[flake8-django]: Implement rule DJ012 (#3659)

crates/ruff/resources/test/fixtures/flake8_django/DJ012.py

@@ -0,0 +1,113 @@
+from django.db import models
+from django.db.models import Model
+
+
+class StrBeforeRandomField(models.Model):
+    """Model with `__str__` before a random property."""
+
+    class Meta:
+        verbose_name = "test"
+        verbose_name_plural = "tests"
+
+    def __str__(self):
+        return ""
+
+    random_property = "foo"
+
+
+class StrBeforeFieldModel(models.Model):
+    """Model with `__str__` before fields."""
+
+    class Meta:
+        verbose_name = "test"
+        verbose_name_plural = "tests"
+
+    def __str__(self):
+        return "foobar"
+
+    first_name = models.CharField(max_length=32)
+
+
+class ManagerBeforeField(models.Model):
+    """Model with manager before fields."""
+
+    objects = "manager"
+
+    class Meta:
+        verbose_name = "test"
+        verbose_name_plural = "tests"
+
+    def __str__(self):
+        return "foobar"
+
+    first_name = models.CharField(max_length=32)
+
+
+class CustomMethodBeforeStr(models.Model):
+    """Model with a custom method before `__str__`."""
+
+    class Meta:
+        verbose_name = "test"
+        verbose_name_plural = "tests"
+
+    def my_method(self):
+        pass
+
+    def __str__(self):
+        return "foobar"
+
+
+class GetAbsoluteUrlBeforeSave(Model):
+    """Model with `get_absolute_url` method before `save` method.
+
+    Subclass this directly using the `Model` class.
+    """
+
+    def get_absolute_url(self):
+        pass
+
+    def save(self):
+        pass
+
+
+class ConstantsAreNotFields(models.Model):
+    """Model with an assignment to a constant after `__str__`."""
+
+    first_name = models.CharField(max_length=32)
+
+    class Meta:
+        verbose_name = "test"
+        verbose_name_plural = "tests"
+
+    def __str__(self):
+        pass
+
+    MY_CONSTANT = id(1)
+
+
+class PerfectlyFine(models.Model):
+    """Model which has everything in perfect order."""
+
+    first_name = models.CharField(max_length=32)
+    last_name = models.CharField(max_length=32)
+    objects = "manager"
+
+    class Meta:
+        verbose_name = "test"
+        verbose_name_plural = "tests"
+
+    def __str__(self):
+        return "Perfectly fine!"
+
+    def save(self, **kwargs):
+        super(PerfectlyFine, self).save(**kwargs)
+
+    def get_absolute_url(self):
+        return "http://%s" % self
+
+    def my_method(self):
+        pass
+
+    @property
+    def random_property(self):
+        return "%s" % self

crates/ruff/src/checkers/ast/mod.rs

@@ -708,6 +708,13 @@ where
                         self.diagnostics.push(diagnostic);
                     }
                 }
+                if self
+                    .settings
+                    .rules
+                    .enabled(Rule::DjangoUnorderedBodyContentInModel)
+                {
+                    flake8_django::rules::unordered_body_content_in_model(self, bases, body);
+                }
                 if self.settings.rules.enabled(Rule::GlobalStatement) {
                     pylint::rules::global_statement(self, name);
                 }

crates/ruff/src/codes.rs

@@ -699,6 +699,7 @@ pub fn code_to_rule(linter: Linter, code: &str) -> Option<Rule> {
         (Flake8Django, "006") => Rule::DjangoExcludeWithModelForm,
         (Flake8Django, "007") => Rule::DjangoAllWithModelForm,
         (Flake8Django, "008") => Rule::DjangoModelWithoutDunderStr,
+        (Flake8Django, "012") => Rule::DjangoUnorderedBodyContentInModel,
         (Flake8Django, "013") => Rule::DjangoNonLeadingReceiverDecorator,
 
         _ => return None,

crates/ruff/src/registry.rs

@@ -642,6 +642,7 @@ ruff_macros::register_rules!(
     rules::flake8_django::rules::DjangoExcludeWithModelForm,
     rules::flake8_django::rules::DjangoAllWithModelForm,
     rules::flake8_django::rules::DjangoModelWithoutDunderStr,
+    rules::flake8_django::rules::DjangoUnorderedBodyContentInModel,
     rules::flake8_django::rules::DjangoNonLeadingReceiverDecorator,
 );
 

crates/ruff/src/rules/flake8_django/mod.rs

@@ -18,6 +18,7 @@ mod tests {
     #[test_case(Rule::DjangoExcludeWithModelForm, Path::new("DJ006.py"); "DJ006")]
     #[test_case(Rule::DjangoAllWithModelForm, Path::new("DJ007.py"); "DJ007")]
     #[test_case(Rule::DjangoModelWithoutDunderStr, Path::new("DJ008.py"); "DJ008")]
+    #[test_case(Rule::DjangoUnorderedBodyContentInModel, Path::new("DJ012.py"); "DJ012")]
     #[test_case(Rule::DjangoNonLeadingReceiverDecorator, Path::new("DJ013.py"); "DJ013")]
     fn rules(rule_code: Rule, path: &Path) -> Result<()> {
         let snapshot = format!("{}_{}", rule_code.noqa_code(), path.to_string_lossy());

