slpc 0.3.4

Read, write, and validate slipcase containers: a ZIP holding a payload file and the TOML metadata that describes it
Documentation 
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// Putting a container on disk: the `fs` feature.
//
// Everything here needs a real filesystem — a rename across one is the whole
// mechanism — so these are files in a temporary directory rather than cursors.
//
// Author: David M. Anderson
// Built with AI assistance (Claude, Anthropic)

#![cfg(feature = "fs")]

mod support;

use std::io::Write;
use std::path::Path;

use support::container;

use slpc::{Destination, Error};

/// Everything in one temporary directory, removed when the test ends.
fn sandbox() -> tempfile::TempDir {
    tempfile::tempdir().unwrap()
}

/// What is in a directory, sorted, so a leftover is visible.
fn entries(dir: &Path) -> Vec<String> {
    let mut names: Vec<String> = std::fs::read_dir(dir)
        .unwrap()
        .map(|e| e.unwrap().file_name().to_string_lossy().into_owned())
        .collect();
    names.sort();
    names
}

#[test]
fn nothing_appears_until_it_is_committed() {
    let s = sandbox();
    let path = s.path().join("report.pdf.slpc");

    let mut d = Destination::new(&path, false).unwrap();
    d.writer()
        .write_all(&container("report.pdf", b"x"))
        .unwrap();
    assert!(!path.exists(), "the destination appeared before the commit");

    d.commit().unwrap();
    assert!(path.exists());
    assert_eq!(entries(s.path()), ["report.pdf.slpc"]);
}

#[test]
fn dropping_one_leaves_nothing_behind() {
    // Including the probe, which is created and removed while the destination
    // is being reserved rather than at the end.
    let s = sandbox();
    let mut d = Destination::new(s.path().join("c.slpc"), false).unwrap();
    d.writer().write_all(b"half a container").unwrap();
    drop(d);
    assert!(entries(s.path()).is_empty(), "{:?}", entries(s.path()));
}

#[test]
fn refuses_an_existing_file_unless_forced() {
    let s = sandbox();
    let path = s.path().join("c.slpc");
    std::fs::write(&path, b"already here").unwrap();

    let e = Destination::new(&path, false).unwrap_err();
    assert!(
        matches!(&e, Error::Io(io) if io.kind() == std::io::ErrorKind::AlreadyExists),
        "{e}"
    );
    assert!(e.to_string().contains("c.slpc"), "{e}");
    assert_eq!(std::fs::read(&path).unwrap(), b"already here");

    let mut d = Destination::new(&path, true).unwrap();
    d.writer().write_all(b"replaced").unwrap();
    d.commit().unwrap();
    assert_eq!(std::fs::read(&path).unwrap(), b"replaced");
}

#[test]
fn refuses_a_directory_that_is_not_there_and_names_it() {
    let s = sandbox();
    let e = Destination::new(s.path().join("nowhere").join("c.slpc"), false).unwrap_err();
    assert!(e.to_string().contains("nowhere"), "{e}");
}

#[test]
fn reads_back_what_was_written() {
    let s = sandbox();
    let bytes = container("report.pdf", b"%PDF");
    let mut d = Destination::new(s.path().join("c.slpc"), false).unwrap();
    d.writer().write_all(&bytes).unwrap();

    // The read-back a caller does before replacing anything with it.
    assert!(slpc::validate(d.written().unwrap())
        .unwrap()
        .is_conformant());
    d.commit().unwrap();
}

#[cfg(unix)]
mod permissions {
    use super::{container, entries, sandbox, Destination};
    use std::io::Write;
    use std::os::unix::fs::PermissionsExt;
    use std::path::Path;

    fn mode(p: &Path) -> u32 {
        std::fs::metadata(p).unwrap().permissions().mode() & 0o777
    }

    /// What a file created the ordinary way gets here, whatever the umask is.
    ///
    /// Measured rather than written down: hard-coding 0644 would pass under one
    /// umask and fail under another, and the claim is that a container comes
    /// out like any other file rather than like a particular number.
    fn ordinary(dir: &Path) -> u32 {
        let p = dir.join("ordinary.txt");
        std::fs::write(&p, b"reference").unwrap();
        let m = mode(&p);
        std::fs::remove_file(&p).unwrap();
        m
    }

    fn write_to(d: &mut Destination) {
        d.writer().write_all(&container("a.txt", b"x")).unwrap();
    }

    #[test]
    fn a_new_file_gets_what_the_umask_decided() {
        // The rename is what makes this worth a test: a temporary file is
        // private to its owner, and carrying that mode onto the destination is
        // the defect this exists to prevent.
        let s = sandbox();
        let want = ordinary(s.path());
        let path = s.path().join("c.slpc");

        let mut d = Destination::new(&path, false).unwrap();
        write_to(&mut d);
        d.commit().unwrap();

        assert_eq!(mode(&path), want, "a renamed file must not come out 0600");
        assert_eq!(entries(s.path()), ["c.slpc"], "the probe was left behind");
    }

    #[test]
    fn forcing_over_a_file_still_gets_what_the_umask_decided() {
        // `new` creates a file at a path the caller named; a file that happened
        // to be in the way does not get to decide who can read what replaces
        // it. Carrying a mode across is what `in_place` is for.
        let s = sandbox();
        let want = ordinary(s.path());
        let path = s.path().join("c.slpc");
        std::fs::write(&path, b"in the way").unwrap();
        std::fs::set_permissions(&path, std::fs::Permissions::from_mode(0o600)).unwrap();

        let mut d = Destination::new(&path, true).unwrap();
        write_to(&mut d);
        d.commit().unwrap();

        assert_eq!(mode(&path), want);
    }

    #[test]
    fn writing_in_place_keeps_the_files_own_permissions() {
        let s = sandbox();
        let path = s.path().join("c.slpc");
        std::fs::write(&path, container("a.txt", b"x")).unwrap();
        std::fs::set_permissions(&path, std::fs::Permissions::from_mode(0o640)).unwrap();

        let mut d = Destination::in_place(&path).unwrap();
        write_to(&mut d);
        d.commit().unwrap();

        assert_eq!(mode(&path), 0o640);
        assert_eq!(entries(s.path()), ["c.slpc"], "in place needs no probe");
    }

    #[test]
    fn writing_in_place_replaces_the_file_and_not_the_link_to_it() {
        let s = sandbox();
        let real = s.path().join("c.slpc");
        let link = s.path().join("link.slpc");
        std::fs::write(&real, container("a.txt", b"x")).unwrap();
        std::os::unix::fs::symlink("c.slpc", &link).unwrap();

        let mut d = Destination::in_place(&link).unwrap();
        d.writer().write_all(&container("b.txt", b"y")).unwrap();
        d.commit().unwrap();

        assert!(link.is_symlink(), "the link was replaced by a file");
        let c = slpc::Container::open(&real).unwrap();
        assert_eq!(c.payload_name(), "b.txt");
    }

    #[test]
    fn in_place_refuses_a_file_that_is_not_there() {
        let s = sandbox();
        assert!(Destination::in_place(s.path().join("absent.slpc")).is_err());
    }
}