rust2rpm: only remove optional target-specific deps from features

rust2rpm/__main__.py

@@ -204,30 +204,41 @@ def filter_out_features_re(dropped_features):
 
 def drop_foreign_dependencies(lines):
     dropped_lines = 0
-    dropped_features = set()
+    dropped_optional_deps = set()
     good_lines = []
 
-    value = True
+    keep = True
+    feature = None
     for line in lines:
         if m := TARGET_DEPENDENCY_LINE.match(line):
             expr = m.group("cfg")
             expr = ast.literal_eval(expr)
             try:
-                value = cfg.parse_and_evaluate(expr)
+                keep = cfg.parse_and_evaluate(expr)
             except (ValueError, cfg.ParseException):
                 log.warn(f"Could not evaluate {expr!r}, treating as true.")
-                value = True
+                keep = True
 
-            if not value:
+            if not keep:
                 feature = m.group("feature")
                 log.info(f"Dropping target-specific dependency on {feature!r}.")
-                dropped_features.add(feature)
+
+        elif line == "optional = true\n" and feature:
+            if not keep:
+                # dropped feature was optional:
+                # remove occurrences from feature dependencies
+                dropped_optional_deps.add(feature)
+            else:
+                # optional dependency occurs in multiple targets:
+                # do not drop from feature dependencies
+                if feature in dropped_optional_deps:
+                    dropped_optional_deps.remove(feature)
 
         elif line.startswith("["):
             # previous section ended, let's keep printing lines again
-            value = True
+            keep = True
 
-        if value:
+        if keep:
             good_lines += [line]
         else:
             dropped_lines += 1
@@ -238,7 +249,7 @@ def drop_foreign_dependencies(lines):
 
     good_lines2 = []
     in_features = False
-    filt = filter_out_features_re(dropped_features)
+    filt = filter_out_features_re(dropped_optional_deps)
     for line in good_lines:
         if line.rstrip() == "[features]":
             in_features = True