stryke/

script_cache.rs

//! rkyv-backed bytecode cache for scripts.
//!
//! Single-file shard at `~/.stryke/scripts.rkyv`. On 2+ runs of a given
//! script, lex/parse/compile is skipped — the cache hit is `mmap` + zero-copy
//! `ArchivedHashMap` lookup + bincode-decode of the inner Program/Chunk blobs.
//!
//! Storage layout (rkyv archived):
//!   ScriptShard {
//!     header: { magic, format_version, stryke_version, pointer_width, built_at_secs },
//!     entries: `HashMap<canonical_path, ScriptEntry>`,
//!   }
//!   ScriptEntry { mtime_secs, mtime_nsecs, binary_mtime_at_cache, cached_at_secs,
//!                 program_blob: `Vec<u8>`, chunk_blob: `Vec<u8>` }
//!
//! Inner `program_blob` / `chunk_blob` are bincode for now — `PerlValue`'s
//! Arc-shared graph and the `CacheConst` adapter aren't trivially rkyv-archivable,
//! so phase 1 keeps that codec inside the rkyv outer container. Phase 2 can
//! derive `Archive` directly on `Chunk` / `Program` for true zero-copy load.
//!
//! Read path:
//!   - Lazy `mmap` of the shard, kept alive for the process lifetime so repeat
//!     lookups (`s test t` running 87 scripts) pay validation once.
//!   - `rkyv::check_archived_root::<ScriptShard>` validates the byte image.
//!   - Header validated for magic / format_version / stryke_version / pointer_width.
//!   - Per-entry: source mtime must match, and `binary_mtime_at_cache` ≥ running
//!     stryke binary's mtime (any rebuild of stryke invalidates entries silently).
//!
//! Write path:
//!   - `flock(LOCK_EX)` on `scripts.rkyv.lock` so concurrent writers serialize.
//!   - Read existing shard into owned form, mutate, `rkyv::to_bytes`,
//!     write to `scripts.rkyv.tmp.<pid>.<nanos>`, fsync, atomic-rename.
//!   - Drop the in-process `mmap` so the next read picks up the new shard.

use std::collections::HashMap;
use std::fs::File;
use std::io::Write as IoWrite;
use std::path::{Path, PathBuf};
use std::sync::OnceLock;
use std::time::{SystemTime, UNIX_EPOCH};

use memmap2::Mmap;
use parking_lot::Mutex;
use rkyv::{Archive, Deserialize as RkyvDeserialize, Serialize as RkyvSerialize};
use serde::{Deserialize, Deserializer, Serialize, Serializer};

use crate::ast::Program;
use crate::bytecode::Chunk;
use crate::error::{PerlError, PerlResult};
use crate::value::PerlValue;

/// Magic header bytes — fail-fast if a wrong-format file is mmap'd.
pub const SHARD_MAGIC: u32 = 0x53545259; // "STRY"
/// Bumped on incompatible rkyv schema changes.
pub const SHARD_FORMAT_VERSION: u32 = 1;

// ── rkyv archived types ──────────────────────────────────────────────────────

#[derive(Archive, RkyvDeserialize, RkyvSerialize, Debug, Clone)]
#[archive(check_bytes)]
pub struct ShardHeader {
    pub magic: u32,
    pub format_version: u32,
    pub stryke_version: String,
    pub pointer_width: u32,
    pub built_at_secs: u64,
}

#[derive(Archive, RkyvDeserialize, RkyvSerialize, Debug, Clone)]
#[archive(check_bytes)]
pub struct ScriptEntry {
    pub mtime_secs: i64,
    pub mtime_nsecs: i64,
    pub binary_mtime_at_cache: i64,
    pub cached_at_secs: i64,
    pub program_blob: Vec<u8>,
    pub chunk_blob: Vec<u8>,
}

#[derive(Archive, RkyvDeserialize, RkyvSerialize, Debug, Clone)]
#[archive(check_bytes)]
pub struct ScriptShard {
    pub header: ShardHeader,
    pub entries: HashMap<String, ScriptEntry>,
}

// ── Constant pool codec for serializing PerlValues in the inner bincode blob ─
//
// The inner `chunk_blob` still uses bincode, and `Chunk.constants: Vec<PerlValue>`
// can't serialize directly because `PerlValue` is an Arc-shared heap graph. This
// codec is referenced by `bytecode.rs:1067` via `#[serde(with = ...)]` and only
// needs to handle the constants the compiler actually pools — `Undef`, ints,
// floats, strings.

