From feb683c4c2c5ecfb61e4cb490c3e357450c0c0e8 Mon Sep 17 00:00:00 2001
From: Mariusz Felisiak <felisiak.mariusz@gmail.com>
Date: Wed, 14 Mar 2018 10:00:07 +0100
Subject: [PATCH] Fixed #29155 -- Fixed crash when database functions are used
 with pattern lookups.

Thanks Tim Graham and Sergey Fedoseev for reviews.
---
 django/db/models/lookups.py |  2 +-
 tests/lookup/models.py      |  1 +
 tests/lookup/tests.py       | 17 +++++++++++++++++
 3 files changed, 19 insertions(+), 1 deletion(-)

diff --git a/django/db/models/lookups.py b/django/db/models/lookups.py
index 00eeda1f39..a4c7459bfe 100644
--- a/django/db/models/lookups.py
+++ b/django/db/models/lookups.py
@@ -397,7 +397,7 @@ class PatternLookup(BuiltinLookup):
 
     def process_rhs(self, qn, connection):
         rhs, params = super().process_rhs(qn, connection)
-        if params and not self.bilateral_transforms:
+        if self.rhs_is_direct_value() and params and not self.bilateral_transforms:
             params[0] = self.param_pattern % connection.ops.prep_for_like_query(params[0])
         return rhs, params
 
diff --git a/tests/lookup/models.py b/tests/lookup/models.py
index ef5e7dfb0e..3f1f14dfbc 100644
--- a/tests/lookup/models.py
+++ b/tests/lookup/models.py
@@ -17,6 +17,7 @@ class Alarm(models.Model):
 
 class Author(models.Model):
     name = models.CharField(max_length=100)
+    alias = models.CharField(max_length=50, null=True, blank=True)
 
     class Meta:
         ordering = ('name',)
diff --git a/tests/lookup/tests.py b/tests/lookup/tests.py
index 7d7216777c..785d3ea478 100644
--- a/tests/lookup/tests.py
+++ b/tests/lookup/tests.py
@@ -5,6 +5,7 @@ from operator import attrgetter
 
 from django.core.exceptions import FieldError
 from django.db import connection
+from django.db.models.functions import Substr
 from django.test import TestCase, skipUnlessDBFeature
 
 from .models import Article, Author, Game, Player, Season, Tag
@@ -878,3 +879,19 @@ class LookupTests(TestCase):
         season = Season.objects.create(year=2012, nulled_text_field=None)
         self.assertTrue(Season.objects.filter(pk=season.pk, nulled_text_field__isnull=True))
         self.assertTrue(Season.objects.filter(pk=season.pk, nulled_text_field=''))
+
+    def test_pattern_lookups_with_substr(self):
+        a = Author.objects.create(name='John Smith', alias='Johx')
+        b = Author.objects.create(name='Rhonda Simpson', alias='sonx')
+        tests = (
+            ('startswith', [a]),
+            ('istartswith', [a]),
+            ('contains', [a, b]),
+            ('icontains', [a, b]),
+            ('endswith', [b]),
+            ('iendswith', [b]),
+        )
+        for lookup, result in tests:
+            with self.subTest(lookup=lookup):
+                authors = Author.objects.filter(**{'name__%s' % lookup: Substr('alias', 1, 3)})
+                self.assertCountEqual(authors, result)