mf2-build 1.0.0

//! Everything that can stop a build.
//!
//! A *diagnostic* — a syntax error in a locale file, a lint — is not one of
//! these: it is a [`Report`](crate::Report) entry with a file, a line and a
//! column, and a build fails on the count of them. This type is for what
//! stops the build before it can report anything: I/O, a malformed
//! `mf2.toml`, a catalog the writer refuses.

use std::io;
use std::path::PathBuf;

/// The result of a build step.
pub type Result<T> = std::result::Result<T, Error>;

/// What stops a build.
#[derive(Debug, thiserror::Error)]
#[non_exhaustive]
pub enum Error {
    /// A file could not be read or written.
    #[error("{path}: {source}")]
    Io {
        /// The file.
        path: PathBuf,
        /// What the operating system said.
        #[source]
        source: io::Error,
    },

    /// `mf2.toml` is not valid TOML, or a key in it is wrong.
    #[error("{path}: {message}")]
    Config {
        /// The configuration file.
        path: PathBuf,
        /// Which key, and what is wrong with it.
        message: String,
    },

    /// A flat JSON corpus is not an object of strings.
    #[error("{path}:{line}:{column}: {message}")]
    Json {
        /// The file.
        path: PathBuf,
        /// One-based line.
        line: u32,
        /// One-based column.
        column: u32,
        /// What is wrong.
        message: String,
    },

    /// The locale directory names a tag the catalog format cannot write.
    #[error("locale {locale:?}: {source}")]
    Locale {
        /// The tag.
        locale: String,
        /// What the locale data said.
        #[source]
        source: mf2_locale_data::Error,
    },

    /// The catalog writer refused a locale's messages.
    #[error("catalog for {locale}: {source}")]
    Write {
        /// The tag.
        locale: String,
        /// What the writer said.
        #[source]
        source: mf2_catalog::WriteError,
    },

    /// The locale data could not be sliced.
    #[error(transparent)]
    LocaleData(#[from] mf2_locale_data::Error),

    /// The manifest could not be written or read back.
    #[error(transparent)]
    Manifest(#[from] mf2_catalog::ManifestError),

    /// A catalog could not be written.
    #[error(transparent)]
    Catalog(#[from] mf2_catalog::WriteError),

    /// A catalog could not be compressed.
    ///
    /// Both encoders write into a `Vec`, so this is a compressor fault, not a
    /// full disk. It is still an error rather than a shrug: a truncated
    /// `.br` would be served immutable beside a `.mf2b` whose content hash
    /// says it is intact, and the client would see a corrupt catalog.
    #[error("catalog for {locale}: {format}: {source}")]
    Compress {
        /// The tag.
        locale: String,
        /// `brotli` or `gzip`.
        format: &'static str,
        /// What the encoder said.
        #[source]
        source: io::Error,
    },

    /// The layout on disk is not what a build needs.
    #[error("{0}")]
    Layout(String),

    /// The build found errors in the corpus; they are in the report.
    #[error("{errors} error{} in {locales} locale{}", plural(*errors), plural(*locales))]
    Corpus {
        /// How many errors.
        errors: usize,
        /// In how many locales.
        locales: usize,
    },
}

fn plural(n: usize) -> &'static str {
    if n == 1 { "" } else { "s" }
}

impl Error {
    /// An I/O error that names its file.
    #[doc(hidden)]
    pub fn io(path: impl Into<PathBuf>, source: io::Error) -> Error {
        Error::Io {
            path: path.into(),
            source,
        }
    }
}