Change book source root depending on language

src/book/mod.rs

@@ -29,6 +29,7 @@ use crate::renderer::{CmdRenderer, HtmlHandlebars, MarkdownRenderer, RenderConte
 use crate::utils;
 
 use crate::config::{Config, RustEdition};
+use crate::build_opts::BuildOpts;
 
 /// The object used to manage and build a book.
 pub struct MDBook {
@@ -38,6 +39,10 @@ pub struct MDBook {
     pub config: Config,
     /// A representation of the book's contents in memory.
     pub book: Book,
+    /// Build options passed from frontend.
+    pub build_opts: BuildOpts,
+
+    /// List of renderers to be run on the book.
     renderers: Vec<Box<dyn Renderer>>,
 
     /// List of pre-processors to be run on the book.
@@ -47,6 +52,12 @@ pub struct MDBook {
 impl MDBook {
     /// Load a book from its root directory on disk.
     pub fn load<P: Into<PathBuf>>(book_root: P) -> Result<MDBook> {
+        MDBook::load_with_build_opts(book_root, BuildOpts::default())
+    }
+
+    /// Load a book from its root directory on disk, passing in options from the
+    /// frontend.
+    pub fn load_with_build_opts<P: Into<PathBuf>>(book_root: P, build_opts: BuildOpts) -> Result<MDBook> {
         let book_root = book_root.into();
         let config_location = book_root.join("book.toml");
 
@@ -75,11 +86,11 @@ impl MDBook {
             }
         }
 
-        MDBook::load_with_config(book_root, config)
+        MDBook::load_with_config(book_root, config, build_opts)
     }
 
-    /// Load a book from its root directory using a custom `Config`.
-    pub fn load_with_config<P: Into<PathBuf>>(book_root: P, config: Config) -> Result<MDBook> {
+    /// Load a book from its root directory using a custom config.
+    pub fn load_with_config<P: Into<PathBuf>>(book_root: P, config: Config, build_opts: BuildOpts) -> Result<MDBook> {
         let root = book_root.into();
 
         let src_dir = root.join(&config.book.src);
@@ -92,6 +103,7 @@ impl MDBook {
             root,
             config,
             book,
+            build_opts,
             renderers,
             preprocessors,
         })
@@ -102,6 +114,7 @@ impl MDBook {
         book_root: P,
         config: Config,
         summary: Summary,
+        build_opts: BuildOpts,
     ) -> Result<MDBook> {
         let root = book_root.into();
 
@@ -115,6 +128,7 @@ impl MDBook {
             root,
             config,
             book,
+            build_opts,
             renderers,
             preprocessors,
         })
@@ -185,6 +199,7 @@ impl MDBook {
         let mut preprocessed_book = self.book.clone();
         let preprocess_ctx = PreprocessorContext::new(
             self.root.clone(),
+            self.build_opts.clone(),
             self.config.clone(),
             renderer.name().to_string(),
         );
@@ -201,7 +216,8 @@ impl MDBook {
 
         let mut render_context = RenderContext::new(
             self.root.clone(),
-            preprocessed_book,
+            preprocessed_book.clone(),
+            self.build_opts.clone(),
             self.config.clone(),
             build_dir,
         );
@@ -241,7 +257,7 @@ impl MDBook {
 
         // FIXME: Is "test" the proper renderer name to use here?
         let preprocess_context =
-            PreprocessorContext::new(self.root.clone(), self.config.clone(), "test".to_string());
+            PreprocessorContext::new(self.root.clone(), self.build_opts.clone(), self.config.clone(), "test".to_string());
 
         let book = LinkPreprocessor::new().run(&preprocess_context, self.book.clone())?;
         // Index Preprocessor is disabled so that chapter paths continue to point to the
@@ -336,7 +352,8 @@ impl MDBook {
 
     /// Get the directory containing this book's source files.
     pub fn source_dir(&self) -> PathBuf {
-        self.root.join(&self.config.book.src)
+        let src = self.config.get_localized_src_path(self.build_opts.language_ident.as_ref()).unwrap();
+        self.root.join(src)
     }
 
