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//! Run configuration tests from build.rs and set available features, similar to *autotools*
//! configure scripts.
//!
//!
//! # Description
//!
//! `ConfTest::run()` called from 'build.rs' parses 'Cargo.toml'. Then for each *[feature]*
//! defined, it checks if that feature was not set manually (with `--features`) and a test in
//! 'conf_tests/' exists. This test is then compiled and build. When that succeeds the
//! feature becomes enabled automatically.
//!
//!
//! # Rationale
//!
//! Operating Systems have sometimes subtle differences in features and standards
//! conformance. Sometimes non-standard features are added for improved performance. These
//! differences make it hard to write portable software that still offer optimal performance
//! for diffent Operatiing Systems. Moreover often a developer doesn't even know what
//! featureset other Operating Systems may provide or this may be changed by kernel or
//! userland version or configuration. Probing the presence of such features at build time
//! can solve these problems.
//!
//!
//! # How To
//!
//! When present 'cargo' (builds and) executes a *build.rs* script while building crate. This
//! is the place where *ConfTest* is hooked in at first:
//!
//! ```rust,ignore
//! use conf_test::ConfTest;
//!
//! fn main() {
//! ConfTest::run();
//! // any other build.rs steps follow below
//! }
//! ```
//!
//! Further one has to define a set of features and dependencies in the 'Cargo.toml'. Note
//! that 'build.rs' will be run before the '[dependencies]' are build. Thus all dependencies
//! needed for the tests must go into '[build-dependencies]' as well. For Example:
//!
//! ```toml
//! [dependencies]
//! libc = "0.2.34"
//!
//! [build-dependencies]
//! libc = "0.2.34"
//! conf_test = "0.1"
//!
//! [features]
//! default = []
//! o_path = []
//! ```
//!
//! And as final step the crate directory 'conf_tests/' need to be created which contain rust
//! files named after the features to be probed. Containing a single `fn main()` which shall
//! probe one single thing.
//!
//! ```rust,ignore
//! // This goes into conf_tests/o_path.rs
//! extern crate libc;
//!
//! fn main() {
//! unsafe {
//! let conf_tests = std::ffi::CString::new("conf_tests").unwrap();
//! // Compilation will fail when the libc does not define O_PATH
//! libc::open(conf_tests.as_ptr(), libc::O_PATH);
//! }
//! }
//! ```
//!
//! Later in the crate implementation source code one uses conditional compilation as usual
//! with `#[cfg(feature = "o_path")]`.
//!
//! ## Test depending on Features
//!
//! Tests may depend on features that are discovered by other tests or set manually. For
//! simplicity there is no dependency resolver about this but tests are run in sort order of
//! the feature name. Every subsequent test is compiled with the the feature flags already
//! discovered so far. To leverage this functionality one rarely needs to change the feature
//! names. For example when 'bar' depends on 'foo' it is required to enforce the sort order by
//! renaming these features to 'aa_foo' and 'bb_bar'. Only features that get discovered are
//! used for the test compilations features set by printing cargo instructions from the test
//! scripts are not used.
//!
//!
//! # Extra Features
//!
//! Tests can emit special instructions to cargo on stdout.
//! These become only effective when the test exits successful.
//! See https://doc.rust-lang.org/cargo/reference/build-scripts.html#outputs-of-the-build-script
//!
//! One can control ConfTest by setting the environment variable `CONF_TEST_INHIBIT` to one of
//! the following:
//! * **skip**
//! Will not execute any conf_tests but proceed with 'build.rs'.
//! * **stop**
//! Exits 'build.rs' sucessfully, not executing any tests.
//! * **fail**
//! Exits 'build.rs' with an failure, not executing any tests.
//!
//! Any other value will make the script panic.
//!
//!
//! # Limitations
//!
//! * The tests running on the machine where the software is build, using the
//! build-dependencies. This will be a problem when Software gets cross-compiled. For cross
//! compilation set 'CONF_TEST_INHIBIT=skip' and set the desired features manually with the
//! '--features' option.
