[ty] Make auto-import ignore symbols in modules starting with a `_`

This applies recursively. So if *any* component of a module name starts
with a `_`, then symbols from that module are excluded from auto-import.

The exception is when it's a module within first party code. Then we
want to include it in auto-import.

crates/ty_ide/src/all_symbols.rs

@@ -36,6 +36,20 @@ pub fn all_symbols<'db>(
                 let Some(file) = module.file(&*db) else {
                     continue;
                 };
+                // By convention, modules starting with an underscore
+                // are generally considered unexported. However, we
+                // should consider first party modules fair game.
+                //
+                // Note that we apply this recursively. e.g.,
+                // `numpy._core.multiarray` is considered private
+                // because it's a child of `_core`.
+                if module.name(&*db).components().any(|c| c.starts_with('_'))
+                    && module
+                        .search_path(&*db)
+                        .is_none_or(|sp| !sp.is_first_party())
+                {
+                    continue;
+                }
                 // TODO: also make it available in `TYPE_CHECKING` blocks
                 // (we'd need https://github.com/astral-sh/ty/issues/1553 to do this well)
                 if !is_typing_extensions_available && module.name(&*db) == &typing_extensions {

crates/ty_ide/src/completion.rs

@@ -5979,6 +5979,94 @@ ZQ<CURSOR>
         ");
     }
 
+    // This test confirms current behavior (as of 2025-12-04), but
+    // it's not consistent with auto-import. That is, it doesn't
+    // strictly respect `__all__` on `bar`, but perhaps it should.
+    //
+    // See: https://github.com/astral-sh/ty/issues/1757
+    #[test]
+    fn object_attr_ignores_all() {
+        let snapshot = CursorTest::builder()
+            .source(
+                "main.py",
+                r#"
+import bar
+bar.ZQ<CURSOR>
+"#,
+            )
+            .source(
+                "bar.py",
+                r#"
+                ZQZQ1 = 1
+                ZQZQ2 = 1
+                __all__ = ['ZQZQ1']
+            "#,
+            )
+            .completion_test_builder()
+            .auto_import()
+            .module_names()
+            .build()
+            .snapshot();
+        // We specifically do not want `ZQZQ2` here, since
+        // it is not part of `__all__`.
+        assert_snapshot!(snapshot, @r"
+        ZQZQ1 :: <no import required>
+        ZQZQ2 :: <no import required>
+        ");
+    }
+
+    #[test]
+    fn auto_import_ignores_modules_with_leading_underscore() {
+        let snapshot = CursorTest::builder()
+            .source(
+                "main.py",
+                r#"
+Quitter<CURSOR>
+"#,
+            )
+            .completion_test_builder()
+            .auto_import()
+            .module_names()
+            .build()
+            .snapshot();
+        // There is a `Quitter` in `_sitebuiltins` in the standard
+        // library. But this is skipped by auto-import because it's
+        // 1) not first party and 2) starts with an `_`.
+        assert_snapshot!(snapshot, @"<No completions found>");
+    }
+
+    #[test]
+    fn auto_import_includes_modules_with_leading_underscore_in_first_party() {
+        let snapshot = CursorTest::builder()
+            .source(
+                "main.py",
+                r#"
+ZQ<CURSOR>
+"#,
+            )
+            .source(
+                "bar.py",
+                r#"
+                ZQZQ1 = 1
+            "#,
+            )
+            .source(
+                "_foo.py",
+                r#"
+                ZQZQ1 = 1
+            "#,
+            )
+            .completion_test_builder()
+            .auto_import()
+            .module_names()
+            .build()
+            .snapshot();
+        assert_snapshot!(snapshot, @r"
+        ZQZQ1 :: _foo
+        ZQZQ1 :: bar
+        ");
+    }
+
     /// A way to create a simple single-file (named `main.py`) completion test
     /// builder.
     ///

crates/ty_python_semantic/src/module_resolver/path.rs

@@ -594,7 +594,7 @@ impl SearchPath {
         )
     }
 
-    pub(crate) fn is_first_party(&self) -> bool {
+    pub fn is_first_party(&self) -> bool {
         matches!(&*self.0, SearchPathInner::FirstParty(_))
     }
 

crates/ty_server/tests/e2e/snapshots/e2e__notebook__auto_import.snap

@@ -6,7 +6,7 @@ expression: completions
   {
     "label": "Literal (import typing)",
     "kind": 6,
-    "sortText": " 58",
+    "sortText": " 35",
     "insertText": "Literal",
     "additionalTextEdits": [
       {
@@ -27,7 +27,7 @@ expression: completions
   {
     "label": "LiteralString (import typing)",
     "kind": 6,
-    "sortText": " 59",
+    "sortText": " 36",
     "insertText": "LiteralString",
     "additionalTextEdits": [
       {

crates/ty_server/tests/e2e/snapshots/e2e__notebook__auto_import_docstring.snap

@@ -6,7 +6,7 @@ expression: completions
   {
     "label": "Literal (import typing)",
     "kind": 6,
-    "sortText": " 58",
+    "sortText": " 35",
     "insertText": "Literal",
     "additionalTextEdits": [
       {
@@ -27,7 +27,7 @@ expression: completions
   {
     "label": "LiteralString (import typing)",
     "kind": 6,
-    "sortText": " 59",
+    "sortText": " 36",
     "insertText": "LiteralString",
     "additionalTextEdits": [
       {

crates/ty_server/tests/e2e/snapshots/e2e__notebook__auto_import_from_future.snap

@@ -6,7 +6,7 @@ expression: completions
   {
     "label": "Literal (import typing)",
     "kind": 6,
-    "sortText": " 58",
+    "sortText": " 35",
     "insertText": "Literal",
     "additionalTextEdits": [
       {
@@ -27,7 +27,7 @@ expression: completions
   {
     "label": "LiteralString (import typing)",
     "kind": 6,
-    "sortText": " 59",
+    "sortText": " 36",
     "insertText": "LiteralString",
     "additionalTextEdits": [
       {

crates/ty_server/tests/e2e/snapshots/e2e__notebook__auto_import_same_cell.snap

@@ -6,7 +6,7 @@ expression: completions
   {
     "label": "Literal (import typing)",
     "kind": 6,
-    "sortText": " 58",
+    "sortText": " 35",
     "insertText": "Literal",
     "additionalTextEdits": [
       {
@@ -27,7 +27,7 @@ expression: completions
   {
     "label": "LiteralString (import typing)",
     "kind": 6,
-    "sortText": " 59",
+    "sortText": " 36",
     "insertText": "LiteralString",
     "additionalTextEdits": [
       {