Fixed SF bug #1297 (Python imports)

This changeset resolves several issues related to python imports.
For example, it's possible now to import modules having same module
names, but belonging to different packages.

From the user's viewpoint, this patch gives a little bit more control on
import directives generated by swig. The user may choose to use relative
or absolute imports (docs are provided in separate PR).

Some details:
  - we (still) generate import directives in form 'import a.b.c' which
    corresponds to absolute imports in python3 and (the only available)
    ambiguous one in python2.
  - added -relativeimport option to use explicit relative import syntax
    (python3),

Tests are under Examples/python, these are in fact regression tests but
with the current swig testing framework it seems to be impossible to put
appropriate tests under test-suite.

Closes #7

Examples/python/import_packages/from_init2/Makefile

@@ -0,0 +1,25 @@
+TOP        = ../../..
+SWIG       = $(realpath $(TOP)/../preinst-swig)
+SWIGOPT    =
+LIBS       =
+PY3        =
+
+ifeq (,$(PY3))
+  PKG1DIR  = "py2"
+else
+  PKG1DIR  = "py3"
+endif
+
+check: build
+	$(MAKE) -f $(TOP)/Makefile python_run
+
+build:
+	cd $(PKG1DIR) && $(MAKE) SWIG='$(SWIG)' SWIGOPT='$(SWIGOPT) -relativeimport' LIBS='$(LIBS)' build
+
+static:
+	cd $(PKG1DIR) && $(MAKE) SWIG='$(SWIG)' SWIGOPT='$(SWIGOPT) -relativeimport' LIBS='$(LIBS)' static
+
+clean:
+	$(MAKE) -f $(TOP)/Makefile python_clean
+	cd py2 && $(MAKE) clean
+	cd py3 && $(MAKE) clean

Examples/python/import_packages/from_init2/README

@@ -0,0 +1,81 @@
+This example tests the %import directive and python import from __init__.py.
+
+This case is not correctly handled by swig 2.
+
+The issue was reported as Source Forge bug #1297 and later as GitHub issue #7.
+
+Use 'python runme.py' to run a test.
+
+Overview:
+---------
+
+The example defines 2 different extension modules--each wrapping a separate C++
+class.
+
+     pyX/pkg2/pkg3/foo.i     - Pkg3_Foo class
+     pyX/pkg2/bar.i        - Pkg2_Bar class derived from Pkg3_Foo
+
+and the package pyX.pkg2 has:
+
+     pyX/pkg2/__init__.py  - which imports something from "bar" module
+
+For example with python 2.x the py2/pkg2/__init__.py imports Pkg2_Bar class as
+follows
+
+    from bar import Pkg2_Bar                      # [1]
+
+Such cases doesn't work when fully qualified python module names are used by
+swig to generate python import directives (SF bug #1297). The generated file
+"py2/pkg2/bar.py" has following lines:
+
+    import py2.pkg2.pkg3.foo                     # [2]
+    class Pkg2_Bar(py2.pkg2.pkg3.foo.Pkg3_Foo):  # [3]
+
+and it's not possible to import anything from py2.pkg2 subpackage, e.g.
+
+    import py2.pkg2
+
+fails with the following exception:
+
+Traceback (most recent call last):
+  File "runme.py", line 3, in <module>
+      import py2.pkg2
+  File "py2/pkg2/__init__.py", line 4, in <module>
+      from bar import Pkg2_Bar
+  File "py2/pkg2/bar.py", line 71, in <module>
+      class Pkg2_Bar(py2.pkg2.pkg3.foo.Pkg3_Foo):
+AttributeError: 'module' object has no attribute 'pkg2'
+
+It seems like during the import [1], the subpackage pkg2 is not yet fully
+initialized, so pyX.pkg2 is not known. The above exception is raised at line [3].
+The problem disappears, for example, if we force swig to use relative package
+names.
+
+The difference between this ('from_init2') case and the case
+'from_init1' is that here it's not sufficient to import relative module
+by just ignoring the package part of the fully qualified module name. IOW
+it is not correct to force swig to put:
+
+    import foo
+    class Pkg2_Bar(foo.Pkg3_Foo)
+
+into pyX/pkg2/bar.py (note, that this would work for 'from_init1' case).
+The import directive shall be rather:
+
+    import pkg3.foo
+
+for python 2.x and:
+
+    from . import pkg3
+    import pkg3.foo
+
+for python 3, and the class definition shall begin with:
+
+    class Pkg2_Bar(pkg3.foo.Pkg3_Foo)
+
+If everything works well, the package pyX.pkg2 shall load properly.
+
+Unix:
+-----
+- Run make
+- Run the test as described above

