Add i18n support

.github/workflows/rbe.yml

@@ -1,12 +1,19 @@
 name: CI
 on: [push, pull_request]
 
+env:
+  # Update the language picker in index.hbs to link new languages.
+  LANGUAGES:
+
 jobs:
   test:
     name: Run tests
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@master
+    - uses: actions/checkout@v4
+      with:
+        # We need the full history below.
+        fetch-depth: 0
 
     - name: Update rustup
       run: rustup self update
@@ -23,6 +30,10 @@ jobs:
         curl -sSL https://github.com/rust-lang/mdBook/releases/download/v0.4.15/mdbook-v0.4.15-x86_64-unknown-linux-gnu.tar.gz | tar -xz --directory=bin
         echo "$(pwd)/bin" >> ${GITHUB_PATH}
 
+    - name: Install mdbook-i18n-helpers
+      run: |
+        cargo install --git https://github.com/google/mdbook-i18n-helpers mdbook-i18n-helpers
+
     - name: Report versions
       run: |
         rustup --version
@@ -41,6 +52,28 @@ jobs:
           https://raw.githubusercontent.com/rust-lang/rust/master/src/tools/linkchecker/linkcheck.sh
         sh linkcheck.sh --all rust-by-example
 
+    - name: Build all translations
+      run: |
+        for po_lang in ${{ env.LANGUAGES }}; do
+          POT_CREATION_DATE=$(grep --max-count 1 '^"POT-Creation-Date:' po/$po_lang.po | sed -E 's/".*: (.*)\\n"/\1/')
+          if [[ $POT_CREATION_DATE == "" ]]; then
+              POT_CREATION_DATE=now
+          fi
+
+          echo "::group::Building $po_lang translation as of $POT_CREATION_DATE"
+          rm -r src/
+          git restore --source "$(git rev-list -n 1 --before "$POT_CREATION_DATE" @)" src/
+
+          # Set language and adjust site URL. Clear the redirects
+          # since they are in sync with the source files, not the
+          # translation.
+          MDBOOK_BOOK__LANGUAGE=$po_lang \
+          MDBOOK_OUTPUT__HTML__SITE_URL=/rust-by-example/$po_lang/ \
+          MDBOOK_OUTPUT__HTML__REDIRECT='{}' \
+          mdbook build -d book/$po_lang
+          echo "::endgroup::"
+        done
+
     - name: Upload Artifact
       uses: actions/upload-artifact@v3
       with:

.gitignore

@@ -1,4 +1,6 @@
 book
 
+po/messages.pot
+
 # Auto-generated files from macOS
-.DS_Store
+.DS_Store

book.toml

@@ -13,6 +13,15 @@ enable = true
 
 [output.html]
 git-repository-url = "https://github.com/rust-lang/rust-by-example"
+additional-css = [
+  "theme/css/language-picker.css",
+]
 
 [rust]
 edition = "2021"
+
+[build]
+extra-watch-dirs = ["po"]
+
+[preprocessor.gettext]
+after = ["links"]

theme/css/language-picker.css

@@ -0,0 +1,13 @@
+#language-list {
+  left: auto;
+  right: 10px;
+}
+
+[dir="rtl"] #language-list {
+  left: 10px;
+  right: auto;
+}
+
+#language-list a {
+  color: inherit;
+}