use persistent nodemap should be fast and easy as it
requires only two things:

1) Updating the requirements
2) Writing a persistent-nodemap on disk

For both of the steps above, we don't need to edit existing revlogs.

This patch makes upgrade only do the above mentioned two steps if we are
only upgarding to use persistent-nodemap feature.

Since `nodemap.persist_nodemap()` assumes that there exists a nodemap file for
the given revlog if we are trying to call it, this patch adds `force` argument
to create a file if does not exist which is true in our upgrade case.

The test changes demonstrate that we no longer write nodemap files for manifest
after upgrade which I think is desirable.

Differential Revision: https://phab.mercurial-scm.org/D9936

use std::fmt;

/// Common error cases that can happen in many different APIs
#[derive(Debug)]
pub enum HgError {
    IoError {
        error: std::io::Error,
        context: IoErrorContext,
    },

    /// A file under `.hg/` normally only written by Mercurial
    ///
    /// The given string is a short explanation for users, not intended to be
    /// machine-readable.
    CorruptedRepository(String),

    /// The respository or requested operation involves a feature not
    /// supported by the Rust implementation. Falling back to the Python
    /// implementation may or may not work.
    ///
    /// The given string is a short explanation for users, not intended to be
    /// machine-readable.
    UnsupportedFeature(String),
}

/// Details about where an I/O error happened
#[derive(Debug, derive_more::From)]
pub enum IoErrorContext {
    /// A filesystem operation returned `std::io::Error`
    #[from]
    File(std::path::PathBuf),
    /// `std::env::current_dir` returned `std::io::Error`
    CurrentDir,
}

impl HgError {
    pub fn corrupted(explanation: impl Into<String>) -> Self {
        // TODO: capture a backtrace here and keep it in the error value
        // to aid debugging?
        // https://doc.rust-lang.org/std/backtrace/struct.Backtrace.html
        HgError::CorruptedRepository(explanation.into())
    }

    pub fn unsupported(explanation: impl Into<String>) -> Self {
        HgError::UnsupportedFeature(explanation.into())
    }
}

// TODO: use `DisplayBytes` instead to show non-Unicode filenames losslessly?
impl fmt::Display for HgError {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        match self {
            HgError::IoError { error, context } => {
                write!(f, "{}: {}", error, context)
            }
            HgError::CorruptedRepository(explanation) => {
                write!(f, "corrupted repository: {}", explanation)
            }
            HgError::UnsupportedFeature(explanation) => {
                write!(f, "unsupported feature: {}", explanation)
            }
        }
    }
}

// TODO: use `DisplayBytes` instead to show non-Unicode filenames losslessly?
impl fmt::Display for IoErrorContext {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        match self {
            IoErrorContext::File(path) => path.display().fmt(f),
            IoErrorContext::CurrentDir => f.write_str("current directory"),
        }
    }
}

pub trait IoResultExt<T> {
    /// Annotate a possible I/O error as related to a file at the given path.
    ///
    /// This allows printing something like “File not found: example.txt”
    /// instead of just “File not found”.
    ///
    /// Converts a `Result` with `std::io::Error` into one with `HgError`.
    fn for_file(self, path: &std::path::Path) -> Result<T, HgError>;
}

impl<T> IoResultExt<T> for std::io::Result<T> {
    fn for_file(self, path: &std::path::Path) -> Result<T, HgError> {
        self.map_err(|error| HgError::IoError {
            error,
            context: IoErrorContext::File(path.to_owned()),
        })
    }
}

pub trait HgResultExt<T> {
    /// Handle missing files separately from other I/O error cases.
    ///
    /// Wraps the `Ok` type in an `Option`:
    ///
    /// * `Ok(x)` becomes `Ok(Some(x))`
    /// * An I/O "not found" error becomes `Ok(None)`
    /// * Other errors are unchanged
    fn io_not_found_as_none(self) -> Result<Option<T>, HgError>;
}

impl<T> HgResultExt<T> for Result<T, HgError> {
    fn io_not_found_as_none(self) -> Result<Option<T>, HgError> {
        match self {
            Ok(x) => Ok(Some(x)),
            Err(HgError::IoError { error, .. })
                if error.kind() == std::io::ErrorKind::NotFound =>
            {
                Ok(None)
            }
            Err(other_error) => Err(other_error),
        }
    }
}