Examples/python/import_packages/from_init2/py2/Makefile

@@ -0,0 +1,14 @@
+TOP        = ../../../..
+SWIG       = $(realpath $(TOP)/../preinst-swig)
+SWIGOPT    =
+LIBS       =
+
+build:
+	cd pkg2 && $(MAKE) SWIG='$(SWIG)' SWIGOPT='$(SWIGOPT)' LIBS='$(LIBS)' build
+
+static:
+	cd pkg2 && $(MAKE) SWIG='$(SWIG)' SWIGOPT='$(SWIGOPT)' LIBS='$(LIBS)' static
+
+clean:
+	$(MAKE) -f $(TOP)/Makefile python_clean
+	cd pkg2 && $(MAKE) clean

Examples/python/import_packages/from_init2/py2/pkg2/Makefile

@@ -0,0 +1,18 @@
+TOP        = ../../../../..
+SWIG       = $(realpath $(TOP)/../preinst-swig)
+SWIGOPT    =
+LIBS       =
+
+build:
+	$(MAKE) -f $(TOP)/Makefile SWIG='$(SWIG)' SWIGOPT='$(SWIGOPT)' \
+	LIBS='$(LIBS)' TARGET='bar' INTERFACE='bar.i' python_cpp
+	cd pkg3 && $(MAKE) SWIG='$(SWIG)' SWIGOPT='$(SWIGOPT)' LIBS='$(LIBS)' build
+
+static:
+	$(MAKE) -f $(TOP)/Makefile SWIG='$(SWIG)' SWIGOPT='$(SWIGOPT)' \
+	LIBS='$(LIBS)' TARGET='bar' INTERFACE='bar.i' python_cpp
+	cd pkg3 && $(MAKE) SWIG='$(SWIG)' SWIGOPT='$(SWIGOPT)' LIBS='$(LIBS)' static
+
+clean:
+	$(MAKE) -f $(TOP)/Makefile TARGET='bar' python_clean
+	cd pkg3 && $(MAKE) clean

Examples/python/import_packages/from_init2/py2/pkg2/__init__.py

@@ -0,0 +1 @@
+from bar import Pkg2_Bar

Examples/python/import_packages/from_init2/py2/pkg2/bar.hpp

@@ -0,0 +1,5 @@
+#ifndef PY2_PKG2_BAR_HPP
+#define PY2_PKG2_BAR_HPP
+#include "../../py2/pkg2/pkg3/foo.hpp"
+struct Pkg2_Bar : Pkg3_Foo {};
+#endif /* PY2_PKG2_BAR_HPP */

Examples/python/import_packages/from_init2/py2/pkg2/bar.i

@@ -0,0 +1,6 @@
+%module(package="py2.pkg2") bar
+%{
+#include "../../py2/pkg2/bar.hpp"
+%}
+%import  "../../py2/pkg2/pkg3/foo.i"
+%include "../../py2/pkg2/bar.hpp"

Examples/python/import_packages/from_init2/py2/pkg2/pkg3/Makefile

@@ -0,0 +1,15 @@
+TOP        = ../../../../../..
+SWIG       = $(realpath $(TOP)/../preinst-swig)
+SWIGOPT    =
+LIBS       =
+
+build:
+	$(MAKE) -f $(TOP)/Makefile SWIG='$(SWIG)' SWIGOPT='$(SWIGOPT)' \
+	LIBS='$(LIBS)' TARGET='foo' INTERFACE='foo.i' python_cpp
+
+static:
+	$(MAKE) -f $(TOP)/Makefile SWIG='$(SWIG)' SWIGOPT='$(SWIGOPT)' \
+	LIBS='$(LIBS)' TARGET='foo' INTERFACE='foo.i' python_cpp_static
+
+clean:
+	$(MAKE) -f $(TOP)/Makefile TARGET='foo' python_clean

Examples/python/import_packages/from_init2/py2/pkg2/pkg3/foo.hpp

@@ -0,0 +1,4 @@
+#ifndef PY2_PKG2_PKG3_FOO_HPP
+#define PY2_PKG2_PKG3_FOO_HPP
+struct Pkg3_Foo {};
+#endif /* PY2_PKG2_PKG3_FOO_HPP */

Examples/python/import_packages/from_init2/py2/pkg2/pkg3/foo.i

@@ -0,0 +1,5 @@
+%module(package="py2.pkg2.pkg3") foo
+%{
+#include "../../../py2/pkg2/pkg3/foo.hpp"
+%}
+%include "../../../py2/pkg2/pkg3/foo.hpp"

