From 2add938798cdd1456616869298319528b0c76913 Mon Sep 17 00:00:00 2001
From: xuri <xuri.me@gmail.com>
Date: Fri, 17 Sep 2021 00:15:51 +0800
Subject: - new formula functions: DATEVALUE, ref #65 - fix ineffectual
 variable assignments - timeout in go test

---
 .github/workflows/go.yml |  2 +-
 calc.go                  | 25 +++++++++++++++++++++++++
 calc_test.go             |  9 +++++++++
 cell.go                  |  2 +-
 4 files changed, 36 insertions(+), 2 deletions(-)

diff --git a/.github/workflows/go.yml b/.github/workflows/go.yml
index 320e3da..5f674c3 100644
--- a/.github/workflows/go.yml
+++ b/.github/workflows/go.yml
@@ -28,7 +28,7 @@ jobs:
       run: go build -v .
 
     - name: Test
-      run: env GO111MODULE=on go test -v -race ./... -coverprofile=coverage.txt -covermode=atomic
+      run: env GO111MODULE=on go test -v -timeout 30m -race ./... -coverprofile=coverage.txt -covermode=atomic
 
     - name: Codecov
       uses: codecov/codecov-action@v1
diff --git a/calc.go b/calc.go
index 9cbc8ec..3e402e6 100644
--- a/calc.go
+++ b/calc.go
@@ -321,6 +321,7 @@ type formulaFuncs struct {
 //    CUMPRINC
 //    DATE
 //    DATEDIF
+//    DATEVALUE
 //    DAY
 //    DB
 //    DDB
@@ -6515,6 +6516,30 @@ func strToDate(str string) (int, int, int, bool, formulaArg) {
 	return year, month, day, timeIsEmpty, newEmptyFormulaArg()
 }
 
+// DATEVALUE function converts a text representation of a date into an Excel
+// date. For example, the function converts a text string representing a
+// date, into the serial number that represents the date in Excel's date-time
+// code.  The syntax of the function is:
+//
+//    DATEVALUE(date_text)
+//
+func (fn *formulaFuncs) DATEVALUE(argsList *list.List) formulaArg {
+	if argsList.Len() != 1 {
+		return newErrorFormulaArg(formulaErrorVALUE, "DATEVALUE requires 1 argument")
+	}
+	dateText := argsList.Front().Value.(formulaArg).Value()
+	if !isDateOnlyFmt(dateText) {
+		if _, _, _, _, _, err := strToTime(dateText); err.Type == ArgError {
+			return err
+		}
+	}
+	y, m, d, _, err := strToDate(dateText)
+	if err.Type == ArgError {
+		return err
+	}
+	return newNumberFormulaArg(daysBetween(excelMinTime1900.Unix(), makeDate(y, time.Month(m), d)) + 1)
+}
+
 // DAY function returns the day of a date, represented by a serial number. The
 // day is given as an integer ranging from 1 to 31. The syntax of the
 // function is:
diff --git a/calc_test.go b/calc_test.go
index 763ea1f..1e4d99b 100644
--- a/calc_test.go
+++ b/calc_test.go
@@ -956,6 +956,11 @@ func TestCalcCellValue(t *testing.T) {
 		"=DATEDIF(43101,43891,\"YD\")": "59",
 		"=DATEDIF(36526,73110,\"YD\")": "60",
 		"=DATEDIF(42171,44242,\"yd\")": "244",
+		// DATEVALUE
+		"=DATEVALUE(\"01/01/16\")":   "42370",
+		"=DATEVALUE(\"01/01/2016\")": "42370",
+		"=DATEVALUE(\"01/01/29\")":   "47119",
+		"=DATEVALUE(\"01/01/30\")":   "10959",
 		// DAY
 		"=DAY(0)":                                "0",
 		"=DAY(INT(7))":                           "7",
@@ -1997,6 +2002,10 @@ func TestCalcCellValue(t *testing.T) {
 		"=DATEDIF(\"\",\"\",\"\")":    "strconv.ParseFloat: parsing \"\": invalid syntax",
 		"=DATEDIF(43891,43101,\"Y\")": "start_date > end_date",
 		"=DATEDIF(43101,43891,\"x\")": "DATEDIF has invalid unit",
+		// DATEVALUE
+		"=DATEVALUE()":             "DATEVALUE requires 1 argument",
+		"=DATEVALUE(\"01/01\")":    "#VALUE!", // valid in Excel, which uses years by the system date
+		"=DATEVALUE(\"1900-0-0\")": "#VALUE!",
 		// DAY
 		"=DAY()":         "DAY requires exactly 1 argument",
 		"=DAY(-1)":       "DAY only accepts positive argument",
diff --git a/cell.go b/cell.go
index 2d49a5e..902f5b7 100644
--- a/cell.go
+++ b/cell.go
@@ -82,7 +82,7 @@ func (f *File) GetCellType(sheet, axis string) (CellType, error) {
 	var (
 		err         error
 		cellTypeStr string
-		cellType    CellType = CellTypeUnset
+		cellType    CellType
 	)
 	if cellTypeStr, err = f.getCellStringFunc(sheet, axis, func(x *xlsxWorksheet, c *xlsxC) (string, bool, error) {
 		return c.T, true, nil
-- 
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