Parse server version x.y as x.0.y, when x is >= 10

Since PostgreSQL 10 the versioning scheme has changed.
10.x really means 10.0.x.  While parsing 10.1
as (10, 1) may seem less confusing, in practice most
version checks are written as version[:2], and we
want to keep that behaviour consistent, i.e not fail
a major version check due to a bugfix release.

asyncpg/serverversion.py

@@ -34,6 +34,15 @@ def split_server_version_string(version_string):
         level = 'final'
         serial = 0
 
+    if int(parts[0]) >= 10:
+        # Since PostgreSQL 10 the versioning scheme has changed.
+        # 10.x really means 10.0.x.  While parsing 10.1
+        # as (10, 1) may seem less confusing, in practice most
+        # version checks are written as version[:2], and we
+        # want to keep that behaviour consistent, i.e not fail
+        # a major version check due to a bugfix release.
+        parts.insert(1, 0)
+
     versions = [int(p) for p in parts][:3]
     if len(versions) < 3:
         versions += [0] * (3 - len(versions))

tests/test_connect.py

@@ -53,11 +53,10 @@ def test_server_version_02(self):
             ("9.4beta1", (9, 4, 0, 'beta', 1),),
             ("10devel", (10, 0, 0, 'devel', 0),),
             ("10beta2", (10, 0, 0, 'beta', 2),),
-
-            # Despite the fact after version 10 Postgre's second number
-            # means "micro", it is parsed "as is" to be
-            # less confusing in comparisons.
-            ("10.1", (10, 1, 0, 'final', 0),),
+            # For PostgreSQL versions >=10 we always
+            # set version.minor to 0.
+            ("10.1", (10, 0, 1, 'final', 0),),
+            ("11.1.2", (11, 0, 1, 'final', 0),),
         ]
         for version, expected in versions:
             result = split_server_version_string(version)