Add a deconstruct() method to Fields.

This allows the field's initial argument to be obtained so it can be
serialised to, and re-created from, a textual format.

3 files changed, 253 insertions, 0 deletions

diff --git a/tests/field_deconstruction/__init__.py b/tests/field_deconstruction/__init__.py
new file mode 100644
index 0000000000..e69de29bb2
--- /dev/null
+++ b/tests/field_deconstruction/__init__.py
diff --git a/tests/field_deconstruction/models.py b/tests/field_deconstruction/models.py
new file mode 100644
index 0000000000..e69de29bb2
--- /dev/null
+++ b/tests/field_deconstruction/models.py
diff --git a/tests/field_deconstruction/tests.py b/tests/field_deconstruction/tests.py
new file mode 100644
index 0000000000..683854940b
--- /dev/null
+++ b/tests/field_deconstruction/tests.py
@@ -0,0 +1,253 @@
+from django.test import TestCase
+from django.db import models
+
+
+class FieldDeconstructionTests(TestCase):
+    """
+    Tests the deconstruct() method on all core fields.
+    """
+
+    def test_name(self):
+        """
+        Tests the outputting of the correct name if assigned one.
+        """
+        # First try using a "normal" field
+        field = models.CharField(max_length=65)
+        name, path, args, kwargs = field.deconstruct()
+        self.assertEqual(name, None)
+        field.set_attributes_from_name("is_awesome_test")
+        name, path, args, kwargs = field.deconstruct()
+        self.assertEqual(name, "is_awesome_test")
+        # Now try with a ForeignKey
+        field = models.ForeignKey("some_fake.ModelName")
+        name, path, args, kwargs = field.deconstruct()
+        self.assertEqual(name, None)
+        field.set_attributes_from_name("author")
+        name, path, args, kwargs = field.deconstruct()
+        self.assertEqual(name, "author")
+
+    def test_auto_field(self):
+        field = models.AutoField(primary_key=True)
+        field.set_attributes_from_name("id")
+        name, path, args, kwargs = field.deconstruct()
+        self.assertEqual(path, "django.db.models.AutoField")
+        self.assertEqual(args, [])
+        self.assertEqual(kwargs, {"primary_key": True})
+
+    def test_big_integer_field(self):
+        field = models.BigIntegerField()
+        name, path, args, kwargs = field.deconstruct()
+        self.assertEqual(path, "django.db.models.BigIntegerField")
+        self.assertEqual(args, [])
+        self.assertEqual(kwargs, {})
+
+    def test_boolean_field(self):
+        field = models.BooleanField()
+        name, path, args, kwargs = field.deconstruct()
+        self.assertEqual(path, "django.db.models.BooleanField")
+        self.assertEqual(args, [])
+        self.assertEqual(kwargs, {})
+        field = models.BooleanField(default=True)
+        name, path, args, kwargs = field.deconstruct()
+        self.assertEqual(path, "django.db.models.BooleanField")
+        self.assertEqual(args, [])
+        self.assertEqual(kwargs, {"default": True})
+
+    def test_char_field(self):
+        field = models.CharField(max_length=65)
+        name, path, args, kwargs = field.deconstruct()
+        self.assertEqual(path, "django.db.models.CharField")
+        self.assertEqual(args, [])
+        self.assertEqual(kwargs, {"max_length": 65})
+        field = models.CharField(max_length=65, null=True, blank=True)
+        name, path, args, kwargs = field.deconstruct()
+        self.assertEqual(path, "django.db.models.CharField")
+        self.assertEqual(args, [])
+        self.assertEqual(kwargs, {"max_length": 65, "null": True, "blank": True})
+
+    def test_csi_field(self):
+        field = models.CommaSeparatedIntegerField(max_length=100)
+        name, path, args, kwargs = field.deconstruct()
+        self.assertEqual(path, "django.db.models.CommaSeparatedIntegerField")
+        self.assertEqual(args, [])
+        self.assertEqual(kwargs, {"max_length": 100})
+
+    def test_date_field(self):
+        field = models.DateField()
+        name, path, args, kwargs = field.deconstruct()
+        self.assertEqual(path, "django.db.models.DateField")
+        self.assertEqual(args, [])
+        self.assertEqual(kwargs, {})
+        field = models.DateField(auto_now=True)
+        name, path, args, kwargs = field.deconstruct()
+        self.assertEqual(path, "django.db.models.DateField")
+        self.assertEqual(args, [])
+        self.assertEqual(kwargs, {"auto_now": True})
+
+    def test_datetime_field(self):
+        field = models.DateTimeField()
+        name, path, args, kwargs = field.deconstruct()
+        self.assertEqual(path, "django.db.models.DateTimeField")
+        self.assertEqual(args, [])
+        self.assertEqual(kwargs, {})
+        field = models.DateTimeField(auto_now_add=True)
+        name, path, args, kwargs = field.deconstruct()
+        self.assertEqual(path, "django.db.models.DateTimeField")
+        self.assertEqual(args, [])
+        self.assertEqual(kwargs, {"auto_now_add": True})
+
+    def test_decimal_field(self):
+        field = models.DecimalField(max_digits=5, decimal_places=2)
+        name, path, args, kwargs = field.deconstruct()
+        self.assertEqual(path, "django.db.models.DecimalField")
+        self.assertEqual(args, [])
+        self.assertEqual(kwargs, {"max_digits": 5, "decimal_places": 2})
+
+    def test_email_field(self):
+        field = models.EmailField()
+        name, path, args, kwargs = field.deconstruct()
+        self.assertEqual(path, "django.db.models.EmailField")
+        self.assertEqual(args, [])
+        self.assertEqual(kwargs, {})
+        field = models.EmailField(max_length=255)
+        name, path, args, kwargs = field.deconstruct()
+        self.assertEqual(path, "django.db.models.EmailField")
+        self.assertEqual(args, [])
+        self.assertEqual(kwargs, {"max_length": 255})
+
+    def test_file_field(self):
+        field = models.FileField(upload_to="foo/bar")
+        name, path, args, kwargs = field.deconstruct()
+        self.assertEqual(path, "django.db.models.FileField")
+        self.assertEqual(args, [])
+        self.assertEqual(kwargs, {"upload_to": "foo/bar"})
+
+    def test_file_path_field(self):
+        field = models.FilePathField(match=".*\.txt$")
+        name, path, args, kwargs = field.deconstruct()
+        self.assertEqual(path, "django.db.models.FilePathField")
+        self.assertEqual(args, [])
+        self.assertEqual(kwargs, {"match": ".*\.txt$"})
+        field = models.FilePathField(recursive=True, allow_folders=True)
+        name, path, args, kwargs = field.deconstruct()
+        self.assertEqual(path, "django.db.models.FilePathField")
+        self.assertEqual(args, [])
+        self.assertEqual(kwargs, {"recursive": True, "allow_folders": True})
+
+    def test_float_field(self):
+        field = models.FloatField()
+        name, path, args, kwargs = field.deconstruct()
+        self.assertEqual(path, "django.db.models.FloatField")
+        self.assertEqual(args, [])
+        self.assertEqual(kwargs, {})
+
+    def test_foreign_key(self):
+        field = models.ForeignKey("auth.User")
+        name, path, args, kwargs = field.deconstruct()
+        self.assertEqual(path, "django.db.models.ForeignKey")
+        self.assertEqual(args, [])
+        self.assertEqual(kwargs, {"to": "auth.User"})
+        field = models.ForeignKey("something.Else")
+        name, path, args, kwargs = field.deconstruct()
+        self.assertEqual(path, "django.db.models.ForeignKey")
+        self.assertEqual(args, [])
+        self.assertEqual(kwargs, {"to": "something.Else"})
+        field = models.ForeignKey("auth.User", on_delete=models.SET_NULL)
+        name, path, args, kwargs = field.deconstruct()
+        self.assertEqual(path, "django.db.models.ForeignKey")
+        self.assertEqual(args, [])
+        self.assertEqual(kwargs, {"to": "auth.User", "on_delete": models.SET_NULL})
+
+    def test_image_field(self):
