Support empty torch versions

* Allow sending torch version as none
* If this is none then torch will not be installed
in the venv
* This is due to not all cog users wanting to
install torch, so if they don’t we may as well not
install it into the venv

src/monobase/build.py

@@ -183,7 +183,6 @@ def assert_env(e: str) -> None:
 
         assert_env('R8_COG_VERSION')
         assert_env('R8_PYTHON_VERSION')
-        assert_env('R8_TORCH_VERSION')
         if not args.skip_cuda:
             assert_env('R8_CUDA_VERSION')
             assert_env('R8_CUDNN_VERSION')
@@ -208,6 +207,12 @@ def pick(
                     raise
                 return {}
 
+        torch = []
+        if 'R8_TORCH_VERSION' in os.environ:
+            torch.append(os.environ['R8_TORCH_VERSION'])
+        else:
+            torch.append(None)
+
         monogens = [
             MonoGen(
                 id=mg.id,
@@ -216,7 +221,7 @@ def pick(
                     mg.cudnn, 'R8_CUDNN_VERSION', fail_on_empty=not args.skip_cuda
                 ),
                 python=pick(mg.python, 'R8_PYTHON_VERSION'),
-                torch=[os.environ['R8_TORCH_VERSION']],
+                torch=torch,
                 pip_pkgs=mg.pip_pkgs,
             )
         ]

src/monobase/user.py

@@ -34,7 +34,7 @@ def build_user_venv(args: argparse.Namespace) -> None:
     log.info(f'Building user venv {udir}...')
 
     python_version = os.environ['R8_PYTHON_VERSION']
-    torch_version = os.environ['R8_TORCH_VERSION']
+    torch_version = os.environ.get('R8_TORCH_VERSION')
     cuda_version = os.environ.get('R8_CUDA_VERSION', 'cpu')
 
     uv = os.path.join(args.prefix, 'bin', 'uv')
@@ -48,7 +48,11 @@ def build_user_venv(args: argparse.Namespace) -> None:
     cog_versions = parse_requirements(cog_req)
 
     gdir = os.path.realpath(os.path.join(args.prefix, 'monobase', 'latest'))
-    venv = f'python{python_version}-torch{torch_version}-{cuda_suffix(cuda_version)}'
+    venv_components = [f'python{python_version}']
+    if torch_version is not None:
+        venv_components.append(f'torch{torch_version}')
+    venv_components.append(f'{cuda_suffix(cuda_version)}')
+    venv = '-'.join(venv_components)
     vdir = os.path.join(gdir, venv)
     log.info(f'Freezing monobase venv {vdir}...')
     mono_req = freeze(uv, vdir)