Fix and test issue 118. Clarify genmodel transformations.

4 files changed, 83 insertions, 60 deletions

diff --git a/migrate/versioning/genmodel.py b/migrate/versioning/genmodel.py
index 6cb8e09..cfe9996 100644
--- a/migrate/versioning/genmodel.py
+++ b/migrate/versioning/genmodel.py
@@ -1,9 +1,9 @@
 """
-   Code to generate a Python model from a database or differences
-   between a model and database.
+Code to generate a Python model from a database or differences
+between a model and database.
 
-   Some of this is borrowed heavily from the AutoCode project at:
-   http://code.google.com/p/sqlautocode/
+Some of this is borrowed heavily from the AutoCode project at:
+http://code.google.com/p/sqlautocode/
 """
 
 import sys
@@ -34,6 +34,13 @@ Base = declarative.declarative_base()
 
 
 class ModelGenerator(object):
+    """Various transformations from an A, B diff.
+
+    In the implementation, A tends to be called the model and B
+    the database (although this is not true of all diffs).
+    The diff is directionless, but transformations apply the diff
+    in a particular direction, described in the method name.
+    """
 
     def __init__(self, diff, engine, declarative=False):
         self.diff = diff
@@ -89,7 +96,7 @@ class ModelGenerator(object):
         else:
             return """Column(%(name)r, %(commonStuff)s)""" % data
 
-    def getTableDefn(self, table):
+    def _getTableDefn(self, table):
         out = []
         tableName = table.name
         if self.declarative:
@@ -117,9 +124,15 @@ class ModelGenerator(object):
             if bool_:
                 for name in names:
                     yield metadata.tables.get(name)
-        
-    def toPython(self):
-        """Assume database is current and model is empty."""
+
+    def genBDefinition(self):
+        """Generates the source code for a definition of B.
+
+        Assumes a diff where A is empty.
+
+        Was: toPython. Assume database (B) is current and model (A) is empty.
+        """
+
         out = []
         if self.declarative:
             out.append(DECLARATIVE_HEADER)
@@ -127,17 +140,22 @@ class ModelGenerator(object):
             out.append(HEADER)
         out.append("")
         for table in self._get_tables(missingA=True):
-            out.extend(self.getTableDefn(table))
+            out.extend(self._getTableDefn(table))
         return '\n'.join(out)
 
-    def toUpgradeDowngradePython(self, indent='    '):
-        ''' Assume model is most current and database is out-of-date. '''
+    def genB2AMigration(self, indent='    '):
+        '''Generate a migration from B to A.
+
+        Was: toUpgradeDowngradePython
+        Assume model (A) is most current and database (B) is out-of-date.
+        '''
+
         decls = ['from migrate.changeset import schema',
                  'meta = MetaData()']
         for table in self._get_tables(
             missingA=True,missingB=True,modified=True
             ):
-            decls.extend(self.getTableDefn(table))
+            decls.extend(self._getTableDefn(table))
 
         upgradeCommands, downgradeCommands = [], []
         for tableName in self.diff.tables_missing_from_A:
@@ -175,16 +193,21 @@ class ModelGenerator(object):
             '\n'.join([pre_command] + ['%s%s' % (indent, line) for line in downgradeCommands]))
 
     def _db_can_handle_this_change(self,td):
+        """Check if the database can handle going from B to A."""
+
         if (td.columns_missing_from_B
             and not td.columns_missing_from_A
             and not td.columns_different):
-            # Even sqlite can handle this.
+            # Even sqlite can handle column additions.
             return True
         else:
             return not self.engine.url.drivername.startswith('sqlite')
 
-    def applyModel(self):
-        """Apply model to current database."""
+    def runB2A(self):
+        """Goes from B to A.
+
+        Was: applyModel. Apply model (A) to current database (B).
+        """
 
         meta = sqlalchemy.MetaData(self.engine)
 
@@ -200,9 +223,9 @@ class ModelGenerator(object):
             dbTable = self.diff.metadataB.tables[tableName]
 
             td = self.diff.tables_different[tableName]
-            
+
             if self._db_can_handle_this_change(td):
-                
+
                 for col in td.columns_missing_from_B:
                     modelTable.columns[col].create()
                 for col in td.columns_missing_from_A:
diff --git a/migrate/versioning/schema.py b/migrate/versioning/schema.py
index 1085538..e4d9365 100644
--- a/migrate/versioning/schema.py
+++ b/migrate/versioning/schema.py
@@ -71,7 +71,7 @@ class ControlledSchema(object):
 
     def changeset(self, version=None):
         """API to Changeset creation.
-        
+
         Uses self.version for start version and engine.name
         to get database name.
         """
@@ -117,7 +117,7 @@ class ControlledSchema(object):
         diff = schemadiff.getDiffOfModelAgainstDatabase(
             model, self.engine, excludeTables=[self.repository.version_table]
             )
-        genmodel.ModelGenerator(diff,self.engine).applyModel()
+        genmodel.ModelGenerator(diff,self.engine).runB2A()
 
         self.update_repository_table(self.version, int(self.repository.latest))
 