//!
//! * Features can only be set, not unset. This is deliberate and not a limitation. Do only
//! positive tests checking for the presence of a feature.
//!
//!
//! # Good Practices
//!
//! * Only use ConfTest when other things (like factoring out OS specific thing into their own
//! crates) are not applicable.
//!
//! * Provide a baseline implementation which is portable with no features enabled. This may
//! not perform as well or lack some special features but should compile nevertheless.
//!
use std::ffi::{OsStr, OsString};
use std::fs::File;
use std::io::prelude::*;
use std::env::var_os as env;
use std::path::{Path, PathBuf};
use std::str;
use cargo_metadata::{Message, MetadataCommand};
use std::process::{Command, Stdio};
use std::collections::{BTreeMap, BTreeSet};
// Empty Type for now, In future this may be extended without breaking existing code.
/// Implements the conf_test API
pub enum ConfTest {}
impl ConfTest {
/// Run the configuration tests in 'conf_tests/'.
#[allow(dead_code)]
pub fn run() {
if let Some(inhibit) = env("CONF_TEST_INHIBIT") {
if inhibit == "skip" {
println!("cargo:warning=Skipping ConfTest via CONF_TEST_INHIBIT");
return;
} else if inhibit == "stop" {
std::process::exit(0);
} else if inhibit == "fail" {
println!("cargo:warning=Requested ConfTest failure via CONF_TEST_INHIBIT");
std::process::exit(1)
} else {
// Bail on any unknown value to catch 'undefined' states/typos
panic!("Unknown CONF_TEST_INHIBIT value: {:?}", inhibit)
}
}
let metadata = MetadataCommand::new()
.no_deps()
.exec()
.expect("Querying cargo metadata failed");
let mut features = BTreeSet::new();
let mut dependencies = BTreeSet::new();
let mut edition: Option<String> = None;
for package in metadata.packages {
if edition == None {
// just pick the first edition seen
edition = Some(package.edition);
}
for (feature, _) in package.features {
features.insert(feature);
}
for dep in package.dependencies {
dependencies.insert(dep.name);
}
}
let edition = edition.unwrap_or_else(|| String::from("2018"));
let extern_libs = Self::get_extern_libs(&dependencies);
let mut test_features = Vec::new();
let mut outputs = Vec::new();
for feature in features {
if env(format!("CARGO_FEATURE_{}", feature.to_uppercase())).is_none() {
outputs.push(format!("# checking for {}\n", &feature));
let mut test_src = PathBuf::from("conf_tests");
test_src.push(&feature);
test_src.set_extension("rs");
if test_src.exists() {
outputs.push(format!("# {} exists\n", test_src.display()));
outputs.push(format!("cargo:rerun-if-changed={}\n", test_src.display()));
if let Some(binary) =
Self::compile_test(&test_src, &edition, &extern_libs, &test_features)
{
outputs.push(format!("# compiling ConfTest for {} success\n", &feature));
if let Some(stdout) = Self::run_test(&binary) {
outputs
.push(format!("# executing ConfTest for {} success\n", &feature));
outputs.push(format!("cargo:rustc-cfg=feature=\"{}\"\n", &feature));
outputs.push(stdout);
test_features.push(feature.clone());
} else {
outputs.push(format!("# executing ConfTest for {} failed\n", &feature));
}
} else {
outputs.push(format!("# compiling ConfTest for {} failed\n", &feature));
}
} else {
outputs.push(format!("# test for '{}' does not exist\n", &feature));
}
} else {
outputs.push(format!("# test for '{}' manually overridden\n", &feature));
}
outputs.push(String::from("\n"));
test_features.push(feature.clone());
}
let mut logfile = PathBuf::new();