#[derive(Debug, Clone, Serialize, Deserialize)]
#[serde(rename_all = "snake_case")]
enum CacheConst {
    Undef,
    Int(i64),
    Float(f64),
    Str(String),
}

fn cache_const_from_perl(v: &PerlValue) -> Result<CacheConst, String> {
    if v.is_undef() {
        return Ok(CacheConst::Undef);
    }
    if let Some(n) = v.as_integer() {
        return Ok(CacheConst::Int(n));
    }
    if let Some(f) = v.as_float() {
        return Ok(CacheConst::Float(f));
    }
    if let Some(s) = v.as_str() {
        return Ok(CacheConst::Str(s.to_string()));
    }
    Err(format!(
        "constant pool value cannot be cached (type {})",
        v.ref_type()
    ))
}

fn perl_from_cache_const(c: CacheConst) -> PerlValue {
    match c {
        CacheConst::Undef => PerlValue::UNDEF,
        CacheConst::Int(n) => PerlValue::integer(n),
        CacheConst::Float(f) => PerlValue::float(f),
        CacheConst::Str(s) => PerlValue::string(s),
    }
}

pub mod constants_pool_codec {
    use super::*;

    pub fn serialize<S>(values: &Vec<PerlValue>, ser: S) -> Result<S::Ok, S::Error>
    where
        S: Serializer,
    {
        let mut out = Vec::with_capacity(values.len());
        for v in values {
            let c = cache_const_from_perl(v).map_err(serde::ser::Error::custom)?;
            out.push(c);
        }
        out.serialize(ser)
    }

    pub fn deserialize<'de, D>(de: D) -> Result<Vec<PerlValue>, D::Error>
    where
        D: Deserializer<'de>,
    {
        let v: Vec<CacheConst> = <Vec<CacheConst> as Deserialize>::deserialize(de)?;
        Ok(v.into_iter().map(perl_from_cache_const).collect())
    }
}

/// Owned bundle handed back from `try_load` / `ScriptCache::get`.
#[derive(Debug, Clone)]
pub struct CachedScript {
    pub program: Program,
    pub chunk: Chunk,
}

// ── mmap'd validated shard view ──────────────────────────────────────────────

/// mmap + validated `*const ArchivedScriptShard`. Self-referential — the pointer
/// is valid for the lifetime of the wrapping struct.
pub struct MmappedShard {
    _mmap: Mmap,
    archived: *const ArchivedScriptShard,
}

// SAFETY: the pointer aliases an immutable mmap that lives as long as Self.
// rkyv-validated reads are immutable.
unsafe impl Send for MmappedShard {}
unsafe impl Sync for MmappedShard {}

impl MmappedShard {
    /// Open + validate a shard file. Returns `None` on any failure (file
    /// missing, mmap failed, validation failed).
    pub fn open(path: &Path) -> Option<Self> {
        let file = File::open(path).ok()?;
        let mmap = unsafe { Mmap::map(&file).ok()? };
        let archived = rkyv::check_archived_root::<ScriptShard>(&mmap[..]).ok()?;
        let archived_ptr = archived as *const ArchivedScriptShard;
        Some(Self {
            _mmap: mmap,
            archived: archived_ptr,
        })
    }

    fn shard(&self) -> &ArchivedScriptShard {
        // SAFETY: see Self impl comment.
        unsafe { &*self.archived }
    }

    /// Header passes magic / format / stryke-version / pointer-width checks.
    fn header_ok(&self) -> bool {
        let h = &self.shard().header;
        let magic: u32 = h.magic.into();
        let fv: u32 = h.format_version.into();
        let pw: u32 = h.pointer_width.into();
        magic == SHARD_MAGIC
            && fv == SHARD_FORMAT_VERSION
            && pw as usize == std::mem::size_of::<usize>()
            && h.stryke_version.as_str() == env!("CARGO_PKG_VERSION")
    }

    fn lookup(&self, path: &str) -> Option<&ArchivedScriptEntry> {
        self.shard().entries.get(path)
    }

    fn entry_count(&self) -> usize {
        self.shard().entries.len()
    }
}

// ── ScriptCache: per-instance handle (used by tests and by the global) ───────

/// Shard cache keyed by canonical script path. One per shard file.
pub struct ScriptCache {
    path: PathBuf,
    lock_path: PathBuf,
    mmap: Mutex<Option<MmappedShard>>,
}

