[ty] Favor in scope completions (#21194)

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## Summary

Resolves https://github.com/astral-sh/ty/issues/1464

We sort the completions before we add the unimported ones, meaning that
imported completions show up before unimported ones.

This is also spoken about in
https://github.com/astral-sh/ty/issues/1274, and this is probably a
duplicate of that.

@AlexWaygood mentions this
[here](https://github.com/astral-sh/ty/issues/1274#issuecomment-3345942698)
too.

## Test Plan

Add a test showing even if an unimported completion "should"
(alphabetically before) come first, we favor the imported one.

crates/ty_completion_eval/completion-evaluation-tasks.csv

@@ -1,5 +1,5 @@
 name,file,index,rank
-auto-import-skips-current-module,main.py,0,4
+auto-import-skips-current-module,main.py,0,1
 fstring-completions,main.py,0,1
 higher-level-symbols-preferred,main.py,0,
 higher-level-symbols-preferred,main.py,1,1
@@ -10,17 +10,17 @@ import-deprioritizes-type_check_only,main.py,1,1
 import-deprioritizes-type_check_only,main.py,2,1
 import-deprioritizes-type_check_only,main.py,3,2
 import-deprioritizes-type_check_only,main.py,4,3
-internal-typeshed-hidden,main.py,0,4
+internal-typeshed-hidden,main.py,0,5
 none-completion,main.py,0,11
 numpy-array,main.py,0,
 numpy-array,main.py,1,1
 object-attr-instance-methods,main.py,0,1
 object-attr-instance-methods,main.py,1,1
 raise-uses-base-exception,main.py,0,2
-scope-existing-over-new-import,main.py,0,474
+scope-existing-over-new-import,main.py,0,13
 scope-prioritize-closer,main.py,0,2
 scope-simple-long-identifier,main.py,0,1
 tstring-completions,main.py,0,1
 ty-extensions-lower-stdlib,main.py,0,8
 type-var-typing-over-ast,main.py,0,3
-type-var-typing-over-ast,main.py,1,270
+type-var-typing-over-ast,main.py,1,277

crates/ty_ide/src/completion.rs

@@ -883,9 +883,16 @@ fn is_in_definition_place(db: &dyn Db, tokens: &[Token], file: File) -> bool {
 /// This has the effect of putting all dunder attributes after "normal"
 /// attributes, and all single-underscore attributes after dunder attributes.
 fn compare_suggestions(c1: &Completion, c2: &Completion) -> Ordering {
-    let (kind1, kind2) = (NameKind::classify(&c1.name), NameKind::classify(&c2.name));
+    fn key<'a>(completion: &'a Completion) -> (bool, NameKind, bool, &'a Name) {
+        (
+            completion.module_name.is_some(),
+            NameKind::classify(&completion.name),
+            completion.is_type_check_only,
+            &completion.name,
+        )
+    }
 
-    (kind1, c1.is_type_check_only, &c1.name).cmp(&(kind2, c2.is_type_check_only, &c2.name))
+    key(c1).cmp(&key(c2))
 }
 
 #[cfg(test)]
@@ -3440,8 +3447,8 @@ from os.<CURSOR>
             .build()
             .snapshot();
         assert_snapshot!(snapshot, @r"
-        AbraKadabra :: Unavailable :: package
         Kadabra :: Literal[1] :: Current module
+        AbraKadabra :: Unavailable :: package
         ");
     }
 
@@ -4168,6 +4175,27 @@ type <CURSOR>
         assert!(!builder.build().completions().is_empty());
     }
 
+    #[test]
+    fn favour_symbols_currently_imported() {
+        let snapshot = CursorTest::builder()
+            .source("main.py", "long_nameb = 1\nlong_name<CURSOR>")
+            .source("foo.py", "def long_namea(): ...")
+            .completion_test_builder()
+            .type_signatures()
+            .auto_import()
+            .module_names()
+            .filter(|c| c.name.contains("long_name"))
+            .build()
+            .snapshot();
+
+        // Even though long_namea is alphabetically before long_nameb,
+        // long_nameb is currently imported and should be preferred.
+        assert_snapshot!(snapshot, @r"
+        long_nameb :: Literal[1] :: Current module
+        long_namea :: Unavailable :: foo
+        ");
+    }
+
     /// A way to create a simple single-file (named `main.py`) completion test
     /// builder.
     ///