Add future=True to create_engine/Session; unify select()

Several weeks of using the future_select() construct
has led to the proposal there be just one select() construct
again which features the new join() method, and otherwise accepts
both the 1.x and 2.x argument styles.   This would make
migration simpler and reduce confusion.

However, confusion may be increased by the fact that select().join()
is different  Current thinking is we may be better off
with a few hard behavioral changes to old and relatively unknown APIs
rather than trying to play both sides within two extremely similar
but subtly different APIs.  At the moment, the .join() thing seems
to be the only behavioral change that occurs without the user
taking any explicit steps.   Session.execute() will still
behave the old way as we are adding a future flag.

This change also adds the "future" flag to Session() and
session.execute(), so that interpretation of the incoming statement,
as well as that the new style result is returned, does not
occur for existing applications unless they add the use
of this flag.

The change in general is moving the "removed in 2.0" system
further along where we want the test suite to fully pass
even if the SQLALCHEMY_WARN_20 flag is set.

Get many tests to pass when SQLALCHEMY_WARN_20 is set; this
should be ongoing after this patch merges.

Improve the RemovedIn20 warning; these are all deprecated
"since" 1.4, so ensure that's what the messages read.
Make sure the inforamtion link is on all warnings.
Add deprecation warnings for parameters present and
add warnings to all FromClause.select() types of methods.

Fixes: #5379
Fixes: #5284
Change-Id: I765a0b912b3dcd0e995426427d8bb7997cbffd51
References: #5159

1 files changed, 43 insertions, 6 deletions

diff --git a/lib/sqlalchemy/util/deprecations.py b/lib/sqlalchemy/util/deprecations.py
index e0669c4e8..0a79344c5 100644
--- a/lib/sqlalchemy/util/deprecations.py
+++ b/lib/sqlalchemy/util/deprecations.py
@@ -8,6 +8,7 @@
 """Helpers related to deprecation of functions, methods, classes, other
 functionality."""
 
+import os
 import re
 import warnings
 
@@ -19,7 +20,19 @@ from .langhelpers import inject_param_text
 from .. import exc
 
 
+SQLALCHEMY_WARN_20 = False
+
+if os.getenv("SQLALCHEMY_WARN_20", "false").lower() in ("true", "yes", "1"):
+    SQLALCHEMY_WARN_20 = True
+
+
 def _warn_with_version(msg, version, type_, stacklevel):
+    if type_ is exc.RemovedIn20Warning and not SQLALCHEMY_WARN_20:
+        return
+
+    if type_ is exc.RemovedIn20Warning:
+        msg += " (Background on SQLAlchemy 2.0 at: http://sqlalche.me/e/b8d9)"
+
     warn = type_(msg)
     warn.deprecated_since = version
 
@@ -41,7 +54,6 @@ def warn_deprecated_limited(msg, args, version, stacklevel=3):
 
 
 def warn_deprecated_20(msg, stacklevel=3):
-    msg += " (Background on SQLAlchemy 2.0 at: http://sqlalche.me/e/b8d9)"
 
     _warn_with_version(
         msg,
@@ -69,7 +81,7 @@ def deprecated_cls(version, message, constructor="__init__"):
 
 def deprecated_20_cls(clsname, alternative=None, constructor="__init__"):
     message = (
-        ".. deprecated:: 2.0 The %s class is considered legacy as of the "
+        ".. deprecated:: 1.4 The %s class is considered legacy as of the "
         "1.x series of SQLAlchemy and will be removed in 2.0." % clsname
     )
 
@@ -108,8 +120,16 @@ def deprecated(
 
     """
 
+    # nothing is deprecated "since" 2.0 at this time.  All "removed in 2.0"
+    # should emit the RemovedIn20Warning, but messaging should be expressed
+    # in terms of "deprecated since 1.4".
+
+    if version == "2.0":
+        if warning is None:
+            warning = exc.RemovedIn20Warning
+        version = "1.4"
     if add_deprecation_to_docstring:
-        header = ".. deprecated:: %s %s" % (version, (message or ""))
+        header = ".. deprecated:: %s %s" % (version, (message or ""),)
     else:
         header = None
 
@@ -119,7 +139,8 @@ def deprecated(
     if warning is None:
         warning = exc.SADeprecationWarning
 
-    message += " (deprecated since: %s)" % version
+    if warning is not exc.RemovedIn20Warning:
+        message += " (deprecated since: %s)" % version
 
     def decorate(fn):
         return _decorate_with_warning(
@@ -162,6 +183,7 @@ def deprecated_params(**specs):
     messages = {}
     versions = {}
     version_warnings = {}
+
     for param, (version, message) in specs.items():
         versions[param] = version
         messages[param] = _sanitize_restructured_text(message)
@@ -173,6 +195,7 @@ def deprecated_params(**specs):
 
     def decorate(fn):
         spec = compat.inspect_getfullargspec(fn)
+
         if spec.defaults is not None:
             defaults = dict(
                 zip(
@@ -186,6 +209,8 @@ def deprecated_params(**specs):
             check_defaults = ()
             check_kw = set(messages)
 
+        check_any_kw = spec.varkw
+
         @decorator
         def warned(fn, *args, **kwargs):
             for m in check_defaults:
@@ -198,6 +223,18 @@ def deprecated_params(**specs):
                         version_warnings[m],
                         stacklevel=3,
                     )
+
+            if check_any_kw in messages and set(kwargs).difference(
+                check_defaults
+            ):
+
+                _warn_with_version(
+                    messages[check_any_kw],
+                    versions[check_any_kw],
+                    version_warnings[check_any_kw],
+                    stacklevel=3,
+                )
+
             for m in check_kw:
                 if m in kwargs:
                     _warn_with_version(
@@ -206,7 +243,6 @@ def deprecated_params(**specs):
                         version_warnings[m],
                         stacklevel=3,
                     )
-
             return fn(*args, **kwargs)
 
         doc = fn.__doc__ is not None and fn.__doc__ or ""
@@ -214,7 +250,8 @@ def deprecated_params(**specs):
             doc = inject_param_text(
                 doc,
                 {
-                    param: ".. deprecated:: %s %s" % (version, (message or ""))
+                    param: ".. deprecated:: %s %s"
+                    % ("1.4" if version == "2.0" else version, (message or ""))
                     for param, (version, message) in specs.items()
                 },
             )