Check external links in CI

.github/workflows/docs.yml

@@ -1,4 +1,4 @@
-name: Build documentation
+name: Check documentation
 
 on:
   push:
@@ -8,6 +8,7 @@ on:
 
 jobs:
   docs:
+    name: Build documentation & check links
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v2.3.4
@@ -17,8 +18,11 @@ jobs:
       - run: |
           pip install --constraint=.github/workflows/constraints.txt pip
           pip install --constraint=.github/workflows/constraints.txt nox
-      - run: nox --force-color --session=docs
+      - name: Build documentation
+        run: nox --force-color --session=docs
       - uses: actions/upload-artifact@v2
         with:
           name: docs
           path: docs/_build
+      - name: Check links
+        run: nox --force-color --session=linkcheck

docs/conf.py

@@ -22,3 +22,4 @@
     "fixed_sidebar": "true",
     "sidebar_width": "250px",
 }
+linkcheck_ignore = ["codeofconduct.html"]

noxfile.py

@@ -5,6 +5,9 @@
 import nox
 from nox.sessions import Session
 
+nox.options.sessions = (
+    "linkcheck",
+)
 
 @nox.session
 def docs(session: Session) -> None:
@@ -24,3 +27,16 @@ def docs(session: Session) -> None:
         session.run("sphinx-autobuild", *args)
     else:
         session.run("sphinx-build", *args)
+
+@nox.session
+def linkcheck(session: Session) -> None:
+    """Build the documentation."""
+    args = session.posargs or ["-W", "-b", "linkcheck", "docs", "docs/_build"]
+
+    builddir = Path("docs", "_build")
+    if builddir.exists():
+        shutil.rmtree(builddir)
+
+    session.install("-r", "docs/requirements.txt")
+
+    session.run("sphinx-build", *args)