Reword implicit left join error; ensure deterministic FROM for columns

Adjusted the error message emitted by :meth:`.Query.join` when a left hand
side can't be located that the :meth:`.Query.select_from` method is the
best way to resolve the issue.  Also, within the 1.3 series, used a
deterministic ordering when determining the FROM clause from a given column
entity passed to :class:`.Query` so that the same expression is determined
each time.

Fixes: #5194
Change-Id: I2e4065fd31e98c57edf2f11d5e831be44d2c1ea2

1 files changed, 18 insertions, 10 deletions

diff --git a/lib/sqlalchemy/orm/query.py b/lib/sqlalchemy/orm/query.py
index 796ebe3ac..fe1ea9bfc 100644
--- a/lib/sqlalchemy/orm/query.py
+++ b/lib/sqlalchemy/orm/query.py
@@ -2530,14 +2530,18 @@ class Query(Generative):
                 raise sa_exc.InvalidRequestError(
                     "Can't determine which FROM clause to join "
                     "from, there are multiple FROMS which can "
-                    "join to this entity. Try adding an explicit ON clause "
-                    "to help resolve the ambiguity."
+                    "join to this entity. Please use the .select_from() "
+                    "method to establish an explicit left side, as well as "
+                    "providing an explcit ON clause if not present already to "
+                    "help resolve the ambiguity."
                 )
             else:
                 raise sa_exc.InvalidRequestError(
-                    "Don't know how to join to %s; please use "
-                    "an ON clause to more clearly establish the left "
-                    "side of this join" % (right,)
+                    "Don't know how to join to %r. "
+                    "Please use the .select_from() "
+                    "method to establish an explicit left side, as well as "
+                    "providing an explcit ON clause if not present already to "
+                    "help resolve the ambiguity." % (right,)
                 )
 
         elif self._entities:
@@ -2572,14 +2576,18 @@ class Query(Generative):
                 raise sa_exc.InvalidRequestError(
                     "Can't determine which FROM clause to join "
                     "from, there are multiple FROMS which can "
-                    "join to this entity. Try adding an explicit ON clause "
-                    "to help resolve the ambiguity."
+                    "join to this entity. Please use the .select_from() "
+                    "method to establish an explicit left side, as well as "
+                    "providing an explcit ON clause if not present already to "
+                    "help resolve the ambiguity."
                 )
             else:
                 raise sa_exc.InvalidRequestError(
-                    "Don't know how to join to %s; please use "
-                    "an ON clause to more clearly establish the left "
-                    "side of this join" % (right,)
+                    "Don't know how to join to %r. "
+                    "Please use the .select_from() "
+                    "method to establish an explicit left side, as well as "
+                    "providing an explcit ON clause if not present already to "
+                    "help resolve the ambiguity." % (right,)
                 )
         else:
             raise sa_exc.InvalidRequestError(