impl ScriptCache {
    /// Open (or prepare) the cache rooted at `path`. The file does not need to
    /// exist yet — it will be created on the first `put`.
    pub fn open(path: &Path) -> std::io::Result<Self> {
        if let Some(parent) = path.parent() {
            std::fs::create_dir_all(parent)?;
        }
        let parent = path.parent().unwrap_or_else(|| Path::new("/tmp"));
        let lock_path = parent.join(format!(
            "{}.lock",
            path.file_name()
                .and_then(|s| s.to_str())
                .unwrap_or("scripts.rkyv")
        ));
        Ok(Self {
            path: path.to_path_buf(),
            lock_path,
            mmap: Mutex::new(None),
        })
    }

    fn ensure_mmap(&self) {
        let mut guard = self.mmap.lock();
        if guard.is_none() {
            *guard = MmappedShard::open(&self.path);
        }
    }

    fn invalidate_mmap(&self) {
        let mut guard = self.mmap.lock();
        *guard = None;
    }

    /// Cache lookup. Returns `None` on miss, mtime mismatch, version drift, or
    /// stryke-binary newer than the cached entry.
    pub fn get(&self, path: &str, mtime_secs: i64, mtime_nsecs: i64) -> Option<CachedScript> {
        self.ensure_mmap();
        let guard = self.mmap.lock();
        let shard = guard.as_ref()?;
        if !shard.header_ok() {
            return None;
        }
        let entry = shard.lookup(path)?;

        let entry_mtime_s: i64 = entry.mtime_secs.into();
        let entry_mtime_ns: i64 = entry.mtime_nsecs.into();
        if entry_mtime_s != mtime_secs || entry_mtime_ns != mtime_nsecs {
            return None;
        }

        if let Some(bin_mtime) = current_binary_mtime_secs() {
            let cached_bin_mtime: i64 = entry.binary_mtime_at_cache.into();
            if cached_bin_mtime < bin_mtime {
                return None;
            }
        }

        let program_bytes: &[u8] = entry.program_blob.as_slice();
        let chunk_bytes: &[u8] = entry.chunk_blob.as_slice();
        let program: Program = bincode::deserialize(program_bytes).ok()?;
        let chunk: Chunk = bincode::deserialize(chunk_bytes).ok()?;
        Some(CachedScript { program, chunk })
    }

    /// Insert / replace an entry. Serializes the whole shard and atomic-renames.
    pub fn put(
        &self,
        path: &str,
        mtime_secs: i64,
        mtime_nsecs: i64,
        program: &Program,
        chunk: &Chunk,
    ) -> PerlResult<()> {
        let program_bytes =
            bincode::serialize(program).map_err(|e| PerlError::runtime(e.to_string(), 0))?;
        let chunk_bytes =
            bincode::serialize(chunk).map_err(|e| PerlError::runtime(e.to_string(), 0))?;

        let _lock = match acquire_lock(&self.lock_path) {
            Some(l) => l,
            None => return Ok(()),
        };

        let mut shard = match read_owned_shard(&self.path) {
            Some(s)
                if s.header.stryke_version == env!("CARGO_PKG_VERSION")
                    && s.header.pointer_width as usize == std::mem::size_of::<usize>()
                    && s.header.format_version == SHARD_FORMAT_VERSION =>
            {
                s
            }
            _ => fresh_shard(),
        };

        let bin_mtime = current_binary_mtime_secs().unwrap_or(0);
        let entry = ScriptEntry {
            mtime_secs,
            mtime_nsecs,
            binary_mtime_at_cache: bin_mtime,
            cached_at_secs: now_secs(),
            program_blob: program_bytes,
            chunk_blob: chunk_bytes,
        };
        shard.entries.insert(path.to_string(), entry);
        shard.header.built_at_secs = now_secs() as u64;

        write_shard_atomic(&self.path, &shard)?;
        self.invalidate_mmap();
        Ok(())
    }

    /// `(count, total_blob_bytes)` snapshot.
    pub fn stats(&self) -> (i64, i64) {
        self.ensure_mmap();
        let guard = self.mmap.lock();
        let Some(shard) = guard.as_ref() else {
            return (0, 0);
        };
        let count = shard.entry_count() as i64;
        let bytes: i64 = shard
            .shard()
            .entries
            .values()
            .map(|e| (e.program_blob.len() + e.chunk_blob.len()) as i64)
            .sum();
        (count, bytes)
    }

