fix scan on empty python dep and add test cases

Author: sobregosodd

guarddog/scanners/pypi_project_scanner.py

@@ -76,8 +76,11 @@ def get_matched_versions(versions: set[str], semver_range: str) -> set[str]:
 
             # Filters to specified versions
             try:
-                spec = Specifier(semver_range)
-                result = [Version(m) for m in spec.filter(versions)]
+                matching_versions = versions
+                if semver_range:
+                    spec = Specifier(semver_range)
+                    matching_versions = set(spec.filter(versions))
+                result = [Version(m) for m in matching_versions]
             except ValueError:
                 # use it raw
                 return set([semver_range])

tests/core/test_npm_requirements_scanner.py

@@ -10,12 +10,18 @@ def test_npm_requirements_scanner():
     {
         "dependencies": {
             "non-existing": "*",
-            "express": "4.x"
+            "express": "4.x",
+            "cors": "*"
         }
     }
     """)
     assert "non-existing" not in result  # ignoring non existing packages
     assert "express" in result
+    lookup = next(
+        filter(lambda r: r.name == "cors", result), None
+    )
+    assert lookup is not None
+    assert len(lookup.versions) == 1
 
 
 def test_npm_find_requirements():

tests/core/test_pypi_requirements_scanner.py

@@ -39,6 +39,7 @@ def test_requirements_scanner_on_git_url_packages():
                 "https://wxpython.org/Phoenix/snapshot-builds/wxPython_Phoenix-3.0.3.dev1820+49a8884-cp34-none-win_amd64.whl",
                 "guarddog @ git+https://github.com/DataDog/guarddog.git",
                 "git+https://github.com/DataDog/guarddog.git",
+                "requests",
             ]
         )
     )
@@ -48,4 +49,10 @@ def test_requirements_scanner_on_git_url_packages():
     assert lookup is not None
     assert "git+https://github.com/DataDog/guarddog.git" in [v.version for v in lookup.versions]
     assert "flask" in result
-    assert len(result) == 2
+    assert len(result) == 3
+    lookup = next(
+        filter(lambda r: r.name == "requests", result), None
+    )
+    assert lookup is not None
+    assert len(lookup.versions) == 1
+