Auto merge of #15649 - zimio:issue-15591-rewrite-ban-type-lint, r=Wafflespeanut

Rewrite the ban-type lint in Python

<!-- Please describe your changes on the following line: -->
Rewrite the ban-type lint in Python.

Question: Should the old ban-type lint written in rust be deleted?

---
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- [x ] `./mach build -d` does not report any errors
- [x ] `./mach test-tidy` does not report any errors
- [x ] These changes fix #15591

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- [ x] There are tests for these changes

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python/tidy/servo_tidy/tidy.py

@@ -549,6 +549,12 @@ def check_rust(file_name, lines):
             (r": &Vec<", "use &[T] instead of &Vec<T>", no_filter),
             # No benefit over using &str
             (r": &String", "use &str instead of &String", no_filter),
+            # There should be any use of banned types:
+            # Cell<JSVal>, Cell<JS<T>>, DOMRefCell<JS<T>>, DOMRefCell<HEAP<T>>
+            (r"(\s|:)+Cell<JSVal>", "Banned type Cell<JSVal> detected. Use MutJS<JSVal> instead", no_filter),
+            (r"(\s|:)+Cell<JS<.+>>", "Banned type Cell<JS<T>> detected. Use MutJS<JS<T>> instead", no_filter),
+            (r"DOMRefCell<JS<.+>>", "Banned type DOMRefCell<JS<T>> detected. Use MutJS<JS<T>> instead", no_filter),
+            (r"DOMRefCell<Heap<.+>>", "Banned type DOMRefCell<Heap<T>> detected. Use MutJS<JS<T>> instead", no_filter),
             # No benefit to using &Root<T>
             (r": &Root<", "use &T instead of &Root<T>", no_filter),
             (r"^&&", "operators should go at the end of the first line", no_filter),

python/tidy/servo_tidy_tests/ban-domrefcell.rs

@@ -0,0 +1,19 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#![feature(plugin)]
+#![plugin(script_plugins)]
+
+extern crate script;
+
+use script::test::DOMRefCell;
+use script::test::JS;
+use script::test::Node;
+
+struct Foo {
+    bar: DOMRefCell<JS<Node>>
+    //~^ ERROR Banned type DOMRefCell<JS<T>> detected. Use MutJS<JS<T>> instead
+}
+
+fn main() {}

python/tidy/servo_tidy_tests/ban.rs

@@ -0,0 +1,21 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#![feature(plugin)]
+#![plugin(script_plugins)]
+
+extern crate js;
+
+use js::jsval::JSVal;
+use std::cell::Cell;
+use std::cell::UnsafeCell;
+
+struct Foo {
+    bar: Cell<JSVal>,
+    //~^ ERROR Banned type Cell<JSVal> detected. Use MutJS<JSVal> instead
+    foo: UnsafeCell<JSVal>
+    //~^ NOT AN ERROR
+}
+
+fn main() {}

python/tidy/servo_tidy_tests/test_tidy.py

@@ -140,6 +140,14 @@ class CheckTidiness(unittest.TestCase):
         self.assertTrue('feature attribute is not in alphabetical order' in feature_errors.next()[2])
         self.assertNoMoreErrors(feature_errors)
 
+        ban_errors = tidy.collect_errors_for_files(iterFile('ban.rs'), [], [tidy.check_rust], print_text=False)
+        self.assertEqual('Banned type Cell<JSVal> detected. Use MutJS<JSVal> instead', ban_errors.next()[2])
+        self.assertNoMoreErrors(ban_errors)
+
+        ban_errors = tidy.collect_errors_for_files(iterFile('ban-domrefcell.rs'), [], [tidy.check_rust], print_text=False)
+        self.assertEqual('Banned type DOMRefCell<JS<T>> detected. Use MutJS<JS<T>> instead', ban_errors.next()[2])
+        self.assertNoMoreErrors(ban_errors)
+
     def test_spec_link(self):
         tidy.SPEC_BASE_PATH = base_path
         errors = tidy.collect_errors_for_files(iterFile('speclink.rs'), [], [tidy.check_spec], print_text=False)