Treat a trailing dot parent as the current directory in isWithin

pkgs/path/CHANGELOG.md

@@ -1,5 +1,7 @@
 ## 1.9.2-wip
 
+- `isWithin` treats a parent that ends in `/.` as that directory, so
+  `isWithin('/dir/.', '/dir/.file')` is true.
 - Make `Url` style better at recognizing schemes and authorities.
   Only consider a path as being a schemed URL if it starts with a
   valid scheme.

pkgs/path/lib/src/context.dart

@@ -731,6 +731,28 @@ final class Context {
     while (parentIndex < parent.length && childIndex < child.length) {
       var parentCodeUnit = parent.codeUnitAt(parentIndex);
       var childCodeUnit = child.codeUnitAt(childIndex);
+
+      // A lone "." component means "this directory". Skip it before comparing
+      // characters so a parent like "/dir/." is the same directory as "/dir"
+      // and still contains children such as "/dir/.file". Matching the "."
+      // against the child's next character would treat ".file" as a different
+      // component and reject a path that is actually inside the parent.
+      if (parentCodeUnit == chars.period && style.isSeparator(lastCodeUnit)) {
+        final nextParentIndex = parentIndex + 1;
+        final dotIsComponent = nextParentIndex == parent.length ||
+            style.isSeparator(parent.codeUnitAt(nextParentIndex));
+        if (dotIsComponent) {
+          parentIndex = nextParentIndex;
+          if (parentIndex < parent.length &&
+              style.isSeparator(parent.codeUnitAt(parentIndex))) {
+            lastParentSeparator = parentIndex;
+            lastCodeUnit = parent.codeUnitAt(parentIndex);
+            parentIndex++;
+          }
+          continue;
+        }
+      }
+
       if (style.codeUnitsEqual(parentCodeUnit, childCodeUnit)) {
         if (style.isSeparator(parentCodeUnit)) {
           lastParentSeparator = parentIndex;

pkgs/path/test/posix_test.dart

@@ -578,6 +578,15 @@ void main() {
       expect(context.isWithin('foo/bar', 'foo/bar///'), isFalse);
       expect(context.isWithin('foo/.bar', 'foo/.bar/baz'), isTrue);
       expect(context.isWithin('foo/./bar', 'foo/.bar/baz'), isFalse);
+      // A trailing "." is the current directory, so it must not be glued onto
+      // a child whose next component merely starts with ".".
+      expect(context.isWithin('/dir/.', '/dir/.file'), isTrue);
+      expect(context.isWithin('/dir/.', '/dir/file'), isTrue);
+      expect(context.isWithin('/dir/.', '/dir'), isFalse);
+      expect(context.isWithin('/dir/.', '/dir/./.file'), isTrue);
+      expect(context.isWithin('foo/.', 'foo/.file'), isTrue);
+      expect(context.equals('/dir/.', '/dir'), isTrue);
+      expect(context.equals('/dir/.', '/dir/.'), isTrue);
       expect(context.isWithin('foo/..bar', 'foo/..bar/baz'), isTrue);
       expect(context.isWithin('foo/bar', 'foo/bar/baz/..'), isFalse);
       expect(context.isWithin('foo/bar', 'foo/bar/baz/../qux'), isTrue);