style: simplify string formatting for readability

examples/nop-preprocessor.rs

@@ -26,7 +26,7 @@ fn main() {
     if let Some(sub_args) = matches.subcommand_matches("supports") {
         handle_supports(&preprocessor, sub_args);
     } else if let Err(e) = handle_preprocessing(&preprocessor) {
-        eprintln!("{}", e);
+        eprintln!("{e}");
         process::exit(1);
     }
 }

src/book/book.rs

@@ -18,11 +18,11 @@ pub fn load_book<P: AsRef<Path>>(src_dir: P, cfg: &BuildConfig) -> Result<Book>
 
     let mut summary_content = String::new();
     File::open(&summary_md)
-        .with_context(|| format!("Couldn't open SUMMARY.md in {:?} directory", src_dir))?
+        .with_context(|| format!("Couldn't open SUMMARY.md in {src_dir:?} directory"))?
         .read_to_string(&mut summary_content)?;
 
     let summary = parse_summary(&summary_content)
-        .with_context(|| format!("Summary parsing failed for file={:?}", summary_md))?;
+        .with_context(|| format!("Summary parsing failed for file={summary_md:?}"))?;
 
     if cfg.create_missing {
         create_missing(src_dir, &summary).with_context(|| "Unable to create missing chapters")?;
@@ -341,7 +341,7 @@ impl<'a> Iterator for BookItems<'a> {
 impl Display for Chapter {
     fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
         if let Some(ref section_number) = self.number {
-            write!(f, "{} ", section_number)?;
+            write!(f, "{section_number} ")?;
         }
 
         write!(f, "{}", self.name)

src/book/mod.rs

@@ -92,7 +92,7 @@ impl MDBook {
         }
 
         if log_enabled!(log::Level::Trace) {
-            for line in format!("Config: {:#?}", config).lines() {
+            for line in format!("Config: {config:#?}").lines() {
                 trace!("{}", line);
             }
         }
@@ -483,15 +483,13 @@ fn determine_preprocessors(config: &Config) -> Result<Vec<Box<dyn Preprocessor>>
             if let Some(before) = table.get("before") {
                 let before = before.as_array().ok_or_else(|| {
                     Error::msg(format!(
-                        "Expected preprocessor.{}.before to be an array",
+                        "Expected preprocessor.{name}.before to be an array"
-                        name
                     ))
                 })?;
                 for after in before {
                     let after = after.as_str().ok_or_else(|| {
                         Error::msg(format!(
-                            "Expected preprocessor.{}.before to contain strings",
+                            "Expected preprocessor.{name}.before to contain strings"
-                            name
                         ))
                     })?;
 
@@ -511,15 +509,13 @@ fn determine_preprocessors(config: &Config) -> Result<Vec<Box<dyn Preprocessor>>
             if let Some(after) = table.get("after") {
                 let after = after.as_array().ok_or_else(|| {
                     Error::msg(format!(
-                        "Expected preprocessor.{}.after to be an array",
+                        "Expected preprocessor.{name}.after to be an array"
-                        name
                     ))
                 })?;
                 for before in after {
                     let before = before.as_str().ok_or_else(|| {
                         Error::msg(format!(
-                            "Expected preprocessor.{}.after to contain strings",
+                            "Expected preprocessor.{name}.after to contain strings"
-                            name
                         ))
                     })?;
 
@@ -581,7 +577,7 @@ fn get_custom_preprocessor_cmd(key: &str, table: &Value) -> String {
         .get("command")
         .and_then(Value::as_str)
         .map(ToString::to_string)
-        .unwrap_or_else(|| format!("mdbook-{}", key))
+        .unwrap_or_else(|| format!("mdbook-{key}"))
 }
 
 fn interpret_custom_renderer(key: &str, table: &Value) -> Box<CmdRenderer> {
@@ -592,7 +588,7 @@ fn interpret_custom_renderer(key: &str, table: &Value) -> Box<CmdRenderer> {
         .and_then(Value::as_str)
         .map(ToString::to_string);
 
-    let command = table_dot_command.unwrap_or_else(|| format!("mdbook-{}", key));
+    let command = table_dot_command.unwrap_or_else(|| format!("mdbook-{key}"));
 
