Optional cffi dependency (#156)

* Update build.py

* Update utils.py

* Update tox.ini

* add cffi extra

* optional cffi without extra

* Update 1_usage.rst

* Update FUNDING.yml

* Update CHANGELOG.rst

.github/FUNDING.yml

@@ -1,3 +1,2 @@
 # These are supported funding model platforms
 github: [jannikmi]
-issuehunt: mrminimal64

CHANGELOG.rst

@@ -12,6 +12,12 @@ Future TODOs:
     * parameterised tests
 
 
+6.1.3 (2022-09-23)
+------------------
+
+* bugfix broken package build in the case of a broken ``cffi`` installation (GitHub issue #155). Skip build process if ``cffi`` fails. For performance reasons using the C extension should remain the default behavior. Hence the ``cffi`` dependency should not be optional.
+
+
 6.1.2 (2022-09-13)
 ------------------
 

build.py

@@ -1,4 +1,4 @@
-""" builds inside polygon algorithm C extension
+""" optionally builds inside polygon algorithm C extension
 
 Resources:
 https://github.com/FirefoxMetzger/mini-extension
@@ -7,10 +7,11 @@
 """
 import pathlib
 import re
+import warnings
 
+import cffi
+import cffi.setuptools_ext
 import setuptools
-from cffi import FFI
-from cffi.setuptools_ext import cffi_modules
 
 EXTENSION_NAME = "inside_polygon_ext"
 H_FILE_NAME = "inside_polygon_int.h"
@@ -20,30 +21,43 @@
 h_file_path = EXTENSION_PATH / H_FILE_NAME
 c_file_path = EXTENSION_PATH / C_FILE_NAME
 
-ffibuilder = FFI()
-ffibuilder.set_source(
-    EXTENSION_NAME,  # name of the output C extension
-    f'#include "{h_file_path}"',
-    sources=[str(c_file_path)],
-)
+try:
+    ffibuilder = cffi.FFI()
+except Exception as exc:
+    warnings.warn(f"C lang extension cannot be build, since cffi failed with this error: {exc}")
+    # Clang extension should be fully optional
+    ffibuilder = None
 
-with open(h_file_path) as h_file:
-    # cffi does not like our preprocessor directives, so we remove them
-    lns = h_file.read().splitlines()
-    flt = filter(lambda ln: not re.match(r" *#", ln), lns)
+if ffibuilder is not None:
+    ffibuilder.set_source(
+        EXTENSION_NAME,  # name of the output C extension
+        f'#include "{h_file_path}"',
+        sources=[str(c_file_path)],
+    )
 
-ffibuilder.cdef("\n".join(flt))
-with open(c_file_path) as c_file:
-    # cffi does not like our preprocessor directives, so we remove them
-    c_file_content = c_file.read()
+    with open(h_file_path) as h_file:
+        # cffi does not like our preprocessor directives, so we remove them
+        lns = h_file.read().splitlines()
+        flt = filter(lambda ln: not re.match(r" *#", ln), lns)
+
+    ffibuilder.cdef("\n".join(flt))
+
+    # with open(c_file_path) as c_file:
+    #     # cffi does not like our preprocessor directives, so we remove them
+    #     c_file_content = c_file.read()
+
+
+def build_c_extension():
+    if ffibuilder is None:
+        """"""
+        return
 
-if __name__ == "__main__":
     # not required
     # ffibuilder.compile(verbose=True)
 
     # Note: built into "timezonefinder" package folder
     distribution = setuptools.Distribution({"package_dir": {"": "timezonefinder"}})
-    cffi_modules(distribution, "cffi_modules", ["build.py:ffibuilder"])
+    cffi.setuptools_ext.cffi_modules(distribution, "cffi_modules", ["build.py:ffibuilder"])
     cmd = distribution.cmdclass["build_ext"](distribution)
     cmd.inplace = 1
     cmd.ensure_finalized()
@@ -54,3 +68,7 @@
         # a build failure in the extension (e.g. C compile is not installed) must not abort the build process,
         # but instead simply not install the failing extension.
         pass
+
+
+if __name__ == "__main__":
+    build_c_extension()

docs/1_usage.rst

@@ -50,9 +50,11 @@ If no timezone has been matched, ``None`` is being returned.
     tz = tf.timezone_at(lng=1.0, lat=50.5)  # 'Etc/GMT'
 
 .. note::
+
     To reduce the risk of mixing up the coordinates, the arguments ``lng`` and ``lat`` have to be given as keyword arguments
 
 .. note::
+
     This function is optimized for speed: The last possible timezone in proximity is always returned (without checking if the point is really included).
 
 

docs/7_performance.rst

@@ -6,10 +6,12 @@ Performance
 C extension
 -----------
 
-During installation ``timezonefinder`` tries to compile a C extension with an implementation of the time critical point in polygon check algorithm.
-If compilation fails ``timezonefinder`` will silently fall back to a pure Python implementation (~400x slower, cf. :ref:`speed test results <speed-tests>` below).
+During installation ``timezonefinder`` automatically tries to compile a C extension with an implementation of the time critical point in polygon check algorithm.
+In order for this to work, a Clang compiler has to be installed.
 
-Please make sure to have C compiler installed when speed matters to you.
+.. note::
+
+    If compilation fails (due to e.g. missing C compiler or broken ``cffi`` installation) ``timezonefinder`` will silently fall back to a pure Python implementation (~400x slower, cf. :ref:`speed test results <speed-tests>` below).
 
 
 For testing if the compiled C implementation of the point in polygon algorithm is being used: