fix(helpers): correctly handle nil args return

Author: Jose Alvarez

lua/null-ls/helpers.lua

@@ -380,11 +380,21 @@ M.make_builtin = function(opts)
             local original_extra_args = user_opts.extra_args
 
             builtin_copy._opts.args = function(params)
-                local original_args_copy = type(original_args) == "function" and original_args(params)
-                    or vim.deepcopy(original_args)
-                    or {}
-                local extra_args_copy = type(original_extra_args) == "function" and original_extra_args(params)
-                    or vim.deepcopy(original_extra_args)
+                local original_args_copy
+                if type(original_args) == "function" then
+                    original_args_copy = original_args(params)
+                else
+                    original_args_copy = vim.deepcopy(original_args)
+                end
+                original_args_copy = original_args_copy or {}
+
+                local extra_args_copy
+                if type(original_extra_args) == "function" then
+                    extra_args_copy = original_extra_args(params)
+                else
+                    extra_args_copy = vim.deepcopy(original_extra_args)
+                end
+                extra_args_copy = extra_args_copy or {}
 
                 -- make sure "-" stays last
                 if original_args_copy[#original_args_copy] == "-" then

test/spec/helpers_spec.lua

@@ -909,6 +909,18 @@ describe("helpers", function()
                 assert.are.same(copy._opts.args(), { "first", "second", "user_first", "user_second" })
             end)
 
+            it("should keep original args if extra_args returns nil", function()
+                local copy = builtin.with({
+                    extra_args = function()
+                        return nil
+                    end,
+                })
+
+                assert.equals(type(copy._opts.args), "function")
+                assert.are.same(copy._opts.args(), { "first", "second" })
+                assert.are.same(copy._opts.args(), { "first", "second" })
+            end)
+
             it("should set args to extra_args if args is nil", function()
                 local test_opts = {
                     method = "mockMethod",
@@ -925,6 +937,24 @@ describe("helpers", function()
                 assert.are.same(copy._opts.args(), { "user_first", "user_second" })
             end)
 
+            it("should set args to extra_args if args returns nil", function()
+                local test_opts = {
+                    method = "mockMethod",
+                    name = "mock-builtin",
+                    filetypes = { "lua" },
+                    generator_opts = {
+                        args = function()
+                            return nil
+                        end,
+                    },
+                }
+                builtin = helpers.make_builtin(test_opts)
+                local copy = builtin.with({ extra_args = { "user_first", "user_second" } })
+
+                assert.equals(type(copy._opts.args), "function")
+                assert.are.same(copy._opts.args(), { "user_first", "user_second" })
+            end)
+
             it("should extend args with extra_args, but keep '-' arg last", function()
                 -- local test_opts = vim.deep_copy(opts) stack overflows
                 local test_opts = {