Cherry-pick PR #48463 into release-4.6 (#48477)

Component commits:
9163143 Fix newline inserted in empty block at end of formatting range

79b600a Clean up

19ef6b6 Fix refactoring mistake

Co-authored-by: Andrew Branch <andrew@wheream.io>

src/services/formatting/formatting.ts

@@ -439,20 +439,21 @@ namespace ts.formatting {
         }
 
         if (previousRange! && formattingScanner.getStartPos() >= originalRange.end) {
-            const token =
+            const tokenInfo =
                 formattingScanner.isOnEOF() ? formattingScanner.readEOFTokenRange() :
                 formattingScanner.isOnToken() ? formattingScanner.readTokenInfo(enclosingNode).token :
                 undefined;
 
-            if (token) {
+            if (tokenInfo) {
+                const parent = findPrecedingToken(tokenInfo.end, sourceFile, enclosingNode)?.parent || previousParent!;
                 processPair(
-                    token,
-                    sourceFile.getLineAndCharacterOfPosition(token.pos).line,
-                    enclosingNode,
+                    tokenInfo,
+                    sourceFile.getLineAndCharacterOfPosition(tokenInfo.pos).line,
+                    parent,
                     previousRange,
                     previousRangeStartLine!,
                     previousParent!,
-                    enclosingNode,
+                    parent,
                     /*dynamicIndentation*/ undefined);
             }
         }

src/services/utilities.ts

@@ -1256,8 +1256,10 @@ namespace ts {
      * Finds the rightmost token satisfying `token.end <= position`,
      * excluding `JsxText` tokens containing only whitespace.
      */
-    export function findPrecedingToken(position: number, sourceFile: SourceFile, startNode?: Node, excludeJsdoc?: boolean): Node | undefined {
-        const result = find(startNode || sourceFile);
+    export function findPrecedingToken(position: number, sourceFile: SourceFileLike, startNode: Node, excludeJsdoc?: boolean): Node | undefined;
+    export function findPrecedingToken(position: number, sourceFile: SourceFile, startNode?: Node, excludeJsdoc?: boolean): Node | undefined;
+    export function findPrecedingToken(position: number, sourceFile: SourceFileLike, startNode?: Node, excludeJsdoc?: boolean): Node | undefined {
+        const result = find((startNode || sourceFile) as Node);
         Debug.assert(!(result && isWhiteSpaceOnlyJsxText(result)));
         return result;
 
@@ -1322,7 +1324,7 @@ namespace ts {
         return isToken(n) && !isWhiteSpaceOnlyJsxText(n);
     }
 
-    function findRightmostToken(n: Node, sourceFile: SourceFile): Node | undefined {
+    function findRightmostToken(n: Node, sourceFile: SourceFileLike): Node | undefined {
         if (isNonWhitespaceToken(n)) {
             return n;
         }
@@ -1339,7 +1341,7 @@ namespace ts {
     /**
      * Finds the rightmost child to the left of `children[exclusiveStartPosition]` which is a non-all-whitespace token or has constituent tokens.
      */
-    function findRightmostChildNodeWithTokens(children: Node[], exclusiveStartPosition: number, sourceFile: SourceFile, parentKind: SyntaxKind): Node | undefined {
+    function findRightmostChildNodeWithTokens(children: Node[], exclusiveStartPosition: number, sourceFile: SourceFileLike, parentKind: SyntaxKind): Node | undefined {
         for (let i = exclusiveStartPosition - 1; i >= 0; i--) {
             const child = children[i];
 

tests/cases/fourslash/formatOnTypeOpenCurlyWithBraceCompletion.ts

@@ -0,0 +1,12 @@
+/// <reference path="fourslash.ts"/>
+
+//// if (foo) {
+////     if (bar) {/**/}
+//// }
+
+goTo.marker("");
+format.onType("", "{");
+verify.currentFileContentIs(
+`if (foo) {
+    if (bar) { }
+}`);