- The :func:`.engine_from_config` function has been improved so that

we will be able to parse dialect-specific arguments from string
configuration dictionaries.  Dialect classes can now provide their
own list of parameter types and string-conversion routines.
The feature is not yet used by the built-in dialects, however.
[ticket:2875]

4 files changed, 36 insertions, 34 deletions

diff --git a/lib/sqlalchemy/engine/__init__.py b/lib/sqlalchemy/engine/__init__.py
index 16d214140..128c4e8f6 100644
--- a/lib/sqlalchemy/engine/__init__.py
+++ b/lib/sqlalchemy/engine/__init__.py
@@ -348,10 +348,13 @@ def engine_from_config(configuration, prefix='sqlalchemy.', **kwargs):
     arguments.
     """
 
-    opts = util._coerce_config(configuration, prefix)
-    opts.update(kwargs)
-    url = opts.pop('url')
-    return create_engine(url, **opts)
+    options = dict((key[len(prefix):], configuration[key])
+                   for key in configuration
+                   if key.startswith(prefix))
+    options['_coerce_config'] = True
+    options.update(kwargs)
+    url = options.pop('url')
+    return create_engine(url, **options)
 
 
 __all__ = (
diff --git a/lib/sqlalchemy/engine/default.py b/lib/sqlalchemy/engine/default.py
index 8fb7c3bb8..dec6f2cdf 100644
--- a/lib/sqlalchemy/engine/default.py
+++ b/lib/sqlalchemy/engine/default.py
@@ -59,6 +59,18 @@ class DefaultDialect(interfaces.Dialect):
 
     supports_simple_order_by_label = True
 
+    engine_config_types = util.immutabledict([
+        ('convert_unicode', util.bool_or_str('force')),
+        ('pool_timeout', int),
+        ('echo', util.bool_or_str('debug')),
+        ('echo_pool', util.bool_or_str('debug')),
+        ('pool_recycle', int),
+        ('pool_size', int),
+        ('max_overflow', int),
+        ('pool_threadlocal', bool),
+        ('use_native_unicode', bool),
+    ])
+
     # if the NUMERIC type
     # returns decimal.Decimal.
     # *not* the FLOAT type however.
diff --git a/lib/sqlalchemy/engine/strategies.py b/lib/sqlalchemy/engine/strategies.py
index 5a3b2c5af..4befe58fd 100644
--- a/lib/sqlalchemy/engine/strategies.py
+++ b/lib/sqlalchemy/engine/strategies.py
@@ -49,18 +49,27 @@ class DefaultEngineStrategy(EngineStrategy):
 
         dialect_cls = u.get_dialect()
 
+        if kwargs.pop('_coerce_config', False):
+            def pop_kwarg(key, default=None):
+                value = kwargs.pop(key, default)
+                if key in dialect_cls.engine_config_types:
+                    value = dialect_cls.engine_config_types[key](value)
+                return value
+        else:
+            pop_kwarg = kwargs.pop
+
         dialect_args = {}
         # consume dialect arguments from kwargs
         for k in util.get_cls_kwargs(dialect_cls):
             if k in kwargs:
-                dialect_args[k] = kwargs.pop(k)
+                dialect_args[k] = pop_kwarg(k)
 
         dbapi = kwargs.pop('module', None)
         if dbapi is None:
             dbapi_args = {}
             for k in util.get_func_kwargs(dialect_cls.dbapi):
                 if k in kwargs:
-                    dbapi_args[k] = kwargs.pop(k)
+                    dbapi_args[k] = pop_kwarg(k)
             dbapi = dialect_cls.dbapi(**dbapi_args)
 
         dialect_args['dbapi'] = dbapi
@@ -70,10 +79,10 @@ class DefaultEngineStrategy(EngineStrategy):
 
         # assemble connection arguments
         (cargs, cparams) = dialect.create_connect_args(u)
-        cparams.update(kwargs.pop('connect_args', {}))
+        cparams.update(pop_kwarg('connect_args', {}))
 
         # look for existing pool or create
-        pool = kwargs.pop('pool', None)
+        pool = pop_kwarg('pool', None)
         if pool is None:
             def connect():
                 try:
@@ -87,9 +96,9 @@ class DefaultEngineStrategy(EngineStrategy):
                         )
                     )
 
-            creator = kwargs.pop('creator', connect)
+            creator = pop_kwarg('creator', connect)
 
-            poolclass = kwargs.pop('poolclass', None)
+            poolclass = pop_kwarg('poolclass', None)
             if poolclass is None:
                 poolclass = dialect_cls.get_pool_class(u)
             pool_args = {}
@@ -106,7 +115,7 @@ class DefaultEngineStrategy(EngineStrategy):
             for k in util.get_cls_kwargs(poolclass):
                 tk = translate.get(k, k)
                 if tk in kwargs:
-                    pool_args[k] = kwargs.pop(tk)
+                    pool_args[k] = pop_kwarg(tk)
             pool = poolclass(creator, **pool_args)
         else:
             if isinstance(pool, poollib._DBProxy):
@@ -119,7 +128,7 @@ class DefaultEngineStrategy(EngineStrategy):
         engine_args = {}
         for k in util.get_cls_kwargs(engineclass):
             if k in kwargs:
-                engine_args[k] = kwargs.pop(k)
+                engine_args[k] = pop_kwarg(k)
 
         _initialize = kwargs.pop('_initialize', True)
 
diff --git a/lib/sqlalchemy/engine/util.py b/lib/sqlalchemy/engine/util.py
index e56452751..f4a2b0cc7 100644
--- a/lib/sqlalchemy/engine/util.py
+++ b/lib/sqlalchemy/engine/util.py
@@ -6,28 +6,6 @@
 
 from .. import util
 
-
-def _coerce_config(configuration, prefix):
-    """Convert configuration values to expected types."""
-
-    options = dict((key[len(prefix):], configuration[key])
-                   for key in configuration
-                   if key.startswith(prefix))
-    for option, type_ in (
-        ('convert_unicode', util.bool_or_str('force')),
-        ('pool_timeout', int),
-        ('echo', util.bool_or_str('debug')),
-        ('echo_pool', util.bool_or_str('debug')),
-        ('pool_recycle', int),
-        ('pool_size', int),
-        ('max_overflow', int),
-        ('pool_threadlocal', bool),
-        ('use_native_unicode', bool),
-    ):
-        util.coerce_kw_type(options, option, type_)
-    return options
-
-
 def connection_memoize(key):
     """Decorator, memoize a function in a connection.info stash.