Support case insensitive systems for file generation

src/librustdoc/config.rs

@@ -265,6 +265,9 @@ crate struct RenderOptions {
     crate document_hidden: bool,
     /// If `true`, generate a JSON file in the crate folder instead of HTML redirection files.
     crate generate_redirect_map: bool,
+    /// If this option is set to `true`, HTML files will be generated as it would on a
+    /// case-insensitive file system.
+    crate generate_case_insensitive: bool,
     crate unstable_features: rustc_feature::UnstableFeatures,
 }
 
@@ -580,6 +583,7 @@ impl Options {
         let document_hidden = matches.opt_present("document-hidden-items");
         let run_check = matches.opt_present("check");
         let generate_redirect_map = matches.opt_present("generate-redirect-map");
+        let generate_case_insensitive = matches.opt_present("generate-case-insensitive");
 
         let (lint_opts, describe_lints, lint_cap) = get_cmd_lint_options(matches, error_format);
 
@@ -638,6 +642,7 @@ impl Options {
                 document_private,
                 document_hidden,
                 generate_redirect_map,
+                generate_case_insensitive,
                 unstable_features: rustc_feature::UnstableFeatures::from_environment(
                     crate_name.as_deref(),
                 ),

src/librustdoc/formats/renderer.rs

@@ -1,10 +1,16 @@
+use rustc_data_structures::fx::{FxHashMap, FxHashSet};
 use rustc_middle::ty::TyCtxt;
 use rustc_span::{edition::Edition, Symbol};
 
+use std::fs;
+use std::io::Write;
+use std::path::Path;
+
 use crate::clean;
 use crate::config::RenderOptions;
 use crate::error::Error;
 use crate::formats::cache::Cache;
+use crate::html::render::print_item::item_path;
 
 /// Allows for different backends to rustdoc to be used with the `run_format()` function. Each
 /// backend renderer has hooks for initialization, documenting an item, entering and exiting a
@@ -26,6 +32,7 @@ crate trait FormatRenderer<'tcx>: Sized {
         edition: Edition,
         cache: Cache,
         tcx: TyCtxt<'tcx>,
+        case_insensitive_conflicts: Option<FxHashSet<String>>,
     ) -> Result<(Self, clean::Crate), Error>;
 
     /// Make a new renderer to render a child of the item currently being rendered.
@@ -52,6 +59,71 @@ crate trait FormatRenderer<'tcx>: Sized {
     fn cache(&self) -> &Cache;
 }
 
+fn handle_module(dst: &Path, item: &clean::Item, paths_map: &mut FxHashMap<String, usize>) {
+    // modules are special because they add a namespace. We also need to
+    // recurse into the items of the module as well.
+    let name = item.name.as_ref().unwrap().to_string();
+    if name.is_empty() {
+        panic!("Unexpected module with empty name");
+    }
+    let module = match *item.kind {
+        clean::StrippedItem(box clean::ModuleItem(ref m)) | clean::ModuleItem(ref m) => m,
+        _ => unreachable!(),
+    };
+    let mod_path = dst.join(&name);
+    for it in &module.items {
+        if it.is_mod() {
+            handle_module(&mod_path, it, paths_map);
+        } else if it.name.is_some() && !it.is_extern_crate() {
+            let name = it.name.as_ref().unwrap();
+            let item_type = it.type_();
+            let file_name = &item_path(item_type, &name.as_str());
+            let insensitive_path = mod_path.join(file_name).display().to_string();
+
+            let entry = paths_map.entry(insensitive_path.to_lowercase()).or_insert(0);
+            *entry += 1;
+        }
+    }
+}
+
+fn build_case_insensitive_map(
+    krate: &clean::Crate,
+    options: &RenderOptions,
+) -> Option<FxHashSet<String>> {
+    let mut paths_map: FxHashMap<String, usize> = FxHashMap::default();
+
+    handle_module(&options.output, &krate.module, &mut paths_map);
+    Some(paths_map.into_iter().filter(|(_, count)| *count > 1).map(|(path, _)| path).collect())
+}
+
+fn check_if_case_insensitive(dst: &Path) -> bool {
+    fn create_and_write(dst: &Path, content: &str) {
+        if let Ok(mut f) = fs::OpenOptions::new().write(true).create(true).truncate(true).open(dst)
+        {
+            // Ignoring potential errors.
+            let _ = f.write(content.as_bytes());
+        }
+    }
+    fn compare_content(dst: &Path, content: &str) -> bool {
+        fs::read_to_string(dst).unwrap_or_else(|_| String::new()).as_str() == content
+    }
+
+    let path1 = dst.join("___a.tmp");
+    let content1 = "a";
+    let path2 = dst.join("___A.tmp");
+    let content2 = "A";
+
+    create_and_write(&path1, content1);
+    create_and_write(&path1, content2);
+
+    let res = compare_content(&path1, content1) && compare_content(&path2, content2);
+    // We ignore the errors when removing the files.
+    let _ = fs::remove_file(&path1);
+    let _ = fs::remove_file(&path2);
+
+    res
+}
+
 /// Main method for rendering a crate.
 crate fn run_format<'tcx, T: FormatRenderer<'tcx>>(
     krate: clean::Crate,
@@ -63,9 +135,16 @@ crate fn run_format<'tcx, T: FormatRenderer<'tcx>>(
 ) -> Result<(), Error> {
     let prof = &tcx.sess.prof;
 
+    let case_insensitive_conflicts =
+        if options.generate_case_insensitive || check_if_case_insensitive(&options.output) {
+            build_case_insensitive_map(&krate, &options)
+        } else {
+            None
+        };
+
     let (mut format_renderer, krate) = prof
         .extra_verbose_generic_activity("create_renderer", T::descr())
-        .run(|| T::init(krate, options, edition, cache, tcx))?;
+        .run(|| T::init(krate, options, edition, cache, tcx, case_insensitive_conflicts))?;
 
     // Render the crate documentation
     let crate_name = krate.name;

src/librustdoc/html/layout.rs

@@ -222,6 +222,42 @@ crate fn render<T: Print, S: Print>(
     )
 }
 
+/// Since this is a "conflict file" on case insensitive file system, it'll be loaded by JS instead
+/// of being loaded directly. Which is why we need to modify its output a bit.
+crate fn conflict_layout<T: Print, S>(page: &Page<'_>, sidebar: S, t: T) -> String
+where
+    S: FnOnce(&mut Buffer) -> Option<String>,
+{
+    let content = Buffer::html().to_display(t).to_string();
+    let mut sidebar_buf = Buffer::html();
+    let script_src = sidebar(&mut sidebar_buf);
+    format!(
+        "\
+document.getElementById('main').innerHTML = \"{content}\";\
+document.getElementsByClassName('sidebar')[0].innerHTML += \"{sidebar}\";\
+document.title = \"{title}\";\
+window.initSidebarVars();\
+rustdocInit();{script}",
+        content = content.replace("\\", "\\\\").replace("\"", "\\\"").replace("\n", "\\n"),
+        title = page.title.replace("\\", "\\\\").replace("\"", "\\\""),
+        sidebar = sidebar_buf
+            .into_inner()
+            .replace("\\", "\\\\")
+            .replace("\"", "\\\"")
+            .replace("\n", "\\n"),
+        script = if let Some(script_src) = script_src {
+            format!(
+                "var script = document.createElement('script');\
+                 script.src = {:?};\
+                 document.body.appendChild(script);",
+                script_src,
+            )
+        } else {
+            String::new()
+        },
+    )
+}
+
 crate fn redirect(url: &str) -> String {
     // <script> triggers a redirect before refresh, so this is fine.
     format!(