crates/ruff/src/rules/flake8_django/rules/all_with_model_form.rs

@@ -49,7 +49,7 @@ impl Violation for DjangoAllWithModelForm {
 
 /// DJ007
 pub fn all_with_model_form(checker: &Checker, bases: &[Expr], body: &[Stmt]) -> Option<Diagnostic> {
-    if !bases.iter().any(|base| is_model_form(checker, base)) {
+    if !bases.iter().any(|base| is_model_form(&checker.ctx, base)) {
         return None;
     }
     for element in body.iter() {

crates/ruff/src/rules/flake8_django/rules/exclude_with_model_form.rs

@@ -49,7 +49,7 @@ pub fn exclude_with_model_form(
     bases: &[Expr],
     body: &[Stmt],
 ) -> Option<Diagnostic> {
-    if !bases.iter().any(|base| is_model_form(checker, base)) {
+    if !bases.iter().any(|base| is_model_form(&checker.ctx, base)) {
         return None;
     }
     for element in body.iter() {

crates/ruff/src/rules/flake8_django/rules/helpers.rs

@@ -1,31 +1,33 @@
+use ruff_python_ast::context::Context;
 use rustpython_parser::ast::Expr;
 
-use crate::checkers::ast::Checker;
-
 /// Return `true` if a Python class appears to be a Django model, based on its base classes.
-pub fn is_model(checker: &Checker, base: &Expr) -> bool {
-    checker
-        .ctx
-        .resolve_call_path(base)
-        .map_or(false, |call_path| {
-            call_path.as_slice() == ["django", "db", "models", "Model"]
-        })
+pub fn is_model(context: &Context, base: &Expr) -> bool {
+    context.resolve_call_path(base).map_or(false, |call_path| {
+        call_path.as_slice() == ["django", "db", "models", "Model"]
+    })
 }
 
 /// Return `true` if a Python class appears to be a Django model form, based on its base classes.
-pub fn is_model_form(checker: &Checker, base: &Expr) -> bool {
-    checker
-        .ctx
-        .resolve_call_path(base)
-        .map_or(false, |call_path| {
-            call_path.as_slice() == ["django", "forms", "ModelForm"]
-                || call_path.as_slice() == ["django", "forms", "models", "ModelForm"]
-        })
+pub fn is_model_form(context: &Context, base: &Expr) -> bool {
+    context.resolve_call_path(base).map_or(false, |call_path| {
+        call_path.as_slice() == ["django", "forms", "ModelForm"]
+            || call_path.as_slice() == ["django", "forms", "models", "ModelForm"]
+    })
+}
+
+/// Return `true` if the expression is constructor for a Django model field.
+pub fn is_model_field(context: &Context, expr: &Expr) -> bool {
+    context.resolve_call_path(expr).map_or(false, |call_path| {
+        call_path
+            .as_slice()
+            .starts_with(&["django", "db", "models"])
+    })
 }
 
 /// Return the name of the field type, if the expression is constructor for a Django model field.
-pub fn get_model_field_name<'a>(checker: &'a Checker, expr: &'a Expr) -> Option<&'a str> {
-    checker.ctx.resolve_call_path(expr).and_then(|call_path| {
+pub fn get_model_field_name<'a>(context: &'a Context, expr: &'a Expr) -> Option<&'a str> {
+    context.resolve_call_path(expr).and_then(|call_path| {
         let call_path = call_path.as_slice();
         if !call_path.starts_with(&["django", "db", "models"]) {
             return None;

crates/ruff/src/rules/flake8_django/rules/mod.rs

@@ -8,6 +8,9 @@ pub use non_leading_receiver_decorator::{
 pub use nullable_model_string_field::{
     nullable_model_string_field, DjangoNullableModelStringField,
 };
+pub use unordered_body_content_in_model::{
+    unordered_body_content_in_model, DjangoUnorderedBodyContentInModel,
+};
 
 mod all_with_model_form;
 mod exclude_with_model_form;
@@ -16,3 +19,4 @@ mod locals_in_render_function;
 mod model_without_dunder_str;
 mod non_leading_receiver_decorator;
 mod nullable_model_string_field;
+mod unordered_body_content_in_model;

crates/ruff/src/rules/flake8_django/rules/model_without_dunder_str.rs

@@ -86,7 +86,7 @@ fn checker_applies(checker: &Checker, bases: &[Expr], body: &[Stmt]) -> bool {
         if is_model_abstract(body) {
             continue;
         }
-        if helpers::is_model(checker, base) {
+        if helpers::is_model(&checker.ctx, base) {
             return true;
         }
     }

crates/ruff/src/rules/flake8_django/rules/nullable_model_string_field.rs

@@ -85,7 +85,7 @@ fn is_nullable_field<'a>(checker: &'a Checker, value: &'a Expr) -> Option<&'a st
         return None;
     };
 
-    let Some(valid_field_name) = helpers::get_model_field_name(checker, func) else {
+    let Some(valid_field_name) = helpers::get_model_field_name(&checker.ctx, func) else {
         return None;
     };