Bugfix to correctly handle empty loop

CHANGELOG.md

@@ -1,3 +1,27 @@
+### 3.31.5
+
+Bugfix to correctly handle empty loops.
+
+Fixes https://github.com/open-xml-templating/docxtemplater/issues/680
+
+Previously the following stack trace would be shown :
+
+```txt
+TypeError: Cannot read properties of undefined (reading 'lIndex')
+    at .../docxtemplater/js/modules/loop.js:331:42
+    at Array.some (<anonymous>)
+    at LoopModule.postparse (.../docxtemplater/js/modules/loop.js:322:15)
+    at .../docxtemplater/js/parser.js:226:24
+    at Array.reduce (<anonymous>)
+    at _postparse (.../docxtemplater/js/parser.js:225:22)
+    at postparse (.../docxtemplater/js/parser.js:228:20)
+    at .../docxtemplater/js/modules/expand-pair-trait.js:268:30
+    at Array.reduce (<anonymous>)
+    at Object.postparse (.../docxtemplater/js/modules/expand-pair-trait.js:248:32)
+```
+
+Now the template is rendered correctly.
+
 ### 3.31.4
 
 Bugfix for table module : merge-cells-col did not work correctly when placed inside a loop.

es6/modules/loop.js

@@ -277,21 +277,21 @@ class LoopModule {
 		}, []);
 	}
 	postparse(parsed, { basePart }) {
-		if (basePart && this.docxtemplater.fileType === "docx") {
+		if (basePart && this.docxtemplater.fileType === "docx" && parsed.length > 0) {
 			basePart.sectPrCount = getSectPrHeaderFooterChangeCount(parsed);
 			this.totalSectPr += basePart.sectPrCount;
 
 			const { sects } = this;
 			sects.some(function (sect, index) {
-				if (sect[0].lIndex > basePart.lIndex) {
+				if (basePart.lIndex < sect[0].lIndex) {
 					if (index + 1 < sects.length && isContinuous(sects[index + 1])) {
 						basePart.addContinuousType = true;
 					}
 					return true;
 				}
 				if (
-					sect[0].lIndex > parsed[0].lIndex &&
-					basePart.lIndex > sect[0].lIndex
+					parsed[0].lIndex < sect[0].lIndex &&
+					sect[0].lIndex < basePart.lIndex
 				) {
 					if (isNextPage(sects[index])) {
 						basePart.addNextPage = { index };

es6/tests/e2e/integration.js

@@ -984,3 +984,12 @@ describe("Load Office 365 file", function () {
 		shouldBeSame({ doc, expectedName: "expected-header-without-digit.docx" });
 	});
 });
+
+describe("Loops", function () {
+	it("should work with template", function () {
+		const tags = { ice: [1, 2, 3] };
+		const doc = createDocV4("empty-loop-regression.docx");
+		doc.render(tags);
+		shouldBeSame({ doc, expectedName: "expected-loop-regression.docx" });
+	});
+});