Accommodate column-based naming conventions for pk constraint

Repaired / implemented support for primary key constraint naming
conventions that use column names/keys/etc as part of the convention. In
particular, this includes that the :class:`.PrimaryKeyConstraint` object
that's automatically associated with a :class:`.schema.Table` will update
its name as new primary key :class:`_schema.Column` objects are added to
the table and then to the constraint. Internal failure modes related to
this constraint construction process including no columns present, no name
present or blank name present are now accommodated.

Fixes: sqlalchemy#5919
Change-Id: Ic2800b50f4a4cd5978bec48cefea0a2e198e0123

Author: zzzeek

doc/build/changelog/unreleased_13/5919.rst

@@ -0,0 +1,12 @@
+.. change::
+    :tags: bug, schema
+    :tickets: 5919
+
+    Repaired / implemented support for primary key constraint naming
+    conventions that use column names/keys/etc as part of the convention. In
+    particular, this includes that the :class:`.PrimaryKeyConstraint` object
+    that's automatically associated with a :class:`.schema.Table` will update
+    its name as new primary key :class:`_schema.Column` objects are added to
+    the table and then to the constraint. Internal failure modes related to
+    this constraint construction process including no columns present, no name
+    present or blank name present are now accommodated.

lib/sqlalchemy/event/base.py

@@ -29,7 +29,13 @@
 
 
 def _is_event_name(name):
-    return not name.startswith("_") and name != "dispatch"
+    # _sa_event prefix is special to support internal-only event names.
+    # most event names are just plain method names that aren't
+    # underscored.
+
+    return (
+        not name.startswith("_") and name != "dispatch"
+    ) or name.startswith("_sa_event")
 
 
 class _UnpickleDispatch(object):

lib/sqlalchemy/sql/events.py

@@ -209,6 +209,12 @@ def after_parent_attach(self, target, parent):
 
         """
 
+    def _sa_event_column_added_to_pk_constraint(self, const, col):
+        """internal event hook used for primary key naming convention
+        updates.
+
+        """
+
     def column_reflect(self, inspector, table, column_info):
         """Called for each unit of 'column info' retrieved when
         a :class:`_schema.Table` is being reflected.

lib/sqlalchemy/sql/naming.py

@@ -39,12 +39,22 @@ def __init__(self, const, table, convention):
     def _key_table_name(self):
         return self.table.name
 
-    def _column_X(self, idx):
+    def _column_X(self, idx, attrname):
         if self._is_fk:
-            fk = self.const.elements[idx]
-            return fk.parent
+            try:
+                fk = self.const.elements[idx]
+            except IndexError:
+                return ""
+            else:
+                return getattr(fk.parent, attrname)
         else:
-            return list(self.const.columns)[idx]
+            cols = list(self.const.columns)
+            try:
+                col = cols[idx]
+            except IndexError:
+                return ""
+            else:
+                return getattr(col, attrname)
 
     def _key_constraint_name(self):
         if isinstance(self._const_name, (type(None), _defer_none_name)):
@@ -61,13 +71,13 @@ def _key_column_X_key(self, idx):
         # note this method was missing before
         # [ticket:3989], meaning tokens like ``%(column_0_key)s`` weren't
         # working even though documented.
-        return self._column_X(idx).key
+        return self._column_X(idx, "key")
 
     def _key_column_X_name(self, idx):
-        return self._column_X(idx).name
+        return self._column_X(idx, "name")
 
     def _key_column_X_label(self, idx):
-        return self._column_X(idx)._ddl_label
+        return self._column_X(idx, "_ddl_label")
 
     def _key_referred_table_name(self):
         fk = self.const.elements[0]
@@ -161,10 +171,28 @@ def _constraint_name_for_table(const, table):
         return None
 
 
+@event.listens_for(
+    PrimaryKeyConstraint, "_sa_event_column_added_to_pk_constraint"
+)
+def _column_added_to_pk_constraint(pk_constraint, col):
+    if pk_constraint._implicit_generated:
+        # only operate upon the "implicit" pk constraint for now,
+        # as we have to force the name to None to reset it.  the
+        # "implicit" constraint will only have a naming convention name
+        # if at all.
+        table = pk_constraint.table
+        pk_constraint.name = None
+        newname = _constraint_name_for_table(pk_constraint, table)
+        if newname:
+            pk_constraint.name = newname
+
+
 @event.listens_for(Constraint, "after_parent_attach")
 @event.listens_for(Index, "after_parent_attach")
 def _constraint_name(const, table):
     if isinstance(table, Column):
+        # this path occurs for a CheckConstraint linked to a Column
+
         # for column-attached constraint, set another event
         # to link the column attached to the table as this constraint
         # associated with the table.
@@ -173,10 +201,11 @@ def _constraint_name(const, table):
             "after_parent_attach",
             lambda col, table: _constraint_name(const, table),
         )
+
     elif isinstance(table, Table):
         if isinstance(const.name, (conv, _defer_name)):
             return
 