@@ -217,4 +217,4 @@ class ControlledSchema(object):
         diff = schemadiff.getDiffOfModelAgainstDatabase(
             MetaData(), engine, excludeTables=[repository.version_table]
             )
-        return genmodel.ModelGenerator(diff, engine, declarative).toPython()
+        return genmodel.ModelGenerator(diff, engine, declarative).genBDefinition()
diff --git a/migrate/versioning/schemadiff.py b/migrate/versioning/schemadiff.py
index 17c2d8e..77661d3 100644
--- a/migrate/versioning/schemadiff.py
+++ b/migrate/versioning/schemadiff.py
@@ -39,11 +39,11 @@ class ColDiff(object):
     Container for differences in one :class:`~sqlalchemy.schema.Column`
     between two :class:`~sqlalchemy.schema.Table` instances, ``A``
     and ``B``.
-    
+
     .. attribute:: col_A
 
       The :class:`~sqlalchemy.schema.Column` object for A.
-      
+
     .. attribute:: col_B
 
       The :class:`~sqlalchemy.schema.Column` object for B.
@@ -51,15 +51,15 @@ class ColDiff(object):
     .. attribute:: type_A
 
       The most generic type of the :class:`~sqlalchemy.schema.Column`
-      object in A. 
-      
+      object in A.
+
     .. attribute:: type_B
 
       The most generic type of the :class:`~sqlalchemy.schema.Column`
-      object in A. 
-      
+      object in A.
+
     """
-    
+
     diff = False
 
     def __init__(self,col_A,col_B):
@@ -87,10 +87,10 @@ class ColDiff(object):
             if not (A is None or B is None) and A!=B:
                 self.diff=True
                 return
-        
+
     def __nonzero__(self):
         return self.diff
-    
+
 class TableDiff(object):
     """
     Container for differences in one :class:`~sqlalchemy.schema.Table`
@@ -101,12 +101,12 @@ class TableDiff(object):
 
       A sequence of column names that were found in B but weren't in
       A.
-      
+
     .. attribute:: columns_missing_from_B
 
       A sequence of column names that were found in A but weren't in
       B.
-      
+
     .. attribute:: columns_different
 
       A dictionary containing information about columns that were
@@ -126,7 +126,7 @@ class TableDiff(object):
             self.columns_missing_from_B or
             self.columns_different
             )
-    
+
 class SchemaDiff(object):
     """
     Compute the difference between two :class:`~sqlalchemy.schema.MetaData`
@@ -139,34 +139,34 @@ class SchemaDiff(object):
     The length of a :class:`SchemaDiff` will give the number of
     changes found, enabling it to be used much like a boolean in
     expressions.
-        
+
     :param metadataA:
       First :class:`~sqlalchemy.schema.MetaData` to compare.
-      
+
     :param metadataB:
       Second :class:`~sqlalchemy.schema.MetaData` to compare.
-      
+
     :param labelA:
       The label to use in messages about the first
-      :class:`~sqlalchemy.schema.MetaData`. 
-    
-    :param labelB: 
+      :class:`~sqlalchemy.schema.MetaData`.
+
+    :param labelB:
       The label to use in messages about the second
-      :class:`~sqlalchemy.schema.MetaData`. 
-    
+      :class:`~sqlalchemy.schema.MetaData`.
+
     :param excludeTables:
       A sequence of table names to exclude.
-      
+
     .. attribute:: tables_missing_from_A
 
       A sequence of table names that were found in B but weren't in
       A.
-      
+
     .. attribute:: tables_missing_from_B
 
       A sequence of table names that were found in A but weren't in
       B.
-      
+
     .. attribute:: tables_different
 
