Rollup merge of rust-lang#101166 - GuillaumeGomez:error-index-mdbook, r=notriddle

Generate error index with mdbook instead of raw HTML pages

This is a follow-up of rust-lang#100922.

This comes from a remark from ```@estebank``` who said that the search was a nice thing on the previous version and that it wasn't possible anymore. An easy way to come around this limitation was to use `mdbook`, which is what I did here.

Now some explanations on the code. I'll explain how I developed this and why I reached this solution. First I did it very basically by simply setting the source directory and the output directory, generated a `SUMMARY.md` manually which listed all error codes and that was it. Two problems arose from this:
 1. A lot of new HTML files were generated at the top level
 2. An `index.html` file was generated at the top-level (the summary in short).

So for `1.`, it's not great to have too many files at the top-level as it could create file conflicts more easily. And for `2.`, this is actually a huge issue because <doc.rust-lang.org> generates an `index.html` file with a links to a few different resources, so it should never be overwritten. <s>Unfortunately, `mdbook` **always** generates an `index.html` file so the only solution I could see (except for sending them a contribution, I'll maybe do that later) was to temporaly move a potentially existing `index.html` file and then puts it back once done. For this last part, to ensure that we don't return *before* it has been put back, I wrapped the `mdbook` generation code inside `render_html_inner` which is called from `render_html` which in turn handle the "save" of `index.html`.</s>

EDIT: `mdbook` completely deletes ALL the content in the target directory so I instead generate into a sub directory and then I move the files to the real target directory.

To keep compatibility with the old version, I also put the `<script>` ```@notriddle``` nicely provided in the previous PR only into the `error-index.html` file to prevent unneeded repetition. I didn't use `mdbook` `additional-js` option because the JS is included at the end of all HTML files, which we don't want for two reasons:
 1. It's slow.
 2. We only want it to be run in `error-index.html` (even if we also ensure in the JS itself too!).

<s>Now the last part: why we generate the summary twice. We actually generate it once to tell `mdbook` what the book will look like and a second time because a create a new chapter content which will actually list all the error codes (with the updated paths).</s>

EDIT: I removed the need for two summaries.

You can test it [here](https://rustdoc.crud.net/imperio/error-index-mdbook/error-index.html).

r? ```@notriddle```

Author: Dylan-DPC

Cargo.lock

@@ -1259,7 +1259,7 @@ dependencies = [
 name = "error_index_generator"
 version = "0.0.0"
 dependencies = [
- "rustdoc",
+ "mdbook",
 ]
 
 [[package]]

src/bootstrap/doc.rs

@@ -793,7 +793,7 @@ impl Step for ErrorIndex {
         t!(fs::create_dir_all(&out));
         let mut index = tool::ErrorIndex::command(builder);
         index.arg("html");
-        index.arg(out.join("error-index.html"));
+        index.arg(out);
         index.arg(&builder.version);
 
         builder.run(&mut index);

src/tools/error_index_generator/Cargo.toml

@@ -4,7 +4,7 @@ version = "0.0.0"
 edition = "2021"
 
 [dependencies]
-rustdoc = { path = "../../librustdoc" }
+mdbook = { version = "0.4", default-features = false, features = ["search"] }
 
 [[bin]]
 name = "error_index_generator"

src/tools/error_index_generator/book_config.toml

@@ -0,0 +1,19 @@
+[book]
+title = "Error codes index"
+description = "Book listing all Rust error codes"
+src = ""
+
+[output.html]
+git-repository-url = "https://github.com/rust-lang/rust/"
+additional-css = ["error-index.css"]
+additional-js = ["error-index.js"]
+
+[output.html.search]
+enable = true
+limit-results = 20
+use-boolean-and = true
+boost-title = 2
+boost-hierarchy = 2
+boost-paragraph = 1
+expand = true
+heading-split-level = 0

src/tools/error_index_generator/error-index.css

@@ -0,0 +1,38 @@
+code.compile_fail {
+	border-left: 2px solid red;
+}
+
+pre .tooltip {
+	position: absolute;
+	left: -25px;
+	top: 0;
+	z-index: 1;
+	color: red;
+	cursor: pointer;
+}
+pre .tooltip::after {
+	display: none;
+	content: "This example deliberately fails to compile";
+	background-color: #000;
+	color: #fff;
+	border-color: #000;
+	text-align: center;
+	padding: 5px 3px 3px 3px;
+	border-radius: 6px;
+	margin-left: 5px;
+}
+pre .tooltip::before {
+	display: none;
+	border-color: transparent black transparent transparent;
+	content: " ";
+	position: absolute;
+	top: 50%;
+	left: 16px;
+	margin-top: -5px;
+	border-width: 5px;
+	border-style: solid;
+}
+
+pre .tooltip:hover::before, pre .tooltip:hover::after {
+	display: inline;
+}

