Make optional backends respect setup.cfg

setup.cfg.template

@@ -54,13 +54,18 @@
 #           otherwise skip silently. This is the default
 #           behavior
 #
+#agg = auto
+#cairo = auto
 #gtk = auto
+#gtk3agg = auto
+#gtk3cairo = auto
 #gtkagg = auto
-#tkagg = auto
 #macosx = auto
+#pyside = auto
+#qt4agg = auto
+#tkagg = auto
 #windowing = auto
-#gtk3cairo = auto
-#gtk3agg = auto
+#wxagg = auto
 
 [rc_options]
 # User-configurable options

setupext.py

@@ -435,38 +435,66 @@ def _check_for_pkg_config(self, package, include_file, min_version=None,
 
 class OptionalPackage(SetupPackage):
     optional = True
+    force = False
+    config_category = "packages"
 
     def get_config(self):
-        install = True
-        if config is not None:
-            try:
-                install = config.getboolean(
-                    'packages', self.name)
-            except:
-                pass
-        return install
+        """
+        Look at `setup.cfg` and return one of ["auto", True, False] indicating
+        if the package is at default state ("auto"), forced by the user (True)
+        or opted-out (False).
+        """
+        try:
+            return config.getboolean(self.config_category, self.name)
+        except:
+            return "auto"
 
     def check(self):
-        self.install = self.get_config()
-        if not self.install:
-            raise CheckFailed("skipping due to configuration")
-        return "installing"
+        """
+        Do not override this method!
 
+        For custom dependency checks override self.check_requirements().
+        Two things are checked: Configuration file and requirements.
+        """
+        # Check configuration file
+        conf = self.get_config()
+        # Default "auto" state or install forced by user
+        if conf in [True, 'auto']:
+            message = "installing"
+            # Set non-optional if user sets `True` in config
+            if conf is True:
+                self.optional = False
+        # Configuration opt-out by user
+        else:
+            # Some backend extensions (e.g. Agg) need to be built for certain
+            # other GUI backends (e.g. TkAgg) even when manually disabled
+            if self.force is True:
+                message = "installing forced (config override)"
+            else:
+                raise CheckFailed("skipping due to configuration")
 
-class OptionalBackendPackage(SetupPackage):
-    optional = True
+        # Check requirements and add extra information (if any) to message.
+        # If requirements are not met a CheckFailed should be raised in there.
+        additional_info = self.check_requirements()
+        if additional_info:
+            message += ", " + additional_info
+
+        # No CheckFailed raised until now, return install message.
+        return message
+
+    def check_requirements(self):
+        """
+        Override this method to do custom dependency checks.
+
+         - Raise CheckFailed() if requirements are not met.
+         - Return message with additional information, or an empty string
+           (or None) for no additional information.
+        """
+        return ""
 
-    def get_config(self):
-        install = 'auto'
-        if config is not None:
-            try:
-                install = config.getboolean(
-                    'gui_support', self.name)
-            except:
-                install = 'auto'
-        if install is True:
-            self.optional = False
-        return install
+
+class OptionalBackendPackage(OptionalPackage):
+    config_category = "gui_support"
 
 
 class Platform(SetupPackage):
@@ -981,16 +1009,6 @@ def get_install_requires(self):
 
 class BackendAgg(OptionalBackendPackage):
     name = "agg"
-    force = False
-
-    def check(self):
-        # The Agg backend extension needs to be built even
-        # for certain GUI backends, such as TkAgg
-        config = self.get_config()
-        if config is False and self.force is False:
-            raise CheckFailed("skipping due to configuration")
-        else:
-            return "installing"
 
     def get_extension(self):
         sources = [
@@ -1012,10 +1030,7 @@ class BackendTkAgg(OptionalBackendPackage):
     def __init__(self):
         self.tcl_tk_cache = None
 
-    def check(self):
-        if self.get_config() is False:
-            raise CheckFailed("skipping due to configuration")
-
+    def check_requirements(self):
         try:
             if sys.version_info[0] < 3:
                 import Tkinter
@@ -1301,10 +1316,7 @@ def add_flags(self, ext):
 class BackendGtk(OptionalBackendPackage):
     name = "gtk"
 
-    def check(self):
-        if self.get_config() is False:
-            raise CheckFailed("skipping due to configuration")
-
+    def check_requirements(self):
         try:
             import gtk
         except ImportError:
@@ -1457,7 +1469,7 @@ def backend_gtk3agg_internal_check(x):
 class BackendGtk3Agg(OptionalBackendPackage):
     name = "gtk3agg"
 
-    def check(self):
+    def check_requirements(self):
         if 'TRAVIS' in os.environ:
             raise CheckFailed("Can't build with Travis")
 
@@ -1520,7 +1532,7 @@ def backend_gtk3cairo_internal_check(x):
 class BackendGtk3Cairo(OptionalBackendPackage):
     name = "gtk3cairo"
 
-    def check(self):
+    def check_requirements(self):
         if 'TRAVIS' in os.environ:
             raise CheckFailed("Can't build with Travis")
 
@@ -1548,7 +1560,7 @@ def get_package_data(self):
 class BackendWxAgg(OptionalBackendPackage):
     name = "wxagg"
 
-    def check(self):
+    def check_requirements(self):
         try:
             import wxversion
         except ImportError:
@@ -1586,10 +1598,7 @@ def check(self):
 class BackendMacOSX(OptionalBackendPackage):
     name = 'macosx'
 
-    def check(self):
-        if self.get_config() is False:
-            raise CheckFailed("skipping due to configuration")
-
+    def check_requirements(self):
         if sys.platform != 'darwin':
             raise CheckFailed("Mac OS-X only")
 
@@ -1616,7 +1625,7 @@ class Windowing(OptionalBackendPackage):
     """
     name = "windowing"
 
-    def check(self):
+    def check_requirements(self):
         if sys.platform != 'win32':
             raise CheckFailed("Microsoft Windows only")
         config = self.get_config()
@@ -1647,7 +1656,7 @@ def convert_qt_version(self, version):
             temp.insert(0, str(int(chunk, 16)))
         return '.'.join(temp)
 
-    def check(self):
+    def check_requirements(self):
         try:
             from PyQt4 import pyqtconfig
         except ImportError:
@@ -1665,7 +1674,7 @@ def check(self):
 class BackendPySide(OptionalBackendPackage):
     name = "pyside"
 
-    def check(self):
+    def check_requirements(self):
         try:
             from PySide import __version__
             from PySide import QtCore
@@ -1681,7 +1690,7 @@ def check(self):
 class BackendCairo(OptionalBackendPackage):
     name = "cairo"
 
-    def check(self):
+    def check_requirements(self):
         try:
             import cairo
         except ImportError: