Bug 1745352 - Add depth param to PathUtils.getParent to get aribtrary ancestors r=Gijs

Differential Revision: https://phabricator.services.mozilla.com/D133842

dom/chrome-webidl/PathUtils.webidl

@@ -20,17 +20,19 @@ namespace PathUtils {
   DOMString filename(DOMString path);
 
   /**
-   * Return the parent directory name of the given path.
+   * Return an ancestor directory of the given path.
    *
    * @param path An absolute path.
+   * @param depth The number of ancestors to remove, defaulting to 1 (i.e., the
+   *              parent).
    *
-   * @return The parent directory.
+   * @return The ancestor directory.
    *
    *         If the path provided is a root path (e.g., `C:` on Windows or `/`
    *         on *NIX), then null is returned.
    */
   [Throws]
-  DOMString? parent(DOMString path);
+  DOMString? parent(DOMString path, optional long depth = 1);
 
   /**
    * Join the given components into a full path.

dom/system/PathUtils.cpp

@@ -142,7 +142,8 @@ void PathUtils::Filename(const GlobalObject&, const nsAString& aPath,
 }
 
 void PathUtils::Parent(const GlobalObject&, const nsAString& aPath,
-                       nsString& aResult, ErrorResult& aErr) {
+                       const int32_t aDepth, nsString& aResult,
+                       ErrorResult& aErr) {
   if (aPath.IsEmpty()) {
     aErr.ThrowNotAllowedError(ERROR_EMPTY_PATH);
     return;
@@ -154,12 +155,20 @@ void PathUtils::Parent(const GlobalObject&, const nsAString& aPath,
     return;
   }
 
-  nsCOMPtr<nsIFile> parent;
-  if (nsresult rv = path->GetParent(getter_AddRefs(parent)); NS_FAILED(rv)) {
-    ThrowError(aErr, rv, ERROR_GET_PARENT);
+  if (aDepth <= 0) {
+    aErr.ThrowNotSupportedError("A depth of at least 1 is required");
     return;
   }
 
+  nsCOMPtr<nsIFile> parent;
+  for (int32_t i = 0; path && i < aDepth; i++) {
+    if (nsresult rv = path->GetParent(getter_AddRefs(parent)); NS_FAILED(rv)) {
+      ThrowError(aErr, rv, ERROR_GET_PARENT);
+      return;
+    }
+    path = parent;
+  }
+
   if (parent) {
     MOZ_ALWAYS_SUCCEEDS(parent->GetPath(aResult));
   } else {

dom/system/PathUtils.h

@@ -41,7 +41,8 @@ class PathUtils final {
                        nsString& aResult, ErrorResult& aErr);
 
   static void Parent(const GlobalObject&, const nsAString& aPath,
-                     nsString& aResult, ErrorResult& aErr);
+                     const int32_t aDepth, nsString& aResult,
+                     ErrorResult& aErr);
 
   static void Join(const GlobalObject&, const Sequence<nsString>& aComponents,
                    nsString& aResult, ErrorResult& aErr);

dom/system/tests/test_pathutils.html

@@ -119,6 +119,37 @@
         "\\\\server",
         "PathUtils.parent() with a UNC server path and child component"
       );
+
+      Assert.throws(
+        () => PathUtils.parent("C:", -1),
+        /^NotSupportedError: PathUtils.parent: A depth of at least 1 is required/,
+        "PathUtils.parent() with a negative depth throws"
+      );
+      Assert.throws(
+        () => PathUtils.parent("C:", 0),
+        /^NotSupportedError: PathUtils.parent: A depth of at least 1 is required/,
+        "PathUtils.parent() with a zero depth throws"
+      );
+
+      {
+        const path = "C:\\Users\\User\\AppData\\Local\\Mozilla\\Firefox\\Profiles\\foo.default";
+
+        const expected = [
+          "C:\\Users\\User\\AppData\\Local\\Mozilla\\Firefox\\Profiles",
+          "C:\\Users\\User\\AppData\\Local\\Mozilla\\Firefox",
+          "C:\\Users\\User\\AppData\\Local\\Mozilla",
+          "C:\\Users\\User\\AppData\\Local",
+          "C:\\Users\\User\\AppData",
+          "C:\\Users\\User",
+          "C:\\Users",
+          "C:",
+          null,
+        ];
+
+        for (const [i, parent] of expected.entries()) {
+          is(PathUtils.parent(path, i + 1), parent, `PathUtils.parent() with depth=${i + 1}`)
+        }
+      }
     } else {
       is(
         PathUtils.parent("/"),
@@ -135,6 +166,37 @@
         "/var",
         "PathUtils.parent() with a 3 component path"
       );
+
+      Assert.throws(
+        () => PathUtils.parent("/", -1),
+        /^NotSupportedError: PathUtils.parent: A depth of at least 1 is required/,
+        "PathUtils.parent() with a negative depth throws"
+      );
+      Assert.throws(
+        () => PathUtils.parent("/", 0),
+        /^NotSupportedError: PathUtils.parent: A depth of at least 1 is required/,
+        "PathUtils.parent() with a zero depth throws"
+      );
+
+      {
+        const path = "/home/user/.mozilla/firefox/foo.default";
+        const expected = [
+          "/home/user/.mozilla/firefox",
+          "/home/user/.mozilla",
+          "/home/user/",
+          "/home",
+          "/",
+          null,
+        ];
+
+        for (const [i, parent] of expected.entries()) {
+          is(
+            PathUtils.parent(path, i + 1),
+            parent,
+            `PathUtils.parent() with depth=${i + 1}`
+          );
+        }
+      }
     }
   });