almost done issue 12: generate downgrade method for schema migration

migrate/versioning/genmodel.py

@@ -80,25 +80,27 @@ class ModelGenerator(object):
             out.append("")
         return '\n'.join(out)
         
-    def toUpgradePython(self, indent='    '):
+    def toUpgradeDowngradePython(self, indent='    '):
         ''' Assume model is most current and database is out-of-date. '''
         
         decls = ['meta = MetaData(migrate_engine)']
         for table in self.diff.tablesMissingInModel + self.diff.tablesMissingInDatabase:
             decls.extend(self.getTableDefn(table))
             
-        cmds = []
+        upgradeCommands, downgradeCommands = [], []
         for table in self.diff.tablesMissingInModel:
             tableName = table.name
-            cmds.append("%(table)s.drop()" % {'table': tableName})
+            upgradeCommands.append("%(table)s.drop()" % {'table': tableName})
+            downgradeCommands.append("%(table)s.create()" % {'table': tableName})
         for table in self.diff.tablesMissingInDatabase:
             tableName = table.name
-            cmds.append("%(table)s.create()" % {'table': tableName})
+            upgradeCommands.append("%(table)s.create()" % {'table': tableName})
+            downgradeCommands.append("%(table)s.drop()" % {'table': tableName})
             
-        return '\n'.join(decls), '\n'.join(['%s%s' % (indent, line) for line in cmds])
-    
-    def toDowngradePython(self, indent='    '):
-        return '    pass  #TODO DOWNGRADE'
+        return ('\n'.join(decls),
+                '\n'.join(['%s%s' % (indent, line) for line in upgradeCommands]),
+                '\n'.join(['%s%s' % (indent, line) for line in downgradeCommands])
+               )
     
     def applyModel(self):
         ''' Apply model to current database. '''

migrate/versioning/script/py.py

@@ -22,7 +22,6 @@ class PythonScript(base.BaseScript):
     @classmethod
     def make_update_script_for_model(cls,engine,oldmodel,model,repository,**opts):
         """Create a migration script"""
-        #cls.require_notfound(path)  # TODO: yank?
         
         # Compute differences.
         if isinstance(repository, basestring):
@@ -31,20 +30,17 @@ class PythonScript(base.BaseScript):
         oldmodel = loadModel(oldmodel)
         model = loadModel(model)
         diff = schemadiff.getDiffOfModelAgainstModel(oldmodel, model, engine, excludeTables=[repository.version_table])
-        upgradeDecls, upgradeCommands = genmodel.ModelGenerator(diff).toUpgradePython()
-        #downgradeCommands = genmodel.ModelGenerator(diff).toDowngradePython()
+        decls, upgradeCommands, downgradeCommands = genmodel.ModelGenerator(diff).toUpgradeDowngradePython()
 
-        # TODO: Use the default script template (defined in the template
-        # module) for now, but we might want to allow people to specify a
-        # different one later.
+        # Store differences into file.
         template_file = None
         src = template.get_script(template_file)
         contents = open(src).read()
         search = 'def upgrade():'
-        contents = contents.replace(search, upgradeDecls + '\n\n' + search, 1)
+        contents = contents.replace(search, decls + '\n\n' + search, 1)
         if upgradeCommands: contents = contents.replace('    pass', upgradeCommands, 1)
-        #if downgradeCommands: contents = contents.replace('    pass', downgradeCommands, 1)  # TODO
-        return contents   # TODO: reinstate? open(path, 'w').write(contents)
+        if downgradeCommands: contents = contents.replace('    pass', downgradeCommands, 1)
+        return contents
 
     @classmethod
     def verify_module(cls,path):

test/versioning/test_schemadiff.py

@@ -50,10 +50,10 @@ class TestSchemaDiff(fixture.DB):
         # Model is defined but database is empty.
         assertDiff(True, [self.table_name], [], [])
         
-        # Check Python upgrade of database from updated model.
+        # Check Python upgrade and downgrade of database from updated model.
         diff = schemadiff.getDiffOfModelAgainstDatabase(self.meta, self.engine, excludeTables=['migrate_version'])
-        decl, commands = genmodel.ModelGenerator(diff).toUpgradePython()
-        self.assertEqualsIgnoreWhitespace(decl, '''
+        decls, upgradeCommands, downgradeCommands = genmodel.ModelGenerator(diff).toUpgradeDowngradePython()
+        self.assertEqualsIgnoreWhitespace(decls, '''
         meta = MetaData(migrate_engine)
         tmp_schemadiff = Table('tmp_schemadiff',meta,
             Column('id',Integer(),primary_key=True,nullable=False),
@@ -61,7 +61,8 @@ class TestSchemaDiff(fixture.DB):
             Column('data',UnicodeText(length=None)),
         )
         ''')
-        self.assertEqualsIgnoreWhitespace(commands, '''tmp_schemadiff.create()''')
+        self.assertEqualsIgnoreWhitespace(upgradeCommands, '''tmp_schemadiff.create()''')
+        self.assertEqualsIgnoreWhitespace(downgradeCommands, '''tmp_schemadiff.drop()''')
         
         # Create table in database, now model should match database.
         self._applyLatestModel()

test/versioning/test_shell.py

@@ -542,7 +542,7 @@ class TestShellDatabase(Shell,fixture.DB):
 
             def downgrade():
                 # Operations to reverse the above upgrade go here.
-                pass
+                tmp_account_rundiffs.drop()
         """)
         
         # Commit the change.