grex_core/tree/
loader.rs

1//! Pluggable [`PackLoader`] for the tree walker.
2//!
3//! The walker never reads the filesystem directly: every manifest arrives via
4//! a [`PackLoader`] impl. This exists so:
5//!
6//! * Tests substitute an in-memory mock and avoid disk I/O entirely.
7//! * A future plugin backend (e.g. an HTTP-fetched manifest or a cached
8//!   manifest store) can slot in without touching walker logic.
9//! * Tree-walk tests stay hermetic on CI.
10
11use std::io;
12use std::path::{Path, PathBuf};
13
14use crate::pack::{parse, PackManifest};
15
16use super::error::{is_not_a_directory, TreeError};
17
18/// Strategy object for turning a path into a parsed manifest.
19///
20/// Implementors must be `Send + Sync` so the walker can be used behind an
21/// `Arc` in a future parallel-walk slice.
22pub trait PackLoader: Send + Sync {
23    /// Resolve `path` and return the parsed manifest.
24    ///
25    /// # Path semantics
26    ///
27    /// * If `path` is a directory, the loader looks up
28    ///   `path.join(".grex/pack.yaml")`.
29    /// * If `path` ends in `.yaml` or `.yml`, it is read verbatim.
30    ///
31    /// The distinction is documented at the trait level so every backend
32    /// observes the same contract.
33    ///
34    /// # Errors
35    ///
36    /// Returns [`TreeError::ManifestNotFound`] when no manifest exists at
37    /// the resolved location; [`TreeError::ManifestPermissionDenied`],
38    /// [`TreeError::ManifestNotADir`], or [`TreeError::ManifestIo`] for
39    /// categorised IO failures; [`TreeError::ManifestRead`] as a
40    /// back-compat catch-all for unmatched `io::ErrorKind` cases; and
41    /// [`TreeError::ManifestParse`] for structural failures.
42    fn load(&self, path: &Path) -> Result<PackManifest, TreeError>;
43}
44
45/// Filesystem-backed [`PackLoader`] used by the real walker.
46#[derive(Debug, Default)]
47pub struct FsPackLoader;
48
49impl FsPackLoader {
50    /// Construct a new loader. Equivalent to [`FsPackLoader::default`].
51    #[must_use]
52    pub const fn new() -> Self {
53        Self
54    }
55}
56
57impl PackLoader for FsPackLoader {
58    fn load(&self, path: &Path) -> Result<PackManifest, TreeError> {
59        let manifest_path = resolve_manifest_path(path);
60        if !manifest_path.is_file() {
61            return Err(TreeError::ManifestNotFound(manifest_path));
62        }
63        let raw = match std::fs::read_to_string(&manifest_path) {
64            Ok(s) => s,
65            Err(e) => return Err(map_manifest_read_error(manifest_path, e)),
66        };
67        parse(&raw)
68            .map_err(|e| TreeError::ManifestParse { path: manifest_path, detail: e.to_string() })
69    }
70}
71
72/// Route a manifest-read [`io::Error`] into the most specific
73/// [`TreeError`] variant available. Unmatched `io::ErrorKind` cases fall
74/// through to [`TreeError::ManifestRead`] for back-compat with v1.2.0+
75/// downstream consumers that may have matched it explicitly.
76fn map_manifest_read_error(manifest_path: PathBuf, e: io::Error) -> TreeError {
77    match e.kind() {
78        io::ErrorKind::NotFound => TreeError::ManifestNotFound(manifest_path),
79        io::ErrorKind::PermissionDenied => {
80            TreeError::ManifestPermissionDenied { path: manifest_path }
81        }
82        _ if is_not_a_directory(&e) => TreeError::ManifestNotADir { path: manifest_path },
83        _ => TreeError::ManifestIo { path: manifest_path, source: e },
84    }
85}
86
87/// Resolve a user-supplied path to the concrete `pack.yaml` location.
88///
89/// Split out so cyclomatic budget on [`FsPackLoader::load`] stays tiny.
90fn resolve_manifest_path(path: &Path) -> PathBuf {
91    if has_yaml_extension(path) {
92        path.to_path_buf()
93    } else {
94        path.join(".grex").join("pack.yaml")
95    }
96}
97
98fn has_yaml_extension(path: &Path) -> bool {
99    matches!(path.extension().and_then(|e| e.to_str()), Some("yaml" | "yml"))
100}
grex_core/tree/loader.rs

grex_core/tree/
loader.rs