       A dictionary containing information about tables that were found
@@ -195,26 +195,26 @@ class SchemaDiff(object):
         self.tables_missing_from_B = sorted(
             A_table_names - B_table_names - excludeTables
             )
-        
+
         self.tables_different = {}
         for table_name in A_table_names.intersection(B_table_names):
 
             td = TableDiff()
-            
+
             A_table = metadataA.tables[table_name]
             B_table = metadataB.tables[table_name]
-            
+
             A_column_names = set(A_table.columns.keys())
             B_column_names = set(B_table.columns.keys())
 
             td.columns_missing_from_A = sorted(
                 B_column_names - A_column_names
                 )
-            
+
             td.columns_missing_from_B = sorted(
                 A_column_names - B_column_names
                 )
-            
+
             td.columns_different = {}
 
             for col_name in A_column_names.intersection(B_column_names):
@@ -226,7 +226,7 @@ class SchemaDiff(object):
 
                 if cd:
                     td.columns_different[col_name]=cd
-                
+
             # XXX - index and constraint differences should
             #       be checked for here
 
@@ -237,7 +237,7 @@ class SchemaDiff(object):
         ''' Summarize differences. '''
         out = []
         column_template ='      %%%is: %%r' % self.label_width
-        
+
         for names,label in (
             (self.tables_missing_from_A,self.labelA),
             (self.tables_missing_from_B,self.labelB),
@@ -248,7 +248,7 @@ class SchemaDiff(object):
                         label,', '.join(sorted(names))
                         )
                     )
-                
+
         for name,td in sorted(self.tables_different.items()):
             out.append(
                '  table with differences: %s' % name
@@ -267,7 +267,7 @@ class SchemaDiff(object):
                 out.append('    column with differences: %s' % name)
                 out.append(column_template % (self.labelA,cd.col_A))
                 out.append(column_template % (self.labelB,cd.col_B))
-                
+
         if out:
             out.insert(0, 'Schema diffs:')
             return '\n'.join(out)
diff --git a/migrate/versioning/script/py.py b/migrate/versioning/script/py.py
index 35fe4aa..3a090d4 100644
--- a/migrate/versioning/script/py.py
+++ b/migrate/versioning/script/py.py
@@ -25,7 +25,7 @@ class PythonScript(base.BaseScript):
     @classmethod
     def create(cls, path, **opts):
         """Create an empty migration script at specified path
-        
+
         :returns: :class:`PythonScript instance <migrate.versioning.script.py.PythonScript>`"""
         cls.require_notfound(path)
 
@@ -38,7 +38,7 @@ class PythonScript(base.BaseScript):
     def make_update_script_for_model(cls, engine, oldmodel,
                                      model, repository, **opts):
         """Create a migration script based on difference between two SA models.
-        
+
         :param repository: path to migrate repository
         :param oldmodel: dotted.module.name:SAClass or SAClass object
         :param model: dotted.module.name:SAClass or SAClass object
@@ -50,7 +50,7 @@ class PythonScript(base.BaseScript):
         :returns: Upgrade / Downgrade script
         :rtype: string
         """
-        
+
         if isinstance(repository, basestring):
             # oh dear, an import cycle!
             from migrate.versioning.repository import Repository
@@ -61,12 +61,12 @@ class PythonScript(base.BaseScript):
 
         # Compute differences.
         diff = schemadiff.getDiffOfModelAgainstModel(
-            oldmodel,
             model,
+            oldmodel,
             excludeTables=[repository.version_table])
         # TODO: diff can be False (there is no difference?)
         decls, upgradeCommands, downgradeCommands = \
-            genmodel.ModelGenerator(diff,engine).toUpgradeDowngradePython()
+            genmodel.ModelGenerator(diff,engine).genB2AMigration()
 
         # Store differences into file.
         src = Template(opts.pop('templates_path', None)).get_script(opts.pop('templates_theme', None))
@@ -86,7 +86,7 @@ class PythonScript(base.BaseScript):
     @classmethod
     def verify_module(cls, path):
         """Ensure path is a valid script
-        
+
         :param path: Script location
         :type path: string
         :raises: :exc:`InvalidScriptError <migrate.exceptions.InvalidScriptError>`
@@ -101,7 +101,7 @@ class PythonScript(base.BaseScript):
         return module
 
     def preview_sql(self, url, step, **args):
-        """Mocks SQLAlchemy Engine to store all executed calls in a string 
+        """Mocks SQLAlchemy Engine to store all executed calls in a string
         and runs :meth:`PythonScript.run <migrate.versioning.script.py.PythonScript.run>`
 
         :returns: SQL file
@@ -119,7 +119,7 @@ class PythonScript(base.BaseScript):
         return go(url, step, **args)
 
     def run(self, engine, step):
-        """Core method of Script file. 
+        """Core method of Script file.
         Exectues :func:`update` or :func:`downgrade` functions
 
         :param engine: SQLAlchemy Engine