Ensure stable order of index URLs

Signed-off-by: Philippe Ombredanne <[email protected]>

Author: pombredanne

src/python_inspector/api.py

@@ -42,6 +42,7 @@
 from python_inspector.resolution import get_reqs_insecurely
 from python_inspector.resolution import get_requirements_from_python_manifest
 from python_inspector.utils import Candidate
+from python_inspector.utils import unique
 from python_inspector.utils_pypi import PLATFORMS_BY_OS
 from python_inspector.utils_pypi import Environment
 from python_inspector.utils_pypi import PypiSimpleRepository
@@ -336,7 +337,7 @@ def get_index_urls(index_urls: Tuple, extra_data: Dict) -> Tuple:
         index_urls = (*index_urls, *tuple(extra_index_urls))
     if isinstance(index_url, str):
         index_urls = (*index_urls, *tuple([index_url]))
-    return tuple(set(index_urls))
+    return tuple(unique(index_urls))
 
 
 resolver_api = resolve_dependencies

src/python_inspector/utils.py

@@ -101,3 +101,20 @@ def remove_test_data_dir_variable_prefix(path, placeholder="<file>"):
         return cleaned.replace("\\", "/")
     else:
         return placeholder
+
+
+def unique(sequence):
+    """
+    Return a list of unique items found in sequence. Preserve the original sequence order.
+    Items must be hashable.
+    For example:
+    >>> unique([1, 5, 3, 5])
+    [1, 5, 3]
+    """
+    seen = set()
+    deduped = []
+    for item in sequence:
+        if item not in seen:
+            deduped.append(item)
+            seen.add(item)
+    return deduped