fix(lsp): treat files in any Flutter SDK as dependencies

lua/flutter-tools/lsp/init.lua

@@ -164,15 +164,16 @@ function M.restart()
   end
 end
 
+---@param buffer_path string? defaults to the current buffer's path
 ---@return string?
-function M.get_project_root_dir()
+function M.get_project_root_dir(buffer_path)
   local conf = require("flutter-tools.config")
-  local current_buffer_path = path.current_buffer_path()
+  buffer_path = buffer_path or path.current_buffer_path()
   -- Check if path is flutter dependency. For dependencies we do not
   -- search for a root directory as they are not projects.
-  if not path.is_flutter_dependency_path(current_buffer_path) then
-    local root_path = lsp_utils.is_valid_path(current_buffer_path)
-        and path.find_root(conf.root_patterns, current_buffer_path)
+  if not path.is_flutter_dependency_path(buffer_path) then
+    local root_path = lsp_utils.is_valid_path(buffer_path)
+        and path.find_root(conf.root_patterns, buffer_path)
       or nil
     if root_path ~= nil then return root_path end
   end
@@ -284,7 +285,7 @@ function M.attach()
     -- This callback can run asynchronously, by which point the user may have
     -- switched to or deleted the buffer we were asked to attach to.
     if not api.nvim_buf_is_valid(buf) then return end
-    c.root_dir = M.get_project_root_dir()
+    c.root_dir = M.get_project_root_dir(buffer_path)
       or fs.dirname(fs.find(conf.root_patterns, {
         path = buffer_path,
         upward = true,

lua/flutter-tools/utils/path.lua

@@ -200,14 +200,29 @@ function M.pub_cache_dir()
   return vim.env.HOME and M.join(vim.env.HOME, ".pub-cache")
 end
 
+---@param dir string
+---@return boolean
+local function is_flutter_sdk_root(dir)
+  return M.is_file(M.join(dir, "bin", "flutter"))
+    and M.is_dir(M.join(dir, "bin", "cache", "dart-sdk"))
+end
+
+---@param full_path string
+---@return boolean
+local function is_inside_flutter_sdk(full_path)
+  for dir in vim.fs.parents(full_path) do
+    if is_flutter_sdk_root(dir) then return true end
+  end
+  return false
+end
+
 function M.is_flutter_dependency_path(full_path)
+  if not full_path or full_path == "" then return false end
   local path_parts = { [[.pub-cache]], [[Pub\Cache]], [[/fvm/versions/]] }
-  if full_path then
-    for _, path_part in ipairs(path_parts) do
-      if full_path:find(path_part, nil, true) then return true end
-    end
+  for _, path_part in ipairs(path_parts) do
+    if full_path:find(path_part, nil, true) then return true end
   end
-  return false
+  return is_inside_flutter_sdk(full_path)
 end
 
 return M

tests/path_spec.lua

@@ -109,3 +109,50 @@ describe("path.pub_cache_dir", function()
     assert.are.equal(expected, path.pub_cache_dir())
   end)
 end)
+
+describe("path.is_flutter_dependency_path", function()
+  local test_dir
+  local sdk
+  local project
+
+  before_each(function()
+    local temp_base = vim.fn.tempname()
+    vim.fn.mkdir(temp_base, "p")
+    test_dir = vim.uv.fs_realpath(temp_base)
+    sdk = test_dir .. "/mise/installs/flutter/3.47.1"
+    project = test_dir .. "/my_app"
+
+    vim.fn.mkdir(sdk .. "/bin/cache/dart-sdk", "p")
+    vim.fn.writefile({}, sdk .. "/bin/flutter")
+    vim.fn.mkdir(sdk .. "/packages/flutter/lib/src/widgets", "p")
+    vim.fn.mkdir(project .. "/lib", "p")
+  end)
+
+  after_each(function() vim.fn.delete(test_dir, "rf") end)
+
+  it("should detect files inside a Flutter SDK installed anywhere", function()
+    local file_path = sdk .. "/packages/flutter/lib/src/widgets/basic.dart"
+    assert.is_true(path.is_flutter_dependency_path(file_path))
+  end)
+
+  it("should not detect a directory without a Dart SDK as a Flutter SDK", function()
+    vim.fn.delete(sdk .. "/bin/cache", "rf")
+    local file_path = sdk .. "/packages/flutter/lib/src/widgets/basic.dart"
+    assert.is_false(path.is_flutter_dependency_path(file_path))
+  end)
+
+  it(
+    "should not detect project files",
+    function() assert.is_false(path.is_flutter_dependency_path(project .. "/lib/main.dart")) end
+  )
+
+  it("should detect pub cache files", function()
+    local file_path = "/home/user/.pub-cache/hosted/pub.dev/http-1.2.0/lib/http.dart"
+    assert.is_true(path.is_flutter_dependency_path(file_path))
+  end)
+
+  it("should handle missing paths", function()
+    assert.is_false(path.is_flutter_dependency_path(nil))
+    assert.is_false(path.is_flutter_dependency_path(""))
+  end)
+end)