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/*
* SPDX-FileCopyrightText: Peter Pentchev <roam@ringlet.net>
* SPDX-License-Identifier: BSD-2-Clause
*/
//! Query a program for its features.
//!
//! The [`obtain_features`] function, when passed
//! a [`Config`][crate::defs::Config] object, will run a program with
//! the appropriate command-line options, analyze its output, and
//! build up a list of the supported features.
//!
//! See the crate-level documentation for sample usage.
use std::process::Command;
use anyhow::Context;
use crate::defs::{Config, ObtainError, Obtained};
use crate::expr::parser;
/// Decode a program's output, assuming it is a valid UTF-8 string.
fn decode_output(program: &str, output: Vec<u8>) -> Result<String, ObtainError> {
// FIXME: handle non-UTF-8 stuff
String::from_utf8(output)
.context("Could not decode a valid UTF-8 string")
.map_err(|err| ObtainError::DecodeOutput(program.to_owned(), err))
}
/// Run the specified program, analyze its output.
///
/// See the crate-level documentation for sample usage.
///
/// # Errors
///
/// Will return [`Obtained::Failed`] if the program cannot be executed.
/// Will propagate errors from decoding the program's output as UTF-8 lines.
#[inline]
#[allow(clippy::module_name_repetitions)]
pub fn obtain_features(config: &Config) -> Result<Obtained, ObtainError> {
match Command::new(&config.program)
.args([&config.option_name])
.output()
.context(format!("Could not execute {}", config.program))
{
Ok(output) => {
if output.status.success() {
decode_output(&config.program, output.stdout)?
.lines()
.find_map(|line| line.strip_prefix(&config.prefix))
.map_or(Ok(Obtained::NotSupported), |line| {
Ok(Obtained::Features(
parser::parse_features_line(line).map_err(ObtainError::Parse)?,
))
})
} else {
Ok(Obtained::NotSupported)
}
}
Err(err) => Ok(Obtained::Failed(ObtainError::RunProgram(
config.program.clone(),
err,
))),
}
}