handle FileNotFoundError in parse_requirements function

pipreqs/pipreqs.py

@@ -312,6 +312,9 @@ def parse_requirements(file_):
     delimiter, get module name by element index, create a dict consisting of
     module:version, and add dict to list of parsed modules.
 
+    If file ´file_´ is not found in the system, the program will print a 
+    helpful message and end its execution immediately.
+
     Args:
         file_: File to parse.
 
@@ -328,9 +331,12 @@ def parse_requirements(file_):
 
     try:
         f = open(file_, "r")
-    except OSError:
-        logging.error("Failed on file: {}".format(file_))
-        raise
+    except FileNotFoundError:
+        print(f"File {file_} was not found. Please, fix it and run again.")
+        sys.exit(1)
+    except OSError as error:
+        logging.error(f"There was an error opening the file {file_}: {str(error)}")
+        raise error
     else:
         try:
             data = [x.strip() for x in f.readlines() if x != "\n"]

tests/test_pipreqs.py

@@ -8,9 +8,12 @@
 Tests for `pipreqs` module.
 """
 
+from io import StringIO
+from unittest.mock import patch
 import unittest
 import os
 import requests
+import sys
 
 from pipreqs import pipreqs
 
@@ -47,6 +50,7 @@ def setUp(self):
         )
         self.requirements_path = os.path.join(self.project, "requirements.txt")
         self.alt_requirement_path = os.path.join(self.project, "requirements2.txt")
+        self.non_existing_filepath = "xpto"
 
     def test_get_all_imports(self):
         imports = pipreqs.get_all_imports(self.project)
@@ -427,6 +431,25 @@ def test_clean_with_imports_to_clean(self):
             data = f.read().lower()
             self.assertTrue(cleaned_module not in data)
 
+    @patch("sys.exit")
+    def test_parse_requirements_handles_file_not_found(self, exit_mock):
+        captured_output = StringIO()
+        sys.stdout = captured_output
+
+        # This assertion is needed, because since "sys.exit" is mocked, the program won't end,
+        # and the code that is after the except block will be run
+        with self.assertRaises(UnboundLocalError):
+            pipreqs.parse_requirements(self.non_existing_filepath)
+
+            exit_mock.assert_called_once_with(1)
+
+            printed_text = captured_output.getvalue().strip()
+            sys.stdout = sys.__stdout__
+
+            self.assertEqual(
+                printed_text, "File xpto was not found. Please, fix it and run again."
+            )
+
     def tearDown(self):
         """
         Remove requiremnts.txt files that were written