fix(sort): make filenames start with digits prior than letters

Author: marjune163

src/util/compareNumInFilename.go

@@ -71,15 +71,7 @@ func compareIgnoreAsciiCase(prev, next []byte) (less, ok bool) {
 	return
 }
 
-func CompareNumInFilename(prev, next []byte) (less, ok bool) {
-	if len(prev) == 0 && len(next) == 0 {
-		return false, false
-	} else if len(prev) == 0 {
-		return true, true
-	} else if len(next) == 0 {
-		return false, true
-	}
-
+func compareNumString(prev, next []byte) (less, ok bool) {
 	common := findCommonPrefix(prev, next)
 	if common > 0 {
 		prev = prev[common:]
@@ -101,7 +93,8 @@ func CompareNumInFilename(prev, next []byte) (less, ok bool) {
 		return prevDigitsLen < nextDigitsLen, true
 	}
 
-	if prevDigitsLen == 0 { // prevDigitsLen and nextDigitsLen is 0
+	if prevDigitsLen == 0 { // prevDigitsLen == nextDigitsLen == 0
+		// "." is the beginning of next part, so current part is ended
 		switch {
 		case prev[0] == '.' && next[0] != '.':
 			return true, true
@@ -112,10 +105,59 @@ func CompareNumInFilename(prev, next []byte) (less, ok bool) {
 		}
 	}
 
+	// prevDigitsLen == nextDigitsLen
 	compareResult := bytes.Compare(prevDigits, nextDigits)
 	if compareResult != 0 {
 		return compareResult < 0, true
-	} else {
-		return CompareNumInFilename(prev[prevDigitsLen:], next[nextDigitsLen:])
 	}
+
+	// prevDigits == nextDigits
+	prev = prev[prevDigitsLen:]
+	next = next[nextDigitsLen:]
+	if len(prev) == 0 && len(next) == 0 {
+		return false, false
+	} else if len(prev) == 0 {
+		return true, true
+	} else if len(next) == 0 {
+		return false, true
+	}
+	return compareNumString(prev, next)
+
+}
+
+func isAlnum(b byte) bool {
+	return (b >= 'a' && b <= 'z') || (b >= 'A' && b <= 'Z') || (b >= '0' && b <= '9')
+}
+
+func isDigit(b byte) bool {
+	return b >= '0' && b <= '9'
+}
+
+func isAlpha(b byte) bool {
+	return (b >= 'a' && b <= 'z') || (b >= 'A' && b <= 'Z')
+}
+
+func CompareNumInFilename(prev, next []byte) (less, ok bool) {
+	if len(prev) == 0 && len(next) == 0 {
+		return false, false
+	} else if len(prev) == 0 {
+		return true, true
+	} else if len(next) == 0 {
+		return false, true
+	}
+
+	// at very first beginning
+	// filename starts with "." is prior, then digits, then letters
+	switch {
+	case prev[0] == '.' && isAlnum(next[0]):
+		return true, true
+	case next[0] == '.' && isAlnum(prev[0]):
+		return false, true
+	case isDigit(prev[0]) && isAlpha(next[0]):
+		return true, true
+	case isDigit(next[0]) && isAlpha(prev[0]):
+		return false, true
+	}
+
+	return compareNumString(prev, next)
 }

src/util/compareNumInFilename_test.go

@@ -61,6 +61,27 @@ func TestCompareNumInFilename(t *testing.T) {
 	if !less {
 		t.Error(prev, next)
 	}
+
+	prev = ".gitignore"
+	next = "a.txt"
+	less, _ = CompareNumInFilename([]byte(prev), []byte(next))
+	if !less {
+		t.Error(prev, next)
+	}
+
+	prev = ".gitignore"
+	next = "1.txt"
+	less, _ = CompareNumInFilename([]byte(prev), []byte(next))
+	if !less {
+		t.Error(prev, next)
+	}
+
+	prev = "1.txt"
+	next = "a.txt"
+	less, _ = CompareNumInFilename([]byte(prev), []byte(next))
+	if !less {
+		t.Error(prev, next)
+	}
 }
 
 func TestExtractPrefixDigits(t *testing.T) {