+        field = models.ImageField(upload_to="foo/barness", width_field="width", height_field="height")
+        name, path, args, kwargs = field.deconstruct()
+        self.assertEqual(path, "django.db.models.ImageField")
+        self.assertEqual(args, [])
+        self.assertEqual(kwargs, {"upload_to": "foo/barness", "width_field": "width", "height_field": "height"})
+
+    def test_integer_field(self):
+        field = models.IntegerField()
+        name, path, args, kwargs = field.deconstruct()
+        self.assertEqual(path, "django.db.models.IntegerField")
+        self.assertEqual(args, [])
+        self.assertEqual(kwargs, {})
+
+    def test_ip_address_field(self):
+        field = models.IPAddressField()
+        name, path, args, kwargs = field.deconstruct()
+        self.assertEqual(path, "django.db.models.IPAddressField")
+        self.assertEqual(args, [])
+        self.assertEqual(kwargs, {})
+
+    def test_generic_ip_address_field(self):
+        field = models.GenericIPAddressField()
+        name, path, args, kwargs = field.deconstruct()
+        self.assertEqual(path, "django.db.models.GenericIPAddressField")
+        self.assertEqual(args, [])
+        self.assertEqual(kwargs, {})
+        field = models.GenericIPAddressField(protocol="IPv6")
+        name, path, args, kwargs = field.deconstruct()
+        self.assertEqual(path, "django.db.models.GenericIPAddressField")
+        self.assertEqual(args, [])
+        self.assertEqual(kwargs, {"protocol": "IPv6"})
+
+    def test_many_to_many_field(self):
+        field = models.ManyToManyField("auth.User")
+        name, path, args, kwargs = field.deconstruct()
+        self.assertEqual(path, "django.db.models.ManyToManyField")
+        self.assertEqual(args, [])
+        self.assertEqual(kwargs, {"to": "auth.User"})
+
+    def test_null_boolean_field(self):
+        field = models.NullBooleanField()
+        name, path, args, kwargs = field.deconstruct()
+        self.assertEqual(path, "django.db.models.NullBooleanField")
+        self.assertEqual(args, [])
+        self.assertEqual(kwargs, {})
+
+    def test_positive_integer_field(self):
+        field = models.PositiveIntegerField()
+        name, path, args, kwargs = field.deconstruct()
+        self.assertEqual(path, "django.db.models.PositiveIntegerField")
+        self.assertEqual(args, [])
+        self.assertEqual(kwargs, {})
+
+    def test_positive_small_integer_field(self):
+        field = models.PositiveSmallIntegerField()
+        name, path, args, kwargs = field.deconstruct()
+        self.assertEqual(path, "django.db.models.PositiveSmallIntegerField")
+        self.assertEqual(args, [])
+        self.assertEqual(kwargs, {})
+
+    def test_slug_field(self):
+        field = models.SlugField()
+        name, path, args, kwargs = field.deconstruct()
+        self.assertEqual(path, "django.db.models.SlugField")
+        self.assertEqual(args, [])
+        self.assertEqual(kwargs, {})
+        field = models.SlugField(db_index=False)
+        name, path, args, kwargs = field.deconstruct()
+        self.assertEqual(path, "django.db.models.SlugField")
+        self.assertEqual(args, [])
+        self.assertEqual(kwargs, {"db_index": False})
+
+    def test_small_integer_field(self):
+        field = models.SmallIntegerField()
+        name, path, args, kwargs = field.deconstruct()
+        self.assertEqual(path, "django.db.models.SmallIntegerField")
+        self.assertEqual(args, [])
+        self.assertEqual(kwargs, {})
+
+    def test_text_field(self):
+        field = models.TextField()
+        name, path, args, kwargs = field.deconstruct()
+        self.assertEqual(path, "django.db.models.TextField")
+        self.assertEqual(args, [])
+        self.assertEqual(kwargs, {})
+
+    def test_url_field(self):
+        field = models.URLField()
+        name, path, args, kwargs = field.deconstruct()
+        self.assertEqual(path, "django.db.models.URLField")
+        self.assertEqual(args, [])
+        self.assertEqual(kwargs, {})