I might not be the first one who've found it, yet here it is -
The Devilution Project.
Discussion on Reddit
Sometime ago an enthusiast known as Galaxyhaxz made his goal to fully recreate Diablo 1 source code. He's not the first one to undertake such a task, but this time it's an open source project.
After more than a thousand hours of work he has achieved such a level of detail that his GitHub project can be actually compiled into a working exe of the game (although it has some graphical issues). And he isn't going to stop at that.
His sources included not only the debug build of the game left by the developers inside the MPQ archives, but also the Japanese release of the
PS1 port which happened to include a file with the details about the source code structure (symbolic file). With this Galaxyhaxz was able to recover function names and variable types. Moreover, ago a beta of the port was found online.
I believe that this source code could be of assistance to whoever might try to TAS the game in the future. Or maybe someone proficient at reverse engineering might even consider helping the project (details in ReadMe.MD).
Also, here's the
list detailing the general purpose of each source file (most of them) I've found somewhere awhile ago.