replace remaining OnceCells w/ Lazys, simplifying

i prefer Lazy because it simplifies initialisation by a lot, allowing for the removal of stuff like `init_db()` and the `clap_version()` functions

CHANGELOG.md

@@ -6,7 +6,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 
 ## Unreleased
 ### Added
-- AIFF (Audio Interchange File Format, a PCM audio format like WAV) detection to [`infer`]
+- AIFF (Audio Interchange File Format, a PCM audio format like WAV) detection to [`infer`] backend
 - `--version` output now includes the (short) hash of the git commit fif was built from
 ### Other
 - Refactoring - split fif into `main.rs` and `lib.rs`, moved file-related functionality (directory scanning, etc.) into
@@ -17,7 +17,7 @@ files module, removed string module, etc.
     headings that (pointlessly?) previously divided the changelog into v0.3, v0.2, and v0.1
   - A few minor grammar tweaks and reorganisations
 - Replaced [`cached`] dependency with a simple HashMap-backed store
-- Use [`once_cell`]'s `Lazy` instead of its `OnceCell` for the `MIMEDB` const
+- Replace all occurrences of [`once_cell`]'s `OnceCell` with equivalent `Lazy`-based implementations
 
 ## v0.3.6 - 2021-08-16
 ### Other

src/files.rs

@@ -1,8 +1,8 @@
+//! File handling - scanning, detecting MIME types, and so on.
+
 use std::collections::{BTreeSet, HashMap};
 use std::fs::File;
-use std::io;
+use std::io::{self, Read, Seek, SeekFrom};
-use std::io::{Read, Seek, SeekFrom};
-use std::ops::Deref;
 use std::path::Path;
 use std::str::FromStr;
 use std::sync::RwLock;
@@ -19,6 +19,7 @@ use crate::mime_db::MimeDb;
 use crate::parameters::ScanOpts;
 use crate::{String, MIMEDB};
 
+/// Cache of mimetypes and their associated extensions, used by [`mime_extension_lookup()`]
 static MIMEXT: Lazy<RwLock<HashMap<String, Option<Vec<String>>>>> = Lazy::new(|| RwLock::new(HashMap::new()));
 
 cfg_if! {
@@ -97,7 +98,7 @@ pub fn wanted_file(
 pub fn scan_file(entry: &DirEntry, canonical_paths: bool) -> Result<Findings, ScanError> {
 	let path = entry.path();
 	// try to determine mimetype for this entry
-	let result = match mime_type(MIMEDB.deref(), path) {
+	let result = match mime_type(&*MIMEDB, path) {
 		// an error occurred while trying to read the file
 		Err(_) => return Err(ScanError::File(path)),
 		// the file was read successfully, but we were unable to determine its mimetype

src/findings.rs

@@ -1,3 +1,6 @@
+//! The [`Findings`] and [`ScanError`] structs, used for conveying whether a given file was able to be scanned and
+//! whether its MIME type could be inferred.
+
 use std::fmt::{Display, Formatter};
 use std::path::{Path, PathBuf};
 

src/formats.rs

@@ -11,7 +11,7 @@ use itertools::{Either, Itertools};
 use snailquote::escape;
 
 use crate::findings::ScanError;
-use crate::utils::clap_long_version;
+use crate::utils::CLAP_LONG_VERSION;
 use crate::Findings;
 use crate::String;
 
@@ -74,7 +74,7 @@ impl<'a> From<&'a OsStr> for Writable<'a> {
 	fn from(p: &'a OsStr) -> Writable<'a> { Writable::Path(p.as_ref()) }
 }
 
-fn generated_by() -> String { format!("Generated by fif {}", clap_long_version()).into() }
+fn generated_by() -> String { format!("Generated by fif {}", CLAP_LONG_VERSION.as_str()).into() }
 
 pub fn smart_write<W: Write>(f: &mut W, writeables: &[Writable]) -> io::Result<()> {
 	// ehhhh

src/lib.rs

@@ -1,5 +1,8 @@
 #![forbid(unsafe_code)]
 #![warn(trivial_casts, unused_lifetimes, unused_qualifications)]
+//! This library consists of all of the things fif needs to run. It only exists as a library to separate code, and to
+//! make testing a bit easier. I don't recommend using this as a library for your crate, as it may have breaking
+//! changes without incrementing the major version, as it's really only meant to be a place for fif's internals to live.
 
