Provision on different drivers dynamically

We want TOX_POSTGRESQL and similar to be the fixed variable
that is configured from CI environment.   These variables should refer
to database servers but individual drivers like asyncpg mysqlconnector
etc. should come from local tox.ini.  add a new system to generate
per-driver URLs from a simple list of hostname-based URLs delivered
from CI environment.

Change-Id: I4267b4a70742765388c7e7c4432c1da9d9adece2

4 files changed, 121 insertions, 10 deletions

diff --git a/lib/sqlalchemy/testing/exclusions.py b/lib/sqlalchemy/testing/exclusions.py
index 1a23ebf41..6ec438193 100644
--- a/lib/sqlalchemy/testing/exclusions.py
+++ b/lib/sqlalchemy/testing/exclusions.py
@@ -272,6 +272,9 @@ class SpecPredicate(Predicate):
     }
 
     def __call__(self, config):
+        if config is None:
+            return False
+
         engine = config.db
 
         if "+" in self.db:
diff --git a/lib/sqlalchemy/testing/plugin/plugin_base.py b/lib/sqlalchemy/testing/plugin/plugin_base.py
index 49ff0f975..b5f2a3e0b 100644
--- a/lib/sqlalchemy/testing/plugin/plugin_base.py
+++ b/lib/sqlalchemy/testing/plugin/plugin_base.py
@@ -17,10 +17,14 @@ is pytest.
 from __future__ import absolute_import
 
 import abc
+import logging
 import re
 import sys
 
 
+log = logging.getLogger("sqlalchemy.testing.plugin_base")
+
+
 py3k = sys.version_info >= (3, 0)
 
 if py3k:
@@ -91,6 +95,15 @@ def setup_options(make_option):
         help="Database uri.  Multiple OK, " "first one is run by default.",
     )
     make_option(
+        "--dbdriver",
+        action="append",
+        type="string",
+        dest="dbdriver",
+        help="Additional database drivers to include in tests.  "
+        "These are linked to the existing database URLs by the "
+        "provisioning system.",
+    )
+    make_option(
         "--dropfirst",
         action="store_true",
         dest="dropfirst",
@@ -350,6 +363,7 @@ def _init_symbols(options, file_config):
 
 @post
 def _engine_uri(options, file_config):
+
     from sqlalchemy.testing import config
     from sqlalchemy import testing
     from sqlalchemy.testing import provision
@@ -359,6 +373,8 @@ def _engine_uri(options, file_config):
     else:
         db_urls = []
 
+    extra_drivers = options.dbdriver or []
+
     if options.db:
         for db_token in options.db:
             for db in re.split(r"[,\s]+", db_token):
@@ -374,7 +390,11 @@ def _engine_uri(options, file_config):
         db_urls.append(file_config.get("db", "default"))
 
     config._current = None
-    for db_url in db_urls:
+
+    expanded_urls = list(provision.generate_db_urls(db_urls, extra_drivers))
+
+    for db_url in expanded_urls:
+        log.info("Adding database URL: %s", db_url)
 
         if options.write_idents and provision.FOLLOWER_IDENT:  # != 'master':
             with open(options.write_idents, "a") as file_:
@@ -596,7 +616,8 @@ def stop_test_class(cls):
 
 
 def _restore_engine():
-    config._current.reset(testing)
+    if config._current:
+        config._current.reset(testing)
 
 
 def final_process_cleanup():
diff --git a/lib/sqlalchemy/testing/plugin/pytestplugin.py b/lib/sqlalchemy/testing/plugin/pytestplugin.py
index 3df239afa..1b2bbca23 100644
--- a/lib/sqlalchemy/testing/plugin/pytestplugin.py
+++ b/lib/sqlalchemy/testing/plugin/pytestplugin.py
@@ -89,9 +89,9 @@ def pytest_addoption(parser):
 
 
 def pytest_configure(config):
-    if hasattr(config, "slaveinput"):
-        plugin_base.restore_important_follower_config(config.slaveinput)
-        plugin_base.configure_follower(config.slaveinput["follower_ident"])
+    if hasattr(config, "workerinput"):
+        plugin_base.restore_important_follower_config(config.workerinput)
+        plugin_base.configure_follower(config.workerinput["follower_ident"])
     else:
         if config.option.write_idents and os.path.exists(
             config.option.write_idents
@@ -162,20 +162,20 @@ if has_xdist:
     import uuid
 
     def pytest_configure_node(node):
-        # the master for each node fills slaveinput dictionary
+        # the master for each node fills workerinput dictionary
         # which pytest-xdist will transfer to the subprocess
 
-        plugin_base.memoize_important_follower_config(node.slaveinput)
+        plugin_base.memoize_important_follower_config(node.workerinput)
 
-        node.slaveinput["follower_ident"] = "test_%s" % uuid.uuid4().hex[0:12]
+        node.workerinput["follower_ident"] = "test_%s" % uuid.uuid4().hex[0:12]
         from sqlalchemy.testing import provision
 
-        provision.create_follower_db(node.slaveinput["follower_ident"])
+        provision.create_follower_db(node.workerinput["follower_ident"])
 
     def pytest_testnodedown(node, error):
         from sqlalchemy.testing import provision
 
-        provision.drop_follower_db(node.slaveinput["follower_ident"])
+        provision.drop_follower_db(node.workerinput["follower_ident"])
 
 
 def pytest_collection_modifyitems(session, config, items):
diff --git a/lib/sqlalchemy/testing/provision.py b/lib/sqlalchemy/testing/provision.py
index 660a3bd24..13a5ea078 100644
--- a/lib/sqlalchemy/testing/provision.py
+++ b/lib/sqlalchemy/testing/provision.py
@@ -1,8 +1,10 @@
 import collections
+import copy
 import logging
 
 from . import config
 from . import engines
+from .. import exc
 from ..engine import url as sa_url
 from ..util import compat
 
@@ -73,6 +75,91 @@ def drop_follower_db(follower_ident):
         drop_db(cfg, cfg.db, follower_ident)
 
 
+def generate_db_urls(db_urls, extra_drivers):
+    """Generate a set of URLs to test given configured URLs plus additional
+    driver names.
+
+    Given::
+
+        --dburi postgresql://db1  \
+        --dburi postgresql://db2  \
+        --dburi postgresql://db2  \
+        --dbdriver=psycopg2 --dbdriver=asyncpg
+
+    Noting that the default postgresql driver is psycopg2.  the output
+    would be::
+
+        postgresql+psycopg2://db1
+        postgresql+asyncpg://db1?async_fallback=true
+        postgresql+psycopg2://db2
+        postgresql+psycopg2://db3
+
+    That is, for the driver in a --dburi, we want to keep that and use that
+    driver for each URL it's part of .   For a driver that is only
+    in --dbdrivers, we want to use it just once for one of the URLs.
+    for a driver that is both coming from --dburi as well as --dbdrivers,
+    we want to keep it in that dburi.
+
+
+    """
+    urls = set()
+
+    backend_to_driver_we_already_have = collections.defaultdict(set)
+
+    urls_plus_dialects = [
+        (url_obj, url_obj.get_dialect())
+        for url_obj in [sa_url.make_url(db_url) for db_url in db_urls]
+    ]
+
+    for url_obj, dialect in urls_plus_dialects:
+        backend_to_driver_we_already_have[dialect.name].add(dialect.driver)
+
+    backend_to_driver_we_need = {}
+
+    for url_obj, dialect in urls_plus_dialects:
+        backend = dialect.name
+        dialect.load_provisioning()
+
+        if backend not in backend_to_driver_we_need:
+            backend_to_driver_we_need[backend] = extra_per_backend = set(
+                extra_drivers
+            ).difference(backend_to_driver_we_already_have[backend])
+        else:
+            extra_per_backend = backend_to_driver_we_need[backend]
+
+        for driver_url in _generate_driver_urls(url_obj, extra_per_backend):
+            if driver_url in urls:
+                continue
+            urls.add(driver_url)
+            yield driver_url
+
+
+def _generate_driver_urls(url, extra_drivers):
+    main_driver = url.get_driver_name()
+    extra_drivers.discard(main_driver)
+
+    yield str(url)
+
+    for drv in list(extra_drivers):
+        new_url = generate_driver_url(url, drv)
+        if new_url:
+            extra_drivers.remove(drv)
+            yield str(new_url)
+
+
+@register.init
+def generate_driver_url(url, driver):
+    backend = url.get_backend_name()
+    new_url = copy.copy(url)
+    new_url.drivername = "%s+%s" % (backend, driver)
+    try:
+        new_url.get_dialect()
+    except exc.NoSuchModuleError:
+        return None
+    else:
+        return new_url
+
+
 def _configs_for_db_operation():
     hosts = set()