Support setting language and output directory in cargo xtask (#2776)

In addition to simplifying building locally (no need to set an
environment variable), this makes it possible to use the `cargo xtask
build` command in the CI and specify any output location, rather than
relying on the build.sh script.

---------

Co-authored-by: Eric Githinji <egithinji@google.com>

README.md

@@ -76,12 +76,12 @@ cargo xtask install-tools
 Here is a summary of the various commands you can run in the project.
 
 | Command               | Description                                                                                                                                                                                                                                                                                                                                                                                                                                  |
-| --------------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
+| --------------------- | -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
 | `cargo install-tools` | Install all the tools the project depends on.                                                                                                                                                                                                                                                                                                                                                                                                |
-| `cargo serve`         | Start a web server with the course. You'll find the content on http://localhost:3000.                                                                                                                                                                                                                                                                                                                         |
+| `cargo serve`         | Start a web server with the course. You'll find the content on http://localhost:3000. To serve any of the translated versions of the course, add the language flag (`--language` or `-l`) followed by xx, where xx is the ISO 639 language code (e.g. `cargo xtask serve -l da` for the Danish translation).                                                                                                                                 |
 | `cargo rust-tests`    | Test the included Rust snippets.                                                                                                                                                                                                                                                                                                                                                                                                             |
 | `cargo web-tests`     | Run the web driver tests in the tests directory.                                                                                                                                                                                                                                                                                                                                                                                             |
-| `cargo build-book`    | Create a static version of the course in the `book/` directory. Note that you have to separately build and zip exercises and add them to book/html. To build any of the translated versions of the course, run MDBOOK_BOOK__LANGUAGE=xx mdbook build -d book/xx where xx is the ISO 639 language code (e.g. da for the Danish translation). [TRANSLATIONS.md](TRANSLATIONS.md) contains further instructions. |
+| `cargo build-book`    | Create a static version of the course in the `book/` directory. Note that you have to separately build and zip exercises and add them to book/html. To build any of the translated versions of the course, add the language flag (`--language` or `-l`) followed by xx, where xx is the ISO 639 language code (e.g. `cargo xtask build -l da` for the Danish translation). [TRANSLATIONS.md](TRANSLATIONS.md) contains further instructions. |
 
 > **Note** On Windows, you need to enable symlinks
 > (`git config --global core.symlinks true`) and Developer Mode.

xtask/src/main.rs

@@ -20,8 +20,8 @@
 //! the tools.
 
 use anyhow::{Ok, Result, anyhow};
-use clap::{Parser, ValueEnum};
+use clap::{Parser, Subcommand};
-use std::path::Path;
+use std::path::{Path, PathBuf};
 use std::{env, process::Command};
 
 fn main() -> Result<()> {
@@ -38,11 +38,11 @@ fn main() -> Result<()> {
 )]
 struct Cli {
     /// The task to execute
-    #[arg(value_enum)]
+    #[command(subcommand)]
     task: Task,
 }
 
-#[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, ValueEnum)]
+#[derive(Subcommand)]
 enum Task {
     /// Installs the tools the project depends on.
     InstallTools,
@@ -51,9 +51,25 @@ enum Task {
     /// Tests all included Rust snippets.
     RustTests,
     /// Starts a web server with the course.
-    Serve,
+    Serve {
-    /// Create a static version of the course in the `book/` directory.
+        /// ISO 639 language code (e.g. da for the Danish translation).
-    Build,
+        #[arg(short, long)]
+        language: Option<String>,
+
+        /// Directory to place the build. If not provided, defaults to the book/ directory (or the book/xx directory if a language is provided).
+        #[arg(short, long)]
+        output: Option<PathBuf>,
+    },
+    /// Create a static version of the course.
+    Build {
+        /// ISO 639 language code (e.g. da for the Danish translation).
+        #[arg(short, long)]
+        language: Option<String>,
+
+        /// Directory to place the build. If not provided, defaults to the book/ directory (or the book/xx directory if a language is provided).
+        #[arg(short, long)]
+        output: Option<PathBuf>,
+    },
 }
 
