preserve selection during filter changes

Summary:
During filter changes, DataTable would loose any selections made, which was posted multiple times as papercut

I didn't implement preserving multi line selections. That should be straightforward, but wasn't sure that'd be desirable or not.

Changelog: DataTable: Data tables will now preserve the current selection and scroll it into view when changing the search filter.

Reviewed By: aigoncharov

Differential Revision: D36736496

fbshipit-source-id: 401ef351c847f58a5d411cf9f352390f6a110b24

desktop/flipper-plugin/src/data-source/DataSource.tsx

@@ -582,6 +582,21 @@ class DataSourceView<T, KeyType> {
     return this._output[this.normalizeIndex(viewIndex)]?.value;
   }
 
+  public getEntry(viewIndex: number): Entry<T> {
+    return this._output[this.normalizeIndex(viewIndex)];
+  }
+
+  public getViewIndexOfEntry(entry: Entry<T>) {
+    // Note: this function leverages the fact that entry is an internal structure that is mutable,
+    // so any changes in the entry being moved around etc will be reflected in the original `entry` object,
+    // and we just want to verify that this entry is indeed still the same element, visible, and still present in
+    // the output data set.
+    if (entry.visible && entry.id === this._output[entry.approxIndex]?.id) {
+      return this.normalizeIndex(entry.approxIndex);
+    }
+    return -1;
+  }
+
   public [Symbol.iterator](): IterableIterator<T> {
     const self = this;
     let offset = this.windowStart;
@@ -797,6 +812,10 @@ class DataSourceView<T, KeyType> {
       output = lodashSort(output, sortHelper); // uses array.sort under the hood
     }
 
+    // write approx indexes for faster lookup of entries in visible output
+    for (let i = 0; i < output.length; i++) {
+      output[i].approxIndex = i;
+    }
     this._output = output;
     this.notifyReset(output.length);
   }

desktop/flipper-plugin/src/ui/data-table/DataTable.tsx

@@ -33,6 +33,7 @@ import {
   computeDataTableFilter,
   createDataTableManager,
   createInitialState,
+  DataManagerState,
   DataTableManager,
   dataTableManagerReducer,
   DataTableReducer,
@@ -323,37 +324,52 @@ export function DataTable<T extends object>(
     [dataSource, tableManager, props.scrollable],
   );
 
+  const [setFilter] = useState(() => (tableState: DataManagerState<T>) => {
+    const selectedEntry =
+      tableState.selection.current >= 0
+        ? dataSource.view.getEntry(tableState.selection.current)
+        : null;
+    dataSource.view.setFilter(
+      computeDataTableFilter(
+        tableState.searchValue,
+        tableState.useRegex,
+        tableState.columns,
+      ),
+    );
+    // TODO: in the future setFilter effects could be async, at the moment it isn't,
+    // so we can safely assume the internal state of the dataSource.view is updated with the
+    // filter changes and try to find the same entry back again
+    if (selectedEntry) {
+      const selectionIndex = dataSource.view.getViewIndexOfEntry(selectedEntry);
+      tableManager.selectItem(selectionIndex, false, false);
+      // we disable autoScroll as is it can accidentally be annoying if it was never turned off and
+      // filter causes items to not fill the available space
+      dispatch({type: 'setAutoScroll', autoScroll: false});
+      virtualizerRef.current?.scrollToIndex(selectionIndex, {align: 'center'});
+      setTimeout(() => {
+        virtualizerRef.current?.scrollToIndex(selectionIndex, {
+          align: 'center',
+        });
+      }, 0);
+    }
+    // TODO: could do the same for multiselections, doesn't seem to be requested so far
+  });
+
   const [debouncedSetFilter] = useState(() => {
     // we don't want to trigger filter changes too quickly, as they can be pretty expensive
     // and would block the user from entering text in the search bar for example
     // (and in the future would really benefit from concurrent mode here :))
-    const setFilter = (
+    // leading is set to true so that an initial filter is immediately applied and a flash of wrong content is prevented
-      search: string,
+    // this also makes clear act faster
-      useRegex: boolean,
-      columns: DataTableColumn<T>[],
-    ) => {
-      dataSource.view.setFilter(
-        computeDataTableFilter(search, useRegex, columns),
-      );
-    };
     return isUnitTest ? setFilter : debounce(setFilter, 250);
   });
+
   useEffect(
     function updateFilter() {
       if (!dataSource.view.isFiltered) {
-        dataSource.view.setFilter(
+        setFilter(tableState);
-          computeDataTableFilter(
-            tableState.searchValue,
-            tableState.useRegex,
-            tableState.columns,
-          ),
-        );
       } else {
-        debouncedSetFilter(
+        debouncedSetFilter(tableState);
-          tableState.searchValue,
-          tableState.useRegex,
-          tableState.columns,
-        );
       }
     },
     // Important dep optimization: we don't want to recalc filters if just the width or visibility changes!

desktop/flipper-plugin/src/ui/data-table/DataTableManager.tsx

@@ -110,7 +110,7 @@ type DataManagerConfig<T> = {
   enablePersistSettings?: boolean;
 };
 
-type DataManagerState<T> = {
+export type DataManagerState<T> = {
   config: DataManagerConfig<T>;
   usesWrapping: boolean;
   storageKey: string;