#
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::{BuildRunner, FileFlavor, Unit, fingerprint};
    10use crate::util::{CargoResult, internal};
    11use cargo_util::paths;
    12use tracing::debug;
    13
    14/// Basically 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_build_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_vec) = build_runner.find_build_script_metadatas(unit) {
    79        for metadata in metadata_vec {
    80            if let Some(output) = build_runner
    81                .build_script_outputs
    82                .lock()
    83                .unwrap()
    84                .get(metadata)
    85            {
    86                for path in &output.rerun_if_changed {
    87                    let package_root = unit.pkg.root();
    88
    89                    let path = if path.as_os_str().is_empty() {
    90                        // Joining with an empty path causes Rust to add a trailing path separator.
    91                        // On Windows, this would add an invalid trailing backslash to the .d file.
    92                        package_root.to_path_buf()
    93                    } else {
    94                        // The paths we have saved from the unit are of arbitrary relativeness and
    95                        // may be relative to the crate root of the dependency.
    96                        package_root.join(path)
    97                    };
    98
    99                    deps.insert(path);
    100                }
    101            }
    102        }
    103    }
    104
    105    // Recursively traverse all transitive dependencies
    106    let unit_deps = Vec::from(build_runner.unit_deps(unit)); // Create vec due to mutable borrow.
    107    for dep in unit_deps {
    108        if dep.unit.is_local() {
    109            add_deps_for_unit(deps, build_runner, &dep.unit, visited)?;
    110        }
    111    }
    112    Ok(())
    113}
    114
    115/// Save a `.d` dep-info file for the given unit. This is the third kind of
    116/// dep-info mentioned in [`fingerprint`] module.
    117///
    118/// Argument `unit` is expected to be the root unit, which will be uplifted.
    119///
    120/// Cargo emits its own dep-info files in the output directory. This is
    121/// only done for every "uplifted" artifact. These are intended to be used
    122/// with external build systems so that they can detect if Cargo needs to be
    123/// re-executed.
    124///
    125/// It includes all the entries from the `rustc` dep-info file, and extends it
    126/// with any `rerun-if-changed` entries from build scripts. It also includes
    127/// sources from any path dependencies. Registry dependencies are not included
    128/// under the assumption that changes to them can be detected via changes to
    129/// `Cargo.lock`.
    130///
    131/// [`fingerprint`]: super::fingerprint#dep-info-files
    132pub fn output_depinfo(build_runner: &mut BuildRunner<'_, '_>, unit: &Unit) -> CargoResult<()> {
    133    let bcx = build_runner.bcx;
    134    let mut deps = BTreeSet::new();
    135    let mut visited = HashSet::new();
    136    let success = add_deps_for_unit(&mut deps, build_runner, unit, &mut visited).is_ok();
    137    let basedir_string;
    138    let basedir = match bcx.gctx.build_config()?.dep_info_basedir.clone() {
    139        Some(value) => {
    140            basedir_string = value
    141                .resolve_path(bcx.gctx)
    142                .as_os_str()
    143                .to_str()
    144                .ok_or_else(|| anyhow::format_err!("build.dep-info-basedir path not utf-8"))?
    145                .to_string();
    146            Some(basedir_string.as_str())
    147        }
    148        None => None,
    149    };
    150    let deps = deps
    151        .iter()
    152        .map(|f| render_filename(f, basedir))
    153        .collect::<CargoResult<Vec<_>>>()?;
    154
    155    for output in build_runner.outputs(unit)?.iter().filter(|o| {
    156        !matches!(
    157            o.flavor,
    158            FileFlavor::DebugInfo | FileFlavor::Auxiliary | FileFlavor::Sbom
    159        )
    160    }) {
    161        if let Some(ref link_dst) = output.hardlink {
    162            let output_path = link_dst.with_extension("d");
    163            if success {
    164                let target_fn = render_filename(link_dst, basedir)?;
    165
    166                // If nothing changed don't recreate the file which could alter
    167                // its mtime
    168                if let Ok(previous) = fingerprint::parse_rustc_dep_info(&output_path) {
    169                    if previous
    170                        .files
    171                        .iter()
    172                        .map(|(path, _checksum)| path)
    173                        .eq(deps.iter().map(Path::new))
    174                    {
    175                        continue;
    176                    }
    177                }
    178
    179                // Otherwise write it all out
    180                let mut outfile = BufWriter::new(paths::create(output_path)?);
    181                write!(outfile, "{}:", target_fn)?;
    182                for dep in &deps {
    183                    write!(outfile, " {}", dep)?;
    184                }
    185                writeln!(outfile)?;
    186
    187            // dep-info generation failed, so delete output file. This will
    188            // usually cause the build system to always rerun the build
    189            // rule, which is correct if inefficient.
    190            } else if output_path.exists() {
    191                paths::remove_file(output_path)?;
    192            }
    193        }
    194    }
    195    Ok(())
    196}