     /// Get the directory containing the theme resources for the book.

src/build_opts.rs

@@ -0,0 +1,10 @@
+//! Build options.
+
+/// Build options passed from the frontend to control how the book is built.
+/// Separate from `Config`, which is global to all book languages.
+#[derive(Debug, Clone, PartialEq, Serialize, Deserialize, Default)]
+#[serde(default, rename_all = "kebab-case")]
+pub struct BuildOpts {
+    /// Language of the book to render.
+    pub language_ident: Option<String>,
+}

src/cmd/build.rs

@@ -1,4 +1,4 @@
-use crate::{get_book_dir, open};
+use crate::{get_book_dir, get_build_opts, open};
 use clap::{App, ArgMatches, SubCommand};
 use mdbook::errors::Result;
 use mdbook::MDBook;
@@ -22,7 +22,8 @@ pub fn make_subcommand<'a, 'b>() -> App<'a, 'b> {
 // Build command implementation
 pub fn execute(args: &ArgMatches) -> Result<()> {
     let book_dir = get_book_dir(args);
-    let mut book = MDBook::load(&book_dir)?;
+    let opts = get_build_opts(args);
+    let mut book = MDBook::load_with_build_opts(&book_dir, opts)?;
 
     if let Some(dest_dir) = args.value_of("dest-dir") {
         book.config.build.build_dir = dest_dir.into();

src/cmd/test.rs

@@ -1,4 +1,4 @@
-use crate::get_book_dir;
+use crate::{get_book_dir, get_build_opts};
 use clap::{App, Arg, ArgMatches, SubCommand};
 use mdbook::errors::Result;
 use mdbook::MDBook;
@@ -34,7 +34,8 @@ pub fn execute(args: &ArgMatches) -> Result<()> {
         .map(std::iter::Iterator::collect)
         .unwrap_or_default();
     let book_dir = get_book_dir(args);
-    let mut book = MDBook::load(&book_dir)?;
+    let build_opts = get_build_opts(args);
+    let mut book = MDBook::load_with_build_opts(&book_dir, build_opts)?;
 
     if let Some(dest_dir) = args.value_of("dest-dir") {
         book.config.build.build_dir = dest_dir.into();

src/config.rs

@@ -252,6 +252,31 @@ impl Config {
         self.get(&key).and_then(Value::as_table)
     }
 
+    /// Get the source directory of a localized book corresponding to language ident `index`.
+    pub fn get_localized_src_path<I: AsRef<str>>(&self, index: Option<I>) -> Option<PathBuf> {
+        match self.language.default_language() {
+            Some(default) => match index {
+                // Make sure that the language we passed was actually
+                // declared in the config, and return `None` if not.
+                Some(lang_ident) => self.language.0.get(lang_ident.as_ref()).map(|_| {
+                    let mut buf = PathBuf::new();
+                    buf.push(self.book.src.clone());
+                    buf.push(lang_ident.as_ref());
+                    buf
+                }),
+                // Use the default specified in book.toml.
+                None => Some(PathBuf::from(default))
+            }
+
+            // No default language was configured in book.toml. Preserve
+            // backwards compatibility by just returning `src`.
+            None => match index {
+                Some(_) => None,
+                None => Some(self.book.src.clone()),
+            }
+        }
+    }
+
     fn from_legacy(mut table: Value) -> Config {
         let mut cfg = Config::default();
 
