Try to detect borked package installations. (#12244)

* Try to detect borked package installations.

Fixes #12223.

Co-authored-by: Sean Quah <8349537+squahtx@users.noreply.github.com>

1 files changed, 23 insertions, 1 deletions

diff --git a/synapse/util/check_dependencies.py b/synapse/util/check_dependencies.py

index 12cd804939..66f1da7502 100644
--- a/synapse/util/check_dependencies.py
+++ b/synapse/util/check_dependencies.py
@@ -128,6 +128,19 @@ def _incorrect_version(
         )
 
 
+def _no_reported_version(requirement: Requirement, extra: Optional[str] = None) -> str:
+    if extra:
+        return (
+            f"Synapse {VERSION} needs {requirement} for {extra}, "
+            f"but can't determine {requirement.name}'s version"
+        )
+    else:
+        return (
+            f"Synapse {VERSION} needs {requirement}, "
+            f"but can't determine {requirement.name}'s version"
+        )
+
+
 def check_requirements(extra: Optional[str] = None) -> None:
     """Check Synapse's dependencies are present and correctly versioned.
 
@@ -163,8 +176,17 @@ def check_requirements(extra: Optional[str] = None) -> None:
                 deps_unfulfilled.append(requirement.name)
                 errors.append(_not_installed(requirement, extra))
         else:
+            if dist.version is None:
+                # This shouldn't happen---it suggests a borked virtualenv. (See #12223)
+                # Try to give a vaguely helpful error message anyway.
+                # Type-ignore: the annotations don't reflect reality: see
+                #     https://github.com/python/typeshed/issues/7513
+                #     https://bugs.python.org/issue47060
+                deps_unfulfilled.append(requirement.name)  # type: ignore[unreachable]
+                errors.append(_no_reported_version(requirement, extra))
+
             # We specify prereleases=True to allow prereleases such as RCs.
-            if not requirement.specifier.contains(dist.version, prereleases=True):
+            elif not requirement.specifier.contains(dist.version, prereleases=True):
                 deps_unfulfilled.append(requirement.name)
                 errors.append(_incorrect_version(requirement, dist.version, extra))