Refs #30446 -- Defined default output_field of text database functions.

This prevented the default behavior of
BaseExpression._resolve_output_field from error'ing out when such
functions accepted both expressions from mixed types
(e.g. SubStr(CharField, IntegerField, IntegerField)).

django/db/models/functions/text.py

@@ -1,6 +1,6 @@
 from django.db import NotSupportedError
 from django.db.models.expressions import Func, Value
-from django.db.models.fields import IntegerField
+from django.db.models.fields import CharField, IntegerField
 from django.db.models.functions import Coalesce
 from django.db.models.lookups import Transform
 
@@ -135,6 +135,7 @@ class Concat(Func):
 class Left(Func):
     function = 'LEFT'
     arity = 2
+    output_field = CharField()
 
     def __init__(self, expression, length, **extra):
         """
@@ -173,6 +174,7 @@ class Lower(Transform):
 
 class LPad(BytesToCharFieldConversionMixin, Func):
     function = 'LPAD'
+    output_field = CharField()
 
     def __init__(self, expression, length, fill_text=Value(' '), **extra):
         if not hasattr(length, 'resolve_expression') and length is not None and length < 0:
@@ -204,6 +206,7 @@ class Ord(Transform):
 
 class Repeat(BytesToCharFieldConversionMixin, Func):
     function = 'REPEAT'
+    output_field = CharField()
 
     def __init__(self, expression, number, **extra):
         if not hasattr(number, 'resolve_expression') and number is not None and number < 0:
@@ -303,6 +306,7 @@ class StrIndex(Func):
 
 class Substr(Func):
     function = 'SUBSTRING'
+    output_field = CharField()
 
     def __init__(self, expression, pos, length=None, **extra):
         """

tests/db_functions/text/test_left.py

@@ -1,4 +1,4 @@
-from django.db.models import CharField, Value
+from django.db.models import IntegerField, Value
 from django.db.models.functions import Left, Lower
 from django.test import TestCase
 
@@ -23,5 +23,5 @@ class LeftTests(TestCase):
             Author.objects.annotate(raises=Left('name', 0))
 
     def test_expressions(self):
-        authors = Author.objects.annotate(name_part=Left('name', Value(3), output_field=CharField()))
+        authors = Author.objects.annotate(name_part=Left('name', Value(3, output_field=IntegerField())))
         self.assertQuerysetEqual(authors.order_by('name'), ['Joh', 'Rho'], lambda a: a.name_part)

tests/db_functions/text/test_pad.py

@@ -1,5 +1,5 @@
 from django.db import connection
-from django.db.models import CharField, Value
+from django.db.models import Value
 from django.db.models.functions import Length, LPad, RPad
 from django.test import TestCase
 
@@ -42,7 +42,7 @@ class PadTests(TestCase):
     def test_combined_with_length(self):
         Author.objects.create(name='Rhonda', alias='john_smith')
         Author.objects.create(name='♥♣♠', alias='bytes')
-        authors = Author.objects.annotate(filled=LPad('name', Length('alias'), output_field=CharField()))
+        authors = Author.objects.annotate(filled=LPad('name', Length('alias')))
         self.assertQuerysetEqual(
             authors.order_by('alias'),
             ['  ♥♣♠', '    Rhonda'],

tests/db_functions/text/test_repeat.py

@@ -1,5 +1,5 @@
 from django.db import connection
-from django.db.models import CharField, Value
+from django.db.models import Value
 from django.db.models.functions import Length, Repeat
 from django.test import TestCase
 
@@ -13,8 +13,8 @@ class RepeatTests(TestCase):
         tests = (
             (Repeat('name', 0), ''),
             (Repeat('name', 2), 'JohnJohn'),
-            (Repeat('name', Length('alias'), output_field=CharField()), 'JohnJohnJohn'),
+            (Repeat('name', Length('alias')), 'JohnJohnJohn'),
-            (Repeat(Value('x'), 3, output_field=CharField()), 'xxx'),
+            (Repeat(Value('x'), 3), 'xxx'),
             (Repeat('name', None), none_value),
             (Repeat('goes_by', 1), none_value),
         )

tests/db_functions/text/test_right.py

@@ -1,4 +1,4 @@
-from django.db.models import CharField, Value
+from django.db.models import IntegerField, Value
 from django.db.models.functions import Lower, Right
 from django.test import TestCase
 
@@ -23,5 +23,5 @@ class RightTests(TestCase):
             Author.objects.annotate(raises=Right('name', 0))
 
     def test_expressions(self):
-        authors = Author.objects.annotate(name_part=Right('name', Value(3), output_field=CharField()))
+        authors = Author.objects.annotate(name_part=Right('name', Value(3, output_field=IntegerField())))
         self.assertQuerysetEqual(authors.order_by('name'), ['ith', 'nda'], lambda a: a.name_part)

tests/db_functions/text/test_substr.py

@@ -1,4 +1,4 @@
-from django.db.models import CharField, Value as V
+from django.db.models import Value as V
 from django.db.models.functions import Lower, StrIndex, Substr, Upper
 from django.test import TestCase
 
@@ -45,7 +45,7 @@ class SubstrTests(TestCase):
     def test_expressions(self):
         Author.objects.create(name='John Smith', alias='smithj')
         Author.objects.create(name='Rhonda')
-        substr = Substr(Upper('name'), StrIndex('name', V('h')), 5, output_field=CharField())
+        substr = Substr(Upper('name'), StrIndex('name', V('h')), 5)
         authors = Author.objects.annotate(name_part=substr)
         self.assertQuerysetEqual(
             authors.order_by('name'), ['HN SM', 'HONDA'],