autocxx-engine 0.3.1

// Copyright 2020 Google LLC
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//    https://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

use proc_macro2::TokenStream;
use std::io::Write;
use std::process::{Command, Stdio};

enum Error {
    RunError(std::io::Error),
    WriteError(std::io::Error),
    Utf8Error(std::string::FromUtf8Error),
    WaitError(std::io::Error),
}

pub(crate) fn pretty_print(ts: &TokenStream) -> String {
    reformat_or_else(ts.to_string())
}

fn reformat_or_else(text: impl std::fmt::Display) -> String {
    match reformat(&text) {
        Ok(s) => s,
        Err(_) => text.to_string(),
    }
}

fn reformat(text: impl std::fmt::Display) -> Result<String, Error> {
    let mut rustfmt = Command::new("rustfmt")
        .stdin(Stdio::piped())
        .stdout(Stdio::piped())
        .spawn()
        .map_err(Error::RunError)?;
    write!(rustfmt.stdin.take().unwrap(), "{}", text).map_err(Error::WriteError)?;
    let output = rustfmt.wait_with_output().map_err(Error::WaitError)?;
    String::from_utf8(output.stdout).map_err(Error::Utf8Error)
}