moveToNewFile: Support selecting the name of a declaration (#24331)

src/services/refactors/moveToNewFile.ts

@@ -22,8 +22,14 @@ namespace ts.refactor {
 
         const startNodeIndex = findIndex(statements, s => s.end > range.pos);
         if (startNodeIndex === -1) return undefined;
+
+        const startStatement = statements[startNodeIndex];
+        if (isNamedDeclaration(startStatement) && startStatement.name && rangeContainsRange(startStatement.name, range)) {
+            return { first: startNodeIndex, afterLast: startNodeIndex + 1 };
+        }
+
         // Can't only partially include the start node or be partially into the next node
-        if (range.pos > statements[startNodeIndex].getStart(file)) return undefined;
+        if (range.pos > startStatement.getStart(file)) return undefined;
         const afterEndNodeIndex = findIndex(statements, s => s.end > range.end, startNodeIndex);
         // Can't be partially into the next node
         if (afterEndNodeIndex !== -1 && (afterEndNodeIndex === 0 || statements[afterEndNodeIndex].getStart(file) < range.end)) return undefined;

tests/cases/fourslash/moveToNewFile_selectionOnName.ts

@@ -0,0 +1,19 @@
+/// <reference path='fourslash.ts' />
+
+// @Filename: /a.ts
+////export {};
+////function e[|f|]f() { gee(); }
+////function gee() { eff(); }
+
+verify.moveToNewFile({
+    newFileContents: {
+        "/a.ts":
+`import { eff } from "./eff";
+
+export {};
+export function gee() { eff(); }`,
+        "/eff.ts":
+`import { gee } from "./a";
+export function eff() { gee(); }`,
+    },
+});