intersphinx: Handle string interpolation failures in _fetch_inventory_group() (#14101)

Co-authored-by: Matthieu DE CIBEINS <matthieu.decibeins@non.se.com>
Co-authored-by: Adam Turner <9087854+aa-turner@users.noreply.github.com>

Author: 3 people

CHANGES.rst

@@ -98,6 +98,8 @@ Features added
   Note that MathJax v3 is mostly compatible with MathJax v4, so existing
   :confval:`mathjax3_config` settings should not need to change.
   Patch by Matthias Geier.
+* #14029: intersphinx: Fix error in format string interpolation.
+  Patch by Matthieu de Cibeins.
 
 Bugs fixed
 ----------

sphinx/ext/intersphinx/_load.py

@@ -19,6 +19,7 @@
 from sphinx.util.inventory import InventoryFile
 
 if TYPE_CHECKING:
+    from collections.abc import Sequence
     from pathlib import Path
 
     from sphinx.application import Sphinx
@@ -226,6 +227,17 @@ def from_config(cls, config: Config) -> _InvConfig:
         )
 
 
+def _display_failures(failures: Sequence[tuple[str, ...]]) -> str:
+    """Format a list of failure tuples into a readable multi-line string."""
+    formatted = []
+    for failure_args in failures:
+        try:
+            formatted.append(failure_args[0] % failure_args[1:])
+        except TypeError:
+            formatted.append(' - '.join(failure_args))
+    return '\n'.join(formatted)
+
+
 def _fetch_inventory_group(
     *,
     project: _IntersphinxProject,
@@ -315,11 +327,9 @@ def _fetch_inventory_group(
         for fail in failures:
             LOGGER.info(*fail)
     else:
-        issues = '\n'.join(f[0] % f[1:] for f in failures)
         LOGGER.warning(
-            '%s\n%s',
-            __('failed to reach any of the inventories with the following issues:'),
-            issues,
+            __('failed to reach any of the inventories with the following issues:\n%s'),
+            _display_failures(failures),
         )
     return updated
 

tests/test_ext_intersphinx/test_ext_intersphinx.py

@@ -18,6 +18,7 @@
 from sphinx.ext.intersphinx import setup as intersphinx_setup
 from sphinx.ext.intersphinx._cli import inspect_main
 from sphinx.ext.intersphinx._load import (
+    _display_failures,
     _fetch_inventory_data,
     _fetch_inventory_group,
     _get_safe_url,
@@ -923,3 +924,22 @@ def test_inventory_text_version(tmp_path, app):
     assert rn['refuri'] == 'https://docs.python.org/foo.html#module-module1'
     assert rn['reftitle'] == '(in foo stable)'
     assert rn[0].astext() == 'Long Module desc'
+
+
+def test_display_failures():
+    failures_args = [
+        ('Failed to fetch %s from %s', 'inventory', 'http://example.com'),
+        ('Timeout after %d seconds',),  # Only one argument
+        (
+            'intersphinx inventory has moved:',
+            'http://example.com',
+            'http://proxyhost.net',
+        ),  # No '%'
+    ]
+    issues = _display_failures(failures_args)
+    assert 'Failed to fetch inventory from http://example.com' in issues
+    assert 'Timeout after %d seconds' in issues
+    assert (
+        'intersphinx inventory has moved: - http://example.com - http://proxyhost.net'
+        in issues
+    )