    /// `(path, program_kb, chunk_kb, version, cached_at_localstr)` per entry,
    /// sorted by `cached_at` desc.
    pub fn list_scripts(&self) -> Vec<(String, f64, f64, String, String)> {
        self.ensure_mmap();
        let guard = self.mmap.lock();
        let Some(shard) = guard.as_ref() else {
            return Vec::new();
        };
        let v = shard.shard().header.stryke_version.as_str().to_string();
        let mut out: Vec<(String, f64, f64, String, String, i64)> = shard
            .shard()
            .entries
            .iter()
            .map(|(k, e)| {
                let prog_kb = e.program_blob.len() as f64 / 1024.0;
                let chunk_kb = e.chunk_blob.len() as f64 / 1024.0;
                let cached_at: i64 = e.cached_at_secs.into();
                let ts = format_local_ts(cached_at);
                (
                    k.as_str().to_string(),
                    prog_kb,
                    chunk_kb,
                    v.clone(),
                    ts,
                    cached_at,
                )
            })
            .collect();
        out.sort_by_key(|x| std::cmp::Reverse(x.5));
        out.into_iter()
            .map(|(p, pk, ck, ver, ts, _)| (p, pk, ck, ver, ts))
            .collect()
    }

    /// Drop entries whose source file vanished or whose mtime changed. Returns
    /// number of entries evicted.
    pub fn evict_stale(&self) -> usize {
        let _lock = match acquire_lock(&self.lock_path) {
            Some(l) => l,
            None => return 0,
        };
        let mut shard = match read_owned_shard(&self.path) {
            Some(s) => s,
            None => return 0,
        };
        let before = shard.entries.len();
        shard.entries.retain(|p, e| match file_mtime(Path::new(p)) {
            Some((s, ns)) => s == e.mtime_secs && ns == e.mtime_nsecs,
            None => false,
        });
        let evicted = before - shard.entries.len();
        if evicted > 0 {
            let _ = write_shard_atomic(&self.path, &shard);
            self.invalidate_mmap();
        }
        evicted
    }

    /// Delete the shard file. Idempotent.
    pub fn clear(&self) -> std::io::Result<()> {
        let _lock = acquire_lock(&self.lock_path);
        let res = match std::fs::remove_file(&self.path) {
            Ok(()) => Ok(()),
            Err(e) if e.kind() == std::io::ErrorKind::NotFound => Ok(()),
            Err(e) => Err(e),
        };
        self.invalidate_mmap();
        res
    }
}

// ── Locking + shard read/write helpers ───────────────────────────────────────

/// Acquire an exclusive `flock` on the lock path. The returned `Flock` releases
/// the lock and closes the file when dropped.
fn acquire_lock(path: &Path) -> Option<nix::fcntl::Flock<File>> {
    let f = File::options()
        .read(true)
        .write(true)
        .create(true)
        .truncate(false)
        .open(path)
        .ok()?;
    nix::fcntl::Flock::lock(f, nix::fcntl::FlockArg::LockExclusive).ok()
}

fn fresh_shard() -> ScriptShard {
    ScriptShard {
        header: ShardHeader {
            magic: SHARD_MAGIC,
            format_version: SHARD_FORMAT_VERSION,
            stryke_version: env!("CARGO_PKG_VERSION").to_string(),
            pointer_width: std::mem::size_of::<usize>() as u32,
            built_at_secs: now_secs() as u64,
        },
        entries: HashMap::new(),
    }
}

fn read_owned_shard(path: &Path) -> Option<ScriptShard> {
    let bytes = std::fs::read(path).ok()?;
    let archived = rkyv::check_archived_root::<ScriptShard>(&bytes[..]).ok()?;
    archived.deserialize(&mut rkyv::Infallible).ok()
}

fn write_shard_atomic(path: &Path, shard: &ScriptShard) -> PerlResult<()> {
    let bytes = rkyv::to_bytes::<_, 4096>(shard)
        .map_err(|e| PerlError::runtime(format!("rkyv serialize: {}", e), 0))?;

    let parent = path.parent().expect("cache path has parent");
    let _ = std::fs::create_dir_all(parent);

    let pid = std::process::id();
    let nanos = SystemTime::now()
        .duration_since(UNIX_EPOCH)
        .map(|d| d.as_nanos())
        .unwrap_or(0);
    let tmp_path = parent.join(format!(
        "{}.tmp.{}.{}",
        path.file_name()
            .and_then(|s| s.to_str())
            .unwrap_or("scripts.rkyv"),
        pid,
        nanos
    ));

