Auto merge of #18179 - davidcl:master, r=jdm

Automatically verify that derive() lists are alphabetically ordered #…

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Automatically verify that derive() lists are alphabetically ordered #18172

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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 #18172 (github issue number if applicable).

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- [X] There are tests for these changes OR
- [ ] These changes do not require tests because _____

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3 files changed, 15 insertions, 0 deletions

diff --git a/python/tidy/servo_tidy/tidy.py b/python/tidy/servo_tidy/tidy.py
index 89e6cef1296..c3c76edbb5f 100644
--- a/python/tidy/servo_tidy/tidy.py
+++ b/python/tidy/servo_tidy/tidy.py
@@ -692,6 +692,19 @@ def check_rust(file_name, lines):
             # we now erase previous entries
             prev_mod = {}
 
+        # derivable traits should be alphabetically ordered
+        if is_attribute:
+            # match the derivable traits filtering out macro expansions
+            match = re.search(r"#\[derive\(([a-zA-Z, ]*)", line)
+            if match:
+                derives = map(lambda w: w.strip(), match.group(1).split(','))
+                # sort, compare and report
+                sorted_derives = sorted(derives)
+                if sorted_derives != derives:
+                    yield(idx + 1, decl_message.format("derivable traits list")
+                              + decl_expected.format(", ".join(sorted_derives))
+                              + decl_found.format(", ".join(derives)))
+
 
 # Avoid flagging <Item=Foo> constructs
 def is_associated_type(match, line):
diff --git a/python/tidy/servo_tidy_tests/rust_tidy.rs b/python/tidy/servo_tidy_tests/rust_tidy.rs
index bed4664a279..c1be1695156 100644
--- a/python/tidy/servo_tidy_tests/rust_tidy.rs
+++ b/python/tidy/servo_tidy_tests/rust_tidy.rs
@@ -21,6 +21,7 @@ extern crate webrender_api;
 extern crate style_traits;
 
 #[foo = "bar,baz"]
+#[derive(Copy,Debug, ComputeSquaredDistance)]
 impl test {
 
     fn test_fun(y:f32)->f32{
diff --git a/python/tidy/servo_tidy_tests/test_tidy.py b/python/tidy/servo_tidy_tests/test_tidy.py
index df8bf316cd0..73a37cd4612 100644
--- a/python/tidy/servo_tidy_tests/test_tidy.py
+++ b/python/tidy/servo_tidy_tests/test_tidy.py
@@ -107,6 +107,7 @@ class CheckTidiness(unittest.TestCase):
         self.assertTrue('mod declaration is not in alphabetical order' in errors.next()[2])
         self.assertEqual('mod declaration spans multiple lines', errors.next()[2])
         self.assertTrue('extern crate declaration is not in alphabetical order' in errors.next()[2])
+        self.assertTrue('derivable traits list is not in alphabetical order' in errors.next()[2])
         self.assertEqual('found an empty line following a {', errors.next()[2])
         self.assertEqual('missing space before ->', errors.next()[2])
         self.assertEqual('missing space after ->', errors.next()[2])