Fixed #14094 -- Added support for unlimited CharField on PostgreSQL.

Co-authored-by: Mariusz Felisiak <felisiak.mariusz@gmail.com>

django/core/management/commands/inspectdb.py

@@ -339,7 +339,8 @@ class Command(BaseCommand):
 
         # Add max_length for all CharFields.
         if field_type == "CharField" and row.display_size:
-            field_params["max_length"] = int(row.display_size)
+            if (size := int(row.display_size)) and size > 0:
+                field_params["max_length"] = size
 
         if field_type in {"CharField", "TextField"} and row.collation:
             field_params["db_collation"] = row.collation

django/db/backends/base/features.py

@@ -345,6 +345,9 @@ class BaseDatabaseFeatures:
     # Set to (exception, message) if null characters in text are disallowed.
     prohibits_null_characters_in_text_exception = None
 
+    # Does the backend support unlimited character columns?
+    supports_unlimited_charfield = False
+
     # Collation names for use by the Django test suite.
     test_collations = {
         "ci": None,  # Case-insensitive.

django/db/backends/postgresql/base.py

@@ -80,6 +80,12 @@ from .operations import DatabaseOperations  # NOQA isort:skip
 from .schema import DatabaseSchemaEditor  # NOQA isort:skip
 
 
+def _get_varchar_column(data):
+    if data["max_length"] is None:
+        return "varchar"
+    return "varchar(%(max_length)s)" % data
+
+
 class DatabaseWrapper(BaseDatabaseWrapper):
     vendor = "postgresql"
     display_name = "PostgreSQL"
@@ -92,7 +98,7 @@ class DatabaseWrapper(BaseDatabaseWrapper):
         "BigAutoField": "bigint",
         "BinaryField": "bytea",
         "BooleanField": "boolean",
-        "CharField": "varchar(%(max_length)s)",
+        "CharField": _get_varchar_column,
         "DateField": "date",
         "DateTimeField": "timestamp with time zone",
         "DecimalField": "numeric(%(max_digits)s, %(decimal_places)s)",

django/db/backends/postgresql/features.py

@@ -110,3 +110,4 @@ class DatabaseFeatures(BaseDatabaseFeatures):
 
     has_bit_xor = property(operator.attrgetter("is_postgresql_14"))
     supports_covering_spgist_indexes = property(operator.attrgetter("is_postgresql_14"))
+    supports_unlimited_charfield = True

django/db/models/fields/__init__.py

@@ -817,9 +817,14 @@ class Field(RegisterLookupMixin):
         # exactly which wacky database column type you want to use.
         data = self.db_type_parameters(connection)
         try:
-            return connection.data_types[self.get_internal_type()] % data
+            column_type = connection.data_types[self.get_internal_type()]
         except KeyError:
             return None
+        else:
+            # column_type is either a single-parameter function or a string.
+            if callable(column_type):
+                return column_type(data)
+            return column_type % data
 
     def rel_db_type(self, connection):
         """
@@ -1130,14 +1135,19 @@ class BooleanField(Field):
 
 
 class CharField(Field):
-    description = _("String (up to %(max_length)s)")
-
     def __init__(self, *args, db_collation=None, **kwargs):
         super().__init__(*args, **kwargs)
         self.db_collation = db_collation
         if self.max_length is not None:
             self.validators.append(validators.MaxLengthValidator(self.max_length))
 
+    @property
+    def description(self):
+        if self.max_length is not None:
+            return _("String (up to %(max_length)s)")
+        else:
+            return _("String (unlimited)")
+
     def check(self, **kwargs):
         databases = kwargs.get("databases") or []
         return [
@@ -1148,6 +1158,12 @@ class CharField(Field):
 
     def _check_max_length_attribute(self, **kwargs):
         if self.max_length is None:
+            if (
+                connection.features.supports_unlimited_charfield
+                or "supports_unlimited_charfield"
+                in self.model._meta.required_db_features
+            ):
+                return []
             return [
                 checks.Error(
                     "CharFields must define a 'max_length' attribute.",