Sort requirements by canonical distribution name

news/134.bugfix

@@ -0,0 +1 @@
+Sort requirement files by canonical requirement name to help ensure stability and comparability.

src/pip_deepfreeze/sync.py

@@ -13,7 +13,7 @@
 from .project_name import get_project_name
 from .req_file_parser import OptionsLine, parse as parse_req_file
 from .req_merge import prepare_frozen_reqs_for_upgrade
-from .req_parser import get_req_names
+from .req_parser import get_req_name, get_req_names
 from .utils import (
     HttpFetcher,
     get_temp_path_in_dir,
@@ -28,6 +28,13 @@
 )
 
 
+def _req_line_sort_key(req_line: str) -> str:
+    req_name = get_req_name(req_line)
+    if req_name is None:
+        return req_line
+    return req_name
+
+
 def sync(
     python: str,
     upgrade_all: bool,
@@ -78,8 +85,9 @@
                 ):
                     if isinstance(parsed_req_line, OptionsLine):
                         print(parsed_req_line.raw_line, file=f)
-            # output frozen dependencies of project
-            for req_line in frozen_reqs:
+            # output frozen dependencies of project,
+            # sorted by canonical requirement name
+            for req_line in sorted(frozen_reqs, key=_req_line_sort_key):
                 print(normalize_req_line(req_line), file=f)
     # uninstall unneeded dependencies, if asked to do so
     unneeded_req_names = sorted(