Split std_links into multiple functions.

The std_links function was getting a little long, this should help
organize a little.

Author: ehuss

mdbook-spec/src/std_links.rs

@@ -5,6 +5,7 @@ use std::fmt::Write as _;
 use std::fs;
 use std::io::{self, Write as _};
 use std::process::{self, Command};
+use tempfile::TempDir;
 
 /// A markdown link (without the brackets) that might possibly be a link to
 /// the standard library using rustdoc's intra-doc notation.
@@ -34,12 +35,65 @@ static STD_LINK_EXTRACT_RE: Lazy<Regex> =
 /// Converts links to the standard library to the online documentation in a
 /// fashion similar to rustdoc intra-doc links.
 pub fn std_links(chapter: &Chapter) -> String {
-    // This is very hacky, but should work well enough.
-    //
-    // Collect all standard library links.
-    //
-    // links are tuples of ("[`std::foo`]", None) for links without dest,
-    // or ("[`foo`]", "std::foo") with a dest.
+    let links = collect_markdown_links(chapter);
+    if links.is_empty() {
+        return chapter.content.clone();
+    }
+
+    // Write a Rust source file to use with rustdoc to generate intra-doc links.
+    let tmp = TempDir::with_prefix("mdbook-spec-").unwrap();
+    run_rustdoc(&tmp, &links, &chapter);
+
+    // 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<_> = STD_LINK_EXTRACT_RE
+        .captures_iter(&generated)
+        .map(|cap| cap.get(1).unwrap().as_str())
+        .collect();
+    if urls.len() != links.len() {
+        eprintln!(
+            "error: expected rustdoc to generate {} links, but found {} in chapter {} ({:?})",
+            links.len(),
+            urls.len(),
+            chapter.name,
+            chapter.source_path.as_ref().unwrap()
+        );
+        process::exit(1);
+    }
+
+    // Replace any disambiguated links with just the disambiguation.
+    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).
+                format!("{}[{}]", &caps[1], dest.as_str())
+            } else {
+                caps[0].to_string()
+            }
+        })
+        .to_string();
+
+    // Append the link definitions to the bottom of the chapter.
+    write!(output, "\n").unwrap();
+    for ((link, dest), url) in links.iter().zip(urls) {
+        if let Some(dest) = dest {
+            write!(output, "[{dest}]: {url}\n").unwrap();
+        } else {
+            write!(output, "{link}: {url}\n").unwrap();
+        }
+    }
+
+    output
+}
+
+/// Collects all markdown links.
+///
+/// Returns a `Vec` of `(link, Option<dest>)` where markdown text like
+/// ``[`std::fmt`]`` would return that as a link. The dest is optional, for
+/// example ``[`Option`](std::option::Option)`` would have the part in
+/// parentheses as the dest.
+fn collect_markdown_links(chapter: &Chapter) -> Vec<(&str, Option<&str>)> {
     let mut links: Vec<_> = STD_LINK_RE
         .captures_iter(&chapter.content)
         .map(|cap| {
@@ -54,13 +108,21 @@ pub fn std_links(chapter: &Chapter) -> String {
         })
         .collect();
     if links.is_empty() {
-        return chapter.content.clone();
+        return vec![];
     }
     links.sort();
     links.dedup();
+    links
+}
 
-    // Write a Rust source file to use with rustdoc to generate intra-doc links.
-    let tmp = tempfile::TempDir::with_prefix("mdbook-spec-").unwrap();
+/// Generates links using rustdoc.
+///
+/// This takes the given links and creates a temporary Rust source file
+/// containing those links within doc-comments, and then runs rustdoc to
+/// generate intra-doc links on them.
+///
+/// The output will be in the given `tmp` directory.
+fn run_rustdoc(tmp: &TempDir, links: &[(&str, Option<&str>)], chapter: &Chapter) {
     let src_path = tmp.path().join("a.rs");
     // Allow redundant since there could some in-scope things that are
     // technically not necessary, but we don't care about (like
@@ -69,7 +131,7 @@ pub fn std_links(chapter: &Chapter) -> String {
         "#![deny(rustdoc::broken_intra_doc_links)]\n\
          #![allow(rustdoc::redundant_explicit_links)]\n"
     );
-    for (link, dest) in &links {
+    for (link, dest) in links {
         write!(src, "//! - {link}").unwrap();
         if let Some(dest) = dest {
             write!(src, "({})", dest).unwrap();
@@ -100,46 +162,4 @@ pub fn std_links(chapter: &Chapter) -> String {
         io::stderr().write_all(&output.stderr).unwrap();
         process::exit(1);
     }
-
-    // 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<_> = STD_LINK_EXTRACT_RE
-        .captures_iter(&generated)
-        .map(|cap| cap.get(1).unwrap().as_str())
-        .collect();
-    if urls.len() != links.len() {
-        eprintln!(
-            "error: expected rustdoc to generate {} links, but found {} in chapter {} ({:?})",
-            links.len(),
-            urls.len(),
-            chapter.name,
-            chapter.source_path.as_ref().unwrap()
-        );
-        process::exit(1);
-    }
-
-    // Replace any disambiguated links with just the disambiguation.
-    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).
-                format!("{}[{}]", &caps[1], dest.as_str())
-            } else {
-                caps[0].to_string()
-            }
-        })
-        .to_string();
-
-    // Append the link definitions to the bottom of the chapter.
-    write!(output, "\n").unwrap();
-    for ((link, dest), url) in links.iter().zip(urls) {
-        if let Some(dest) = dest {
-            write!(output, "[{dest}]: {url}\n").unwrap();
-        } else {
-            write!(output, "{link}: {url}\n").unwrap();
-        }
-    }
-
-    output
 }