 pub mod files;
 pub mod findings;
@@ -27,9 +30,9 @@ cfg_if! {
 cfg_if! {
 	if #[cfg(any(all(unix, feature = "infer-backend"), all(not(unix), not(feature = "xdg-mime-backend"))))] {
 		/// A [Lazy] holding an instance of [mime_db::MimeDb].
-		pub static MIMEDB: Lazy<mime_db::InferDb> = Lazy::new(|| crate::mime_db::InferDb::init());
+		pub static MIMEDB: Lazy<mime_db::InferDb> = Lazy::new(crate::mime_db::InferDb::init);
 	} else {
 		/// A [Lazy] holding an instance of [mime_db::MimeDb].
-		pub static MIMEDB: Lazy<mime_db::XdgDb> = Lazy::new(|| crate::mime_db::XdgDb::init());
+		pub static MIMEDB: Lazy<mime_db::XdgDb> = Lazy::new(crate::mime_db::XdgDb::init);
 	}
 }

src/main.rs

@@ -24,7 +24,7 @@ use clap::Clap;
 use fif::files::{scan_directory, scan_from_walkdir};
 use fif::formats::Format;
 use fif::parameters::OutputFormat;
-use fif::utils::{clap_long_version, os_name};
+use fif::utils::{os_name, CLAP_LONG_VERSION};
 use fif::{formats, parameters};
 use log::{debug, error, info, trace, warn, Level};
 
@@ -54,7 +54,7 @@ fn main() {
 
 	trace!(
 		"fif {}, running on {} {}",
-		clap_long_version(),
+		CLAP_LONG_VERSION.as_str(),
 		std::env::consts::ARCH,
 		os_name()
 	);

src/mime_db.rs

@@ -4,7 +4,9 @@ use cfg_if::cfg_if;
 use mime::Mime;
 
 pub trait MimeDb {
+	/// Initialise the database.
 	fn init() -> Self;
+	/// Given a slice of bytes, returns the inferred mimetype, if any.
 	fn get_type(&self, data: &[u8]) -> Option<Mime>;
 }
 

src/parameters.rs

@@ -6,7 +6,7 @@ use std::path::PathBuf;
 use cfg_if::cfg_if;
 use clap::{AppSettings, Clap};
 
-use crate::utils::{clap_long_version, clap_version};
+use crate::utils::{CLAP_LONG_VERSION, CLAP_VERSION};
 use crate::String as StringType;
 
 cfg_if! {
@@ -35,8 +35,8 @@ pub enum OutputFormat {
 #[derive(Clap, Debug)]
 #[allow(clippy::struct_excessive_bools)]
 #[clap(
-	version = clap_version(),
+	version = CLAP_VERSION.as_str(),
-	long_version = clap_long_version(),
+	long_version = CLAP_LONG_VERSION.as_str(),
 	author = option_env!("CARGO_PKG_AUTHORS").unwrap_or("Lynnesbian"),
 	about = option_env!("CARGO_PKG_DESCRIPTION").unwrap_or("File Info Fixer"),
 	before_help = "Copyright © 2021 Lynnesbian under the GPL3 (or later) License.",
@@ -258,7 +258,7 @@ pub enum ExtensionSet {
 	#[clap(alias = "videos")]
 	Video,
 	/// Extensions used for media file formats. This acts as a combination of the [Images](ExtensionSet::Images),
-	/// [Audio](ExtensionSet::Audio) and [Videos](ExtensionSet::Videos) variants.
+	/// [Audio](ExtensionSet::Audio) and [Video](ExtensionSet::Video) variants.
 	Media,
 	/// Extensions used for document file formats, such as `pdf`, `odt`, `docx`, etc.
 	Documents,

src/tests/mod.rs

@@ -3,12 +3,11 @@ use std::ffi::OsStr;
 use std::path::{Path, PathBuf};
 
 use clap::Clap;
-use fif::files::{mime_extension_lookup, BUF_SIZE};
+use fif::files::{mime_extension_lookup, scan_directory, scan_from_walkdir, BUF_SIZE};
-use fif::files::{scan_directory, scan_from_walkdir};
 use fif::findings::Findings;
 use fif::formats::{Format, PowerShell, Shell};
 use fif::mime_db::MimeDb;
-use fif::String;
+use fif::{String, MIMEDB};
 use mime::{Mime, APPLICATION_OCTET_STREAM, APPLICATION_PDF, IMAGE_JPEG, IMAGE_PNG};
 
 use crate::parameters::ExtensionSet;
@@ -19,18 +18,6 @@ const PNG_BYTES: &[u8] = b"\x89\x50\x4E\x47\x0D\x0A\x1A\x0A";
 const PDF_BYTES: &[u8] = b"%PDF-";
 const ZIP_BYTES: &[u8] = b"PK\x03\x04";
 