    {
        let mut f = File::create(&tmp_path).map_err(|e| PerlError::runtime(e.to_string(), 0))?;
        f.write_all(&bytes)
            .map_err(|e| PerlError::runtime(e.to_string(), 0))?;
        f.sync_all()
            .map_err(|e| PerlError::runtime(e.to_string(), 0))?;
    }

    std::fs::rename(&tmp_path, path).map_err(|e| PerlError::runtime(e.to_string(), 0))?;
    Ok(())
}

fn now_secs() -> i64 {
    SystemTime::now()
        .duration_since(UNIX_EPOCH)
        .map(|d| d.as_secs() as i64)
        .unwrap_or(0)
}

fn format_local_ts(secs: i64) -> String {
    let dt = chrono::DateTime::<chrono::Local>::from(
        UNIX_EPOCH + std::time::Duration::from_secs(secs.max(0) as u64),
    );
    dt.format("%Y-%m-%d %H:%M:%S").to_string()
}

// ── Free-standing helpers ────────────────────────────────────────────────────

/// Get mtime from file metadata as `(secs, nsecs)`.
pub fn file_mtime(path: &Path) -> Option<(i64, i64)> {
    use std::os::unix::fs::MetadataExt;
    let meta = std::fs::metadata(path).ok()?;
    Some((meta.mtime(), meta.mtime_nsec()))
}

/// Mtime of the running stryke binary. Cached for the lifetime of the process.
fn current_binary_mtime_secs() -> Option<i64> {
    static BIN_MTIME: OnceLock<Option<i64>> = OnceLock::new();
    *BIN_MTIME.get_or_init(|| {
        let exe = std::env::current_exe().ok()?;
        let (secs, _) = file_mtime(&exe)?;
        Some(secs)
    })
}

/// Default shard path: `~/.stryke/scripts.rkyv`.
pub fn default_cache_path() -> PathBuf {
    dirs::home_dir()
        .unwrap_or_else(|| PathBuf::from("/tmp"))
        .join(".stryke/scripts.rkyv")
}

/// `STRYKE_CACHE=0|false|no` disables the cache entirely.
pub fn cache_enabled() -> bool {
    !matches!(
        std::env::var("STRYKE_CACHE").as_deref(),
        Ok("0") | Ok("false") | Ok("no")
    )
}

// ── Process-global cache (lazy-initialized) ──────────────────────────────────

/// Process-wide `ScriptCache` rooted at `default_cache_path()`. `None` when the
/// cache is disabled or the path could not be opened.
pub static CACHE: once_cell::sync::Lazy<Option<ScriptCache>> = once_cell::sync::Lazy::new(|| {
    if !cache_enabled() {
        return None;
    }
    ScriptCache::open(&default_cache_path()).ok()
});

/// Try to load a cached script by source path. Returns `None` on any miss.
pub fn try_load(path: &Path) -> Option<CachedScript> {
    let cache = CACHE.as_ref()?;
    let canonical = path.canonicalize().ok()?;
    let path_str = canonical.to_string_lossy();
    let (mtime_s, mtime_ns) = file_mtime(&canonical)?;
    cache.get(&path_str, mtime_s, mtime_ns)
}

/// Store a compiled script in the cache.
pub fn try_save(path: &Path, program: &Program, chunk: &Chunk) -> PerlResult<()> {
    let Some(cache) = CACHE.as_ref() else {
        return Ok(());
    };
    let canonical = match path.canonicalize() {
        Ok(p) => p,
        Err(_) => return Ok(()),
    };
    let path_str = canonical.to_string_lossy();
    let (mtime_s, mtime_ns) = match file_mtime(&canonical) {
        Some(m) => m,
        None => return Ok(()),
    };
    cache.put(&path_str, mtime_s, mtime_ns, program, chunk)
}

/// Global cache stats.
pub fn stats() -> Option<(i64, i64)> {
    CACHE.as_ref().map(|c| c.stats())
}

/// Evict stale entries from global cache.
pub fn evict_stale() -> usize {
    CACHE.as_ref().map(|c| c.evict_stale()).unwrap_or(0)
}

/// Clear the global cache.
pub fn clear() -> bool {
    CACHE.as_ref().map(|c| c.clear().is_ok()).unwrap_or(false)
}

// ── Tests ────────────────────────────────────────────────────────────────────

#[cfg(test)]
mod tests {
    use super::*;
    use tempfile::tempdir;

