Fix prefix removal without a trailing dash

Author: nex3

lib/src/migrators/module.dart

@@ -1256,7 +1256,12 @@ class _ModuleMigrationVisitor extends MigrationVisitor {
     var unprivateName = isPrivate ? _privateToPublic(name) : name;
     var prefix = _prefixFor(unprivateName);
     if (prefix == null) return name;
-    return (isPrivate ? '-' : '') + unprivateName.substring(prefix.length);
+
+    var withoutPrefix = unprivateName.substring(prefix.length);
+    if (_isPrivate(withoutPrefix)) {
+      withoutPrefix = _privateToPublic(withoutPrefix);
+    }
+    return (isPrivate ? '-' : '') + withoutPrefix;
   }
 
   /// Returns the namespace that built-in module [module] is loaded under.

test/migrators/module/remove_prefix_flag/without_dash.hrx

@@ -0,0 +1,39 @@
+<==> arguments
+--remove-prefix=lib
+
+<==> input/entrypoint.scss
+$lib-a: 5;
+$lib_b: $lib-a + 2;
+
+@function lib-fn($lib-local) {
+  @return $lib-local;
+}
+
+@mixin lib-mixin {
+  lib-property: lib-value;
+}
+
+lib-selector {
+  lib-property: lib-fn(0);
+  @include lib-mixin;
+}
+
+<==> output/entrypoint.scss
+$a: 5;
+$b: $a + 2;
+
+@function fn($lib-local) {
+  @return $lib-local;
+}
+
+@mixin mixin {
+  lib-property: lib-value;
+}
+
+lib-selector {
+  lib-property: fn(0);
+  @include mixin;
+}
+
+<==> output/entrypoint.import.scss
+@forward "entrypoint" as lib-*;