fix gopls without setting ale_go_gopls_init_options (#5059)

lua/ale/lsp.lua

@@ -8,6 +8,14 @@ module.start = function(config)
         config.init_options[true] = nil
     end
 
+    -- ensure init_options uses empty_dict if empty
+    if type(config.init_options) == "table"
+    and next(config.init_options) == nil
+    and getmetatable(config.init_options) == nil
+    then
+        config.init_options = vim.empty_dict()
+    end
+
     -- If configuring LSP via a socket connection, then generate the cmd
     -- using vim.lsp.rpc.connect(), as defined in Neovim documentation.
     if config.host then

test/linter/test_gopls.vader

@@ -94,3 +94,25 @@ Execute('go.mod' should be ignored if modules are off):
   call delete(b:git_dir, 'd')
   unlet! b:parent_dir
   unlet! b:git_dir
+
+Execute(Init options should handle empty and non-empty values correctly):
+  " Regression test for: Invalid settings: invalid options type []interface {}
+  " This ensures empty init_options {} is passed as an object, not array
+  call ale#test#SetFilename('../test-files/go/go1/prj1/file.go')
+  
+  " Test 1: Default empty dict
+  AssertLSPOptions {}
+  
+  " Test 2: Explicitly set to empty
+  let b:ale_go_gopls_init_options = {}
+  AssertLSPOptions {}
+  
+  " Test 3: Non-empty options should be preserved
+  let b:ale_go_gopls_init_options = {
+  \   'ui.diagnostic.analyses': {'composites': v:false},
+  \   'completeUnimported': v:true
+  \}
+  AssertLSPOptions {
+  \   'ui.diagnostic.analyses': {'composites': v:false},
+  \   'completeUnimported': v:true
+  \}

test/lua/ale_lsp_spec.lua

@@ -13,6 +13,10 @@ describe("ale.lsp.start", function()
             defer_fn = function(func, delay)
                 table.insert(defer_calls, {func, delay})
             end,
+            empty_dict = function()
+                -- Returns a table with a metatable to distinguish it from arrays
+                return setmetatable({}, {__empty_dict = true})
+            end,
             fn = setmetatable({}, {
                 __index = function(_, key)
                     return function(...)
@@ -105,6 +109,50 @@ describe("ale.lsp.start", function()
         eq({}, vim_fn_calls)
     end)
 
+    it("should convert empty init_options to vim.empty_dict", function()
+        -- Mock vim.empty_dict
+        local empty_dict_called = false
+        _G.vim.empty_dict = function()
+            empty_dict_called = true
+            return setmetatable({}, {__empty_dict = true})
+        end
+
+        lsp.start({
+            name = "gopls:/code",
+            cmd = "gopls",
+            root_dir = "/code",
+            -- Empty table without metatable (like from VimScript {})
+            init_options = {},
+        })
+
+        -- Verify that empty_dict was called
+        eq(true, empty_dict_called)
+
+        -- Verify init_options has metatable now
+        eq(1, #start_calls)
+        local init_opts = start_calls[1][1].init_options
+        eq(true, getmetatable(init_opts) ~= nil)
+    end)
+
+    it("should preserve non-empty init_options", function()
+        lsp.start({
+            name = "gopls:/code",
+            cmd = "gopls",
+            root_dir = "/code",
+            init_options = {foo = "bar", nested = {baz = 123}},
+        })
+
+        -- Remove functions we can't compare
+        for _, args in pairs(start_calls) do
+            args[1].handlers = nil
+            args[1].on_init = nil
+            args[1].get_language_id = nil
+        end
+
+        eq(1, #start_calls)
+        eq({foo = "bar", nested = {baz = 123}}, start_calls[1][1].init_options)
+    end)
+
     it("should start lsp socket connections with the correct arguments", function()
         lsp.start({
             name = "localhost:1234:/code",