src/tools/error_index_generator/error-index.js

@@ -0,0 +1,9 @@
+for (const elem of document.querySelectorAll("pre.playground")) {
+    if (elem.querySelector(".compile_fail") === null) {
+        continue;
+    }
+    const child = document.createElement("div");
+    child.className = "tooltip";
+    child.textContent = "ⓘ";
+    elem.appendChild(child);
+}

src/tools/error_index_generator/main.rs

@@ -1,20 +1,21 @@
 #![feature(rustc_private)]
 
 extern crate rustc_driver;
-extern crate rustc_span;
 
+// We use the function we generate from `register_diagnostics!`.
 use crate::error_codes::error_codes;
 
 use std::env;
 use std::error::Error;
-use std::fs::{create_dir_all, File};
+use std::fs::{self, File};
 use std::io::Write;
 use std::path::Path;
 use std::path::PathBuf;
 
-use rustc_span::edition::DEFAULT_EDITION;
+use std::str::FromStr;
 
-use rustdoc::html::markdown::{ErrorCodes, HeadingOffset, IdMap, Markdown, Playground};
+use mdbook::book::{parse_summary, BookItem, Chapter};
+use mdbook::{Config, MDBook};
 
 macro_rules! register_diagnostics {
     ($($error_code:ident: $message:expr,)+ ; $($undocumented:ident,)* ) => {
@@ -33,104 +34,21 @@ macro_rules! register_diagnostics {
 mod error_codes;
 
 enum OutputFormat {
-    HTML(HTMLFormatter),
+    HTML,
     Markdown,
     Unknown(String),
 }
 
 impl OutputFormat {
-    fn from(format: &str, resource_suffix: &str) -> OutputFormat {
+    fn from(format: &str) -> OutputFormat {
         match &*format.to_lowercase() {
-            "html" => OutputFormat::HTML(HTMLFormatter(resource_suffix.to_owned())),
+            "html" => OutputFormat::HTML,
             "markdown" => OutputFormat::Markdown,
             s => OutputFormat::Unknown(s.to_owned()),
         }
     }
 }
 
-struct HTMLFormatter(String);
-
-impl HTMLFormatter {
-    fn create_error_code_file(
-        &self,
-        err_code: &str,
-        explanation: &str,
-        parent_dir: &Path,
-    ) -> Result<(), Box<dyn Error>> {
-        let mut output_file = File::create(parent_dir.join(err_code).with_extension("html"))?;
-
-        self.header(&mut output_file, "../", "")?;
-        self.title(&mut output_file, &format!("Error code {}", err_code))?;
-
-        let mut id_map = IdMap::new();
-        let playground =
-            Playground { crate_name: None, url: String::from("https://play.rust-lang.org/") };
-        write!(
-            output_file,
-            "{}",
-            Markdown {
-                content: explanation,
-                links: &[],
-                ids: &mut id_map,
-                error_codes: ErrorCodes::Yes,
-                edition: DEFAULT_EDITION,
-                playground: &Some(playground),
-                heading_offset: HeadingOffset::H1,
-            }
-            .into_string()
-        )?;
-        write!(
-            output_file,
-            "<p>\
-                <a style='text-align: center;display: block;width: 100%;' \
-                   href='../error-index.html'>Back to list of error codes</a>\
-             </p>",
-        )?;
-
-        self.footer(&mut output_file)
-    }
-
-    fn header(
-        &self,
-        output: &mut dyn Write,
-        extra_path: &str,
-        extra: &str,
-    ) -> Result<(), Box<dyn Error>> {
-        write!(
-            output,
-            r##"<!DOCTYPE html>
-<html>
-<head>
-<title>Rust Compiler Error Index</title>
-<meta charset="utf-8">
-<!-- Include rust.css after light.css so its rules take priority. -->
-<link rel="stylesheet" type="text/css" href="{extra_path}rustdoc{suffix}.css"/>
-<link rel="stylesheet" type="text/css" href="{extra_path}light{suffix}.css"/>
-<link rel="stylesheet" type="text/css" href="{extra_path}rust.css"/>
-<style>
-.error-undescribed {{
-    display: none;
-}}
-</style>{extra}
-</head>
-<body>
-"##,
-            suffix = self.0,
-        )?;
-        Ok(())
-    }
-
-    fn title(&self, output: &mut dyn Write, title: &str) -> Result<(), Box<dyn Error>> {
-        write!(output, "<h1>{}</h1>\n", title)?;
-        Ok(())
-    }
-
-    fn footer(&self, output: &mut dyn Write) -> Result<(), Box<dyn Error>> {
-        write!(output, "</body></html>")?;
-        Ok(())
-    }
-}
-
 /// Output an HTML page for the errors in `err_map` to `output_path`.
 fn render_markdown(output_path: &Path) -> Result<(), Box<dyn Error>> {
     let mut output_file = File::create(output_path)?;
@@ -147,61 +65,119 @@ fn render_markdown(output_path: &Path) -> Result<(), Box<dyn Error>> {
     Ok(())
 }
 
