New flag --interactive opens a REPL prompt with project loaded (h/t Richard Geary)

src/_premake_init.lua

@@ -832,6 +832,12 @@
 		description = "Display this information"
 	}
 
+	newoption
+	{
+		trigger = "interactive",
+		description = "Interactive command prompt"
+	}
+
 	newoption
 	{
 		trigger     = "os",

src/_premake_main.lua

@@ -41,6 +41,7 @@
 		-- can be picked up by the scripts.
 
 		premake.action.set(_ACTION)
+		local action = premake.action.current()
 
 		-- If there is a project script available, run it to get the
 		-- project information, available options and actions, etc.
@@ -59,34 +60,46 @@
 			return 1
 		end
 
-		-- If no action was specified, show a short help message
-
-		if (not _ACTION) then
-			print(shorthelp)
-			return 1
-		end
-
-		-- If there wasn't a project script I've got to bail now
-
-		if not hasScript then
-			error("No Premake script (premake5.lua) found!", 0)
-		end
-
 		-- Validate the command-line arguments. This has to happen after the
 		-- script has run to allow for project-specific options
 
-		action = premake.action.current()
-		if not action then
-			error("Error: no such action '" .. _ACTION .. "'", 0)
+		ok, err = premake.option.validate(_OPTIONS)
+		if not ok then
+			print("Error: " .. err)
+			return 1
 		end
 
-		ok, err = premake.option.validate(_OPTIONS)
-		if not ok then error("Error: " .. err, 0) end
+		-- If no further action is possible, show a short help message
+
+		if not _OPTIONS.interactive then
+			if not _ACTION then
+				print(shorthelp)
+				return 1
+			end
+
+			if not action then
+				print("Error: no such action '" .. _ACTION .. "'")
+				return 1
+			end
+
+			if not hasScript then
+				print("No Premake script (premake5.lua) found!")
+				return 1
+			end
+		end
 
 		-- "Bake" the project information, preparing it for use by the action
 
-		print("Building configurations...")
-		premake.oven.bake()
+		if action then
+			print("Building configurations...")
+			premake.oven.bake()
+		end
+
+		-- Run the interactive prompt, if requested
+
+		if _OPTIONS.interactive then
+			debug.prompt()
+		end
 
 		-- Sanity check the current project setup
 
@@ -99,6 +112,5 @@
 
 		print("Done.")
 		return 0
-
 	end
 

src/host/debug_prompt.c

@@ -0,0 +1,47 @@
+/**
+ * \file   debug_prompt.c
+ * \brief  Display a prompt and enter interactive REPL mode.
+ * \author Copyright (c) 2014 Jason Perkins and the Premake project
+ */
+
+#include "premake.h"
+
+/* Build on the REPL built into Lua already */
+#define main lua_main
+#include "lua-5.1.4/src/lua.c"
+
+
+/* Based on dotty() in lua.c */
+int debug_prompt(lua_State* L)
+{
+	int status;
+
+	const char* oldProgName = progname;
+	progname = NULL;
+
+	while ((status = loadline(L)) != -1) {
+		if (status == 0) {
+			status = docall(L, 0, 0);
+		}
+
+		report(L, status);
+
+		if (status == 0 && lua_gettop(L) > 0) {  /* any result to print? */
+			lua_getglobal(L, "print");
+			lua_insert(L, 1);
+			if (lua_pcall(L, lua_gettop(L) - 1, 0, 0) != 0) {
+				l_message(progname, lua_pushfstring(L,
+					"error calling " LUA_QL("print") " (%s)",
+					lua_tostring(L, -1))
+				);
+			}
+		}
+	}
+
+	lua_settop(L, 0);  /* clear stack */
+	fputs("\n", stdout);
+	fflush(stdout);
+	progname = oldProgName;
+	return 0;
+}
+

src/host/premake.c

@@ -42,6 +42,11 @@ static const luaL_Reg criteria_functions[] = {
 	{ NULL, NULL }
 };
 
+static const luaL_Reg debug_functions[] = {
+	{ "prompt", debug_prompt },
+	{ NULL, NULL }
+};
+
 static const luaL_Reg path_functions[] = {
 	{ "getabsolute", path_getabsolute },
 	{ "getrelative", path_getrelative },
@@ -87,6 +92,7 @@ static const luaL_Reg string_functions[] = {
 int premake_init(lua_State* L)
 {
 	luaL_register(L, "criteria", criteria_functions);
+	luaL_register(L, "debug",    debug_functions);
 	luaL_register(L, "path",     path_functions);
 	luaL_register(L, "os",       os_functions);
 	luaL_register(L, "string",   string_functions);

src/host/premake.h

@@ -65,6 +65,7 @@ void do_translate(char* value, const char sep);
 int criteria_compile(lua_State* L);
 int criteria_delete(lua_State* L);
 int criteria_matches(lua_State* L);
+int debug_prompt(lua_State* L);
 int path_getabsolute(lua_State* L);
 int path_getrelative(lua_State* L);
 int path_isabsolute(lua_State* L);