Add tests for go-to-definition on relative import module names

Summary:
Go-to-definition on the module name part of a relative import (e.g., clicking
on `bar` in `from .bar import value`) returns empty results because
`find_definition` does not resolve relative imports via `new_maybe_relative`.

This adds two LSP interaction tests that reproduce the bug with a nested config
layout (pyrefly.toml at both root and src/), and a unit test for relative import
resolution. The tests currently assert the broken behavior (empty response).

Reviewed By: yangdanny97

Differential Revision: D95303805

fbshipit-source-id: f0bea8f64e76996440bf77bb9f1cf106bab11c3a

Author: kinto0

pyrefly/lib/test/imports.rs

@@ -1272,3 +1272,20 @@ assert_type(x, int)
 assert_type(y, str)
 "#,
 );
+
+fn env_relative_import_in_subdirectory() -> TestEnv {
+    let mut t = TestEnv::new();
+    t.add_with_path("test.foo", "test/foo.py", "from .foo2 import bar");
+    t.add_with_path("test.foo2", "test/foo2.py", "bar: int = 100");
+    t
+}
+
+testcase!(
+    test_relative_import_in_subdirectory,
+    env_relative_import_in_subdirectory(),
+    r#"
+from typing import assert_type
+from test.foo import bar
+assert_type(bar, int)
+"#,
+);

pyrefly/lib/test/lsp/lsp_interaction/definition.rs

@@ -11,6 +11,7 @@ use lsp_server::RequestId;
 use lsp_types::GotoDefinitionResponse;
 use lsp_types::Location;
 use lsp_types::Url;
+use pyrefly::commands::lsp::IndexingMode;
 use pyrefly::lsp::non_wasm::protocol::Message;
 use pyrefly::lsp::non_wasm::protocol::Request;
 use serde_json::json;
@@ -652,3 +653,63 @@ fn test_goto_def_dunder_all_submodule() {
         .unwrap();
     interaction.shutdown().unwrap();
 }
+
+/// Go-to-definition on the module name part of a relative import
+/// (e.g., clicking on `bar` in `from .bar import value`) does not resolve
+/// because `find_definition` does not resolve relative imports.
+#[test]
+fn definition_relative_import_with_nested_config() {
+    let root = get_test_files_root();
+    let root_path = root
+        .path()
+        .join("nested_config_relative_import/src")
+        .to_path_buf();
+    let scope_uri = Url::from_file_path(&root_path).unwrap();
+    let mut interaction = LspInteraction::new_with_indexing_mode(IndexingMode::LazyBlocking);
+    interaction.set_root(root_path);
+    interaction
+        .initialize(InitializeSettings {
+            workspace_folders: Some(vec![("test".to_owned(), scope_uri)]),
+            ..Default::default()
+        })
+        .unwrap();
+    interaction.client.did_open("main.py");
+    interaction.client.did_open("pkg/foo.py");
+    // Go-to-definition on `bar` module in `from .bar import value` (line 5, char 6)
+    // BUG: returns null because find_definition doesn't resolve relative imports.
+    interaction
+        .client
+        .definition("pkg/foo.py", 5, 6)
+        .expect_response(json!([]))
+        .unwrap();
+    interaction.shutdown().unwrap();
+}
+
+/// Same as above but with workspace root above src/.
+#[test]
+fn definition_relative_import_with_nested_config_workspace_at_root() {
+    let root = get_test_files_root();
+    let root_path = root
+        .path()
+        .join("nested_config_relative_import")
+        .to_path_buf();
+    let scope_uri = Url::from_file_path(&root_path).unwrap();
+    let mut interaction = LspInteraction::new_with_indexing_mode(IndexingMode::LazyBlocking);
+    interaction.set_root(root_path);
+    interaction
+        .initialize(InitializeSettings {
+            workspace_folders: Some(vec![("test".to_owned(), scope_uri)]),
+            ..Default::default()
+        })
+        .unwrap();
+    interaction.client.did_open("src/main.py");
+    interaction.client.did_open("src/pkg/foo.py");
+    // Go-to-definition on `bar` module in `from .bar import value` (line 5, char 6)
+    // BUG: returns empty because find_definition doesn't resolve relative imports.
+    interaction
+        .client
+        .definition("src/pkg/foo.py", 5, 6)
+        .expect_response(json!([]))
+        .unwrap();
+    interaction.shutdown().unwrap();
+}

pyrefly/lib/test/lsp/lsp_interaction/test_files/nested_config_relative_import/pyrefly.toml

@@ -0,0 +1 @@
+project_includes = ["src"]

pyrefly/lib/test/lsp/lsp_interaction/test_files/nested_config_relative_import/src/main.py

@@ -0,0 +1,6 @@
+# Copyright (c) Meta Platforms, Inc. and affiliates.
+#
+# This source code is licensed under the MIT license found in the
+# LICENSE file in the root directory of this source tree.
+
+from pkg.foo import value

pyrefly/lib/test/lsp/lsp_interaction/test_files/nested_config_relative_import/src/pkg/bar.py

@@ -0,0 +1,6 @@
+# Copyright (c) Meta Platforms, Inc. and affiliates.
+#
+# This source code is licensed under the MIT license found in the
+# LICENSE file in the root directory of this source tree.
+
+value: int = 42

pyrefly/lib/test/lsp/lsp_interaction/test_files/nested_config_relative_import/src/pkg/foo.py

@@ -0,0 +1,6 @@
+# Copyright (c) Meta Platforms, Inc. and affiliates.
+#
+# This source code is licensed under the MIT license found in the
+# LICENSE file in the root directory of this source tree.
+
+from .bar import value

pyrefly/lib/test/lsp/lsp_interaction/test_files/nested_config_relative_import/src/pyrefly.toml

@@ -0,0 +1 @@
+project_includes = ["."]