fix(xlsx): read filled-down formulas, formula errors and times as shown

src/integrations/misc/__tests__/extract-text-from-xlsx.test.ts

@@ -214,6 +214,110 @@ describe("formatWorkbook", () => {
 			expect(result).toContain("30") // Formula with result
 			expect(result).toContain("[Formula: SUM(B1:B10)]") // Formula without result
 		})
+
+		it("should read every cell of a filled-down formula", () => {
+			const workbook = new ExcelJS.Workbook()
+			const worksheet = workbook.addWorksheet("Sheet1")
+
+			// Excel saves a formula filled down a column as one shared formula
+			worksheet.getCell("A1").value = { formula: "B1*2", result: 2 }
+			worksheet.getCell("A2").value = { sharedFormula: "A1", result: 4 }
+			worksheet.getCell("A3").value = { sharedFormula: "A1" }
+
+			const result = formatWorkbook(workbook)
+
+			expect(result).toBe("--- Sheet: Sheet1 ---\n2\n4\n[Formula: B3*2]")
+		})
+
+		it("should read a cached 0 or false formula result, not the formula", () => {
+			const workbook = new ExcelJS.Workbook()
+			const worksheet = workbook.addWorksheet("Sheet1")
+
+			// ExcelJS keeps a falsy cached result in cell.result but leaves it out of cell.value
+			worksheet.getCell("A1").value = { formula: "B1*2", result: 0 }
+			worksheet.getCell("A2").value = { sharedFormula: "A1", result: 0 }
+			worksheet.getCell("A3").value = { formula: "B1>1", result: false }
+
+			const result = formatWorkbook(workbook)
+
+			expect(result).toBe("--- Sheet: Sheet1 ---\n0\n0\nfalse")
+		})
+
+		it("should read every cell of a merged formula through the top-left cell", () => {
+			const workbook = new ExcelJS.Workbook()
+			const worksheet = workbook.addWorksheet("Sheet1")
+
+			// The other cells of a merged range return the top-left cell's value, but not its result
+			worksheet.getCell("A1").value = { formula: "C1*2", result: 4 }
+			worksheet.mergeCells("A1:B1")
+			worksheet.getCell("A2").value = { formula: "C2*2", result: 0 }
+			worksheet.mergeCells("A2:B2")
+			worksheet.getCell("A3").value = { formula: "C3+30", result: new Date("2024-10-30T00:00:00.000Z") }
+			worksheet.getCell("A3").numFmt = "yyyy-mm-dd"
+			worksheet.mergeCells("A3:B3")
+
+			const result = formatWorkbook(workbook)
+
+			expect(result).toBe("--- Sheet: Sheet1 ---\n4\t4\n0\t0\n2024-10-30\t2024-10-30")
+		})
+
+		it("should read formula errors and dates like plain values", () => {
+			const workbook = new ExcelJS.Workbook()
+			const worksheet = workbook.addWorksheet("Sheet1")
+
+			worksheet.getCell("A1").value = { formula: "1/0", result: { error: "#DIV/0!" } }
+			worksheet.getCell("B1").value = { formula: "A2+30", result: new Date("2024-10-30T00:00:00.000Z") }
+			worksheet.getCell("B1").numFmt = "yyyy-mm-dd"
+
+			const result = formatWorkbook(workbook)
+
+			expect(result).toBe("--- Sheet: Sheet1 ---\n[Error: #DIV/0!]\t2024-10-30")
+		})
+
+		it("should keep the time of dates and read times of day and durations", () => {
+			const workbook = new ExcelJS.Workbook()
+			const worksheet = workbook.addWorksheet("Sheet1")
+
+			// ExcelJS reads a time of day or a duration as a Date counted from 1899-12-30
+			const cells: [string, string, string][] = [
+				["2024-09-30T14:04:59.900Z", "yyyy-mm-dd h:mm", "2024-09-30 14:05:00"],
+				["2024-09-30T09:30:00.000Z", "DD.MM.YYYY HH:MM", "2024-09-30 09:30:00"],
+				["2024-05-01T00:00:00.000Z", "mmm yyyy", "2024-05-01"],
+				["2024-09-30T00:00:00.000Z", "d-mmm", "2024-09-30"],
+				["1899-12-30T06:00:00.000Z", "h:mm", "06:00:00"],
+				["1899-12-30T12:00:00.000Z", "[$-x-systime]h:mm:ss AM/PM", "12:00:00"],
+				["1899-12-30T18:00:00.000Z", 'h:mm" daily"', "18:00:00"],
+				["1899-12-31T12:00:00.000Z", "[h]:mm:ss", "36:00:00"],
+				["1899-12-31T12:00:30.000Z", "[h]:mm", "36:00"],
+				["1899-12-31T01:00:30.000Z", "[m]", "1500"],
+				["1899-12-31T01:00:30.000Z", "[mm]:ss", "1500:30"],
+				["1899-12-30T01:30:00.000Z", "[ss]", "5400"],
+				["2024-09-30T00:00:00.000Z", "mmmm", "2024-09-30"],
+				["1899-12-30T18:00:00.000Z", "h:mm\\ \\d\\a\\i\\l\\y", "18:00:00"],
+			]
+			cells.forEach(([date, numFmt], index) => {
+				const cell = worksheet.getRow(1).getCell(index + 1)
+				cell.value = new Date(date)
+				cell.numFmt = numFmt
+			})
+
+			const result = formatWorkbook(workbook)
+
+			expect(result).toBe(`--- Sheet: Sheet1 ---\n${cells.map(([, , text]) => text).join("\t")}`)
+		})
+
+		it("should count durations from 1904-01-01 in a 1904 workbook", () => {
+			const workbook = new ExcelJS.Workbook()
+			workbook.properties.date1904 = true
+			const worksheet = workbook.addWorksheet("Sheet1")
+
+			worksheet.getCell("A1").value = new Date("1904-01-02T12:00:00.000Z")
+			worksheet.getCell("A1").numFmt = "[h]:mm"
+
+			const result = formatWorkbook(workbook)
+
+			expect(result).toBe("--- Sheet: Sheet1 ---\n36:00")
+		})
 	})
 