    #[test]
    fn round_trip() {
        let dir = tempdir().unwrap();
        let cache_path = dir.path().join("scripts.rkyv");
        let cache = ScriptCache::open(&cache_path).unwrap();

        let script_path = dir.path().join("test.stk");
        std::fs::write(&script_path, "p 42").unwrap();

        let (mtime_s, mtime_ns) = file_mtime(&script_path).unwrap();
        let path_str = script_path.to_string_lossy().to_string();

        let program = crate::parse("p 42").unwrap();
        let chunk = crate::compiler::Compiler::new()
            .compile_program(&program)
            .unwrap();

        cache
            .put(&path_str, mtime_s, mtime_ns, &program, &chunk)
            .unwrap();

        let loaded = cache.get(&path_str, mtime_s, mtime_ns).unwrap();
        assert_eq!(loaded.chunk.ops.len(), chunk.ops.len());

        let (count, _bytes) = cache.stats();
        assert_eq!(count, 1);
    }

    #[test]
    fn mtime_invalidation() {
        let dir = tempdir().unwrap();
        let cache_path = dir.path().join("scripts.rkyv");
        let cache = ScriptCache::open(&cache_path).unwrap();

        let script_path = dir.path().join("test.stk");
        std::fs::write(&script_path, "p 42").unwrap();

        let (mtime_s, mtime_ns) = file_mtime(&script_path).unwrap();
        let path_str = script_path.to_string_lossy().to_string();

        let program = crate::parse("p 42").unwrap();
        let chunk = crate::compiler::Compiler::new()
            .compile_program(&program)
            .unwrap();

        cache
            .put(&path_str, mtime_s, mtime_ns, &program, &chunk)
            .unwrap();

        assert!(cache.get(&path_str, mtime_s + 1, mtime_ns).is_none());
    }

    #[test]
    fn second_put_replaces_first() {
        let dir = tempdir().unwrap();
        let cache_path = dir.path().join("scripts.rkyv");
        let cache = ScriptCache::open(&cache_path).unwrap();

        let p1 = dir.path().join("a.stk");
        let p2 = dir.path().join("b.stk");
        std::fs::write(&p1, "1").unwrap();
        std::fs::write(&p2, "2").unwrap();

        let (m1s, m1n) = file_mtime(&p1).unwrap();
        let (m2s, m2n) = file_mtime(&p2).unwrap();

        let prog1 = crate::parse("1").unwrap();
        let chunk1 = crate::compiler::Compiler::new()
            .compile_program(&prog1)
            .unwrap();
        let prog2 = crate::parse("2").unwrap();
        let chunk2 = crate::compiler::Compiler::new()
            .compile_program(&prog2)
            .unwrap();

        cache
            .put(&p1.to_string_lossy(), m1s, m1n, &prog1, &chunk1)
            .unwrap();
        cache
            .put(&p2.to_string_lossy(), m2s, m2n, &prog2, &chunk2)
            .unwrap();

        let (count, _) = cache.stats();
        assert_eq!(count, 2);
        assert!(cache.get(&p1.to_string_lossy(), m1s, m1n).is_some());
        assert!(cache.get(&p2.to_string_lossy(), m2s, m2n).is_some());
    }

    #[test]
    fn corrupt_file_returns_no_mmap() {
        let dir = tempdir().unwrap();
        let cache_path = dir.path().join("scripts.rkyv");
        std::fs::write(&cache_path, b"this is not a valid rkyv archive").unwrap();
        let cache = ScriptCache::open(&cache_path).unwrap();
        // get on a missing path with corrupt file: header_ok blocks on the
        // archived-root validation already failing, so MmappedShard::open
        // returns None and lookups all miss.
        assert!(cache.get("/nope", 0, 0).is_none());
    }

    #[test]
    fn clear_removes_file() {
        let dir = tempdir().unwrap();
        let cache_path = dir.path().join("scripts.rkyv");
        let cache = ScriptCache::open(&cache_path).unwrap();

        let script_path = dir.path().join("test.stk");
        std::fs::write(&script_path, "p 42").unwrap();
        let (mtime_s, mtime_ns) = file_mtime(&script_path).unwrap();
        let program = crate::parse("p 42").unwrap();
        let chunk = crate::compiler::Compiler::new()
            .compile_program(&program)
            .unwrap();
        cache
            .put(
                &script_path.to_string_lossy(),
                mtime_s,
                mtime_ns,
                &program,
                &chunk,
            )
            .unwrap();
        assert!(cache_path.exists());

        cache.clear().unwrap();
        assert!(!cache_path.exists());
    }
}