From e26727e03bb02d26b3f0d83f748dbd8eb88e4940 Mon Sep 17 00:00:00 2001
From: Nat Goodspeed <nat@lindenlab.com>
Date: Tue, 18 Jun 2024 13:13:39 -0400
Subject: Remove special-case ~LuaState() code to call fiber.run().

Instead, make fiber.lua call LL.atexit(fiber.run) to schedule that final run()
call at ~LuaState() time using the generic mechanism.

Append an explicit fiber.run() call to a specific test in llluamanager_test.cpp
because the test code wants to interact with multiple Lua fibers *before* we
destroy the LuaState.
---
 indra/llcommon/lua_function.cpp             | 52 -----------------------------
 indra/newview/scripts/lua/require/fiber.lua |  6 ++++
 indra/newview/tests/llluamanager_test.cpp   |  6 ++++
 3 files changed, 12 insertions(+), 52 deletions(-)

diff --git a/indra/llcommon/lua_function.cpp b/indra/llcommon/lua_function.cpp
index 7894c7b96a..7c5a939d8a 100644
--- a/indra/llcommon/lua_function.cpp
+++ b/indra/llcommon/lua_function.cpp
@@ -627,58 +627,6 @@ std::pair<int, LLSD> LuaState::expr(const std::string& desc, const std::string&
     }
     // pop everything
     lua_settop(mState, 0);
-
-    // If we ran a script that loaded the fiber module, finish up with a call
-    // to fiber.run(). That allows a script to kick off some number of fibers,
-    // do some work on the main thread and then fall off the end of the script
-    // without explicitly appending a call to fiber.run(). run() ensures the
-    // rest of the fibers run to completion (or error).
-    luaL_checkstack(mState, 4, nullptr);
-    // Push _MODULES table on stack
-    luaL_findtable(mState, LUA_REGISTRYINDEX, "_MODULES", 1);
-    int index = lua_gettop(mState);
-    bool found = false;
-    // Did this chunk already require('fiber')? To find out, we must search
-    // the _MODULES table, because our require() implementation uses the
-    // pathname of the module file as the key. Push nil key to start.
-    lua_pushnil(mState);
-    while (lua_next(mState, index) != 0)
-    {
-        // key is at index -2, value at index -1
-        // "While traversing a table, do not call lua_tolstring directly on a
-        // key, unless you know that the key is actually a string. Recall that
-        // lua_tolstring changes the value at the given index; this confuses
-        // the next call to lua_next."
-        // https://www.lua.org/manual/5.1/manual.html#lua_next
-        if (lua_type(mState, -2) == LUA_TSTRING &&
-            fsyspath(lua_tostdstring(mState, -2)).stem() == "fiber")
-        {
-            found = true;
-            break;
-        }
-        // pop value so key is at top for lua_next()
-        lua_pop(mState, 1);
-    }
-    if (found)
-    {
-        // okay, index -1 is a table loaded from a file 'fiber.xxx' --
-        // does it have a function named 'run'?
-        auto run_type{ lua_getfield(mState, -1, "run") };
-        if (run_type == LUA_TFUNCTION)
-        {
-            // there's a fiber.run() function sitting on the top of the stack
-            // -- call it with no arguments, discarding anything it returns
-            LL_INFOS("Lua") << desc << " p.s. fiber.run()" << LL_ENDL;
-            if (! checkLua(desc, lua_pcall(mState, 0, 0, 0)))
-            {
-                LL_WARNS("Lua") << desc << " p.s. fiber.run() error: " << mError << LL_ENDL;
-                return { -1, mError };
-            }
-            LL_INFOS("Lua") << desc << " p.s. done." << LL_ENDL;
-        }
-    }
-    // pop everything again
-    lua_settop(mState, 0);
     return result;
 }
 
diff --git a/indra/newview/scripts/lua/require/fiber.lua b/indra/newview/scripts/lua/require/fiber.lua
index cae27b936b..b3c684dd67 100644
--- a/indra/newview/scripts/lua/require/fiber.lua
+++ b/indra/newview/scripts/lua/require/fiber.lua
@@ -337,4 +337,10 @@ function fiber.run()
     return idle_done
 end
 
+-- Make sure we finish up with a call to run(). That allows a consuming script
+-- to kick off some number of fibers, do some work on the main thread and then
+-- fall off the end of the script without explicitly calling fiber.run().
+-- run() ensures the rest of the fibers run to completion (or error).
+LL.atexit(fiber.run)
+
 return fiber
diff --git a/indra/newview/tests/llluamanager_test.cpp b/indra/newview/tests/llluamanager_test.cpp
index 2d525f7913..206dbd9e71 100644
--- a/indra/newview/tests/llluamanager_test.cpp
+++ b/indra/newview/tests/llluamanager_test.cpp
@@ -385,6 +385,12 @@ namespace tut
             "fiber.launch('catch_special', drain, catch_special)\n"
             "fiber.launch('requester(a)', requester, 'a')\n"
             "fiber.launch('requester(b)', requester, 'b')\n"
+            // A script can normally count on an implicit fiber.run() call
+            // because fiber.lua calls LL.atexit(fiber.run). But atexit()
+            // functions are called by ~LuaState(), which (in the code below)
+            // won't be called until *after* we expect to interact with the
+            // various fibers. So make an explicit call for test purposes.
+            "fiber.run()\n"
         );
 
         LLSD requests;
-- 
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