     Box::new(CmdRenderer::new(key.to_string(), command))
 }
@@ -786,7 +782,7 @@ mod tests {
                 for preprocessor in &preprocessors {
                     eprintln!("  {}", preprocessor.name());
                 }
-                panic!("{} should come before {}", before, after);
+                panic!("{before} should come before {after}");
             }
         };
 

src/book/summary.rs

@@ -616,7 +616,7 @@ impl Display for SectionNumber {
             write!(f, "0")
         } else {
             for item in &self.0 {
-                write!(f, "{}.", item)?;
+                write!(f, "{item}.")?;
             }
             Ok(())
         }
@@ -763,7 +763,7 @@ mod tests {
 
         let href = match parser.stream.next() {
             Some((Event::Start(Tag::Link { dest_url, .. }), _range)) => dest_url.to_string(),
-            other => panic!("Unreachable, {:?}", other),
+            other => panic!("Unreachable, {other:?}"),
         };
 
         let got = parser.parse_link(href);

src/cmd/serve.rs

@@ -54,7 +54,7 @@ pub fn execute(args: &ArgMatches) -> Result<()> {
     let hostname = args.get_one::<String>("hostname").unwrap();
     let open_browser = args.get_flag("open");
 
-    let address = format!("{}:{}", hostname, port);
+    let address = format!("{hostname}:{port}");
 
     let update_config = |book: &mut MDBook| {
         book.config
@@ -89,7 +89,7 @@ pub fn execute(args: &ArgMatches) -> Result<()> {
         serve(build_dir, sockaddr, reload_tx, &file_404);
     });
 
-    let serving_url = format!("http://{}", address);
+    let serving_url = format!("http://{address}");
     info!("Serving on: {}", serving_url);
 
     if open_browser {

src/config.rs

@@ -145,7 +145,7 @@ impl Config {
                 if let serde_json::Value::Object(ref map) = parsed_value {
                     // To `set` each `key`, we wrap them as `prefix.key`
                     for (k, v) in map {
-                        let full_key = format!("{}.{}", key, k);
+                        let full_key = format!("{key}.{k}");
                         self.set(&full_key, v).expect("unreachable");
                     }
                     return;

src/preprocess/links.rs

@@ -493,7 +493,7 @@ mod tests {
         let s = "Some random text with {{#playground file.rs}} and {{#playground test.rs }}...";
 
         let res = find_links(s).collect::<Vec<_>>();
-        println!("\nOUTPUT: {:?}\n", res);
+        println!("\nOUTPUT: {res:?}\n");
 
         assert_eq!(
             res,
@@ -519,7 +519,7 @@ mod tests {
         let s = "Some random text with {{#playground foo-bar\\baz/_c++.rs}}...";
 
         let res = find_links(s).collect::<Vec<_>>();
-        println!("\nOUTPUT: {:?}\n", res);
+        println!("\nOUTPUT: {res:?}\n");
 
