[PackageMetadata] Where are the sources?

This file (top_level.txt) is written by setuptools to indicate where the sources of the package are found.

It can be either a folder or a python module.

z3c/dependencychecker/package.py

@@ -24,6 +24,7 @@ def __init__(self, path):
         self.egg_info_dir = self._get_egg_info_dir()
         self.name = self._get_package_name()
         self._working_set = self._generate_working_set_with_ourselves()
+        self.top_level = self._get_sources_top_level()
 
     @staticmethod
     def _get_distribution_root(path):
@@ -138,3 +139,40 @@ def get_extras_dependencies(self):
                 for req in extra_requirements
             )
             yield extra_name, dotted_names
+
+    def _get_sources_top_level(self):
+        path = os.path.join(
+            self.egg_info_dir,
+            'top_level.txt',
+        )
+        if not os.path.exists(path):
+            logger.error(
+                'top_level.txt could not be found on %s.\n'
+                'It is needed for dependencychecker to work properly.',
+                self.egg_info_dir,
+            )
+            sys.exit(1)
+
+        with open(path) as top_level_file:
+            content = top_level_file.read().strip()
+
+        sources_top_level = os.path.join(
+            self.package_dir,
+            content,
+        )
+
+        if os.path.exists(sources_top_level):
+            return sources_top_level
+
+        single_module_top_level = '{0}.py'.format(sources_top_level)
+        if os.path.exists(single_module_top_level):
+            return single_module_top_level
+
+        logger.error(
+            '%s does not exist but %s%stop_level.txt points there.\n'
+            'Maybe you need to put the package in development again?',
+            sources_top_level,
+            self.egg_info_dir,
+            os.sep,
+        )
+        sys.exit(1)

z3c/dependencychecker/tests/conftest.py

@@ -80,6 +80,7 @@ def _add_egg_info(folder):
 
     _write_pkg_info_file(egg_info_folder_path)
     _write_requires_file(egg_info_folder_path)
+    _write_top_level_file(egg_info_folder_path, package_name)
 
     return package_name
 
@@ -101,3 +102,19 @@ def _write_requires_file(folder):
             'two',
         ])
         requires_file.write(lines)
+
+
+def _write_top_level_file(folder_path, package_name):
+    file_path = os.path.join(folder_path, 'top_level.txt')
+    with open(file_path, 'w') as top_level_file:
+        lines = '\n'.join([
+            package_name,
+        ])
+        top_level_file.write(lines)
+
+    sources_top_folder = os.path.join(
+        folder_path,
+        '..',
+        package_name,
+    )
+    os.makedirs(sources_top_folder)

z3c/dependencychecker/tests/sample1/src/sample1.egg-info_in/top_level.txt

@@ -0,0 +1 @@
+sample1

z3c/dependencychecker/tests/test_package_metadata.py

@@ -39,10 +39,26 @@ def test_package_dir_on_distribution_root(minimal_structure):
 
 
 def test_package_dir_on_src_folder(minimal_structure):
+    def move_top_level_to_src(package_path, egg_folder, src_path):
+        top_level_file_path = os.path.join(
+            egg_folder,
+            'top_level.txt'
+        )
+        with open(top_level_file_path) as top_level_file:
+            top_level_folder = top_level_file.read().strip()
+
+        top_level_sources = os.path.join(package_path, top_level_folder)
+
+        shutil.move(top_level_sources, src_path)
+        shutil.move(egg_folder, src_path)
+
     path, package_name = minimal_structure
+
     egg_info_folder = os.path.join(path, '{0}.egg-info'.format(package_name))
     src_folder = os.path.join(path, 'src')
-    shutil.move(egg_info_folder, src_folder)
+
+    move_top_level_to_src(path, egg_info_folder, src_folder)
+
     metadata = PackageMetadata(path)
 
     assert metadata.package_dir == src_folder
@@ -260,3 +276,63 @@ def test_no_extras(minimal_structure):
 
     extras = [x for x in metadata.get_extras_dependencies()]
     assert len(extras) == 0
+
+
+def test_top_level_txt_file_found(minimal_structure):
+    path, package_name = minimal_structure
+    metadata = PackageMetadata(path)
+
+    assert metadata.top_level == os.path.join(path, package_name)
+
+
+def test_no_top_level_txt_file_found(minimal_structure):
+    path, package_name = minimal_structure
+    os.remove(
+        os.path.join(
+            path,
+            '{0}.egg-info'.format(package_name),
+            'top_level.txt'
+        )
+    )
+
+    sys_exit = False
+    try:
+        PackageMetadata(path)
+    except SystemExit:
+        sys_exit = True
+
+    assert sys_exit
+
+
+def test_no_sources_top_level_folder_found(minimal_structure):
+    path, package_name = minimal_structure
+    os.removedirs(
+        os.path.join(
+            path,
+            package_name
+        )
+    )
+
+    sys_exit = False
+    try:
+        PackageMetadata(path)
+    except SystemExit:
+        sys_exit = True
+
+    assert sys_exit
+
+
+def test_top_level_is_module(minimal_structure):
+    path, package_name = minimal_structure
+    top_level_path = os.path.join(
+        path,
+        package_name
+    )
+    os.removedirs(top_level_path)
+    top_level_module_path = '{0}.py'.format(top_level_path)
+    with open(top_level_module_path, 'w') as top_level_file:
+        top_level_file.write('Does not matter')
+
+    metadata = PackageMetadata(path)
+
+    assert metadata.top_level == top_level_module_path