[ty] Add a test capturing sub-optimal auto-import heuristic

Specifically, here, we'd probably like to add `TypedDict` to
the existing `from typing import ...` statement instead of
using the fully qualified `typing.TypedDict` form.

To test this, we add another snapshot mode for including imports
that a completion will insert when selected.

Ref https://github.com/astral-sh/ty/issues/1274#issuecomment-3352233790

crates/ty_ide/src/completion.rs

@@ -6613,6 +6613,27 @@ def f(zqzqzq: str):
         );
     }
 
+    #[test]
+    fn auto_import_prioritizes_reusing_import_from_statements() {
+        let builder = completion_test_builder(
+            "\
+import typing
+from typing import Callable
+TypedDi<CURSOR>
+",
+        );
+        assert_snapshot!(
+            builder.imports().build().snapshot(),
+            @r"
+        typing.TypedDict :: <no import edit>
+        typing.is_typeddict :: <no import edit>
+        _FilterConfigurationTypedDict :: from logging.config import _FilterConfigurationTypedDict
+
+        _FormatterConfigurationTypedDict :: from logging.config import _FormatterConfigurationTypedDict
+        ",
+        );
+    }
+
     /// A way to create a simple single-file (named `main.py`) completion test
     /// builder.
     ///
@@ -6638,6 +6659,7 @@ def f(zqzqzq: str):
         skip_builtins: bool,
         skip_keywords: bool,
         type_signatures: bool,
+        imports: bool,
         module_names: bool,
         // This doesn't seem like a "very complex" type to me... ---AG
         #[allow(clippy::type_complexity)]
@@ -6670,6 +6692,7 @@ def f(zqzqzq: str):
                 original,
                 filtered,
                 type_signatures: self.type_signatures,
+                imports: self.imports,
                 module_names: self.module_names,
             }
         }
@@ -6730,6 +6753,15 @@ def f(zqzqzq: str):
             self
         }
 
+        /// When set, include the import associated with the
+        /// completion.
+        ///
+        /// Not enabled by default.
+        fn imports(mut self) -> CompletionTestBuilder {
+            self.imports = true;
+            self
+        }
+
         /// When set, the module name for each symbol is included
         /// in the snapshot (if available).
         fn module_names(mut self) -> CompletionTestBuilder {
@@ -6762,6 +6794,9 @@ def f(zqzqzq: str):
         /// Whether type signatures should be included in the snapshot
         /// generated by `CompletionTest::snapshot`.
         type_signatures: bool,
+        /// Whether to show the import that will be inserted when this
+        /// completion is selected.
+        imports: bool,
         /// Whether module names should be included in the snapshot
         /// generated by `CompletionTest::snapshot`.
         module_names: bool,
@@ -6797,6 +6832,17 @@ def f(zqzqzq: str):
                             .unwrap_or("<no import required>");
                         snapshot = format!("{snapshot} :: {module_name}");
                     }
+                    if self.imports {
+                        if let Some(ref edit) = c.import {
+                            if let Some(import) = edit.content() {
+                                snapshot = format!("{snapshot} :: {import}");
+                            } else {
+                                snapshot = format!("{snapshot} :: <import deletion>");
+                            }
+                        } else {
+                            snapshot = format!("{snapshot} :: <no import edit>");
+                        }
+                    }
                     snapshot
                 })
                 .collect::<Vec<String>>()
@@ -6845,6 +6891,7 @@ def f(zqzqzq: str):
                 skip_builtins: false,
                 skip_keywords: false,
                 type_signatures: false,
+                imports: false,
                 module_names: false,
                 predicate: None,
             }