Redesign prompt system: revert #09, use standard _PROMPT (issue #21)

Revert the bespoke __prompt()/__prompt2() function mechanism from issue
#09 and return to stock Lua's _PROMPT/_PROMPT2 globals (which already
support dynamic prompts via __tostring metatables). Set default
_PROMPT = "lush> " in doREPL if not already defined by config.

issues/09-prompt.md

@@ -1,6 +1,7 @@
 # 09 — Programmable prompt
 
-**Status:** done
+**Status:** open
+**Blocked by:** #08
 
 Users should be able to customize the shell prompt by defining a Lua function, similar to how other shells use `PS1`/`PROMPT_COMMAND`/`precmd`.
 

issues/21-prompt-redesign.md

@@ -1,6 +1,6 @@
 # 21 — Prompt redesign
 
-**Status:** open
+**Status:** done
 
 Reconsider the prompt system. Some observations:
 

lua.c

@@ -541,38 +541,19 @@ static void lua_initreadline (lua_State *L) {
 #endif				/* } */
 
 
-static int last_exit_code = 0;  /* tracks exit code for __prompt() */
-
-
 /*
 ** Return the string to be used as a prompt by the interpreter. Leave
 ** the string (or nil, if using the default value) on the stack, to keep
 ** it anchored.
-**
-** Fallback chain: __prompt()/__prompt2() → _PROMPT/_PROMPT2 → "> "/">> "
 */
 static const char *get_prompt (lua_State *L, int firstline) {
-  const char *fname = firstline ? "__prompt" : "__prompt2";
+  if (lua_getglobal(L, firstline ? "_PROMPT" : "_PROMPT2") == LUA_TNIL)
-  if (lua_getglobal(L, fname) == LUA_TFUNCTION) {
+    return (firstline ? LUA_PROMPT : LUA_PROMPT2);  /* use the default */
-    lua_pushinteger(L, last_exit_code);
+  else {  /* apply 'tostring' over the value */
-    if (lua_pcall(L, 1, 1, 0) == LUA_OK) {
-      const char *p = lua_tostring(L, -1);
-      if (p != NULL) return p;  /* string stays on stack, anchored */
-    }
-    lua_pop(L, 1);  /* pop error message or non-string result */
-  } else {
-    lua_pop(L, 1);  /* pop the non-function value */
-  }
-  /* fallback: check _PROMPT/_PROMPT2 globals (standard Lua compat) */
-  if (lua_getglobal(L, firstline ? "_PROMPT" : "_PROMPT2") != LUA_TNIL) {
     const char *p = luaL_tolstring(L, -1, NULL);
     lua_remove(L, -2);  /* remove original value */
     return p;
   }
-  lua_pop(L, 1);  /* pop nil */
-  /* final fallback: push default string so pushline can pop it */
-  lua_pushstring(L, firstline ? LUA_PROMPT : LUA_PROMPT2);
-  return lua_tostring(L, -1);
 }
 
 /* mark in error messages for incomplete statements */
@@ -692,26 +673,6 @@ static int loadline (lua_State *L) {
 }
 
 
-/*
-** Install default __prompt function if not already defined (e.g. by config).
-** Shows current directory with ~ substitution for HOME.
-*/
-static void install_default_prompt (lua_State *L) {
-  if (lua_getglobal(L, "__prompt") == LUA_TNIL) {
-    luaL_dostring(L,
-      "function __prompt(exitcode)\n"
-      "  local cwd = os.getenv('PWD') or '?'\n"
-      "  local home = os.getenv('HOME') or ''\n"
-      "  if home ~= '' and cwd:sub(1, #home) == home then\n"
-      "    cwd = '~' .. cwd:sub(#home + 1)\n"
-      "  end\n"
-      "  return cwd .. '> '\n"
-      "end\n");
-  }
-  lua_pop(L, 1);  /* pop the getglobal result */
-}
-
-
 /*
 ** Prints (calling the Lua 'print' function) any values on the stack
 */
@@ -737,7 +698,14 @@ static void doREPL (lua_State *L) {
   const char *oldprogname = progname;
   progname = NULL;  /* no 'progname' on errors in interactive mode */
   lua_initreadline(L);
-  install_default_prompt(L);
+  /* set default _PROMPT if not already defined (e.g. by config) */
+  if (lua_getglobal(L, "_PROMPT") == LUA_TNIL) {
+    lua_pop(L, 1);
+    lua_pushliteral(L, "lush> ");
+    lua_setglobal(L, "_PROMPT");
+  } else {
+    lua_pop(L, 1);
+  }
   setsignal(SIGINT, repl_sigint_handler);
   if (sigsetjmp(repl_jmp, 1)) {
     /* Ctrl-C during input — print newline, clear stack, re-prompt */
@@ -748,7 +716,6 @@ static void doREPL (lua_State *L) {
   while ((status = loadline(L)) != -1) {
     if (status == LUA_OK)
       status = docall(L, 0, LUA_MULTRET);
-    last_exit_code = status;  /* track for __prompt() */
     if (status == LUA_OK) l_print(L);
     else report(L, status);
     setsignal(SIGINT, repl_sigint_handler);  /* re-install after docall */

testes/lush/prompt.lua

@@ -1,7 +1,7 @@
 -- testes/lush/prompt.lua
--- Tests for programmable prompt (issue #09).
+-- Tests for prompt system (issue #21).
 
