Move regular expressions to be global statics.

This just makes it a little easier to refer to them.

mdbook-spec/Cargo.toml

@@ -8,6 +8,7 @@ license = "MIT OR Apache-2.0"
 [dependencies]
 anyhow = "1.0.79"
 mdbook = { version = "0.4.36", default-features = false }
+once_cell = "1.19.0"
 pathdiff = "0.2.1"
 regex = "1.10.3"
 semver = "1.0.21"

mdbook-spec/src/main.rs

@@ -2,6 +2,7 @@ use mdbook::book::{Book, Chapter};
 use mdbook::errors::Error;
 use mdbook::preprocess::{CmdPreprocessor, Preprocessor, PreprocessorContext};
 use mdbook::BookItem;
+use once_cell::sync::Lazy;
 use regex::{Captures, Regex};
 use semver::{Version, VersionReq};
 use std::collections::BTreeMap;
@@ -11,6 +12,40 @@ use std::io::{self, Write as _};
 use std::path::PathBuf;
 use std::process::{self, Command};
 
+/// The Regex for rules like `r[foo]`.
+static RULE_RE: Lazy<Regex> = Lazy::new(|| Regex::new(r"(?m)^r\[([^]]+)]$").unwrap());
+
+/// The Regex for the syntax for blockquotes that have a specific CSS class,
+/// like `> [!WARNING]`.
+static ADMONITION_RE: Lazy<Regex> = Lazy::new(|| {
+    Regex::new(r"(?m)^ *> \[!(?<admon>[^]]+)\]\n(?<blockquote>(?: *> .*\n)+)").unwrap()
+});
+
+/// A markdown link (without the brackets) that might possibly be a link to
+/// the standard library using rustdoc's intra-doc notation.
+const STD_LINK: &str = r"(?: [a-z]+@ )?
+                         (?: std|core|alloc|proc_macro|test )
+                         (?: ::[A-Za-z_!:<>{}()\[\]]+ )?";
+
+/// The Regex for a markdown link that might be a link to the standard library.
+static STD_LINK_RE: Lazy<Regex> = Lazy::new(|| {
+    Regex::new(&format!(
+        r"(?x)
+            (?:
+                ( \[`[^`]+`\] ) \( ({STD_LINK}) \)
+            )
+            | (?:
+                ( \[`{STD_LINK}`\] )
+            )
+         "
+    ))
+    .unwrap()
+});
+
+/// The Regex used to extract the std links from the HTML generated by rustdoc.
+static STD_LINK_EXTRACT_RE: Lazy<Regex> =
+    Lazy::new(|| Regex::new(r#"<li><a [^>]*href="(https://doc.rust-lang.org/[^"]+)""#).unwrap());
+
 fn main() {
     let mut args = std::env::args().skip(1);
     match args.next().as_deref() {
@@ -56,41 +91,15 @@ fn handle_preprocessing(pre: &dyn Preprocessor) -> Result<(), Error> {
 }
 
 struct Spec {
+    /// Whether or not warnings should be errors (set by SPEC_DENY_WARNINGS
+    /// environment variable).
     deny_warnings: bool,
-    rule_re: Regex,
-    admonition_re: Regex,
-    std_link_re: Regex,
-    std_link_extract_re: Regex,
 }
 
 impl Spec {
     pub fn new() -> Spec {
-        // This is roughly a rustdoc intra-doc link definition.
-        let std_link = r"(?: [a-z]+@ )?
-                         (?: std|core|alloc|proc_macro|test )
-                         (?: ::[A-Za-z_!:<>{}()\[\]]+ )?";
         Spec {
             deny_warnings: std::env::var("SPEC_DENY_WARNINGS").as_deref() == Ok("1"),
-            rule_re: Regex::new(r"(?m)^r\[([^]]+)]$").unwrap(),
-            admonition_re: Regex::new(
-                r"(?m)^ *> \[!(?<admon>[^]]+)\]\n(?<blockquote>(?: *> .*\n)+)",
-            )
-            .unwrap(),
-            std_link_re: Regex::new(&format!(
-                r"(?x)
-                    (?:
-                        ( \[`[^`]+`\] ) \( ({std_link}) \)
-                    )
-                    | (?:
-                        ( \[`{std_link}`\] )
-                    )
-                 "
-            ))
-            .unwrap(),
-            std_link_extract_re: Regex::new(
-                r#"<li><a [^>]*href="(https://doc.rust-lang.org/[^"]+)""#,
-            )
-            .unwrap(),
         }
     }
 
@@ -103,7 +112,7 @@ impl Spec {
     ) -> String {
         let source_path = chapter.source_path.clone().unwrap_or_default();
         let path = chapter.path.clone().unwrap_or_default();
-        self.rule_re
+        RULE_RE
             .replace_all(&chapter.content, |caps: &Captures| {
                 let rule_id = &caps[1];
                 if let Some((old, _)) =
@@ -165,7 +174,7 @@ impl Spec {
     /// be a CSS class is valid. The actual styling needs to be added in a CSS
     /// file.
     fn admonitions(&self, chapter: &Chapter) -> String {
-        self.admonition_re
+        ADMONITION_RE
             .replace_all(&chapter.content, |caps: &Captures| {
                 let lower = caps["admon"].to_lowercase();
                 format!(
@@ -185,8 +194,7 @@ impl Spec {
         //
         // links are tuples of ("[`std::foo`]", None) for links without dest,
         // or ("[`foo`]", "std::foo") with a dest.
-        let mut links: Vec<_> = self
-            .std_link_re
+        let mut links: Vec<_> = STD_LINK_RE
             .captures_iter(&chapter.content)
             .map(|cap| {
                 if let Some(no_dest) = cap.get(3) {
@@ -250,8 +258,7 @@ impl Spec {
         // Extract the links from the generated html.
         let generated =
             fs::read_to_string(tmp.path().join("doc/a/index.html")).expect("index.html generated");
-        let urls: Vec<_> = self
-            .std_link_extract_re
+        let urls: Vec<_> = STD_LINK_EXTRACT_RE
             .captures_iter(&generated)
             .map(|cap| cap.get(1).unwrap().as_str())
             .collect();
@@ -267,8 +274,7 @@ impl Spec {
         }
 
         // Replace any disambiguated links with just the disambiguation.
-        let mut output = self
-            .std_link_re
+        let mut output = STD_LINK_RE
             .replace_all(&chapter.content, |caps: &Captures| {
                 if let Some(dest) = caps.get(2) {
                     // Replace destination parenthesis with a link definition (square brackets).