Add support for cached generators

.gitignore

@@ -49,6 +49,7 @@ docs/_build
 # IDE junk
 .idea/*
 *.swp
+.vscode/*
 
 # build output (testing)
 skbuild/_cmake_test_compile/*

skbuild/cmaker.py

@@ -81,6 +81,28 @@ def __init__(self):
 
         self.platform = get_platform()
 
+    def get_cached_generator_name(self):
+        """Reads and returns the cached generator from the BUILD_DIR; returns None
+        if not found.
+        """
+        try:
+            cmake_generator = 'CMAKE_GENERATOR:INTERNAL='
+            with open(os.path.join(CMAKE_BUILD_DIR, 'CMakeCache.txt')) as fp:
+                for line in fp:
+                    if line.startswith(cmake_generator):
+                        return line[len(cmake_generator):].strip()
+        except (OSError, IOError):
+            pass
+
+        return None
+
+    def get_cached_env(self):
+        generator_name = self.get_cached_generator_name()
+        if generator_name is not None:
+            return self.platform.get_generator(generator_name).env
+
+        return None
+
     def configure(self, clargs=(), generator_name=None,
                   cmake_source_dir='.', cmake_install_dir='',
                   languages=('C', 'CXX'), cleanup=True):

skbuild/constants.py

@@ -14,3 +14,4 @@
 CMAKE_BUILD_DIR = os.path.join(SKBUILD_DIR, "cmake-build")
 CMAKE_INSTALL_DIR = os.path.join(SKBUILD_DIR, "cmake-install")
 SETUPTOOLS_INSTALL_DIR = os.path.join(SKBUILD_DIR, "setuptools")
+CMAKE_ARGUMENTS_FILE = os.path.join(CMAKE_BUILD_DIR, "CMakeArguments.json")

skbuild/platform_specifics/abstract.py

@@ -62,6 +62,16 @@ def get_cmake_exe_path(self):
         """
         return "cmake"
 
+    def get_generator(self, generator_name):
+        """Loop over generators and return the first that matches the given
+        name.
+        """
+        for default_generator in self.default_generators:
+            if default_generator.name == generator_name:
+                return default_generator
+
+        return CMakeGenerator(generator_name)
+
     # TODO: this method name is not great.  Does anyone have a better idea for
     # renaming it?
     def get_best_generator(

skbuild/setuptools_wrap.py

@@ -9,6 +9,7 @@
 import os.path
 import sys
 import argparse
+import json
 
 from contextlib import contextmanager
 from distutils.errors import (DistutilsArgError,
@@ -23,6 +24,11 @@
 except ImportError:
     from io import StringIO
 
+try:
+    from shutil import which
+except ImportError:
+    from distutils.spawn import find_executable as which
+
 from setuptools import setup as upstream_setup
 from setuptools.dist import Distribution as upstream_Distribution
 
@@ -31,7 +37,7 @@
                       install, install_lib, install_scripts,
                       bdist, bdist_wheel, egg_info,
                       sdist, generate_source_manifest, test)
-from .constants import CMAKE_INSTALL_DIR
+from .constants import CMAKE_INSTALL_DIR, CMAKE_ARGUMENTS_FILE
 from .exceptions import SKBuildError, SKBuildGeneratorNotFoundError
 from .utils import (mkdir_p, PythonModuleFinder, to_platform_path, to_unix_path)
 
@@ -290,6 +296,27 @@ def _should_run_cmake(commands, cmake_with_sdist):
     return False
 
 
+def _save_cmake_args(args):
+    """Save the CMake arguments to disk"""
+    # We use JSON here because readability is more important than performance
+    try:
+        os.makedirs(os.path.dirname(CMAKE_ARGUMENTS_FILE))
+    except OSError:
+        pass
+
+    with open(CMAKE_ARGUMENTS_FILE, 'w+') as fp:
+        json.dump(args, fp)
+
+
+def _load_cmake_args():
+    """Load and return the CMake arguments from disk"""
+    try:
+        with open(CMAKE_ARGUMENTS_FILE) as fp:
+            return json.load(fp)
+    except (OSError, IOError, ValueError):
+        return None
+
+
 # pylint:disable=too-many-locals, too-many-branches
 def setup(*args, **kw):  # noqa: C901
     """This function wraps setup() so that we can run cmake, make,
@@ -437,17 +464,27 @@ def setup(*args, **kw):  # noqa: C901
     # weight and when CMake is given multiple times a argument, only the last
     # one is considered, let's prepend the one provided in the setup call.
     cmake_args = skbuild_kw['cmake_args'] + cmake_args
+
+    # Used to confirm that the cmake executable is the same
+    cmake_cmd = [which('cmake')] + cmake_args
 
     # Languages are used to determine a working generator
     cmake_languages = skbuild_kw['cmake_languages']
 
     try:
         cmkr = cmaker.CMaker()
         if not skip_cmake:
-            env = cmkr.configure(cmake_args,
-                                 cmake_source_dir=cmake_source_dir,
-                                 cmake_install_dir=skbuild_kw['cmake_install_dir'],
-                                 languages=cmake_languages)
+            # skip the configure step for a cached build
+            env = cmkr.get_cached_env()
+            if env is None or cmake_cmd != _load_cmake_args():
+                env = cmkr.configure(
+                    cmake_args,
+                    cmake_source_dir=cmake_source_dir,
+                    cmake_install_dir=skbuild_kw['cmake_install_dir'],
+                    languages=cmake_languages
+                )
+                _save_cmake_args(cmake_cmd)
+
             cmkr.make(make_args, env=env)
     except SKBuildGeneratorNotFoundError as ex:
         sys.exit(ex)

tests/test_platform.py

@@ -8,6 +8,7 @@
 """
 
 import os
+import sys
 import platform
 import pytest
 
@@ -109,3 +110,12 @@ def test_unsupported_platform(mocker):
 
     assert failed
     assert "Unsupported platform: bogus." in message
+
+
+@pytest.mark.skipif(sys.platform != 'win32', reason='Requires Windows')
+def test_cached_generator():
+    platform = get_platform()
+    generator = platform.get_generator('Ninja')
+    env = generator.env
+
+    assert 'Visual Studio' in env['LIB'] or 'Visual C++' in env['LIB']