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extern crate proc_macro;
use log::LevelFilter;
use proc_macro2::TokenStream;
use quote::{quote, ToTokens};
use syn::{
parse::{Parse, ParseStream, Result},
spanned::Spanned,
Block, Ident, ItemFn, Token, Type,
};
macro_rules! bail {
($msg:expr) => {
return Err(syn::Error::new(Span::call_site(), $msg))
};
($span:expr, $msg:expr) => {
return Err(syn::Error::new($span, $msg))
};
}
macro_rules! compile_error {
($inner:expr) => {
match $inner {
Ok(v) => v,
Err(e) => return e.into_compile_error().into(),
}
};
}
#[proc_macro_attribute]
pub fn ick(
metadata: proc_macro::TokenStream,
s: proc_macro::TokenStream,
) -> proc_macro::TokenStream {
let main = syn::parse_macro_input!(s as Main);
let default_log_level = compile_error!(parse_log_level(metadata));
let quick = Quick {
main,
default_log_level,
};
quote!(#quick).into()
}
fn parse_log_level(metadata: proc_macro::TokenStream) -> Result<LevelFilter> {
struct ParseLevelFilter(Option<LevelFilter>);
impl Parse for ParseLevelFilter {
fn parse(input: ParseStream) -> Result<Self> {
if input.is_empty() {
return Ok(ParseLevelFilter(None));
}
let label: Ident = input.parse()?;
if label != "default_log_level" {
bail!(label.span(), "expected `default_log_level`");
}
let _: Token![=] = input.parse()?;
let level: Ident = input.parse()?;
let level = if level == "off" {
LevelFilter::Off
} else if level == "error" {
LevelFilter::Error
} else if level == "warn" {
LevelFilter::Warn
} else if level == "info" {
LevelFilter::Info
} else if level == "debug" {
LevelFilter::Debug
} else if level == "trace" {
LevelFilter::Trace
} else {
bail!(
level.span(),
"expected one of `off`, `error`, `warn`, `info`, `debug`, `trace`"
)
};
Ok(ParseLevelFilter(Some(level)))
}
}
syn::parse(metadata).map(|v: ParseLevelFilter| v.0.unwrap_or(LevelFilter::Info))
}
struct Quick {
main: Main,
default_log_level: LevelFilter,
}
impl Quick {
fn log_level_as_int(&self) -> i8 {
match self.default_log_level {
LevelFilter::Off => 0,
LevelFilter::Error => 1,
LevelFilter::Warn => 2,
LevelFilter::Info => 3,
LevelFilter::Debug => 4,
LevelFilter::Trace => 5,
}
}
}
struct Main {
opt: Option<Opt>,
body: Box<Block>,
}
struct Opt {
name: Ident,
type_: Type,
}
impl Parse for Main {
fn parse(input: ParseStream) -> Result<Self> {
let inner: ItemFn = Parse::parse(input)?;
let inputs = &inner.sig.inputs;
if inputs.len() > 1 {
bail!(
inputs.span(),
"main function should have at most 1 argument"
);
}
let opt = if let Some(input) = inputs.first() {
Some(get_ident(input)?)
} else {
None
};
Ok(Main {
opt,
body: inner.block,
})
}
}
impl ToTokens for Quick {
fn to_tokens(&self, tokens: &mut TokenStream) {
let body = &self.main.body;
let default_log = self.log_level_as_int();
let mut custom_opt = quote!();
let mut inner_args = quote!();
let mut inner_call = quote!();
if let Some(Opt { name, type_ }) = &self.main.opt {
custom_opt = quote! {
#[structopt(flatten)]
#name: #type_,
};
inner_args = quote!(#name: #type_);
inner_call = quote!(opts.#name);
};
tokens.extend(quote! {
#[derive(StructOpt)]
struct __wrapping_Opt {
#custom_opt
#[structopt(short, long, parse(from_occurrences))]
pub quiet: i8,
#[structopt(short, long, parse(from_occurrences))]
pub verbose: i8,
}
fn _main_inner(#inner_args) -> ::qu::ick_use::Result {
#body
}
fn main() {
let opts: __wrapping_Opt = ::qu::ick_use::StructOpt::from_args();
let log_level = match #default_log.saturating_add(opts.verbose).saturating_sub(opts.quiet) {
0 => ::qu::ick_use::log::LevelFilter::Off,
1 => ::qu::ick_use::log::LevelFilter::Error,
2 => ::qu::ick_use::log::LevelFilter::Warn,
3 => ::qu::ick_use::log::LevelFilter::Info,
4 => ::qu::ick_use::log::LevelFilter::Debug,
_ => ::qu::ick_use::log::LevelFilter::Trace,
};
::qu::env_logger::builder()
.filter_level(log_level)
.init();
if let Err(e) = _main_inner(#inner_call) {
::qu::ick_use::log::error!("{:?}", e);
::std::process::exit(1);
}
}
});
}
}
fn get_ident(input: &syn::FnArg) -> Result<Opt> {
use syn::{FnArg, Pat};
Ok(match input {
FnArg::Typed(v) => match &*v.pat {
Pat::Ident(v_inner) => Opt {
name: v_inner.ident.clone(),
type_: (*v.ty).clone(),
},
_ => bail!(v.pat.span(), "should be an ident (e.g. `opt`)"),
},
_ => bail!(input.span(), "argument should be in form `opt: Opt`)"),
})
}