linkcheck: disallow 'None' value for 'linkcheck_allowed_redirects' setting

CHANGES.rst

@@ -18,7 +18,7 @@ Features added
   Patch by Till Hoffmann.
 * #13439: linkcheck: Permit warning on every redirect with
   ``linkcheck_allowed_redirects = {}``.
-  Patch by Adam Turner.
+  Patch by Adam Turner and James Addison.
 
 Bugs fixed
 ----------

sphinx/builders/linkcheck.py

@@ -179,7 +179,7 @@ def process_result(self, result: CheckResult) -> None:
                         text = 'with unknown code'
                 linkstat['text'] = text
                 redirection = f'{text} to {result.message}'
-                if self.config.linkcheck_allowed_redirects is not None:
+                if self.config.linkcheck_allowed_redirects is not _sentinel_lar:
                     msg = f'redirect  {res_uri} - {redirection}'
                     logger.warning(msg, location=(result.docname, result.lineno))
                 else:
@@ -387,7 +387,7 @@ def __init__(
         )
         self.check_anchors: bool = config.linkcheck_anchors
         self.allowed_redirects: dict[re.Pattern[str], re.Pattern[str]]
-        self.allowed_redirects = config.linkcheck_allowed_redirects or {}
+        self.allowed_redirects = config.linkcheck_allowed_redirects
         self.retries: int = config.linkcheck_retries
         self.rate_limit_timeout = config.linkcheck_rate_limit_timeout
         self._allow_unauthorized = config.linkcheck_allow_unauthorized
@@ -722,6 +722,8 @@ def handle_starttag(self, tag: Any, attrs: Any) -> None:
 def _allowed_redirect(
     url: str, new_url: str, allowed_redirects: dict[re.Pattern[str], re.Pattern[str]]
 ) -> bool:
+    if allowed_redirects is _sentinel_lar:
+        return True
     return any(
         from_url.match(url) and to_url.match(new_url)
         for from_url, to_url in allowed_redirects.items()
@@ -751,7 +753,6 @@ def rewrite_github_anchor(app: Sphinx, uri: str) -> str | None:
 def compile_linkcheck_allowed_redirects(app: Sphinx, config: Config) -> None:
     """Compile patterns to the regexp objects."""
     if config.linkcheck_allowed_redirects is _sentinel_lar:
-        config.linkcheck_allowed_redirects = None
         return
     if not isinstance(config.linkcheck_allowed_redirects, dict):
         raise ConfigError

tests/test_builders/test_build_linkcheck.py

@@ -680,7 +680,7 @@ def check_headers(self):
     assert content['status'] == 'working'
 
 
-def make_redirect_handler(*, support_head: bool) -> type[BaseHTTPRequestHandler]:
+def make_redirect_handler(*, support_head: bool = True) -> type[BaseHTTPRequestHandler]:
     class RedirectOnceHandler(BaseHTTPRequestHandler):
         protocol_version = 'HTTP/1.1'
 
@@ -715,13 +715,11 @@ def log_date_time_string(self):
 )
 def test_follows_redirects_on_HEAD(app, capsys):
     with serve_application(app, make_redirect_handler(support_head=True)) as address:
+        compile_linkcheck_allowed_redirects(app, app.config)
         app.build()
     _stdout, stderr = capsys.readouterr()
     content = (app.outdir / 'output.txt').read_text(encoding='utf8')
-    assert content == (
-        'index.rst:1: [redirected with Found] '
-        f'http://{address}/ to http://{address}/?redirected=1\n'
-    )
+    assert content == ''
     assert stderr == textwrap.dedent(
         """\
         127.0.0.1 - - [] "HEAD / HTTP/1.1" 302 -
@@ -738,13 +736,11 @@ def test_follows_redirects_on_HEAD(app, capsys):
 )
 def test_follows_redirects_on_GET(app, capsys):
     with serve_application(app, make_redirect_handler(support_head=False)) as address:
+        compile_linkcheck_allowed_redirects(app, app.config)
         app.build()
     _stdout, stderr = capsys.readouterr()
     content = (app.outdir / 'output.txt').read_text(encoding='utf8')
-    assert content == (
-        'index.rst:1: [redirected with Found] '
-        f'http://{address}/ to http://{address}/?redirected=1\n'
-    )
+    assert content == ''
     assert stderr == textwrap.dedent(
         """\
         127.0.0.1 - - [] "HEAD / HTTP/1.1" 405 -
@@ -755,6 +751,31 @@ def test_follows_redirects_on_GET(app, capsys):
     assert app.warning.getvalue() == ''
 
 
+@pytest.mark.sphinx(
+    'linkcheck',
+    testroot='linkcheck-localserver',
+    freshenv=True,
+    confoverrides={'linkcheck_allowed_redirects': {}},  # do not follow any redirects
+)
+def test_warns_disallowed_redirects(app, capsys):
+    with serve_application(app, make_redirect_handler()) as address:
+        compile_linkcheck_allowed_redirects(app, app.config)
+        app.build()
+    _stdout, stderr = capsys.readouterr()
+    content = (app.outdir / 'output.txt').read_text(encoding='utf8')
+    assert content == (
+        'index.rst:1: [redirected with Found] '
+        f'http://{address}/ to http://{address}/?redirected=1\n'
+    )
+    assert stderr == textwrap.dedent(
+        """\
+        127.0.0.1 - - [] "HEAD / HTTP/1.1" 302 -
+        127.0.0.1 - - [] "HEAD /?redirected=1 HTTP/1.1" 204 -
+        """,
+    )
+    assert len(app.warning.getvalue().splitlines()) == 1
+
+
 def test_linkcheck_allowed_redirects_config(
     make_app: Callable[..., SphinxTestApp], tmp_path: Path
 ) -> None: