Make tccbox an optional dependency

.github/workflows/test.yml

@@ -94,6 +94,9 @@ jobs:
         python -m pip install build hatchling
         python -m build --sdist --wheel
         python -m pip install dist/sasmodels*whl
+        python -m pip check
+        python -c "from importlib.metadata import requires; req = [r for r in requires('sasmodels') if r.startswith('tccbox')]; assert len(req) == 1 and \"sys_platform == 'win32'\" in req[0] and \"extra == 'tinycc'\" in req[0], req"
+        python -c "import sasmodels.kerneldll"
 
     - name: Publish sdist and wheel package
       if: env.BUILD_WHEEL
@@ -122,6 +125,11 @@ jobs:
       run: |
         python -m pip install -r build_tools/requirements.txt -r build_tools/requirements-test.txt -r build_tools/requirements-opencl.txt
 
+    - name: Install optional TinyCC compiler (Windows)
+      if: matrix.os == 'windows-latest'
+      run: |
+        python -m pip install -r build_tools/requirements-tinycc.txt
+
     ### Build and test sasmodels
 
     - name: Test with pytest
@@ -130,4 +138,3 @@ jobs:
         SAS_OPENCL: none
       run: |
         pytest -v
-

build_tools/requirements-tinycc.txt

@@ -0,0 +1 @@
+tccbox; sys_platform == "win32"

build_tools/requirements.txt

@@ -4,4 +4,3 @@ matplotlib
 numpy
 scipy
 siphash24
-tccbox

pyproject.toml

@@ -12,7 +12,6 @@ requires = [
   "scipy",
   "siphash24",
   "sphinx",
-  "tccbox",
 ]
 build-backend = "hatchling.build"
 
@@ -75,6 +74,7 @@ server = [ "build_tools/requirements-server.txt" ]
 OpenCL = [ "build_tools/requirements-opencl.txt" ]
 CUDA = [ "build_tools/requirements-cuda.txt" ]
 docs = [ "build_tools/requirements-docs.txt" ]
+tinycc = [ "build_tools/requirements-tinycc.txt" ]
 
 
 [tool.hatch.version]

sasmodels/kerneldll.py

@@ -6,14 +6,14 @@
 available kernels.  This may or may not be available on your compiler
 toolchain.  Depending on operating system and environment.
 
-Windows does not have provide a compiler with the operating system.
-Instead, we assume that TinyCC is installed and available.  This can
-be done with a simple pip command if it is not already available::
+Windows does not provide a compiler with the operating system. TinyCC support
+is available as an optional dependency and can be installed with::
 
-    pip install tinycc
+    python -m pip install "sasmodels[tinycc]"
 
-If Microsoft Visual C++ is available (because VCINSTALLDIR is
-defined in the environment), then that will be used instead.
+If TinyCC is not installed and Microsoft Visual C++ is available (because
+VCINSTALLDIR is defined in the environment), then Microsoft Visual C++ will
+be used instead.
 Microsoft Visual C++ for Python is available from Microsoft:
 
     `<http://www.microsoft.com/en-us/download/details.aspx?id=44266>`_
@@ -26,7 +26,7 @@
 You can control which compiler to use by setting SAS_COMPILER in the
 environment:
 
-  - tinycc (Windows): use the TinyCC compiler shipped with SasView
+  - tinycc (Windows): use TinyCC from the optional tccbox package
   - msvc (Windows): use the Microsoft Visual C++ compiler
   - mingw (Windows): use the MinGW GNU cc compiler
   - unix (Linux): use the system cc compiler.
@@ -168,6 +168,11 @@ def compile_command(source, output):
         return CC + ["/Tp%s"%source] + LN + ["/OUT:%s"%output]
 elif COMPILER == "tinycc":
     # TinyCC compiler.
+    if tccbox is None:
+        raise RuntimeError(
+            "SAS_COMPILER=tinycc requires the optional tccbox package. "
+            "Install it with: python -m pip install 'sasmodels[tinycc]'"
+        )
     CC = [
         tccbox.tcc_bin_path(),
         "-nostdinc",