#
cargo/core/compiler/
output_depinfo.rs

    1//! dep-info files for external build system integration.
    2//! See [`output_depinfo`] for more.
    3
    4use cargo_util::paths::normalize_path;
    5use std::collections::{BTreeSet, HashSet};
    6use std::io::{BufWriter, Write};
    7use std::path::{Path, PathBuf};
    8
    9use super::{fingerprint, BuildRunner, FileFlavor, Unit};
    10use crate::util::{internal, CargoResult};
    11use cargo_util::paths;
    12use tracing::debug;
    13
    14/// Bacially just normalizes a given path and converts it to a string.
    15fn render_filename<P: AsRef<Path>>(path: P, basedir: Option<&str>) -> CargoResult<String> {
    16    fn wrap_path(path: &Path) -> CargoResult<String> {
    17        path.to_str()
    18            .ok_or_else(|| internal(format!("path `{:?}` not utf-8", path)))
    19            .map(|f| f.replace(" ", "\\ "))
    20    }
    21
    22    let path = path.as_ref();
    23    if let Some(basedir) = basedir {
    24        let norm_path = normalize_path(path);
    25        let norm_basedir = normalize_path(basedir.as_ref());
    26        match norm_path.strip_prefix(norm_basedir) {
    27            Ok(relpath) => wrap_path(relpath),
    28            _ => wrap_path(path),
    29        }
    30    } else {
    31        wrap_path(path)
    32    }
    33}
    34
    35/// Collects all dependencies of the `unit` for the output dep info file.
    36///
    37/// Dependencies will be stored in `deps`, including:
    38///
    39/// * dependencies from [fingerprint dep-info]
    40/// * paths from `rerun-if-changed` build script instruction
    41/// * ...and traverse transitive dependencies recursively
    42///
    43/// [fingerprint dep-info]: super::fingerprint#fingerprint-dep-info-files
    44fn add_deps_for_unit(
    45    deps: &mut BTreeSet<PathBuf>,
    46    build_runner: &mut BuildRunner<'_, '_>,
    47    unit: &Unit,
    48    visited: &mut HashSet<Unit>,
    49) -> CargoResult<()> {
    50    if !visited.insert(unit.clone()) {
    51        return Ok(());
    52    }
    53
    54    // units representing the execution of a build script don't actually
    55    // generate a dep info file, so we just keep on going below
    56    if !unit.mode.is_run_custom_build() {
    57        // Add dependencies from rustc dep-info output (stored in fingerprint directory)
    58        let dep_info_loc = fingerprint::dep_info_loc(build_runner, unit);
    59        if let Some(paths) = fingerprint::parse_dep_info(
    60            unit.pkg.root(),
    61            build_runner.files().host_root(),
    62            &dep_info_loc,
    63        )? {
    64            for path in paths.files.into_keys() {
    65                deps.insert(path);
    66            }
    67        } else {
    68            debug!(
    69                "can't find dep_info for {:?} {}",
    70                unit.pkg.package_id(),
    71                unit.target
    72            );
    73            return Err(internal("dep_info missing"));
    74        }
    75    }
    76
    77    // Add rerun-if-changed dependencies
    78    if let Some(metadata) = build_runner.find_build_script_metadata(unit) {
    79        if let Some(output) = build_runner
    80            .build_script_outputs
    81            .lock()
    82            .unwrap()
    83            .get(metadata)
    84        {
    85            for path in &output.rerun_if_changed {
    86                // The paths we have saved from the unit are of arbitrary relativeness and may be
    87                // relative to the crate root of the dependency.
    88                let path = unit.pkg.root().join(path);
    89                deps.insert(path);
    90            }
    91        }
    92    }
    93
    94    // Recursively traverse all transitive dependencies
    95    let unit_deps = Vec::from(build_runner.unit_deps(unit)); // Create vec due to mutable borrow.
    96    for dep in unit_deps {
    97        if dep.unit.is_local() {
    98            add_deps_for_unit(deps, build_runner, &dep.unit, visited)?;
    99        }
    100    }
    101    Ok(())
    102}
    103
    104/// Save a `.d` dep-info file for the given unit. This is the third kind of
    105/// dep-info mentioned in [`fingerprint`] module.
    106///
    107/// Argument `unit` is expected to be the root unit, which will be uplifted.
    108///
    109/// Cargo emits its own dep-info files in the output directory. This is
    110/// only done for every "uplifted" artifact. These are intended to be used
    111/// with external build systems so that they can detect if Cargo needs to be
    112/// re-executed.
    113///
    114/// It includes all the entries from the `rustc` dep-info file, and extends it
    115/// with any `rerun-if-changed` entries from build scripts. It also includes
    116/// sources from any path dependencies. Registry dependencies are not included
    117/// under the assumption that changes to them can be detected via changes to
    118/// `Cargo.lock`.
    119///
    120/// [`fingerprint`]: super::fingerprint#dep-info-files
    121pub fn output_depinfo(build_runner: &mut BuildRunner<'_, '_>, unit: &Unit) -> CargoResult<()> {
    122    let bcx = build_runner.bcx;
    123    let mut deps = BTreeSet::new();
    124    let mut visited = HashSet::new();
    125    let success = add_deps_for_unit(&mut deps, build_runner, unit, &mut visited).is_ok();
    126    let basedir_string;
    127    let basedir = match bcx.gctx.build_config()?.dep_info_basedir.clone() {
    128        Some(value) => {
    129            basedir_string = value
    130                .resolve_path(bcx.gctx)
    131                .as_os_str()
    132                .to_str()
    133                .ok_or_else(|| anyhow::format_err!("build.dep-info-basedir path not utf-8"))?
    134                .to_string();
    135            Some(basedir_string.as_str())
    136        }
    137        None => None,
    138    };
    139    let deps = deps
    140        .iter()
    141        .map(|f| render_filename(f, basedir))
    142        .collect::<CargoResult<Vec<_>>>()?;
    143
    144    for output in build_runner.outputs(unit)?.iter().filter(|o| {
    145        !matches!(
    146            o.flavor,
    147            FileFlavor::DebugInfo | FileFlavor::Auxiliary | FileFlavor::Sbom
    148        )
    149    }) {
    150        if let Some(ref link_dst) = output.hardlink {
    151            let output_path = link_dst.with_extension("d");
    152            if success {
    153                let target_fn = render_filename(link_dst, basedir)?;
    154
    155                // If nothing changed don't recreate the file which could alter
    156                // its mtime
    157                if let Ok(previous) = fingerprint::parse_rustc_dep_info(&output_path) {
    158                    if previous
    159                        .files
    160                        .iter()
    161                        .map(|(path, _checksum)| path)
    162                        .eq(deps.iter().map(Path::new))
    163                    {
    164                        continue;
    165                    }
    166                }
    167
    168                // Otherwise write it all out
    169                let mut outfile = BufWriter::new(paths::create(output_path)?);
    170                write!(outfile, "{}:", target_fn)?;
    171                for dep in &deps {
    172                    write!(outfile, " {}", dep)?;
    173                }
    174                writeln!(outfile)?;
    175
    176            // dep-info generation failed, so delete output file. This will
    177            // usually cause the build system to always rerun the build
    178            // rule, which is correct if inefficient.
    179            } else if output_path.exists() {
    180                paths::remove_file(output_path)?;
    181            }
    182        }
    183    }
    184    Ok(())
    185}