feat: optional dependencies support for pip, pipenv and setuptools. (#234)

* feat: add suport for optional dependencies

* feat: added tests for optional dependencies

* feat: addres PR comments

Author: MarcusArdelean

lib/dependencies/inspect-implementation.ts

@@ -55,6 +55,7 @@ export function getMetaData(
 // https://www.npmjs.com/package/pkg#detecting-assets-in-source-code
 function createAssets() {
   return [
+    path.join(__dirname, '../../pysrc/constants.py'),
     path.join(__dirname, '../../pysrc/pip_resolve.py'),
     path.join(__dirname, '../../pysrc/distPackage.py'),
     path.join(__dirname, '../../pysrc/package.py'),

pysrc/constants.py

@@ -0,0 +1,25 @@
+import os
+from collections import namedtuple
+
+
+DepsManagerItem = namedtuple(
+    'DepsManagerItem', ['package_manager', 'file']
+)
+
+
+# TODO: When support for Python 2.7 - 3.3 will be removed, use Enums instead
+#  of namedtuple, this is just a workaround to support Python2.7 syntax.
+class DepsManager:
+    PIP = DepsManagerItem(package_manager="pip", file="requirements.txt")
+    PIPENV = DepsManagerItem(package_manager="pipenv", file="Pipfile")
+    SETUPTOOLS = DepsManagerItem(package_manager="setuptools", file="setup.py")
+
+    @classmethod
+    def discover(cls, requirements_file_path):
+        """Establishes the dependency manager based on the used files"""
+        if os.path.basename(requirements_file_path) == 'Pipfile':
+            return cls.PIPENV
+        if os.path.basename(requirements_file_path) == 'setup.py':
+            return cls.SETUPTOOLS
+
+        return cls.PIP