autocxx-engine 0.5.2

// 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 autocxx_parser::file_locations::FileLocationStrategy;
use proc_macro2::TokenStream;

use crate::{ParseError, ParsedFile, RebuildDependencyRecorder};
use std::io::Write;
use std::path::{Path, PathBuf};
use std::{ffi::OsStr, io, process};
use std::{fmt::Display, fs::File};

/// Errors returned during creation of a cc::Build from an include_cxx
/// macro.
#[derive(Debug)]
pub enum BuilderError {
    /// The cxx module couldn't parse the code generated by autocxx.
    /// This could well be a bug in autocxx.
    InvalidCxx(cxx_gen::Error),
    /// The .rs file didn't exist or couldn't be parsed.
    ParseError(ParseError),
    /// We couldn't write the c++ code to disk.
    FileWriteFail(std::io::Error, PathBuf),
    /// No `include_cxx` macro was found anywhere.
    NoIncludeCxxMacrosFound,
    /// Unable to create one of the directories to which we need to write
    UnableToCreateDirectory(std::io::Error, PathBuf),
}

impl Display for BuilderError {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        match self {
            BuilderError::ParseError(pe) => write!(f, "Unable to parse .rs file: {}", pe)?,
            BuilderError::InvalidCxx(ee) => write!(f, "cxx was unable to understand the code generated by autocxx (likely a bug in autocxx; please report.) {}", ee)?,
            BuilderError::FileWriteFail(ee, pb) => write!(f, "Unable to write to {}: {}", pb.to_string_lossy(), ee)?,
            BuilderError::NoIncludeCxxMacrosFound => write!(f, "No include_cpp! macro found")?,
            BuilderError::UnableToCreateDirectory(ee, pb) => write!(f, "Unable to create directory {}: {}", pb.to_string_lossy(), ee)?,
        }
        Ok(())
    }
}

pub type BuilderBuild = cc::Build;

pub struct BuilderSuccess(pub BuilderBuild, pub Vec<PathBuf>);

/// Results of a build.
pub type BuilderResult = Result<BuilderSuccess, BuilderError>;

/// Build autocxx C++ files and return a cc::Build you can use to build
/// more from a build.rs file.
/// You need to provide the Rust file path and the iterator of paths
/// which should be used as include directories.
pub fn build<P1, I, T>(
    rs_file: P1,
    autocxx_incs: I,
    dependency_recorder: Option<Box<dyn RebuildDependencyRecorder>>,
) -> BuilderResult
where
    P1: AsRef<Path>,
    I: IntoIterator<Item = T>,
    T: AsRef<OsStr>,
{
    build_to_custom_directory(rs_file, autocxx_incs, None, dependency_recorder)
}

/// Builds successfully, or exits the process displaying a suitable
/// message.
pub fn expect_build<P1, I, T>(
    rs_file: P1,
    autocxx_incs: I,
    dependency_recorder: Option<Box<dyn RebuildDependencyRecorder>>,
) -> BuilderSuccess
where
    P1: AsRef<Path>,
    I: IntoIterator<Item = T>,
    T: AsRef<OsStr>,
{
    build(rs_file, autocxx_incs, dependency_recorder).unwrap_or_else(|err| {
        let _ = writeln!(io::stderr(), "\n\nautocxx error: {}\n\n", report(err));
        process::exit(1);
    })
}

