From 824e4e01b5fe3720168c23fe94be4391be67ea7c Mon Sep 17 00:00:00 2001
From: Florian Damhaut <flda@odoo.com>
Date: Tue, 2 Dec 2025 16:50:10 +0100
Subject: [PATCH] [IMP] formats: Set format when writing date on number format

Task: 5349524
---
 .../src/plugins/core/cell.ts                  | 13 +++++++++++-
 tests/formats/formatting_plugin.test.ts       | 20 +++++++++++++++++++
 2 files changed, 32 insertions(+), 1 deletion(-)

diff --git a/packages/o-spreadsheet-engine/src/plugins/core/cell.ts b/packages/o-spreadsheet-engine/src/plugins/core/cell.ts
index ba294ed64d..f54758fa12 100644
--- a/packages/o-spreadsheet-engine/src/plugins/core/cell.ts
+++ b/packages/o-spreadsheet-engine/src/plugins/core/cell.ts
@@ -29,6 +29,7 @@ import { parseLiteral } from "../../helpers/cells/cell_evaluation";
 import {
   detectDateFormat,
   detectNumberFormat,
+  isDateTimeFormat,
   isExcelCompatible,
   isTextFormat,
 } from "../../helpers/format/format";
@@ -510,8 +511,18 @@ export class CellPlugin extends CorePlugin<CoreState> implements CoreState {
 
     // Compute the new cell properties
     const afterContent = hasContent ? replaceNewLines(after?.content) : before?.content || "";
-    const format = "format" in after ? after.format : before && before.format;
 
+    let format: Format | undefined = undefined;
+    if (after.format !== undefined) {
+      format = after.format;
+    } else if (before?.format && (before?.format === "@" || isDateTimeFormat(before?.format))) {
+      format = before.format;
+    } else if (after.content) {
+      format = detectDateFormat(after.content, this.getters.getLocale());
+    }
+    if (format === undefined) {
+      format = before?.format || undefined;
+    }
     /* Read the following IF as:
      * we need to remove the cell if it is completely empty, but we can know if it completely empty if:
      * - the command says the new content is empty and has no format
diff --git a/tests/formats/formatting_plugin.test.ts b/tests/formats/formatting_plugin.test.ts
index 7b2fdeaf38..fdc1327c8d 100644
--- a/tests/formats/formatting_plugin.test.ts
+++ b/tests/formats/formatting_plugin.test.ts
@@ -445,6 +445,26 @@ describe("formatting values (when change decimal)", () => {
     expect(getCell(model, "A1")!.format).toBe("0%");
   });
 
+  test.each(["", "0%", "#,##0", "#,##0[$ THUNE ]"])(
+    "Set Date to a cell formatted with format %s, format should be adapted",
+    (format: string) => {
+      const model = new Model();
+      setFormat(model, "A1", format);
+      setCellContent(model, "A1", "12/12/2025");
+      expect(getEvaluatedCell(model, "A1").format).toBe("m/d/yyyy");
+    }
+  );
+
+  test.each(["@", "d/m/yyyy"])(
+    "Set date to a cell formatted with format %s, format should not be adapted",
+    (format: string) => {
+      const model = new Model();
+      setFormat(model, "A1", format);
+      setCellContent(model, "A1", "12/12/2025");
+      expect(getEvaluatedCell(model, "A1").format).toBe(format);
+    }
+  );
+
   test.each([
     ["0%", "0.0%", "0.00%"],
     ["#,##0", "#,##0.0", "#,##0.00"],