Rust编写的JavaScript引擎,该项目是一个试验性质的项目。
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#![deny(unused_qualifications, clippy::correctness, clippy::style)]
#![warn(clippy::perf)]
#![allow(clippy::cognitive_complexity)]
use boa::builtins::console::log;
use boa::serde_json;
use boa::syntax::ast::{expr::Expr, token::Token};
use boa::{exec::Executor, forward_val, realm::Realm};
use std::io::{self, Write};
use std::{fs::read_to_string, path::PathBuf};
use structopt::clap::arg_enum;
use structopt::StructOpt;
/// CLI configuration for Boa.
//
// Added #[allow(clippy::option_option)] because to StructOpt an Option<Option<T>>
// is an optional argument that optionally takes a value ([--opt=[val]]).
// https://docs.rs/structopt/0.3.11/structopt/#type-magic
#[allow(clippy::option_option)]
#[derive(Debug, StructOpt)]
#[structopt(author, about)]
struct Opt {
/// The JavaScript file(s) to be evaluated.
#[structopt(name = "FILE", parse(from_os_str))]
files: Vec<PathBuf>,
/// Dump the token stream to stdout with the given format.
#[structopt(
long,
short = "-t",
value_name = "FORMAT",
possible_values = &DumpFormat::variants(),
case_insensitive = true,
conflicts_with = "dump-ast"
)]
dump_tokens: Option<Option<DumpFormat>>,
/// Dump the ast to stdout with the given format.
#[structopt(
long,
short = "-a",
value_name = "FORMAT",
possible_values = &DumpFormat::variants(),
case_insensitive = true
)]
dump_ast: Option<Option<DumpFormat>>,
}
impl Opt {
/// Returns whether a dump flag has been used.
fn has_dump_flag(&self) -> bool {
self.dump_tokens.is_some() || self.dump_ast.is_some()
}
}
arg_enum! {
/// The different types of format available for dumping.
///
// NOTE: This can easily support other formats just by
// adding a field to this enum and adding the necessary
// implementation. Example: Toml, Html, etc.
//
// NOTE: The fields of this enum are not doc comments because
// arg_enum! macro does not support it.
#[derive(Debug)]
enum DumpFormat {
// This is the default format that you get from std::fmt::Debug.
Debug,
// This is a minified json format.
Json,
// This is a pretty printed json format.
JsonPretty,
}
}
/// Lexes the given source code into a stream of tokens and return it.
///
/// Returns a error of type String with a message,
/// if the source has a syntax error.
fn lex_source(src: &str) -> Result<Vec<Token>, String> {
use boa::syntax::lexer::Lexer;
let mut lexer = Lexer::new(src);
lexer.lex().map_err(|e| format!("SyntaxError: {}", e))?;
Ok(lexer.tokens)
}
/// Parses the the token stream into a ast and returns it.
///
/// Returns a error of type String with a message,
/// if the token stream has a parsing error.
fn parse_tokens(tokens: Vec<Token>) -> Result<Expr, String> {
use boa::syntax::parser::Parser;
Parser::new(tokens)
.parse_all()
.map_err(|e| format!("ParsingError: {}", e))
}
/// Dumps the token stream or ast to stdout depending on the given arguments.
///
/// Returns a error of type String with a error message,
/// if the source has a syntax or parsing error.
fn dump(src: &str, args: &Opt) -> Result<(), String> {
let tokens = lex_source(src)?;
if let Some(ref arg) = args.dump_tokens {
match arg {
Some(format) => match format {
DumpFormat::Debug => println!("{:#?}", tokens),
DumpFormat::Json => println!("{}", serde_json::to_string(&tokens).unwrap()),
DumpFormat::JsonPretty => {
println!("{}", serde_json::to_string_pretty(&tokens).unwrap())
}
},
// Default token stream dumping format.
None => println!("{:#?}", tokens),
}
} else if let Some(ref arg) = args.dump_ast {
let ast = parse_tokens(tokens)?;
match arg {
Some(format) => match format {
DumpFormat::Debug => println!("{:#?}", ast),
DumpFormat::Json => println!("{}", serde_json::to_string(&ast).unwrap()),
DumpFormat::JsonPretty => {
println!("{}", serde_json::to_string_pretty(&ast).unwrap())
}
},
// Default ast dumping format.
None => println!("{:#?}", ast),
}
}
Ok(())
}
pub fn main() -> Result<(), std::io::Error> {
let args = Opt::from_args();
let realm = Realm::create().register_global_func("print", log);
let mut engine = Executor::new(realm);
for file in &args.files {
let buffer = read_to_string(file)?;
if args.has_dump_flag() {
match dump(&buffer, &args) {
Ok(_) => {}
Err(e) => eprintln!("{}", e),
}
} else {
match forward_val(&mut engine, &buffer) {
Ok(v) => print!("{}", v.to_string()),
Err(v) => eprint!("{}", v.to_string()),
}
}
}
if args.files.is_empty() {
loop {
let mut buffer = String::new();
io::stdin().read_line(&mut buffer)?;
if args.has_dump_flag() {
match dump(&buffer, &args) {
Ok(_) => {}
Err(e) => eprintln!("{}", e),
}
} else {
match forward_val(&mut engine, buffer.trim_end()) {
Ok(v) => println!("{}", v.to_string()),
Err(v) => eprintln!("{}", v.to_string()),
}
}
// The flush is needed because where in a REPL and we do not want buffering.
std::io::stdout().flush().unwrap();
}
}
Ok(())
}