         assert_eq!(
             res,
@@ -536,7 +536,7 @@ mod tests {
     fn test_find_links_with_range() {
         let s = "Some random text with {{#include file.rs:10:20}}...";
         let res = find_links(s).collect::<Vec<_>>();
-        println!("\nOUTPUT: {:?}\n", res);
+        println!("\nOUTPUT: {res:?}\n");
         assert_eq!(
             res,
             vec![Link {
@@ -555,7 +555,7 @@ mod tests {
     fn test_find_links_with_line_number() {
         let s = "Some random text with {{#include file.rs:10}}...";
         let res = find_links(s).collect::<Vec<_>>();
-        println!("\nOUTPUT: {:?}\n", res);
+        println!("\nOUTPUT: {res:?}\n");
         assert_eq!(
             res,
             vec![Link {
@@ -574,7 +574,7 @@ mod tests {
     fn test_find_links_with_from_range() {
         let s = "Some random text with {{#include file.rs:10:}}...";
         let res = find_links(s).collect::<Vec<_>>();
-        println!("\nOUTPUT: {:?}\n", res);
+        println!("\nOUTPUT: {res:?}\n");
         assert_eq!(
             res,
             vec![Link {
@@ -593,7 +593,7 @@ mod tests {
     fn test_find_links_with_to_range() {
         let s = "Some random text with {{#include file.rs::20}}...";
         let res = find_links(s).collect::<Vec<_>>();
-        println!("\nOUTPUT: {:?}\n", res);
+        println!("\nOUTPUT: {res:?}\n");
         assert_eq!(
             res,
             vec![Link {
@@ -612,7 +612,7 @@ mod tests {
     fn test_find_links_with_full_range() {
         let s = "Some random text with {{#include file.rs::}}...";
         let res = find_links(s).collect::<Vec<_>>();
-        println!("\nOUTPUT: {:?}\n", res);
+        println!("\nOUTPUT: {res:?}\n");
         assert_eq!(
             res,
             vec![Link {
@@ -631,7 +631,7 @@ mod tests {
     fn test_find_links_with_no_range_specified() {
         let s = "Some random text with {{#include file.rs}}...";
         let res = find_links(s).collect::<Vec<_>>();
-        println!("\nOUTPUT: {:?}\n", res);
+        println!("\nOUTPUT: {res:?}\n");
         assert_eq!(
             res,
             vec![Link {
@@ -650,7 +650,7 @@ mod tests {
     fn test_find_links_with_anchor() {
         let s = "Some random text with {{#include file.rs:anchor}}...";
         let res = find_links(s).collect::<Vec<_>>();
-        println!("\nOUTPUT: {:?}\n", res);
+        println!("\nOUTPUT: {res:?}\n");
         assert_eq!(
             res,
             vec![Link {
@@ -670,7 +670,7 @@ mod tests {
         let s = "Some random text with escaped playground \\{{#playground file.rs editable}} ...";
 
         let res = find_links(s).collect::<Vec<_>>();
-        println!("\nOUTPUT: {:?}\n", res);
+        println!("\nOUTPUT: {res:?}\n");
 
         assert_eq!(
             res,
@@ -690,7 +690,7 @@ mod tests {
                  more\n text {{#playground my.rs editable no_run should_panic}} ...";
 
         let res = find_links(s).collect::<Vec<_>>();
-        println!("\nOUTPUT: {:?}\n", res);
+        println!("\nOUTPUT: {res:?}\n");
         assert_eq!(
             res,
             vec![
@@ -721,7 +721,7 @@ mod tests {
                  no_run should_panic}} ...";
 
         let res = find_links(s).collect::<Vec<_>>();
-        println!("\nOUTPUT: {:?}\n", res);
+        println!("\nOUTPUT: {res:?}\n");
         assert_eq!(res.len(), 3);
         assert_eq!(
             res[0],

src/renderer/html_handlebars/hbs_renderer.rs

@@ -153,13 +153,13 @@ impl HtmlHandlebars {
         let content_404 = if let Some(ref filename) = html_config.input_404 {
             let path = src_dir.join(filename);
             std::fs::read_to_string(&path)
-                .with_context(|| format!("unable to open 404 input file {:?}", path))?
+                .with_context(|| format!("unable to open 404 input file {path:?}"))?
         } else {
             // 404 input not explicitly configured try the default file 404.md
             let default_404_location = src_dir.join("404.md");
             if default_404_location.exists() {
                 std::fs::read_to_string(&default_404_location).with_context(|| {
-                    format!("unable to open 404 input file {:?}", default_404_location)
+                    format!("unable to open 404 input file {default_404_location:?}")
                 })?
             } else {
                 "# Document not found (404)\n\nThis URL is invalid, sorry. Please use the \
@@ -237,7 +237,7 @@ impl HtmlHandlebars {
         )?;
 
         if let Some(cname) = &html_config.cname {
-            write_file(destination, "CNAME", format!("{}\n", cname).as_bytes())?;
+            write_file(destination, "CNAME", format!("{cname}\n").as_bytes())?;
         }
 
         write_file(destination, "book.js", &theme.js)?;
@@ -834,11 +834,7 @@ fn insert_link_into_header(
         .unwrap_or_default();
 
     format!(
-        r##"<h{level} id="{id}"{classes}><a class="header" href="#{id}">{text}</a></h{level}>"##,
+        r##"<h{level} id="{id}"{classes}><a class="header" href="#{id}">{content}</a></h{level}>"##
-        level = level,
-        id = id,
-        text = content,
-        classes = classes
     )
 }
 