 fn execute_task() -> Result<()> {
@@ -62,15 +78,14 @@ fn execute_task() -> Result<()> {
         Task::InstallTools => install_tools()?,
         Task::WebTests => run_web_tests()?,
         Task::RustTests => run_rust_tests()?,
-        Task::Serve => start_web_server()?,
+        Task::Serve { language, output } => start_web_server(language, output)?,
-        Task::Build => build()?,
+        Task::Build { language, output } => build(language, output)?,
     }
     Ok(())
 }
 
 fn install_tools() -> Result<()> {
     println!("Installing project tools...");
-
     let path_to_mdbook_exerciser =
         Path::new(env!("CARGO_WORKSPACE_DIR")).join("mdbook-exerciser");
     let path_to_mdbook_course =
@@ -136,7 +151,6 @@ fn run_web_tests() -> Result<()> {
 
 fn run_rust_tests() -> Result<()> {
     println!("Running rust tests...");
-
     let path_to_workspace_root = Path::new(env!("CARGO_WORKSPACE_DIR"));
 
     let status = Command::new("mdbook")
@@ -156,15 +170,26 @@ fn run_rust_tests() -> Result<()> {
     Ok(())
 }
 
-fn start_web_server() -> Result<()> {
+fn start_web_server(
+    language: Option<String>,
+    output_arg: Option<PathBuf>,
+) -> Result<()> {
     println!("Starting web server ...");
     let path_to_workspace_root = Path::new(env!("CARGO_WORKSPACE_DIR"));
 
-    let status = Command::new("mdbook")
+    let mut command = Command::new("mdbook");
-        .current_dir(path_to_workspace_root.to_str().unwrap())
+    command.current_dir(path_to_workspace_root.to_str().unwrap());
-        .arg("serve")
+    command.arg("serve");
-        .status()
+
-        .expect("Failed to execute mdbook serve");
+    if let Some(language) = &language {
+        println!("Language: {}", &language);
+        command.env("MDBOOK_BOOK__LANGUAGE", &language);
+    }
+
+    command.arg("-d");
+    command.arg(get_output_dir(language, output_arg));
+
+    let status = command.status().expect("Failed to execute mdbook serve");
 
     if !status.success() {
         let error_message = format!(
@@ -176,15 +201,23 @@ fn start_web_server() -> Result<()> {
     Ok(())
 }
 
-fn build() -> Result<()> {
+fn build(language: Option<String>, output_arg: Option<PathBuf>) -> Result<()> {
     println!("Building course...");
     let path_to_workspace_root = Path::new(env!("CARGO_WORKSPACE_DIR"));
 
-    let status = Command::new("mdbook")
+    let mut command = Command::new("mdbook");
-        .current_dir(path_to_workspace_root.to_str().unwrap())
+    command.current_dir(path_to_workspace_root.to_str().unwrap());
-        .arg("build")
+    command.arg("build");
-        .status()
+
-        .expect("Failed to execute mdbook build");
+    if let Some(language) = &language {
+        println!("Language: {}", &language);
+        command.env("MDBOOK_BOOK__LANGUAGE", language);
+    }
+
+    command.arg("-d");
+    command.arg(get_output_dir(language, output_arg));
+
+    let status = command.status().expect("Failed to execute mdbook build");
 
     if !status.success() {
         let error_message = format!(
@@ -195,3 +228,13 @@ fn build() -> Result<()> {
     }
     Ok(())
 }
+
+fn get_output_dir(language: Option<String>, output_arg: Option<PathBuf>) -> PathBuf {
+    // If the 'output' arg is specified by the caller, use that, otherwise output to the 'book/' directory
+    // (or the 'book/xx' directory if a language was specified).
+    if let Some(d) = output_arg {
+        d
+    } else {
+        Path::new("book").join(language.unwrap_or("".to_string()))
+    }
+}