fn report(err: BuilderError) -> String {
    err.to_string()
}

/// Like build, but you can specify the location where files should be generated.
/// Not generally recommended for use in build scripts.
pub(crate) fn build_to_custom_directory<P1, I, T>(
    rs_file: P1,
    autocxx_incs: I,
    custom_gendir: Option<PathBuf>,
    dependency_recorder: Option<Box<dyn RebuildDependencyRecorder>>,
) -> BuilderResult
where
    P1: AsRef<Path>,
    I: IntoIterator<Item = T>,
    T: AsRef<OsStr>,
{
    rust_version_check();
    let gen_location_strategy = match custom_gendir {
        None => FileLocationStrategy::new(),
        Some(custom_dir) => FileLocationStrategy::Custom(custom_dir),
    };
    let incdir = gen_location_strategy.get_include_dir();
    ensure_created(&incdir)?;
    let cxxdir = gen_location_strategy.get_cxx_dir();
    ensure_created(&cxxdir)?;
    let rsdir = gen_location_strategy.get_rs_dir();
    ensure_created(&rsdir)?;
    // We are incredibly unsophisticated in our directory arrangement here
    // compared to cxx. I have no doubt that we will need to replicate just
    // about everything cxx does, in due course...
    // Write cxx.h to that location, as it may be needed by
    // some of our generated code.
    write_to_file(&incdir, "cxx.h", crate::HEADER.as_bytes())?;

    let autocxx_inc = build_autocxx_inc(autocxx_incs, &incdir);
    // pass on th
    gen_location_strategy.set_cargo_env_vars_for_build();

    let mut parsed_file = crate::parse_file(rs_file).map_err(BuilderError::ParseError)?;
    parsed_file
        .resolve_all(autocxx_inc, dependency_recorder)
        .map_err(BuilderError::ParseError)?;
    build_with_existing_parsed_file(parsed_file, cxxdir, incdir, rsdir)
}

pub(crate) fn build_with_existing_parsed_file(
    parsed_file: ParsedFile,
    cxxdir: PathBuf,
    incdir: PathBuf,
    rsdir: PathBuf,
) -> BuilderResult {
    let mut counter = 0;
    let mut builder = cc::Build::new();
    builder.cpp(true);
    let mut generated_rs = Vec::new();
    for include_cpp in parsed_file.get_autocxxes() {
        for inc_dir in include_cpp.include_dirs() {
            builder.include(inc_dir);
        }
        let generated_code = include_cpp
            .generate_h_and_cxx()
            .map_err(BuilderError::InvalidCxx)?;
        for filepair in generated_code.0 {
            let fname = format!("gen{}.cxx", counter);
            counter += 1;
            let gen_cxx_path = write_to_file(&cxxdir, &fname, &filepair.implementation)?;
            builder.file(gen_cxx_path);

            write_to_file(&incdir, &filepair.header_name, &filepair.header)?;
            let fname = include_cpp.get_rs_filename();
            let rs = include_cpp.generate_rs();
            generated_rs.push(write_rs_to_file(&rsdir, &fname, rs)?);
        }
    }
    if counter == 0 {
        Err(BuilderError::NoIncludeCxxMacrosFound)
    } else {
        Ok(BuilderSuccess(builder, generated_rs))
    }
}

fn ensure_created(dir: &Path) -> Result<(), BuilderError> {
    std::fs::create_dir_all(dir)
        .map_err(|e| BuilderError::UnableToCreateDirectory(e, dir.to_path_buf()))
}

fn build_autocxx_inc<I, T>(paths: I, extra_path: &Path) -> Vec<PathBuf>
where
    I: IntoIterator<Item = T>,
    T: AsRef<OsStr>,
{
    paths
        .into_iter()
        .map(|p| PathBuf::from(p.as_ref()))
        .chain(std::iter::once(extra_path.to_path_buf()))
        .collect()
}

fn write_to_file(dir: &Path, filename: &str, content: &[u8]) -> Result<PathBuf, BuilderError> {
    let path = dir.join(filename);
    try_write_to_file(&path, content).map_err(|e| BuilderError::FileWriteFail(e, path.clone()))?;
    Ok(path)
}

fn try_write_to_file(path: &Path, content: &[u8]) -> std::io::Result<()> {
    let mut f = File::create(path)?;
    f.write_all(content)
}

fn write_rs_to_file(
    dir: &Path,
    filename: &str,
    content: TokenStream,
) -> Result<PathBuf, BuilderError> {
    write_to_file(dir, filename, content.to_string().as_bytes())
}

fn rust_version_check() {
    if !version_check::is_min_version("1.48.0").unwrap_or(false) {
        panic!("Rust 1.48 or later is required.")
    }
}