         newname = _constraint_name_for_table(const, table)
-        if newname is not None:
+        if newname:
             const.name = newname

lib/sqlalchemy/sql/schema.py

@@ -1777,6 +1777,8 @@ def _set_parent(self, table, allow_replacements=True):
 
         table._columns.replace(self)
 
+        self.table = table
+
         if self.primary_key:
             table.primary_key._replace(self)
         elif self.key in table.primary_key:
@@ -1786,8 +1788,6 @@ def _set_parent(self, table, allow_replacements=True):
                 % (self.key, table.fullname)
             )
 
-        self.table = table
-
         if self.index:
             if isinstance(self.index, util.string_types):
                 raise exc.ArgumentError(
@@ -3838,7 +3838,6 @@ def _reload(self, columns):
         are already present.
 
         """
-
         # set the primary key flag on new columns.
         # note any existing PK cols on the table also have their
         # flag still set.
@@ -3854,6 +3853,8 @@ def _replace(self, col):
         PrimaryKeyConstraint._autoincrement_column._reset(self)
         self.columns.replace(col)
 
+        self.dispatch._sa_event_column_added_to_pk_constraint(self, col)
+
     @property
     def columns_autoinc_first(self):
         autoinc = self._autoincrement_column

test/sql/test_metadata.py

@@ -4841,6 +4841,73 @@ def test_colliding_col_label_from_unique_flag_no_conv(self):
             AddConstraint(const[0]), "ALTER TABLE foo ADD UNIQUE (id)"
         )
 
+    @testing.combinations(
+        ("nopk",),
+        ("column",),
+        ("constraint",),
+        ("explicit_name",),
+        argnames="pktype",
+    )
+    @testing.combinations(
+        ("pk_%(table_name)s", "pk_t1"),
+        ("pk_%(column_0_name)s", "pk_x"),
+        ("pk_%(column_0_N_name)s", "pk_x_y"),
+        ("pk_%(column_0_N_label)s", "pk_t1_x_t1_y"),
+        ("%(column_0_name)s", "x"),
+        ("%(column_0N_name)s", "xy"),
+        argnames="conv, expected_name",
+    )
+    def test_pk_conventions(self, conv, expected_name, pktype):
+        m1 = MetaData(naming_convention={"pk": conv})
+
+        if pktype == "column":
+            t1 = Table(
+                "t1",
+                m1,
+                Column("x", Integer, primary_key=True),
+                Column("y", Integer, primary_key=True),
+            )
+        elif pktype == "constraint":
+            t1 = Table(
+                "t1",
+                m1,
+                Column("x", Integer),
+                Column("y", Integer),
+                PrimaryKeyConstraint("x", "y"),
+            )
+        elif pktype == "nopk":
+            t1 = Table(
+                "t1",
+                m1,
+                Column("x", Integer, nullable=False),
+                Column("y", Integer, nullable=False),
+            )
+            expected_name = None
+        elif pktype == "explicit_name":
+            t1 = Table(
+                "t1",
+                m1,
+                Column("x", Integer, primary_key=True),
+                Column("y", Integer, primary_key=True),
+                PrimaryKeyConstraint("x", "y", name="myname"),
+            )
+            expected_name = "myname"
+
+        if expected_name:
+            eq_(t1.primary_key.name, expected_name)
+
+        if pktype == "nopk":
+            self.assert_compile(
+                schema.CreateTable(t1),
+                "CREATE TABLE t1 (x INTEGER NOT NULL, y INTEGER NOT NULL)",
+            )
+        else:
+            self.assert_compile(
+                schema.CreateTable(t1),
+                "CREATE TABLE t1 (x INTEGER NOT NULL, y INTEGER NOT NULL, "
+                "CONSTRAINT %s PRIMARY KEY (x, y))" % expected_name,
+            )
+
     def test_uq_name(self):
         u1 = self._fixture(
             naming_convention={"uq": "uq_%(table_name)s_%(column_0_name)s"}