feat: add codemod to add a length parameter to get_random_string()

django_codemod/visitors/__init__.py

@@ -1,5 +1,6 @@
 from .admin import InlineHasAddPermissionsTransformer
 from .core import URLResolversTransformer
+from .crypto import GetRandomStringTransformer
 from .decorators import AvailableAttrsTransformer, ContextDecoratorTransformer
 from .encoding import (
     ForceTextTransformer,
@@ -46,6 +47,7 @@
     "FloatRangeFormFieldTransformer",
     "FloatRangeModelFieldTransformer",
     "ForceTextTransformer",
+    "GetRandomStringTransformer",
     "HttpRequestXReadLinesTransformer",
     "HttpUrlQuotePlusTransformer",
     "HttpUrlQuoteTransformer",

django_codemod/visitors/crypto.py

@@ -0,0 +1,36 @@
+from typing import Sequence
+
+from libcst import Arg, Call, Integer
+
+from django_codemod.constants import DJANGO_3_1, DJANGO_4_0
+from django_codemod.utils.calls import find_keyword_arg
+from django_codemod.visitors.base import BaseFuncRenameTransformer
+
+
+class GetRandomStringTransformer(BaseFuncRenameTransformer):
+    """Update lengthless uses of get_random_string()"""
+
+    deprecated_in = DJANGO_3_1
+    removed_in = DJANGO_4_0
+    rename_from = "django.utils.crypto.get_random_string"
+    rename_to = "django.utils.crypto.get_random_string"
+
+    # The default value Django specifies is 12.
+    default_length_value = Integer("12")
+
+    def update_call_args(self, node: Call) -> Sequence[Arg]:
+        # No args? Just add the default 12.
+        if not node.args:
+            return [Arg(value=self.default_length_value)]
+
+        # If there's only an allowed chars kwarg, prepend the length arg.
+        allowed_chars_kwarg = find_keyword_arg(node.args, "allowed_chars")
+
+        if len(node.args) == 1 and allowed_chars_kwarg:
+            return [
+                Arg(value=self.default_length_value),
+                allowed_chars_kwarg,
+            ]
+
+        # Otherwise don't do anything.
+        return node.args

tests/visitors/test_crypto.py

@@ -0,0 +1,87 @@
+from django_codemod.visitors.crypto import GetRandomStringTransformer
+from tests.visitors.base import BaseVisitorTest
+
+
+class TestGetRandomStringTransformer(BaseVisitorTest):
+
+    transformer = GetRandomStringTransformer
+
+    def test_noop_1(self) -> None:
+        """Test when nothing should change."""
+        before = """
+        from django.utils.crypto import get_random_string
+
+        get_random_string(16)
+        """
+
+        after = """
+        from django.utils.crypto import get_random_string
+
+        get_random_string(16)
+        """
+
+        self.assertCodemod(before, after)
+
+    def test_noop_2(self) -> None:
+        """Test when nothing should change."""
+        before = """
+        from django.utils.crypto import get_random_string
+
+        get_random_string(16, allowed_chars="abc")
+        """
+
+        after = """
+        from django.utils.crypto import get_random_string
+
+        get_random_string(16, allowed_chars="abc")
+        """
+
+        self.assertCodemod(before, after)
+
+    def test_noop_3(self) -> None:
+        """Test when nothing should change."""
+        before = """
+        from django.utils.crypto import get_random_string
+
+        get_random_string(length=16, allowed_chars="abc")
+        """
+
+        after = """
+        from django.utils.crypto import get_random_string
+
+        get_random_string(length=16, allowed_chars="abc")
+        """
+
+        self.assertCodemod(before, after)
+
+    def test_simple_substitution(self) -> None:
+        """Test adding the length parameter."""
+        before = """
+        from django.utils.crypto import get_random_string
+
+        get_random_string()
+        """
+
+        after = """
+        from django.utils.crypto import get_random_string
+
+        get_random_string(12)
+        """
+
+        self.assertCodemod(before, after)
+
+    def test_allowed_chars_present(self) -> None:
+        """Test adding the length parameter when allowed_chars is present."""
+        before = """
+        from django.utils.crypto import get_random_string
+
+        get_random_string(allowed_chars="abc")
+        """
+
+        after = """
+        from django.utils.crypto import get_random_string
+
+        get_random_string(12, allowed_chars="abc")
+        """
+
+        self.assertCodemod(before, after)