logfile.push(env("OUT_DIR").unwrap());
logfile.push("conf_test");
logfile.push("conf_test.log");
let mut logfile = File::create(logfile).expect("Failed to create logfile");
for output in outputs {
logfile.write_all(output.as_bytes()).unwrap();
print!("{}", output);
}
}
fn run_test(test_binary: &Path) -> Option<String> {
let command = Command::new(test_binary).output().ok()?;
if command.status.success() {
Some(String::from_utf8_lossy(&command.stdout).to_string())
} else {
None
}
}
fn compile_test(
src: &Path,
edition: &str,
extern_libs: &BTreeMap<OsString, (String, PathBuf)>,
features: &[String],
) -> Option<PathBuf> {
let mut out_file = PathBuf::new();
out_file.push(env("OUT_DIR").expect("env var OUT_DIR is not set"));
out_file.push("conf_test");
out_file.push(src.file_stem().unwrap());
let mut rust_cmd = Command::new(env("RUSTC").unwrap_or_else(|| OsString::from("rustc")));
let rust_cmd = rust_cmd
.arg("--crate-type")
.arg("bin")
.arg("--edition")
.arg(edition)
.arg("-o")
.arg(&out_file)
.arg("-v")
.arg(src);
for (name, filename) in extern_libs.values() {
rust_cmd.arg("--extern").arg(format!(
"{}={}", //FIXME: needs some better way to compose an OsString here
name,
filename.to_str().expect("invalid file name")
));
}
for feature in features {
rust_cmd
.arg("--cfg")
.arg(format!("feature=\"{}\"", feature));
}
let rust_output = rust_cmd.output().ok()?;
if rust_output.status.success() {
Some(out_file)
} else {
None
}
}
fn get_extern_libs(dependencies: &BTreeSet<String>) -> BTreeMap<OsString, (String, PathBuf)> {
let mut extern_libs = BTreeMap::new();
//PLANNED: get rid of extra target dir, is there any way to work around the build lock?
let mut target_dir = PathBuf::new();
target_dir.push(env("OUT_DIR").expect("env var OUT_DIR is not set"));
target_dir.push("conf_test");
// let cargo start a rustc process that does not build the project but returns the
// metadata about compilation artifacts
let mut cargo = Command::new(env("CARGO").unwrap_or_else(|| OsString::from("cargo")))
.arg("rustc")
.arg("--message-format")
.arg("json")
.arg("--target-dir")
.arg(target_dir)
.arg("--")
.arg("--emit")
.arg("metadata")
.env("CONF_TEST_INHIBIT", "stop")
.stdout(Stdio::piped())
.spawn()
.unwrap();
let reader = std::io::BufReader::new(cargo.stdout.take().unwrap());
for message in cargo_metadata::Message::parse_stream(reader) {
if let Message::CompilerArtifact(artifact) = message.unwrap() {
if dependencies.contains(&artifact.target.name) {
for filename in artifact.filenames {
let filename = PathBuf::from(filename);
let id = OsString::from(filename.file_stem().expect("invalid file name"));
let extension = filename.extension();
let name = String::from(&artifact.target.name);
match extension.and_then(OsStr::to_str) {
Some("rlib") => {
extern_libs.insert(id, (name, filename));
}
Some("rmeta") => {
if extern_libs.contains_key(&id) {
let stored_extension = extern_libs[&id]
.1
.extension()
.and_then(OsStr::to_str)
.unwrap();
if stored_extension == "rlib" {
continue;
}
extern_libs.insert(id, (name, filename));
}
}
Some(_other) => {
if extern_libs.contains_key(&id) {
let stored_extension = extern_libs[&id]
.1
.extension()
.and_then(OsStr::to_str)
.unwrap();
if stored_extension == "rmeta" || stored_extension == "rlib" {
continue;
}
extern_libs.insert(id, (name, filename));
}
}
None => {
panic!("extension is not utf8 {:?}", extension);
}
}
}
}
}
}
cargo.wait().expect("Couldn't get cargo's exit status");
extern_libs
}
}