@@ -354,7 +379,6 @@ impl<'de> Deserialize<'de> for Config {
                 .count();
 
             if default_languages != 1  {
-                use serde::de::Error;
                 return Err(D::Error::custom(
                     "If languages are specified, exactly one must be set as 'default'"
                 ));
@@ -727,10 +751,10 @@ pub struct Language {
 
 impl LanguageConfig {
     /// Returns the default language specified in the config.
-    pub fn default_language(&self) -> Option<&Language> {
+    pub fn default_language(&self) -> Option<&String> {
         self.0.iter()
               .find(|(_, lang)| lang.default)
-              .map(|(_, lang)| lang)
+              .map(|(lang_ident, _)| lang_ident)
     }
 }
 

src/lib.rs

@@ -98,6 +98,7 @@ extern crate serde_json;
 extern crate pretty_assertions;
 
 pub mod book;
+pub mod build_opts;
 pub mod config;
 pub mod preprocess;
 pub mod renderer;

src/main.rs

@@ -9,6 +9,7 @@ use clap::{App, AppSettings, Arg, ArgMatches, Shell, SubCommand};
 use env_logger::Builder;
 use log::LevelFilter;
 use mdbook::utils;
+use mdbook::build_opts::BuildOpts;
 use std::env;
 use std::ffi::OsStr;
 use std::io::Write;
@@ -131,6 +132,14 @@ fn get_book_dir(args: &ArgMatches) -> PathBuf {
     }
 }
 
+fn get_build_opts(args: &ArgMatches) -> BuildOpts {
+    let language = args.value_of("language");
+
+    BuildOpts {
+        language_ident: language.map(String::from)
+    }
+}
+
 fn open<P: AsRef<OsStr>>(path: P) {
     info!("Opening web browser");
     if let Err(e) = open::that(path) {

src/preprocess/cmd.rs

@@ -179,6 +179,7 @@ impl Preprocessor for CmdPreprocessor {
 mod tests {
     use super::*;
     use crate::MDBook;
+    use crate::build_opts::BuildOpts;
     use std::path::Path;
 
     fn guide() -> MDBook {
@@ -192,6 +193,7 @@ mod tests {
         let md = guide();
         let ctx = PreprocessorContext::new(
             md.root.clone(),
+            BuildOpts::default(),
             md.config.clone(),
             "some-renderer".to_string(),
         );

src/preprocess/index.rs

@@ -26,7 +26,7 @@ impl Preprocessor for IndexPreprocessor {
     }
 
     fn run(&self, ctx: &PreprocessorContext, mut book: Book) -> Result<Book> {
-        let source_dir = ctx.root.join(&ctx.config.book.src);
+        let source_dir = ctx.source_dir();
         book.for_each_mut(|section: &mut BookItem| {
             if let BookItem::Chapter(ref mut ch) = *section {
                 if let Some(ref mut path) = ch.path {

src/preprocess/links.rs

@@ -42,7 +42,7 @@ impl Preprocessor for LinkPreprocessor {
     }
 
     fn run(&self, ctx: &PreprocessorContext, mut book: Book) -> Result<Book> {
-        let src_dir = ctx.root.join(&ctx.config.book.src);
+        let src_dir = ctx.source_dir();
 
         book.for_each_mut(|section: &mut BookItem| {
             if let BookItem::Chapter(ref mut ch) = *section {

src/preprocess/mod.rs

@@ -10,6 +10,7 @@ mod links;
 
 use crate::book::Book;
 use crate::config::Config;
+use crate::build_opts::BuildOpts;
 use crate::errors::*;
 
 use std::cell::RefCell;
@@ -22,6 +23,8 @@ use std::path::PathBuf;
 pub struct PreprocessorContext {
     /// The location of the book directory on disk.
     pub root: PathBuf,
+    /// The build options passed from the frontend.
+    pub build_opts: BuildOpts,
     /// The book configuration (`book.toml`).
     pub config: Config,
     /// The `Renderer` this preprocessor is being used with.
@@ -36,16 +39,23 @@ pub struct PreprocessorContext {
 
 impl PreprocessorContext {
     /// Create a new `PreprocessorContext`.
-    pub(crate) fn new(root: PathBuf, config: Config, renderer: String) -> Self {
+    pub(crate) fn new(root: PathBuf, build_opts: BuildOpts, config: Config, renderer: String) -> Self {
         PreprocessorContext {
             root,
+            build_opts,
             config,
             renderer,
             mdbook_version: crate::MDBOOK_VERSION.to_string(),
             chapter_titles: RefCell::new(HashMap::new()),
             __non_exhaustive: (),
         }
     }
+
+    /// Get the directory containing this book's source files.
+    pub fn source_dir(&self) -> PathBuf {
+        let src = self.config.get_localized_src_path(self.build_opts.language_ident.as_ref()).unwrap();
+        self.root.join(src)
+    }
 }
 
