Fix setupext.py for the case where both PyQt4 and PyQt5 are installed

Martin Fitzpatrick · Martin Fitzpatrick · commit c98406da768a · 2014-05-20T17:12:57.000+01:00
If both PyQt4 and PyQt5 are installed in the same Python the setup check
for the modules will cause a RuntimeError as they are both imported.

The Gtk module uses a multiprocessing pool to perform the imports, and this
approach is used here. However, if we import PyQt4 normally, then PyQt5
using multiprocessing the import is incomplete (no version information).
Instead, we default to multiprocessing for both PyQt4 and PyQt5 and only
fall to normal imports if that is not available.

In the case of a RuntimeError on a normal-style import the error is raised
as `CheckFailed("Could not import: are PyQt4 &amp; PyQt5 both installed?")` to
give a hint as to the problem.
diff --git a/setupext.py b/setupext.py
@@ -1852,8 +1852,7 @@ def get_extension(self):
         return ext
 
 
-class BackendQt4(OptionalBackendPackage):
-    name = "qt4agg"
+class BackendQtBase(OptionalBackendPackage):
 
     def convert_qt_version(self, version):
         version = '%x' % version
@@ -1864,38 +1863,84 @@ def convert_qt_version(self, version):
         return '.'.join(temp)
 
     def check_requirements(self):
+        '''
+        If PyQt4/PyQt5 is already imported, importing PyQt5/PyQt4 will fail
+        so we need to test in a subprocess (as for Gtk3).
+        '''
         try:
-            from PyQt4 import QtCore
-        except ImportError:
-            raise CheckFailed("PyQt4 not found")
-        # Import may still be broken for our python
-        try:
-            qt_version = QtCore.QT_VERSION
-            pyqt_version_str = QtCore.PYQT_VERSION_STR
-        except AttributeError:
-            raise CheckFailed('PyQt4 not correctly imported')
-        BackendAgg.force = True
-        return ("Qt: %s, PyQt4: %s" %
-                (self.convert_qt_version(
-                    qt_version),
-                    pyqt_version_str))
+            p = multiprocessing.Pool()
+
+        except:
+            # Can't do multiprocessing, fall back to normal approach ( this will fail if importing both PyQt4 and PyQt5 )
+            try:
+                # Try in-process
+                msg = self.callback(self)
+                
+            except RuntimeError:
+                raise CheckFailed("Could not import: are PyQt4 & PyQt5 both installed?")
+                
+            except:
+                # Raise any other exceptions
+                raise
+                
+        else:
+            # Multiprocessing OK
+            try:
+                msg = p.map(self.callback, [self])[0]
+            except:
+                # If we hit an error on multiprocessing raise it
+                raise
+            finally:
+                # Tidy up multiprocessing
+                p.close()
+                p.join()    
+                
+        return msg
+
+
+def backend_qt4_internal_check(self):
+    try:
+        from PyQt4 import QtCore
+    except ImportError:
+        raise CheckFailed("PyQt4 not found")
+    try:
+        qt_version = QtCore.QT_VERSION
+        pyqt_version_str = QtCore.QT_VERSION_STR
+    except AttributeError:
+        raise CheckFailed('PyQt4 not correctly imported')
+
+    return ("Qt: %s, PyQt: %s" % (self.convert_qt_version(qt_version), pyqt_version_str))
+
 
-class BackendQt5(BackendQt4):
+class BackendQt4(BackendQtBase):
+    name = "qt4agg"
+
+    def __init__(self, *args, **kwargs):
+        BackendQtBase.__init__(self, *args, **kwargs)
+        self.callback = backend_qt4_internal_check
+
+
+def backend_qt5_internal_check(self):
+    try:
+        from PyQt5 import QtCore
+    except ImportError:
+        raise CheckFailed("PyQt5 not found")
+    try:
+        qt_version = QtCore.QT_VERSION
+        pyqt_version_str = QtCore.QT_VERSION_STR
+    except AttributeError:
+        raise CheckFailed('PyQt5 not correctly imported')
+
+    return ("Qt: %s, PyQt: %s" % (self.convert_qt_version(qt_version), pyqt_version_str))
+
+
+class BackendQt5(BackendQtBase):
     name = "qt5agg"
 
-    def check_requirements(self):
-        try:
-            from PyQt5 import QtCore
-        except ImportError:
-            raise CheckFailed("PyQt5 not found")
-        # Import may still be broken for our python
-        try:
-            qtconfig = QtCore.PYQT_CONFIGURATION
-        except AttributeError:
-            raise CheckFailed('PyQt5 not correctly imported')
-        BackendAgg.force = True
-        # FIXME: How to return correct version information?
-        return ("Qt: 5, PyQt5: %s" % (QtCore.PYQT_VERSION_STR) )
+    def __init__(self, *args, **kwargs):
+        BackendQtBase.__init__(self, *args, **kwargs)
+        self.callback = backend_qt5_internal_check
+
 
 class BackendPySide(OptionalBackendPackage):
     name = "pyside"