 	describe("edge cases", () => {

src/integrations/misc/extract-text-from-xlsx.ts

@@ -11,20 +11,71 @@
 
 const ROW_LIMIT = 50000
 
-function formatCellValue(cell: ExcelJS.Cell): string {
-	const value = cell.value
+/**
+ * Excel stores a date or a time as a day count shown through the cell's number format, and
+ * ExcelJS hands it over as a UTC Date. Outside quoted text, escaped characters and [...] sections,
+ * a format with a day, a year, or a month with no hour or second beside it (mmm) shows a date.
+ * Any other format is a time of day or, with [h], [m] or [s], an elapsed duration. Those count
+ * from day 0 (1899-12-30, or 1904-01-01 in a 1904 workbook), so they must not read as a date.
+ */
+function formatDate(date: Date, cell: ExcelJS.Cell): string {
+	// Round to the second, as Excel shows it: a NOW() stamp of 14:04:59.9 reads 14:05:00
+	const time = Math.round(date.getTime() / 1000) * 1000
+	const iso = new Date(time).toISOString()
+	const numFmt = cell.numFmt ?? ""
+	const elapsed = /\[(h+|m+|s+)\]/i.exec(numFmt)
+	const tokens = numFmt.replace(/"[^"]*"|\\.|\[[^\]]*\]/g, "")
+	const isDate = !numFmt || /[dy]/i.test(tokens) || (/m/i.test(tokens) && !/[hs]/i.test(tokens))
+	if (!elapsed && isDate) {
+		return iso.endsWith("T00:00:00.000Z") ? iso.slice(0, 10) : iso.slice(0, 19).replace("T", " ")
+	}
+	if (!elapsed) {
+		return iso.slice(11, 19)
+	}
+	const epoch = cell.worksheet.workbook.properties.date1904 ? Date.UTC(1904, 0, 1) : Date.UTC(1899, 11, 30)
+	const seconds = (time - epoch) / 1000
+	const pad = (n: number) => String(n).padStart(2, "0")
+	// Elapsed time counts in the unit of its bracket: [mm]:ss of 25 hours reads 1500:00. Seconds
+	// show only when the format has them: [h]:mm of 36 hours reads 36:00
+	const unit = elapsed[1][0].toLowerCase()
+	const secondsShown = /s/i.test(tokens) ? `:${pad(seconds % 60)}` : ""
+	if (unit === "s") {
+		return String(seconds)
+	}
+	if (unit === "m") {
+		return `${Math.floor(seconds / 60)}${secondsShown}`
+	}
+	return `${Math.floor(seconds / 3600)}:${pad(Math.floor(seconds / 60) % 60)}${secondsShown}`
+}
+
+function formatCellValue(mergedOrCell: ExcelJS.Cell): string {
+	// The other cells of a merged range return the top-left cell's value but not its formula
+	// result, so the whole range is read through that cell
+	const cell = mergedOrCell.type === ExcelJS.ValueType.Merge ? mergedOrCell.master : mergedOrCell
+	let value = cell.value
 	if (value === null || value === undefined) {
 		return ""
 	}
 
+	// Handle formulas - read the calculated result like a plain value. The cells of a formula
+	// filled down or across hold { sharedFormula, result }; cell.formula gives their formula.
+	// The result comes from cell.result: ExcelJS leaves a cached 0 or false out of cell.value.
+	if (typeof value === "object" && ("formula" in value || "sharedFormula" in value)) {
+		const result = cell.result
+		if (result === undefined || result === null) {
+			return `[Formula: ${cell.formula}]`
+		}
+		value = result
+	}
+
 	// Handle error values (#DIV/0!, #N/A, etc.)
 	if (typeof value === "object" && "error" in value) {
 		return `[Error: ${value.error}]`
 	}
 
 	// Handle dates - ExcelJS can parse them as Date objects
 	if (value instanceof Date) {
-		return value.toISOString().split("T")[0]
+		return formatDate(value, cell)
 	}
 
 	// Handle rich text
@@ -37,15 +88,6 @@
 		return `${value.text} (${value.hyperlink})`
 	}
 
-	// Handle formulas - get the calculated result
-	if (typeof value === "object" && "formula" in value) {
-		if ("result" in value && value.result !== undefined && value.result !== null) {
-			return value.result.toString()
-		} else {
-			return `[Formula: ${value.formula}]`
-		}
-	}
-
 	return value.toString()
 }