respect initial order of changes

Author: vladima

src/harness/unittests/textChanges.ts

@@ -650,5 +650,22 @@ import {
                 changeTracker.insertNodeInListAfter(sourceFile, findChild("x", sourceFile), createImportSpecifier(undefined, createIdentifier("a")));
             })
         }
+        {
+            const text = `
+class A {
+    x;
+}`;
+            runSingleFileTest("insertNodeAfterMultipleNodes", noop, text, /*validateNodes*/ false, (sourceFile, changeTracker) => {
+                let newNodes = [];
+                for (let i = 0; i < 11 /*error doesn't occur with fewer nodes*/; ++i) {
+                    newNodes.push(
+                        createProperty(undefined, undefined, i + "", undefined, undefined, undefined));
+                }
+                const insertAfter = findChild("x", sourceFile);
+                for (const newNode of newNodes) {
+                    changeTracker.insertNodeAfter(sourceFile, insertAfter, newNode, { suffix: newLineCharacter });
+                }
+            });
+        }
     });
 }

src/services/textChanges.ts

@@ -407,10 +407,8 @@ namespace ts.textChanges {
             changesPerFile.forEachValue(path => {
                 const changesInFile = changesPerFile.get(path);
                 const sourceFile = changesInFile[0].sourceFile;
-                ChangeTracker.normalize(changesInFile);
-
                 const fileTextChanges: FileTextChanges = { fileName: sourceFile.fileName, textChanges: [] };
-                for (const c of changesInFile) {
+                for (const c of ChangeTracker.normalize(changesInFile)) {
                     fileTextChanges.textChanges.push({
                         span: this.computeSpan(c, sourceFile),
                         newText: this.computeNewText(c, sourceFile)
@@ -463,11 +461,15 @@ namespace ts.textChanges {
 
         private static normalize(changes: Change[]) {
             // order changes by start position
-            changes.sort((a, b) => a.range.pos - b.range.pos);
+            const normalized = changes
+                .map((c, i) => ({ c, i }))
+                .sort(({ c: a, i: i1 }, { c: b, i: i2 }) => (a.range.pos - b.range.pos) || i1 - i2)
+                .map(({ c }) => c);
             // verify that end position of the change is less than start position of the next change
-            for (let i = 0; i < changes.length - 2; i++) {
-                Debug.assert(changes[i].range.end <= changes[i + 1].range.pos);
+            for (let i = 0; i < normalized.length - 2; i++) {
+                Debug.assert(normalized[i].range.end <= normalized[i + 1].range.pos);
             }
+            return normalized;
         }
     }
 

tests/baselines/reference/textChanges/insertNodeAfterMultipleNodes.js

@@ -0,0 +1,21 @@
+===ORIGINAL===
+
+class A {
+    x;
+}
+===MODIFIED===
+
+class A {
+    x;
+    0;
+    1;
+    2;
+    3;
+    4;
+    5;
+    6;
+    7;
+    8;
+    9;
+    10;
+}