-fn render_html(output_path: &Path, formatter: HTMLFormatter) -> Result<(), Box<dyn Error>> {
-    let mut output_file = File::create(output_path)?;
+// By default, mdbook doesn't consider code blocks as Rust ones contrary to rustdoc so we have
+// to manually add `rust` attribute whenever needed.
+fn add_rust_attribute_on_codeblock(explanation: &str) -> String {
+    // Very hacky way to add the rust attribute on all code blocks.
+    let mut skip = true;
+    explanation.split("\n```").fold(String::new(), |mut acc, part| {
+        if !acc.is_empty() {
+            acc.push_str("\n```");
+        }
+        if !skip {
+            if let Some(attrs) = part.split('\n').next() {
+                if !attrs.contains("rust")
+                    && (attrs.is_empty()
+                        || attrs.contains("compile_fail")
+                        || attrs.contains("ignore")
+                        || attrs.contains("edition"))
+                {
+                    if !attrs.is_empty() {
+                        acc.push_str("rust,");
+                    } else {
+                        acc.push_str("rust");
+                    }
+                }
+            }
+        }
+        skip = !skip;
+        acc.push_str(part);
+        acc
+    })
+}
 
-    let error_codes_dir = "error_codes";
+fn render_html(output_path: &Path) -> Result<(), Box<dyn Error>> {
+    let mut introduction = format!(
+        "<script src='redirect.js'></script>
+# Rust error codes index
 
-    let parent = output_path.parent().expect("There should have a parent").join(error_codes_dir);
+This page lists all the error codes emitted by the Rust compiler.
 
-    if !parent.exists() {
-        create_dir_all(&parent)?;
-    }
+"
+    );
 
-    formatter.header(
-        &mut output_file,
-        "",
-        &format!(
-            r#"<script>(function() {{
-    if (window.location.hash) {{
-        let code = window.location.hash.replace(/^#/, '');
-        // We have to make sure this pattern matches to avoid inadvertently creating an
-        // open redirect.
-        if (/^E[0-9]+$/.test(code)) {{
-            window.location = './{error_codes_dir}/' + code + '.html';
-        }}
-    }}
-}})()</script>"#
-        ),
-    )?;
-    formatter.title(&mut output_file, "Rust Compiler Error Index")?;
+    let err_codes = error_codes();
+    let mut chapters = Vec::with_capacity(err_codes.len());
 
