Ensure that showSaveFilePicker always shows the extension on Mac.

While not a very strong security boundary, making it possible for
users to know what extension a file will be saved with is a good idea.

This also fixes support for compound extensions with the File System
Access API (i.e. ".tar.gz"). The mac file dialog already had a
workaround if the default path ended in such an extension, but the
same problem occurs if the file type filters include a type with a
compound extension.

Bug: 1137247
Change-Id: I492bf36baced3de044b8fed5d57fc7b9b5b64400
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2582842Reviewed-by: Daniel Cheng <dcheng@chromium.org>
Reviewed-by: Avi Drissman <avi@chromium.org>
Commit-Queue: Marijn Kruisselbrink <mek@chromium.org>
Cr-Commit-Position: refs/heads/master@{#835803}

components/remote_cocoa/app_shim/select_file_dialog_bridge.mm

@@ -206,6 +206,8 @@ void SelectFileDialogBridge::Show(
     }
   }
 
+  const bool keep_extension_visible =
+      file_types ? file_types->keep_extension_visible : false;
   if (type_ != SelectFileDialogType::kFolder &&
       type_ != SelectFileDialogType::kUploadFolder &&
       type_ != SelectFileDialogType::kExistingFolder) {
@@ -227,7 +229,7 @@ void SelectFileDialogBridge::Show(
     // this by never hiding extensions in that case.
     base::FilePath::StringType penultimate_extension =
         default_path.RemoveFinalExtension().FinalExtension();
-    if (!penultimate_extension.empty()) {
+    if (!penultimate_extension.empty() || keep_extension_visible) {
       [dialog setExtensionHidden:NO];
     } else {
       [dialog setExtensionHidden:YES];

components/remote_cocoa/common/select_file_dialog.mojom

@@ -28,6 +28,9 @@ struct SelectFileTypeInfo {
 
   // Specifies whether or not there is be a filter added for all files.
   bool include_all_files;
+
+  // Specifies whether the (save) file dialog should keep the extension visible.
+  bool keep_extension_visible;
 };
 
 // The interface to a file selection (Save As, Upload, etc) dialog.

content/browser/file_system_access/file_system_chooser.cc

@@ -173,6 +173,7 @@ ui::SelectFileDialog::FileTypeInfo ConvertAcceptsToFileTypeInfo(
     file_types.include_all_files = true;
 
   file_types.allowed_paths = ui::SelectFileDialog::FileTypeInfo::ANY_PATH;
+  file_types.keep_extension_visible = true;
 
   return file_types;
 }

ui/shell_dialogs/select_file_dialog.cc

@@ -26,8 +26,7 @@ ui::SelectFileDialogFactory* dialog_factory_ = NULL;
 
 namespace ui {
 
-SelectFileDialog::FileTypeInfo::FileTypeInfo()
-    : include_all_files(false), allowed_paths(NATIVE_PATH) {}
+SelectFileDialog::FileTypeInfo::FileTypeInfo() = default;
 
 SelectFileDialog::FileTypeInfo::FileTypeInfo(const FileTypeInfo& other) =
     default;

ui/shell_dialogs/select_file_dialog.h

@@ -135,7 +135,13 @@ class SHELL_DIALOGS_EXPORT SelectFileDialog
     std::vector<base::string16> extension_description_overrides;
 
     // Specifies whether there will be a filter added for all files (i.e. *.*).
-    bool include_all_files;
+    bool include_all_files = false;
+
+    // Some implementations by default hide the extension of a file, in
+    // particular in a save file dialog. If this is set to true, where
+    // supported, the save file dialog will instead keep the file extension
+    // visible.
+    bool keep_extension_visible = false;
 
     // Specifies which type of paths the caller can handle.
     enum AllowedPaths {
@@ -153,7 +159,7 @@ class SHELL_DIALOGS_EXPORT SelectFileDialog
       // docs.google.com URL.
       ANY_PATH_OR_URL
     };
-    AllowedPaths allowed_paths;
+    AllowedPaths allowed_paths = NATIVE_PATH;
   };
 
   // Returns a file path with a base name at most 255 characters long. This

ui/shell_dialogs/select_file_dialog_mac.mm

@@ -135,6 +135,8 @@ void SelectFileDialogImpl::SelectFileImpl(
     mojo_file_types->extension_description_overrides =
         file_types->extension_description_overrides;
     mojo_file_types->include_all_files = file_types->include_all_files;
+    mojo_file_types->keep_extension_visible =
+        file_types->keep_extension_visible;
   }
 
   auto callback = base::BindOnce(&SelectFileDialogImpl::FileWasSelected,

ui/shell_dialogs/select_file_dialog_mac_unittest.mm

@@ -503,8 +503,29 @@ TEST_F(SelectFileDialogMacTest, MultipleExtension) {
   EXPECT_FALSE([panel isExtensionHidden]);
 }
 
-// Test to ensure lifetime is sound if a reference to the panel outlives the
-// delegate.
+// Verify that the file dialog does not hide extension when the
+// `keep_extension_visible` flag is set to true.
+TEST_F(SelectFileDialogMacTest, KeepExtensionVisible) {
+  const std::string extensions_arr[][2] = {{"html", "htm"}, {"jpeg", "jpg"}};
+
+  SelectFileDialog::FileTypeInfo file_type_info;
+  file_type_info.extensions.push_back(
+      GetVectorFromArray<std::string>(extensions_arr[0]));
+  file_type_info.extensions.push_back(
+      GetVectorFromArray<std::string>(extensions_arr[1]));
+  file_type_info.keep_extension_visible = true;
+
+  FileDialogArguments args(GetDefaultArguments());
+  args.file_types = &file_type_info;
+
+  SelectFileWithParams(args);
+  NSSavePanel* panel = GetPanel();
+  EXPECT_FALSE([panel canSelectHiddenExtension]);
+  EXPECT_FALSE([panel isExtensionHidden]);
+}
+
+// Test to ensure lifetime is sound if a reference to
+// the panel outlives the delegate.
 TEST_F(SelectFileDialogMacTest, Lifetime) {
   base::scoped_nsobject<NSSavePanel> panel;
   @autoreleasepool {