-cfg_if::cfg_if! {
-	if #[cfg(any(all(unix, feature = "infer-backend"), all(not(unix), not(feature = "xdg-mime-backend"))))] {
-		fn get_mime_db() -> fif::mime_db::InferDb {
-			fif::mime_db::InferDb::init()
-		}
-	} else {
-		fn get_mime_db() -> fif::mime_db::XdgDb {
-			fif::mime_db::XdgDb::init()
-		}
-	}
-}
-
 fn application_zip() -> Mime {
 	use std::str::FromStr;
 	Mime::from_str("application/zip").unwrap()
@@ -55,11 +42,10 @@ fn get_ext() {
 #[test]
 /// Ensure that the mime types for JPEG, PNG, PDF, and ZIP are detected from their magic numbers.
 fn detect_type() {
-	let db = get_mime_db();
+	assert_eq!(MIMEDB.get_type(JPEG_BYTES), Some(IMAGE_JPEG));
-	assert_eq!(db.get_type(JPEG_BYTES), Some(IMAGE_JPEG));
+	assert_eq!(MIMEDB.get_type(PNG_BYTES), Some(IMAGE_PNG));
-	assert_eq!(db.get_type(PNG_BYTES), Some(IMAGE_PNG));
+	assert_eq!(MIMEDB.get_type(PDF_BYTES), Some(APPLICATION_PDF));
-	assert_eq!(db.get_type(PDF_BYTES), Some(APPLICATION_PDF));
+	assert_eq!(MIMEDB.get_type(ZIP_BYTES), Some(application_zip()));
-	assert_eq!(db.get_type(ZIP_BYTES), Some(application_zip()));
 }
 
 #[test]
@@ -317,14 +303,13 @@ fn rejects_bad_args() {
 /// mime database somehow panics or hangs.
 fn identify_random_bytes() {
 	use rand::RngCore;
-	let db = get_mime_db();
 	let mut rng = rand::thread_rng();
 	let mut bytes: [u8; BUF_SIZE * 2] = [0; BUF_SIZE * 2];
 	let mut results: HashMap<Mime, i32> = HashMap::new();
 
 	for _ in 1..1000 {
 		rng.fill_bytes(&mut bytes);
-		if let Some(detected_type) = db.get_type(&bytes) {
+		if let Some(detected_type) = MIMEDB.get_type(&bytes) {
 			*results.entry(detected_type).or_insert(0) += 1;
 		}
 	}

src/utils.rs

@@ -1,5 +1,7 @@
+//! Various minor utilities.
+
 use cfg_if::cfg_if;
-use once_cell::sync::OnceCell;
+use once_cell::sync::Lazy;
 
 use crate::String;
 
@@ -16,21 +18,12 @@ cfg_if! {
 	}
 }
 
-// the version and long_version given to clap need to be a &str, but we want to use format!, which returns a String.
+/// The version defined in Cargo.toml, prefixed with a v (e.g. "v0.3.1")
-// we can't just do something like `version = format!(...).as_str()`, because clap needs to know that the version will
+pub(crate) static CLAP_VERSION: Lazy<String> = Lazy::new(|| String::from("v") + VERSION.unwrap_or("???"));
-// live for a given lifetime, which we need to satisfy by making our String static. of course, you can't use format!
-// statically, so we need to use a OnceCell or similar to get around this.
-static CLAP_VERSION: OnceCell<String> = OnceCell::new();
-static CLAP_LONG_VERSION: OnceCell<String> = OnceCell::new();
 
-/// Sets [`CLAP_VERSION`] to be the version defined in Cargo.toml, prefixed with a v (e.g. "v0.3.1"), then returns it as
+/// Similar to [`CLAP_VERSION`], followed by the chosen backend and abbreviated git commit hash in parentheses - For
-/// an str.
+/// example, "v0.3.6 (XDG-Mime backend, commit #043e097)"
-pub fn clap_version() -> &'static str { CLAP_VERSION.get_or_init(|| String::from("v") + VERSION.unwrap_or("???")) }
+pub static CLAP_LONG_VERSION: Lazy<String> = Lazy::new(|| {
-
-/// Sets [`CLAP_LONG_VERSION`] to be similar to [`CLAP_VERSION`], followed by the chosen backend and abbreviated git
-/// commit hash in parentheses (e.g. "v0.3.6 (XDG-Mime backend, commit #043e097)"), then returns it as an str.
-pub fn clap_long_version() -> &'static str {
-	CLAP_LONG_VERSION.get_or_init(|| {
 	format!(
 		"v{} ({} backend, commit #{})",
 		VERSION.unwrap_or("???"),
@@ -38,8 +31,7 @@ pub fn clap_long_version() -> &'static str {
 		option_env!("GIT_SHA").unwrap_or("???")
 	)
 	.into()
-	})
+});
-}
 
 /// Returns the name of the target operating system with proper casing, like "Windows" or "macOS".
 #[allow(clippy::option_map_unit_fn)]