Bug 1741548 - Add ignoreAbsent option to `IOUtils.getChildren` method. r=barret

Remove an incorrect comment.

Differential Revision: https://phabricator.services.mozilla.com/D131323

dom/chrome-webidl/IOUtils.webidl

@@ -176,8 +176,7 @@ namespace IOUtils {
   Promise<long long> setModificationTime(DOMString path, optional long long modification);
   /**
    * Retrieves a (possibly empty) list of immediate children of the directory at
-   * |path|. If the file at |path| is not a directory, this method resolves with
-   * an empty list.
+   * |path|.
    *
    * @param path An absolute file path.
    *
@@ -185,7 +184,7 @@ namespace IOUtils {
    *         children of the directory at |path|, otherwise rejects with a
    *         DOMException.
    */
-  Promise<sequence<DOMString>> getChildren(DOMString path);
+  Promise<sequence<DOMString>> getChildren(DOMString path, optional GetChildrenOptions options = {});
   /**
    * Set the permissions of the file at |path|.
    *
@@ -413,6 +412,16 @@ dictionary CopyOptions {
   boolean recursive = false;
 };
 
+/**
+ * Options to be passed to the |IOUtils.getChildren| method.
+ */
+dictionary GetChildrenOptions {
+  /**
+   * If true, no error will be reported if the target file is missing.
+   */
+  boolean ignoreAbsent = false;
+};
+
 /**
  * Types of files that are recognized by the |IOUtils.stat| method.
  */

dom/system/IOUtils.cpp

@@ -737,8 +737,9 @@ already_AddRefed<Promise> IOUtils::SetModificationTime(
 }
 
 /* static */
-already_AddRefed<Promise> IOUtils::GetChildren(GlobalObject& aGlobal,
-                                               const nsAString& aPath) {
+already_AddRefed<Promise> IOUtils::GetChildren(
+    GlobalObject& aGlobal, const nsAString& aPath,
+    const GetChildrenOptions& aOptions) {
   MOZ_DIAGNOSTIC_ASSERT(XRE_IsParentProcess());
   RefPtr<Promise> promise = CreateJSPromise(aGlobal);
   if (!promise) {
@@ -751,7 +752,9 @@ already_AddRefed<Promise> IOUtils::GetChildren(GlobalObject& aGlobal,
 
     DispatchAndResolve<nsTArray<nsString>>(
         state.ref()->mEventQueue, promise,
-        [file = std::move(file)]() { return GetChildrenSync(file); });
+        [file = std::move(file), ignoreAbsent = aOptions.mIgnoreAbsent]() {
+          return GetChildrenSync(file, ignoreAbsent);
+        });
   } else {
     RejectShuttingDown(promise);
   }
@@ -1465,11 +1468,15 @@ Result<int64_t, IOUtils::IOError> IOUtils::SetModificationTimeSync(
 
 /* static */
 Result<nsTArray<nsString>, IOUtils::IOError> IOUtils::GetChildrenSync(
-    nsIFile* aFile) {
+    nsIFile* aFile, bool aIgnoreAbsent) {
   MOZ_ASSERT(!NS_IsMainThread());
 
+  nsTArray<nsString> children;
   nsCOMPtr<nsIDirectoryEnumerator> iter;
   nsresult rv = aFile->GetDirectoryEntries(getter_AddRefs(iter));
+  if (aIgnoreAbsent && IsFileNotFound(rv)) {
+    return children;
+  }
   if (NS_FAILED(rv)) {
     IOError err(rv);
     if (IsFileNotFound(rv)) {
@@ -1484,7 +1491,6 @@ Result<nsTArray<nsString>, IOUtils::IOError> IOUtils::GetChildrenSync(
     }
     return Err(err);
   }
-  nsTArray<nsString> children;
 
   bool hasMoreElements = false;
   MOZ_TRY(iter->HasMoreElements(&hasMoreElements));

dom/system/IOUtils.h

@@ -112,8 +112,9 @@ class IOUtils final {
       GlobalObject& aGlobal, const nsAString& aPath,
       const Optional<int64_t>& aModification);
 
-  static already_AddRefed<Promise> GetChildren(GlobalObject& aGlobal,
-                                               const nsAString& aPath);
+  static already_AddRefed<Promise> GetChildren(
+      GlobalObject& aGlobal, const nsAString& aPath,
+      const GetChildrenOptions& aOptions);
 
   static already_AddRefed<Promise> SetPermissions(GlobalObject& aGlobal,
                                                   const nsAString& aPath,
@@ -339,7 +340,8 @@ class IOUtils final {
    * @return An array of absolute paths identifying the children of |aFile|.
    *         If there are no children, an empty array. Otherwise, an error.
    */
-  static Result<nsTArray<nsString>, IOError> GetChildrenSync(nsIFile* aFile);
+  static Result<nsTArray<nsString>, IOError> GetChildrenSync(
+      nsIFile* aFile, bool aIgnoreAbsent);
 
   /**
    * Set the permissions of the given file.

dom/system/tests/ioutils/test_ioutils_dir_iteration.html

@@ -72,6 +72,20 @@
 
       await cleanup(emptyDir);
     });
+
+    add_task(async function iterate_ignore_missing_dir() {
+      info("Try to get the children of a missing file with ignoreAbsent");
+
+      const tmpDir = await PathUtils.getTempDir();
+      const notExists = PathUtils.join(tmpDir, "does_not_exist_dir.tmp.d");
+
+      is(
+        (await IOUtils.getChildren(notExists, { ignoreAbsent: true })).length,
+        0,
+        "IOUtils::getChildren returns an empty array when called with ignoreAbsent on a missing file"
+      );
+      ok(!await fileExists(notExists), `Expected ${notExists} not to exist`);
+    });
   </script>
 </head>