-    write!(
-        output_file,
-        "<p>This page lists all the error codes emitted by the Rust compiler. If you want a full \
-            explanation on an error code, click on it.</p>\
-         <ul>",
-    )?;
-    for (err_code, explanation) in error_codes().iter() {
+    for (err_code, explanation) in err_codes.iter() {
         if let Some(explanation) = explanation {
-            write!(
-                output_file,
-                "<li><a href='./{0}/{1}.html'>{1}</a></li>",
-                error_codes_dir, err_code
-            )?;
-            formatter.create_error_code_file(err_code, explanation, &parent)?;
+            introduction.push_str(&format!(" * [{0}](./{0}.html)\n", err_code));
+
+            let content = add_rust_attribute_on_codeblock(explanation);
+            chapters.push(BookItem::Chapter(Chapter {
+                name: err_code.to_string(),
+                content: format!("# Error code {}\n\n{}\n", err_code, content),
+                number: None,
+                sub_items: Vec::new(),
+                // We generate it into the `error_codes` folder.
+                path: Some(PathBuf::from(&format!("{}.html", err_code))),
+                source_path: None,
+                parent_names: Vec::new(),
+            }));
         } else {
-            write!(output_file, "<li>{}</li>", err_code)?;
+            introduction.push_str(&format!(" * {}\n", err_code));
         }
     }
-    write!(output_file, "</ul>")?;
-    formatter.footer(&mut output_file)
+
+    let mut config = Config::from_str(include_str!("book_config.toml"))?;
+    config.build.build_dir = output_path.join("error_codes").to_path_buf();
+    let mut book = MDBook::load_with_config_and_summary(
+        env!("CARGO_MANIFEST_DIR"),
+        config,
+        parse_summary("")?,
+    )?;
+    let chapter = Chapter {
+        name: "Rust error codes index".to_owned(),
+        content: introduction,
+        number: None,
+        sub_items: chapters,
+        // Very important: this file is named as `error-index.html` and not `index.html`!
+        path: Some(PathBuf::from("error-index.html")),
+        source_path: None,
+        parent_names: Vec::new(),
+    };
+    book.book.sections.push(BookItem::Chapter(chapter));
+    book.build()?;
+
+    // We can't put this content into another file, otherwise `mbdbook` will also put it into the
+    // output directory, making a duplicate.
+    fs::write(
+        output_path.join("error-index.html"),
+        r#"<!DOCTYPE html>
+<html>
+    <head>
+        <title>Rust error codes index - Error codes index</title>
+        <meta content="text/html; charset=utf-8" http-equiv="Content-Type">
+        <meta name="description" content="Book listing all Rust error codes">
+        <script src="error_codes/redirect.js"></script>
+    </head>
+    <body>
+        <div>If you are not automatically redirected to the error code index, please <a id="index-link" href="./error_codes/error-index.html">here</a>.
+        <script>document.getElementById("index-link").click()</script>
+    </body>
+</html>"#,
+    )?;
+
+    // No need for a 404 file, it's already handled by the server.
+    fs::remove_file(output_path.join("error_codes/404.html"))?;
+
+    Ok(())
 }
 
 fn main_with_result(format: OutputFormat, dst: &Path) -> Result<(), Box<dyn Error>> {
     match format {
         OutputFormat::Unknown(s) => panic!("Unknown output format: {}", s),
-        OutputFormat::HTML(h) => render_html(dst, h),
+        OutputFormat::HTML => render_html(dst),
         OutputFormat::Markdown => render_markdown(dst),
     }
 }
@@ -210,12 +186,9 @@ fn parse_args() -> (OutputFormat, PathBuf) {
     let mut args = env::args().skip(1);
     let format = args.next();
     let dst = args.next();
-    let resource_suffix = args.next().unwrap_or_else(String::new);
-    let format = format
-        .map(|a| OutputFormat::from(&a, &resource_suffix))
-        .unwrap_or(OutputFormat::from("html", &resource_suffix));
+    let format = format.map(|a| OutputFormat::from(&a)).unwrap_or(OutputFormat::from("html"));
     let dst = dst.map(PathBuf::from).unwrap_or_else(|| match format {
-        OutputFormat::HTML(..) => PathBuf::from("doc/error-index.html"),
+        OutputFormat::HTML => PathBuf::from("doc"),
         OutputFormat::Markdown => PathBuf::from("doc/error-index.md"),
         OutputFormat::Unknown(..) => PathBuf::from("<nul>"),
     });
@@ -225,9 +198,8 @@ fn parse_args() -> (OutputFormat, PathBuf) {
 fn main() {
     rustc_driver::init_env_logger("RUST_LOG");
     let (format, dst) = parse_args();
-    let result =
-        rustc_span::create_default_session_globals_then(move || main_with_result(format, &dst));
+    let result = main_with_result(format, &dst);
     if let Err(e) = result {
-        panic!("{}", e.to_string());
+        panic!("{:?}", e);
     }
 }

src/tools/error_index_generator/redirect.js

@@ -0,0 +1,16 @@
+(function() {
+    if (window.location.hash) {
+        let code = window.location.hash.replace(/^#/, '');
+        // We have to make sure this pattern matches to avoid inadvertently creating an
+        // open redirect.
+        if (!/^E[0-9]+$/.test(code)) {
+            return;
+        }
+        if (window.location.pathname.indexOf("/error_codes/") !== -1) {
+            // We're not at the top level, so we don't prepend with "./error_codes/".
+            window.location = './' + code + '.html';
+        } else {
+            window.location = './error_codes/' + code + '.html';
+        }
+    }
+})()