//! An example that shows how to implement a simple custom file database.
//! The database uses 32-bit file-ids, which could be useful for optimizing
//! memory usage.
//!
//! To run this example, execute the following command from the top level of
//! this repository:
//!
//! ```sh
//! cargo run --example custom_files
//! ```
use codespan_reporting::diagnostic::{Diagnostic, Label};
use codespan_reporting::term;
use codespan_reporting::term::termcolor::{ColorChoice, StandardStream};
use std::ops::Range;
fn main() -> anyhow::Result<()> {
let mut files = files::Files::new();
let file_id0 = files.add("0.greeting", "hello world!").unwrap();
let file_id1 = files.add("1.greeting", "bye world").unwrap();
let messages = vec![
Message::UnwantedGreetings {
greetings: vec![(file_id0, 0..5), (file_id1, 0..3)],
},
Message::OverTheTopExclamations {
exclamations: vec![(file_id0, 11..12)],
},
];
let writer = StandardStream::stderr(ColorChoice::Always);
let config = term::Config::default();
for message in &messages {
let writer = &mut writer.lock();
term::emit(writer, &config, &files, &message.to_diagnostic())?;
}
Ok(())
}
/// A module containing the file implementation
mod files {
use codespan_reporting::files;
use std::ops::Range;
/// A file that is backed by an `Arc<String>`.
#[derive(Debug, Clone)]
struct File {
/// The name of the file.
name: String,
/// The source code of the file.
source: String,
/// The starting byte indices in the source code.
line_starts: Vec<usize>,
}
impl File {
fn line_start(&self, line_index: usize) -> Result<usize, files::Error> {
use std::cmp::Ordering;
match line_index.cmp(&self.line_starts.len()) {
Ordering::Less => Ok(self
.line_starts
.get(line_index)
.expect("failed despite previous check")
.clone()),
Ordering::Equal => Ok(self.source.len()),
Ordering::Greater => Err(files::Error::LineTooLarge {
given: line_index,
max: self.line_starts.len() - 1,
}),
}
}
}
/// An opaque file identifier.
#[derive(Copy, Clone, PartialEq, Eq)]
pub struct FileId(u32);
#[derive(Debug, Clone)]
pub struct Files {
files: Vec<File>,
}
impl Files {
/// Create a new files database.
pub fn new() -> Files {
Files { files: Vec::new() }
}
/// Add a file to the database, returning the handle that can be used to
/// refer to it again.
pub fn add(
&mut self,
name: impl Into<String>,
source: impl Into<String>,
) -> Option<FileId> {
use std::convert::TryFrom;
let file_id = FileId(u32::try_from(self.files.len()).ok()?);
let name = name.into();
let source = source.into();
let line_starts = files::line_starts(&source).collect();
self.files.push(File {
name,
line_starts,
source,
});
Some(file_id)
}
/// Get the file corresponding to the given id.
fn get(&self, file_id: FileId) -> Result<&File, files::Error> {
self.files
.get(file_id.0 as usize)
.ok_or(files::Error::FileMissing)
}
}
impl<'files> files::Files<'files> for Files {
type FileId = FileId;
type Name = &'files str;
type Source = &'files str;
fn name(&self, file_id: FileId) -> Result<&str, files::Error> {
Ok(self.get(file_id)?.name.as_ref())
}
fn source(&self, file_id: FileId) -> Result<&str, files::Error> {
Ok(&self.get(file_id)?.source)
}
fn line_index(&self, file_id: FileId, byte_index: usize) -> Result<usize, files::Error> {
self.get(file_id)?
.line_starts
.binary_search(&byte_index)
.or_else(|next_line| Ok(next_line - 1))
}
fn line_range(
&self,
file_id: FileId,
line_index: usize,
) -> Result<Range<usize>, files::Error> {
let file = self.get(file_id)?;
let line_start = file.line_start(line_index)?;
let next_line_start = file.line_start(line_index + 1)?;
Ok(line_start..next_line_start)
}
}
}
/// A Diagnostic message.
enum Message {
UnwantedGreetings {
greetings: Vec<(files::FileId, Range<usize>)>,
},
OverTheTopExclamations {
exclamations: Vec<(files::FileId, Range<usize>)>,
},
}
impl Message {
fn to_diagnostic(&self) -> Diagnostic<files::FileId> {
match self {
Message::UnwantedGreetings { greetings } => Diagnostic::error()
.with_message("greetings are not allowed")
.with_labels(
greetings
.iter()
.map(|(file_id, range)| {
Label::primary(*file_id, range.clone()).with_message("a greeting")
})
.collect(),
)
.with_notes(vec![
"found greetings!".to_owned(),
"pleas no greetings :(".to_owned(),
]),
Message::OverTheTopExclamations { exclamations } => Diagnostic::error()
.with_message("over-the-top exclamations")
.with_labels(
exclamations
.iter()
.map(|(file_id, range)| {
Label::primary(*file_id, range.clone()).with_message("an exclamation")
})
.collect(),
)
.with_notes(vec!["ridiculous!".to_owned()]),
}
}
}
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