bat/build/syntax_mapping.rs

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use std::{convert::Infallible, env, fs, path::Path, str::FromStr};
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use anyhow::{anyhow, bail};
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use indexmap::IndexMap;
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use itertools::Itertools;
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use serde::Deserialize;
use serde_with::DeserializeFromStr;
use walkdir::WalkDir;
/// Known mapping targets.
///
/// Corresponds to `syntax_mapping::MappingTarget`.
#[derive(Clone, Debug, Eq, PartialEq, Hash, DeserializeFromStr)]
pub enum MappingTarget {
MapTo(String),
MapToUnknown,
MapExtensionToUnknown,
}
impl FromStr for MappingTarget {
type Err = Infallible;
fn from_str(s: &str) -> Result<Self, Self::Err> {
match s {
"MappingTarget::MapToUnknown" => Ok(Self::MapToUnknown),
"MappingTarget::MapExtensionToUnknown" => Ok(Self::MapExtensionToUnknown),
syntax => Ok(Self::MapTo(syntax.into())),
}
}
}
impl MappingTarget {
fn codegen(&self) -> String {
match self {
Self::MapTo(syntax) => format!(r###"MappingTarget::MapTo(r#"{syntax}"#)"###),
Self::MapToUnknown => "MappingTarget::MapToUnknown".into(),
Self::MapExtensionToUnknown => "MappingTarget::MapExtensionToUnknown".into(),
}
}
}
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#[derive(Clone, Debug, DeserializeFromStr)]
/// A single matcher.
///
/// Corresponds to `syntax_mapping::BuiltinMatcher`.
struct Matcher(Vec<MatcherSegment>);
/// Parse a matcher.
///
/// Note that this implementation is rather strict: when it sees a '$', '{', or
/// '}' where it does not make sense, it will immediately hard-error.
///
/// The reason for this strictness is I currently cannot think of a valid reason
/// why you would ever need '$', '{', or '}' as plaintext in a glob pattern.
/// Therefore any such occurrences are likely human errors.
///
/// If we later discover some edge cases, it's okay to make it more permissive.
impl FromStr for Matcher {
type Err = anyhow::Error;
fn from_str(s: &str) -> Result<Self, Self::Err> {
use MatcherSegment as Seg;
if s.is_empty() {
bail!("Empty string is not a valid glob matcher");
}
let mut segments = Vec::new();
let mut buf = String::new();
let mut is_in_var = false;
let mut char_it = s.chars();
loop {
match char_it.next() {
Some('$') => {
if is_in_var {
bail!(r#"Saw a '$' when already in a variable: "{s}""#);
}
match char_it.next() {
Some('{') => {
// push text unless empty
if !buf.is_empty() {
segments.push(Seg::Text(buf.clone()));
buf.clear();
}
// open var
is_in_var = true;
}
Some(_) | None => {
bail!(r#"Expected a '{{' after '$': "{s}""#);
}
}
}
Some('{') => {
bail!(r#"Saw a hanging '{{': "{s}""#);
}
Some('}') => {
if !is_in_var {
bail!(r#"Saw a '}}' when not in a variable: "{s}""#);
}
if buf.is_empty() {
// `${}`
bail!(r#"Variable name cannot be empty: "{s}""#);
}
// push variable
segments.push(Seg::Env(buf.clone()));
buf.clear();
// close var
is_in_var = false;
}
Some(' ') if is_in_var => {
bail!(r#"' ' Cannot be part of a variable's name: "{s}""#);
}
Some(c) => {
// either plaintext or variable name
buf.push(c);
}
None => {
if is_in_var {
bail!(r#"Variable unclosed: "{s}""#);
}
segments.push(Seg::Text(buf.clone()));
break;
}
}
}
Ok(Self(segments))
}
}
impl Matcher {
fn codegen(&self) -> String {
match self.0.len() {
0 => unreachable!("0-length matcher should never be created"),
// if-let guard would be ideal here
// see: https://github.com/rust-lang/rust/issues/51114
1 if matches!(self.0[0], MatcherSegment::Text(_)) => {
let MatcherSegment::Text(ref s) = self.0[0] else {
unreachable!()
};
format!(r###"BuiltinMatcher::Fixed(r#"{s}"#)"###)
}
// parser logic ensures that this case can only happen when there are dynamic segments
_ => {
let segments_codegen = self.0.iter().map(MatcherSegment::codegen).join(", ");
let closure = format!("|| build_glob_string(&[{segments_codegen}])");
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format!("BuiltinMatcher::Dynamic(Lazy::new({closure}))")
}
}
}
}
/// A segment in a matcher.
///
/// Corresponds to `syntax_mapping::MatcherSegment`.
#[derive(Debug, Clone)]
enum MatcherSegment {
Text(String),
Env(String),
}
impl MatcherSegment {
fn codegen(&self) -> String {
match self {
Self::Text(s) => format!(r###"MatcherSegment::Text(r#"{s}"#)"###),
Self::Env(s) => format!(r###"MatcherSegment::Env(r#"{s}"#)"###),
}
}
}
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/// A struct that models a single .toml file in /src/syntax_mapping/builtins/.
#[derive(Clone, Debug, Deserialize)]
struct MappingDefModel {
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mappings: IndexMap<MappingTarget, Vec<Matcher>>,
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}
impl MappingDefModel {
fn into_mapping_list(self) -> MappingList {
let list = self
.mappings
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.into_iter()
.flat_map(|(target, matcher)| {
matcher
.into_iter()
.map(|rule| (rule, target.clone()))
.collect::<Vec<_>>()
})
.collect();
MappingList(list)
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}
}
#[derive(Clone, Debug)]
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struct MappingList(Vec<(Matcher, MappingTarget)>);
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impl MappingList {
fn codegen(&self) -> String {
let array_items: Vec<_> = self
.0
.iter()
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.map(|(matcher, target)| {
format!("({m}, {t})", m = matcher.codegen(), t = target.codegen())
})
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.collect();
let len = array_items.len();
format!(
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"static STATIC_RULES: [(BuiltinMatcher, MappingTarget); {len}] = [\n{items}\n];",
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items = array_items.join(",\n")
)
}
}
fn read_all_mappings() -> anyhow::Result<MappingList> {
let mut all_mappings = vec![];
for entry in WalkDir::new("src/syntax_mapping/builtins")
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.sort_by_file_name()
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.into_iter()
.map(|entry| entry.unwrap_or_else(|err| panic!("failed to visit a file: {err}")))
.filter(|entry| {
let path = entry.path();
path.is_file() && path.extension().map(|ext| ext == "toml").unwrap_or(false)
})
{
let toml_string = fs::read_to_string(entry.path())?;
let mappings = toml::from_str::<MappingDefModel>(&toml_string)?.into_mapping_list();
all_mappings.extend(mappings.0);
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}
Ok(MappingList(all_mappings))
}
/// Build the static syntax mappings defined in /src/syntax_mapping/builtins/
/// into a .rs source file, which is to be inserted with `include!`.
pub fn build_static_mappings() -> anyhow::Result<()> {
let mappings = read_all_mappings()?;
let codegen_path = Path::new(&env::var_os("OUT_DIR").ok_or(anyhow!("OUT_DIR is unset"))?)
.join("codegen_static_syntax_mappings.rs");
fs::write(codegen_path, mappings.codegen())?;
Ok(())
}