-print "testing programmable prompt"
+print "testing prompt system"
 
 -- helper: get a unique temp directory
 local tmpbase = os.tmpname()
@@ -39,95 +39,47 @@ local function run_lua(input, config_content)
 end
 
 
--- ===== TEST 1: Default __prompt is installed =====
+-- ===== TEST 1: Default _PROMPT is "lush> " =====
--- After starting the REPL, __prompt should be a function
 do
-  local out = run_lua('"print(type(__prompt))"')
+  local out = run_lua('"print(_PROMPT)"')
-  assert(out:find("function"),
+  assert(out:find("lush> ", 1, true),
-    "default __prompt should be installed as function: " .. out)
+    "default _PROMPT should be 'lush> ': " .. out)
 end
 
 
--- ===== TEST 2: Default __prompt returns cwd =====
+-- ===== TEST 2: _PROMPT can be overridden by config =====
 do
-  local cwd = os.getenv("PWD") or ""
+  local out = run_lua('"print(_PROMPT)"',
-  local home = os.getenv("HOME") or ""
+    '_PROMPT = "custom> "\n')
-  local expected
-  if home ~= "" and cwd:sub(1, #home) == home then
-    expected = "~" .. cwd:sub(#home + 1)
-  else
-    expected = cwd
-  end
-  local out = run_lua('"print(__prompt(0))"')
-  assert(out:find(expected, 1, true),
-    "default __prompt should return cwd: expected '" ..
-    expected .. "' in: " .. out)
-end
-
-
--- ===== TEST 3: Custom __prompt() overrides default =====
-do
-  local out = run_lua('"print(__prompt(0))"',
-    'function __prompt() return "custom> " end\n')
   assert(out:find("custom> ", 1, true),
-    "custom __prompt should be used: " .. out)
+    "config should override _PROMPT: " .. out)
 end
 
 
--- ===== TEST 4: __prompt() receives exit code =====
+-- ===== TEST 3: _PROMPT with __tostring metatable (dynamic prompt) =====
 do
-  local out = run_lua(
+  local out = run_lua('"print(_PROMPT)"',
-    '"error()" "print(__prompt())" "os.exit()"',
+    '_PROMPT = setmetatable({}, { __tostring = function() return "dynamic> " end })\n')
-    'function __prompt(code)\n'
+  assert(out:find("dynamic> ", 1, true),
-    .. '  return "exit:" .. tostring(code) .. "> "\n'
+    "_PROMPT with __tostring should work: " .. out)
-    .. 'end\n')
-  -- After error(), the next prompt call should receive non-zero code.
-  -- But since we're calling __prompt() manually via print, we test
-  -- the mechanism differently: call it with a code directly.
-  local out2 = run_lua('"print(__prompt(42))"',
-    'function __prompt(code)\n'
-    .. '  return "exit:" .. tostring(code) .. "> "\n'
-    .. 'end\n')
-  assert(out2:find("exit:42> ", 1, true),
-    "exit code should be passed to __prompt: " .. out2)
 end
 
 
--- ===== TEST 5: __prompt2 for continuation =====
+-- ===== TEST 4: _PROMPT2 works for continuation =====
 do
-  local out = run_lua('"print(type(__prompt2))"')
+  local out = run_lua('"print(_PROMPT2)"',
-  -- __prompt2 is not installed by default
+    '_PROMPT2 = "...> "\n')
-  assert(out:find("nil") or out:find("function"),
+  assert(out:find("...> ", 1, true),
-    "__prompt2 should be nil or function: " .. out)
+    "_PROMPT2 should be settable: " .. out)
 end
 
 
--- ===== TEST 6: Broken __prompt() falls back gracefully =====
+-- ===== TEST 5: _PROMPT = nil falls back gracefully =====
 do
-  local out = run_lua('"print(42)"',
+  -- Set _PROMPT to nil during the REPL; get_prompt falls back to LUA_PROMPT.
-    'function __prompt() error("boom") end\n')
+  local out = run_lua('"_PROMPT = nil" "print(42)"')
   assert(out:find("42"),
-    "broken __prompt should still allow REPL to work: " .. out)
+    "_PROMPT = nil should still allow REPL to work: " .. out)
-end
-
-
--- ===== TEST 7: _PROMPT still works (backward compat) =====
-do
-  -- When __prompt is defined (default), it takes priority.
-  -- To test _PROMPT fallback, unset __prompt.
-  local out = run_lua('"print(42)"',
-    '__prompt = nil\n_PROMPT = "old> "\n')
-  assert(out:find("42"),
-    "_PROMPT fallback should still work: " .. out)
-end
-
-
--- ===== TEST 8: Config-defined __prompt is not overwritten =====
-do
-  local out = run_lua('"print(__prompt(0))"',
-    'function __prompt() return "from_config> " end\n')
-  assert(out:find("from_config> ", 1, true),
-    "config __prompt should not be overwritten: " .. out)
 end