Python: Add module import test case

This one will require some explanation...

First, the file structure. This commit adds a test consisting
representing a few different kinds of imports.

- Absolute imports, from `module.py` to `main.py` when the latter is
  executed directly.
- A package (contained in the `package` folder)
- A namespace package (contained in the `namespace_package` folder)

All of these are inside a folder called `code` for reasons I will
detail later.

The file `main.py` is identified as a script, by the presence of the
`!#` comment in its first line.

The files themselves are executable, and `python3 main.py` will print
out all modules in the order they are imported.

The test itself is very simple. It simply lists all modules and their
corresponding names. As is plainly visible, without modification we
only pick up `package` and its component modules as having names. This
is the bit that needs to be fixed.

Convincing the test runner to extract this test in a way that mimics
reality is, unfortunately, a bit complicated. By default, the test
runner itself includes any Python files in the test directory as
modules in the invocation of the extractor, and so we must hide
everything in the `code` subdirectory.

Secondly, a `--path` argument (set to the test directory) is
automatically added, and this would also interfere with extraction,
and hence we must prevent this. Luckily, if we supply our own `--path`
argument -- even if it doesn't make any sense -- then the other
argument is left out.

Finally, we must actually tell the extractor to extract the files (or
it would just happily pass the test with zero files extracted), so the
`-R .` argument ensures that we recurse over the files in the test
directory after all.

python/ql/test/3/library-tests/modules/entry_point/code/main.py

@@ -0,0 +1,7 @@
+#! /usr/bin/python3
+print(__file__)
+import module
+import package
+import namespace_package
+import namespace_package.namespace_package_main
+print(module.message)

python/ql/test/3/library-tests/modules/entry_point/code/module.py

@@ -0,0 +1,2 @@
+print(__file__.split("entry_point")[1])
+message = "Hello world!"

python/ql/test/3/library-tests/modules/entry_point/code/namespace_package/namespace_package_main.py

@@ -0,0 +1,2 @@
+print(__file__.split("entry_point")[1])
+import namespace_package.namespace_package_module

python/ql/test/3/library-tests/modules/entry_point/code/namespace_package/namespace_package_module.py

@@ -0,0 +1 @@
+print(__file__.split("entry_point")[1])

python/ql/test/3/library-tests/modules/entry_point/code/package/__init__.py

@@ -0,0 +1,2 @@
+print(__file__.split("entry_point")[1])
+from . import package_main

python/ql/test/3/library-tests/modules/entry_point/code/package/package_main.py

@@ -0,0 +1,2 @@
+print(__file__.split("entry_point")[1])
+from . import package_module

python/ql/test/3/library-tests/modules/entry_point/code/package/package_module.py

@@ -0,0 +1 @@
+print(__file__.split("entry_point")[1])

python/ql/test/3/library-tests/modules/entry_point/modules.expected

@@ -0,0 +1,4 @@
+| package | code/package:0:0:0:0 | Package package |
+| package.__init__ | code/package/__init__.py:0:0:0:0 | Module package.__init__ |
+| package.package_main | code/package/package_main.py:0:0:0:0 | Module package.package_main |
+| package.package_module | code/package/package_module.py:0:0:0:0 | Module package.package_module |

python/ql/test/3/library-tests/modules/entry_point/modules.ql

@@ -0,0 +1,4 @@
+import python
+
+from Module m
+select m.getName(), m

python/ql/test/3/library-tests/modules/entry_point/options

@@ -0,0 +1 @@
+semmle-extractor-options: --lang=3 --path bogus -R .