 /// An operation which is run immediately after loading a book into memory and

src/renderer/html_handlebars/hbs_renderer.rs

@@ -460,7 +460,7 @@ impl Renderer for HtmlHandlebars {
     fn render(&self, ctx: &RenderContext) -> Result<()> {
         let book_config = &ctx.config.book;
         let html_config = ctx.config.html_config().unwrap_or_default();
-        let src_dir = ctx.root.join(&ctx.config.book.src);
+        let src_dir = ctx.source_dir();
         let destination = &ctx.destination;
         let book = &ctx.book;
         let build_dir = ctx.root.join(&ctx.config.build.build_dir);

src/renderer/mod.rs

@@ -26,6 +26,7 @@ use std::process::{Command, Stdio};
 
 use crate::book::Book;
 use crate::config::Config;
+use crate::build_opts::BuildOpts;
 use crate::errors::*;
 use toml::Value;
 
@@ -58,6 +59,8 @@ pub struct RenderContext {
     pub root: PathBuf,
     /// A loaded representation of the book itself.
     pub book: Book,
+    /// The build options passed from the frontend.
+    pub build_opts: BuildOpts,
     /// The loaded configuration file.
     pub config: Config,
     /// Where the renderer *must* put any build artefacts generated. To allow
@@ -72,13 +75,14 @@ pub struct RenderContext {
 
 impl RenderContext {
     /// Create a new `RenderContext`.
-    pub fn new<P, Q>(root: P, book: Book, config: Config, destination: Q) -> RenderContext
+    pub fn new<P, Q>(root: P, book: Book, build_opts: BuildOpts, config: Config, destination: Q) -> RenderContext
     where
         P: Into<PathBuf>,
         Q: Into<PathBuf>,
     {
         RenderContext {
             book,
+            build_opts,
             config,
             version: crate::MDBOOK_VERSION.to_string(),
             root: root.into(),
@@ -90,7 +94,8 @@ impl RenderContext {
 
     /// Get the source directory's (absolute) path on disk.
     pub fn source_dir(&self) -> PathBuf {
-        self.root.join(&self.config.book.src)
+        let src = self.config.get_localized_src_path(self.build_opts.language_ident.as_ref()).unwrap();
+        self.root.join(src)
     }
 
     /// Load a `RenderContext` from its JSON representation.

tests/build_process.rs

@@ -2,6 +2,7 @@ mod dummy_book;
 
 use crate::dummy_book::DummyBook;
 use mdbook::book::Book;
+use mdbook::build_opts::BuildOpts;
 use mdbook::config::Config;
 use mdbook::errors::*;
 use mdbook::preprocess::{Preprocessor, PreprocessorContext};
@@ -48,8 +49,9 @@ fn mdbook_runs_preprocessors() {
 
     let temp = DummyBook::new().build().unwrap();
     let cfg = Config::default();
+    let build_opts = BuildOpts::default();
 
-    let mut book = MDBook::load_with_config(temp.path(), cfg).unwrap();
+    let mut book = MDBook::load_with_config(temp.path(), cfg, build_opts).unwrap();
     book.with_preprocessor(Spy(Arc::clone(&spy)));
     book.build().unwrap();
 
@@ -68,8 +70,9 @@ fn mdbook_runs_renderers() {
 
     let temp = DummyBook::new().build().unwrap();
     let cfg = Config::default();
+    let build_opts = BuildOpts::default();
 
-    let mut book = MDBook::load_with_config(temp.path(), cfg).unwrap();
+    let mut book = MDBook::load_with_config(temp.path(), cfg, build_opts).unwrap();
     book.with_renderer(Spy(Arc::clone(&spy)));
     book.build().unwrap();