Examples/python/import_packages/from_init2/py3/Makefile

@@ -0,0 +1,14 @@
+TOP        = ../../../..
+SWIG       = $(realpath $(TOP)/../preinst-swig)
+SWIGOPT    =
+LIBS       =
+
+build:
+	cd pkg2 && $(MAKE) SWIG='$(SWIG)' SWIGOPT='$(SWIGOPT)' LIBS='$(LIBS)' build
+
+static:
+	cd pkg2 && $(MAKE) SWIG='$(SWIG)' SWIGOPT='$(SWIGOPT)' LIBS='$(LIBS)' static
+
+clean:
+	$(MAKE) -f $(TOP)/Makefile python_clean
+	cd pkg2 && $(MAKE) clean

Examples/python/import_packages/from_init2/py3/pkg2/Makefile

@@ -0,0 +1,18 @@
+TOP        = ../../../../..
+SWIG       = $(realpath $(TOP)/../preinst-swig)
+SWIGOPT    =
+LIBS       =
+
+build:
+	$(MAKE) -f $(TOP)/Makefile SWIG='$(SWIG)' SWIGOPT='$(SWIGOPT)' \
+	LIBS='$(LIBS)' TARGET='bar' INTERFACE='bar.i' python_cpp
+	cd pkg3 && $(MAKE) SWIG='$(SWIG)' SWIGOPT='$(SWIGOPT)' LIBS='$(LIBS)' build
+
+static:
+	$(MAKE) -f $(TOP)/Makefile SWIG='$(SWIG)' SWIGOPT='$(SWIGOPT)' \
+	LIBS='$(LIBS)' TARGET='bar' INTERFACE='bar.i' python_cpp
+	cd pkg3 && $(MAKE) SWIG='$(SWIG)' SWIGOPT='$(SWIGOPT)' LIBS='$(LIBS)' static
+
+clean:
+	$(MAKE) -f $(TOP)/Makefile TARGET='bar' python_clean
+	cd pkg3 && $(MAKE) clean

Examples/python/import_packages/from_init2/py3/pkg2/__init__.py

@@ -0,0 +1 @@
+from .bar import Pkg2_Bar

Examples/python/import_packages/from_init2/py3/pkg2/bar.hpp

@@ -0,0 +1,5 @@
+#ifndef PY3_PKG2_BAR_HPP
+#define PY3_PKG2_BAR_HPP
+#include "../../py3/pkg2/pkg3/foo.hpp"
+struct Pkg2_Bar : Pkg3_Foo {};
+#endif /* PY3_PKG2_BAR_HPP */

Examples/python/import_packages/from_init2/py3/pkg2/bar.i

@@ -0,0 +1,6 @@
+%module(package="py3.pkg2") bar
+%{
+#include "../../py3/pkg2/bar.hpp"
+%}
+%import  "../../py3/pkg2/pkg3/foo.i"
+%include "../../py3/pkg2/bar.hpp"

Examples/python/import_packages/from_init2/py3/pkg2/pkg3/Makefile

@@ -0,0 +1,15 @@
+TOP        = ../../../../../..
+SWIG       = $(realpath $(TOP)/../preinst-swig)
+SWIGOPT    =
+LIBS       =
+
+build:
+	$(MAKE) -f $(TOP)/Makefile SWIG='$(SWIG)' SWIGOPT='$(SWIGOPT)' \
+	LIBS='$(LIBS)' TARGET='foo' INTERFACE='foo.i' python_cpp
+
+static:
+	$(MAKE) -f $(TOP)/Makefile SWIG='$(SWIG)' SWIGOPT='$(SWIGOPT)' \
+	LIBS='$(LIBS)' TARGET='foo' INTERFACE='foo.i' python_cpp_static
+
+clean:
+	$(MAKE) -f $(TOP)/Makefile TARGET='foo' python_clean

Examples/python/import_packages/from_init2/py3/pkg2/pkg3/foo.hpp

@@ -0,0 +1,4 @@
+#ifndef PY3_PKG2_PKG3_FOO_HPP
+#define PY3_PKG2_PKG3_FOO_HPP
+struct Pkg3_Foo {};
+#endif /* PY3_PKG2_PKG3_FOO_HPP */

Examples/python/import_packages/from_init2/py3/pkg2/pkg3/foo.i

@@ -0,0 +1,5 @@
+%module(package="py3.pkg2.pkg3") foo
+%{
+#include "../../../py3/pkg2/pkg3/foo.hpp"
+%}
+%include "../../../py3/pkg2/pkg3/foo.hpp"

Examples/python/import_packages/from_init2/runme.py

@@ -0,0 +1,9 @@
+# Test import of modules content from within __init__.py
+print "Testing %module(package=...) + python 'import' in __init__.py"
+import sys
+if sys.version_info < (3,0):
+  import py2.pkg2
+  print "  Finished importing py2.pkg2"
+else:
+  import py3.pkg2
+  print "  Finished importing py3.pkg2"