@@ -861,10 +857,7 @@ fn fix_code_blocks(html: &str) -> String {
             let after = &caps[3];
 
             format!(
-                r#"<code{before}class="{classes}"{after}>"#,
+                r#"<code{before}class="{classes}"{after}>"#
-                before = before,
-                classes = classes,
-                after = after
             )
         })
         .into_owned()
@@ -923,7 +916,7 @@ fn add_playground_pre(
                             // we need to inject our own main
                             let (attrs, code) = partition_source(code);
 
-                            format!("# #![allow(unused)]\n{}#fn main() {{\n{}#}}", attrs, code)
+                            format!("# #![allow(unused)]\n{attrs}#fn main() {{\n{code}#}}")
                                 .into()
                         };
                         content

src/renderer/html_handlebars/search.rs

@@ -50,7 +50,7 @@ pub fn create_files(search_config: &Search, destination: &Path, book: &Book) ->
         utils::fs::write_file(
             destination,
             "searchindex.js",
-            format!("Object.assign(window.search, {});", index).as_bytes(),
+            format!("Object.assign(window.search, {index});").as_bytes(),
         )?;
         utils::fs::write_file(destination, "searcher.js", searcher::JS)?;
         utils::fs::write_file(destination, "mark.min.js", searcher::MARK_JS)?;
@@ -83,7 +83,7 @@ fn add_doc(
     });
 
     let url = if let Some(id) = section_id {
-        Cow::Owned(format!("{}#{}", anchor_base, id))
+        Cow::Owned(format!("{anchor_base}#{id}"))
     } else {
         Cow::Borrowed(anchor_base)
     };
@@ -203,7 +203,7 @@ fn render_item(
             Event::FootnoteReference(name) => {
                 let len = footnote_numbers.len() + 1;
                 let number = footnote_numbers.entry(name).or_insert(len);
-                body.push_str(&format!(" [{}] ", number));
+                body.push_str(&format!(" [{number}] "));
             }
             Event::TaskListMarker(_checked) => {}
         }

src/utils/fs.rs

@@ -228,47 +228,47 @@ mod tests {
     fn copy_files_except_ext_test() {
         let tmp = match tempfile::TempDir::new() {
             Ok(t) => t,
-            Err(e) => panic!("Could not create a temp dir: {}", e),
+            Err(e) => panic!("Could not create a temp dir: {e}"),
         };
 
         // Create a couple of files
         if let Err(err) = fs::File::create(tmp.path().join("file.txt")) {
-            panic!("Could not create file.txt: {}", err);
+            panic!("Could not create file.txt: {err}");
         }
         if let Err(err) = fs::File::create(tmp.path().join("file.md")) {
-            panic!("Could not create file.md: {}", err);
+            panic!("Could not create file.md: {err}");
         }
         if let Err(err) = fs::File::create(tmp.path().join("file.png")) {
-            panic!("Could not create file.png: {}", err);
+            panic!("Could not create file.png: {err}");
         }
         if let Err(err) = fs::create_dir(tmp.path().join("sub_dir")) {
-            panic!("Could not create sub_dir: {}", err);
+            panic!("Could not create sub_dir: {err}");
         }
         if let Err(err) = fs::File::create(tmp.path().join("sub_dir/file.png")) {
-            panic!("Could not create sub_dir/file.png: {}", err);
+            panic!("Could not create sub_dir/file.png: {err}");
         }
         if let Err(err) = fs::create_dir(tmp.path().join("sub_dir_exists")) {
-            panic!("Could not create sub_dir_exists: {}", err);
+            panic!("Could not create sub_dir_exists: {err}");
         }
         if let Err(err) = fs::File::create(tmp.path().join("sub_dir_exists/file.txt")) {
-            panic!("Could not create sub_dir_exists/file.txt: {}", err);
+            panic!("Could not create sub_dir_exists/file.txt: {err}");
         }
         if let Err(err) = symlink(tmp.path().join("file.png"), tmp.path().join("symlink.png")) {
-            panic!("Could not symlink file.png: {}", err);
+            panic!("Could not symlink file.png: {err}");
         }
 
         // Create output dir
         if let Err(err) = fs::create_dir(tmp.path().join("output")) {
-            panic!("Could not create output: {}", err);
+            panic!("Could not create output: {err}");
         }
         if let Err(err) = fs::create_dir(tmp.path().join("output/sub_dir_exists")) {
-            panic!("Could not create output/sub_dir_exists: {}", err);
+            panic!("Could not create output/sub_dir_exists: {err}");
         }
 
         if let Err(e) =
             copy_files_except_ext(tmp.path(), &tmp.path().join("output"), true, None, &["md"])
         {
-            panic!("Error while executing the function:\n{:?}", e);
+            panic!("Error while executing the function:\n{e:?}");
         }
 
         // Check if the correct files where created

src/utils/mod.rs

@@ -77,7 +77,7 @@ pub fn unique_id_from_content(content: &str, id_counter: &mut HashMap<String, us
     let id_count = id_counter.entry(id.clone()).or_insert(0);
     let unique_id = match *id_count {
         0 => id,
-        id_count => format!("{}-{}", id, id_count),
+        id_count => format!("{id}-{id_count}"),
     };
     *id_count += 1;
     unique_id
@@ -105,7 +105,7 @@ fn adjust_links<'a>(event: Event<'a>, path: Option<&Path>) -> Event<'a> {
                 if base.ends_with(".md") {
                     base.replace_range(base.len() - 3.., ".html");
                 }
-                return format!("{}{}", base, dest).into();
+                return format!("{base}{dest}").into();
             } else {
                 return dest;
             }
@@ -121,7 +121,7 @@ fn adjust_links<'a>(event: Event<'a>, path: Option<&Path>) -> Event<'a> {
                     .to_str()
                     .expect("utf-8 paths only");
                 if !base.is_empty() {
-                    write!(fixed_link, "{}/", base).unwrap();
+                    write!(fixed_link, "{base}/").unwrap();
                 }
             }
 

tests/alternative_backends.rs

@@ -117,12 +117,12 @@ fn dummy_book_with_backend(
 
     let mut config = Config::default();
     config
-        .set(format!("output.{}.command", name), command)
+        .set(format!("output.{name}.command"), command)
         .unwrap();
 
     if backend_is_optional {
         config
-            .set(format!("output.{}.optional", name), true)
+            .set(format!("output.{name}.optional"), true)
             .unwrap();
     }
 

tests/init.rs

@@ -23,7 +23,7 @@ fn base_mdbook_init_should_create_default_content() {
     for file in &created_files {
         let target = temp.path().join(file);
         println!("{}", target.display());
-        assert!(target.exists(), "{} doesn't exist", file);
+        assert!(target.exists(), "{file} doesn't exist");
     }
 
     let contents = fs::read_to_string(temp.path().join("book.toml")).unwrap();
@@ -59,7 +59,7 @@ fn run_mdbook_init_should_create_content_from_summary() {
     for file in &created_files {
         let target = src_dir.join(file);
         println!("{}", target.display());
-        assert!(target.exists(), "{} doesn't exist", file);
+        assert!(target.exists(), "{file} doesn't exist");
     }
 }
 
@@ -73,8 +73,7 @@ fn run_mdbook_init_with_custom_book_and_src_locations() {
     for file in &created_files {
         assert!(
             !temp.path().join(file).exists(),
-            "{} shouldn't exist yet!",
+            "{file} shouldn't exist yet!"
-            file
         );
     }
 
@@ -88,8 +87,7 @@ fn run_mdbook_init_with_custom_book_and_src_locations() {
         let target = temp.path().join(file);
         assert!(
             target.exists(),
-            "{} should have been created by `mdbook init`",
+            "{file} should have been created by `mdbook init`"
-            file
         );
     }