Configure LuaLS for single-file script workspaces

docs/manual/scripting/lua.md

@@ -218,6 +218,8 @@ not encrypted code. A C++-only project continues to export without the Lua VM.
 
 Run `faset_lua_setup`. It copies annotation-only declarations to
 `.faset/lua/faset.lua` and creates `.luarc.json` **only if it does not already exist**.
+It also creates `Scripts/.luarc.json` for editors that open an individual Lua file
+with `Scripts` as the workspace root. Existing configuration files are preserved.
 For an existing LuaLS configuration, merge these settings yourself:
 
 ```json

src/editor/session.cpp

@@ -493,16 +493,26 @@ void Session::register_commands() {
             const auto source = config_.engine_root / "tools/lua";
             const auto annotations = project_path(config_.project_root, ".faset/lua/faset.lua");
             const auto configuration = project_path(config_.project_root, ".luarc.json");
+            const auto scripts_configuration =
+                project_path(config_.project_root, "Scripts/.luarc.json");
             atomic_write(annotations, read_text(source / "faset.lua"));
             const bool create_configuration = !std::filesystem::exists(configuration);
             if (create_configuration)
                 atomic_write_json(configuration, read_json(source / "luarc.json"));
+            // Zed can open a script as a single-file workspace rooted at Scripts.
+            // Give that workspace its own relative path to the API declarations.
+            const bool create_scripts_configuration =
+                !std::filesystem::exists(scripts_configuration);
+            if (create_scripts_configuration)
+                atomic_write_json(scripts_configuration,
+                                  read_json(source / "luarc-scripts.json"));
             log(create_configuration
                     ? "LuaLS configured: .luarc.json and .faset/lua/faset.lua"
                     : "LuaLS annotations updated; existing .luarc.json preserved. Add .faset/lua "
                       "to workspace.library if needed");
             return Json{{"annotations", ".faset/lua/faset.lua"},
-                        {"configuration_created", create_configuration}};
+                        {"configuration_created", create_configuration},
+                        {"scripts_configuration_created", create_scripts_configuration}};
         });
     commands_.add(
         "faset_script_open",

tests/editor_session_tests.cpp

@@ -71,16 +71,24 @@ int main() {
                 "test", "Project settings erased Lua configuration or external editor command");
         const auto setup = commands.call("faset_lua_setup", Json::object());
         require(setup.at("configuration_created") == true &&
+                    setup.at("scripts_configuration_created") == true &&
                     std::filesystem::is_regular_file(root / ".faset/lua/faset.lua") &&
                     read_json(root / ".luarc.json").at("runtime.version") == "Lua 5.4",
                 "test", "LuaLS setup did not install annotations and configuration");
+        require(read_json(root / "Scripts/.luarc.json").at("workspace.library") ==
+                    Json::array({"../.faset/lua"}),
+                "test", "Single-file Lua workspace cannot find Faset annotations");
         const Json custom_luarc = {{"runtime.version", "Lua 5.4"},
                                    {"workspace.library", {"Custom/Lua"}},
                                    {"custom_setting", true}};
+        const Json custom_scripts_luarc = {{"workspace.library", {"../Custom/Lua"}}};
         atomic_write_json(root / ".luarc.json", custom_luarc);
-        require(commands.call("faset_lua_setup", Json::object()).at("configuration_created") ==
-                        false &&
-                    read_json(root / ".luarc.json") == custom_luarc,
+        atomic_write_json(root / "Scripts/.luarc.json", custom_scripts_luarc);
+        const auto repeated_setup = commands.call("faset_lua_setup", Json::object());
+        require(repeated_setup.at("configuration_created") == false &&
+                    repeated_setup.at("scripts_configuration_created") == false &&
+                    read_json(root / ".luarc.json") == custom_luarc &&
+                    read_json(root / "Scripts/.luarc.json") == custom_scripts_luarc,
                 "test", "LuaLS setup overwrote the user's configuration");
         auto reject_command = [&](const std::string& name, const Json& args,
                                   const std::string& code) {

tools/lua/luarc-scripts.json

@@ -0,0 +1,7 @@
+{
+  "runtime.version": "Lua 5.4",
+  "runtime.path": ["?.lua", "?/init.lua"],
+  "workspace.library": ["../.faset/lua"],
+  "workspace.checkThirdParty": false,
+  "diagnostics.globals": ["faset"]
+}