From 55c65beb4bd4ca08b4ff3776c574be7317b4845d Mon Sep 17 00:00:00 2001
From: Konsta Vesterinen <konsta.vesterinen@gmail.com>
Date: Mon, 8 Jun 2015 09:42:20 +0300
Subject: [PATCH] Add default param for array_agg

---
 CHANGES.rst                      |  3 ++-
 sqlalchemy_utils/__init__.py     |  2 +-
 sqlalchemy_utils/expressions.py  | 13 ++++++++++---
 tests/functions/test_get_type.py |  1 -
 tests/test_expressions.py        | 20 +++++++++++++++++---
 5 files changed, 30 insertions(+), 9 deletions(-)

diff --git a/CHANGES.rst b/CHANGES.rst
index f3a4d15..b8e27f0 100644
--- a/CHANGES.rst
+++ b/CHANGES.rst
@@ -4,10 +4,11 @@ Changelog
 Here you can see the full list of changes between each SQLAlchemy-Utils release.
 
 
-0.30.9 (2015-06-05)
+0.30.9 (2015-06-08)
 ^^^^^^^^^^^^^^^^^^^
 
 - Added get_type utility function
+- Added default parameter for array_agg function
 
 
 0.30.8 (2015-06-05)
diff --git a/sqlalchemy_utils/__init__.py b/sqlalchemy_utils/__init__.py
index 8acf281..aaa425a 100644
--- a/sqlalchemy_utils/__init__.py
+++ b/sqlalchemy_utils/__init__.py
@@ -8,7 +8,7 @@ from .asserts import (  # noqa
 )
 from .exceptions import ImproperlyConfigured  # noqa
 from .expression_parser import ExpressionParser  # noqa
-from .expressions import array_agg, Asterisk, row_to_json  # noqa
+from .expressions import Asterisk, row_to_json  # noqa
 from .functions import (  # noqa
     analyze,
     create_database,
diff --git a/sqlalchemy_utils/expressions.py b/sqlalchemy_utils/expressions.py
index d92f081..4d2c112 100644
--- a/sqlalchemy_utils/expressions.py
+++ b/sqlalchemy_utils/expressions.py
@@ -1,5 +1,5 @@
 import sqlalchemy as sa
-from sqlalchemy.dialects.postgresql import ARRAY, JSON
+from sqlalchemy.dialects.postgresql import array, ARRAY, JSON
 from sqlalchemy.ext.compiler import compiles
 from sqlalchemy.sql.expression import (
     _literal_as_text,
@@ -116,14 +116,21 @@ class array_agg(GenericFunction):
     name = 'array_agg'
     type = ARRAY
 
-    def __init__(self, arg, **kw):
+    def __init__(self, arg, default=None, **kw):
         self.type = ARRAY(arg.type)
+        self.default = default
         GenericFunction.__init__(self, arg, **kw)
 
 
 @compiles(array_agg, 'postgresql')
 def compile_array_agg(element, compiler, **kw):
-    return "%s(%s)" % (element.name, compiler.process(element.clauses))
+    compiled = "%s(%s)" % (element.name, compiler.process(element.clauses))
+    if element.default is None:
+        return compiled
+    return str(sa.func.coalesce(
+        sa.text(compiled),
+        sa.cast(array(element.default), element.type)
+    ).compile(compiler))
 
 
 class Asterisk(ColumnElement):
diff --git a/tests/functions/test_get_type.py b/tests/functions/test_get_type.py
index 0287325..8990be4 100644
--- a/tests/functions/test_get_type.py
+++ b/tests/functions/test_get_type.py
@@ -2,7 +2,6 @@ import sqlalchemy as sa
 from sqlalchemy.ext.declarative import declarative_base
 
 from sqlalchemy_utils import get_type
-from tests import TestCase
 
 
 class TestGetType(object):
diff --git a/tests/test_expressions.py b/tests/test_expressions.py
index 8945820..1bcd223 100644
--- a/tests/test_expressions.py
+++ b/tests/test_expressions.py
@@ -2,7 +2,7 @@ import sqlalchemy as sa
 from pytest import raises
 from sqlalchemy.dialects import postgresql
 
-from sqlalchemy_utils import array_agg, Asterisk, row_to_json
+from sqlalchemy_utils import Asterisk, row_to_json
 from sqlalchemy_utils.expressions import explain, explain_analyze
 from tests import TestCase
 
@@ -129,10 +129,10 @@ class TestRowToJson(object):
 class TestArrayAgg(object):
     def test_compiler_with_default_dialect(self):
         with raises(sa.exc.CompileError):
-            str(array_agg(sa.text('u.name')))
+            str(sa.func.array_agg(sa.text('u.name')))
 
     def test_compiler_with_postgresql(self):
-        assert str(array_agg(sa.text('u.name')).compile(
+        assert str(sa.func.array_agg(sa.text('u.name')).compile(
             dialect=postgresql.dialect()
         )) == "array_agg(u.name)"
 
@@ -141,3 +141,17 @@ class TestArrayAgg(object):
             sa.func.array_agg(sa.text('u.name')).type,
             postgresql.ARRAY
         )
+
+    def test_array_agg_with_default(self):
+        Base = sa.ext.declarative.declarative_base()
+
+        class Article(Base):
+            __tablename__ = 'article'
+            id = sa.Column(sa.Integer, primary_key=True)
+
+        assert str(sa.func.array_agg(Article.id, [1]).compile(
+            dialect=postgresql.dialect()
+        )) == (
+            'coalesce(array_agg(article.id), CAST(ARRAY[%(param_1)s]'
+            ' AS INTEGER[]))'
+        )