From 8fff795a4449c12a2b5ad2bc8aeb1708cf467b61 Mon Sep 17 00:00:00 2001
From: agrancaric <agrancaric@croz.net>
Date: Mon, 19 Aug 2024 09:35:56 +0200
Subject: [PATCH] Limit quoting strings in excel to string that starts with one
 of formula characters

---
 .../nrich/excel/generator/PoiExcelReportGenerator.java   | 9 +++++++--
 .../excel/generator/PoiExcelReportGeneratorTest.java     | 4 ++--
 2 files changed, 9 insertions(+), 4 deletions(-)

diff --git a/nrich-excel/src/main/java/net/croz/nrich/excel/generator/PoiExcelReportGenerator.java b/nrich-excel/src/main/java/net/croz/nrich/excel/generator/PoiExcelReportGenerator.java
index 878fecc6..e4c0b68c 100644
--- a/nrich-excel/src/main/java/net/croz/nrich/excel/generator/PoiExcelReportGenerator.java
+++ b/nrich-excel/src/main/java/net/croz/nrich/excel/generator/PoiExcelReportGenerator.java
@@ -49,6 +49,8 @@ public class PoiExcelReportGenerator implements ExcelReportGenerator {
 
     private static final Pattern TEMPLATE_VARIABLE_PATTERN = Pattern.compile("\\$\\{(.*?)}");
 
+    private static final List<String> FORMULA_CHARACTER_LIST = List.of("=", "+", "-", "@");
+
     private final List<CellValueConverter> cellValueConverterList;
 
     private final OutputStream outputStream;
@@ -149,8 +151,11 @@ private void setCellValue(Cell cell, Object value, CellStyle style) {
             .orElse(null);
 
         if (converter == null) {
-            cell.setCellValue(value.toString());
-            cell.getCellStyle().setQuotePrefixed(true);
+            String stringValue = value.toString();
+            cell.setCellValue(stringValue);
+            if (stringValue != null && FORMULA_CHARACTER_LIST.stream().anyMatch(stringValue::startsWith)) {
+                cell.getCellStyle().setQuotePrefixed(true);
+            }
         }
         else {
             converter.setCellValue(cellHolder, value);
diff --git a/nrich-excel/src/test/java/net/croz/nrich/excel/generator/PoiExcelReportGeneratorTest.java b/nrich-excel/src/test/java/net/croz/nrich/excel/generator/PoiExcelReportGeneratorTest.java
index ba3f7aee..4002c491 100644
--- a/nrich-excel/src/test/java/net/croz/nrich/excel/generator/PoiExcelReportGeneratorTest.java
+++ b/nrich-excel/src/test/java/net/croz/nrich/excel/generator/PoiExcelReportGeneratorTest.java
@@ -90,10 +90,10 @@ void shouldExportDataToExcel() {
         Instant now = Instant.now().truncatedTo(ChronoUnit.DAYS);
         Object[] rowData = new Object[] {
             1.1, "value", new Date(now.toEpochMilli()), ZonedDateTime.now().truncatedTo(ChronoUnit.DAYS), OffsetDateTime.now().truncatedTo(ChronoUnit.DAYS), now, now, 1, 1.5F, (short) 1,
-            LocalDate.now(), LocalDateTime.now().truncatedTo(ChronoUnit.DAYS), BigDecimal.valueOf(1.5), 10L, TestEnum.FIRST, TestEnum.SECOND, null
+            LocalDate.now(), LocalDateTime.now().truncatedTo(ChronoUnit.DAYS), BigDecimal.valueOf(1.5), 10L, TestEnum.FIRST, TestEnum.SECOND, null, "=123"
         };
         // when resolving data from cells all dates are converted to instant, all decimal numbers are converted to double and all whole numbers are converted to integer
-        Object[] expectedRowData = new Object[] { 1.1, "value", now, now, now, now, now, 1, 1.5, 1, now, now, 1.5, 10, "First", "SECOND", null };
+        Object[] expectedRowData = new Object[] { 1.1, "value", now, now, now, now, now, 1, 1.5, 1, now, now, 1.5, 10, "First", "SECOND", null, "=123" };
 
         // when
         excelReportGenerator.writeRowData(rowData);