add minus of start parameter support for gstr.Substr, like the substr function in PHP (#2297)

* Make the substr like the substr in PHP

Make the substr like the substr in PHP

* Update gstr_z_unit_test.go

* Update gstr_z_unit_test.go

* Make the SubStrRune like the mb_substr in PHP

Make the SubStrRune like the mb_substr in PHP

* Update gstr_z_unit_test.go

* Update gstr_z_unit_test.go

* Update gins_z_unit_view_test.go

* Update gview_z_unit_test.go

Author: cnjinhy

frame/gins/gins_z_unit_view_test.go

@@ -22,7 +22,7 @@ func Test_View(t *testing.T) {
 		t.AssertNE(View(), nil)
 		b, e := View().ParseContent(context.TODO(), `{{"我是中国人" | substr 2 -1}}`, nil)
 		t.Assert(e, nil)
-		t.Assert(b, "中国人")
+		t.Assert(b, "中国")
 	})
 	gtest.C(t, func(t *gtest.T) {
 		tpl := "t.tpl"
@@ -32,7 +32,7 @@ func Test_View(t *testing.T) {
 
 		b, e := View().Parse(context.TODO(), "t.tpl", nil)
 		t.Assert(e, nil)
-		t.Assert(b, "中国人")
+		t.Assert(b, "中国")
 	})
 	gtest.C(t, func(t *gtest.T) {
 		path := fmt.Sprintf(`%s/%d`, gfile.Temp(), gtime.TimestampNano())
@@ -45,7 +45,7 @@ func Test_View(t *testing.T) {
 
 		b, e := View().Parse(context.TODO(), "t.tpl", nil)
 		t.Assert(e, nil)
-		t.Assert(b, "中国人")
+		t.Assert(b, "中国")
 	})
 }
 

os/gview/gview_z_unit_test.go

@@ -141,7 +141,7 @@ func Test_Func(t *testing.T) {
 		str = `{{"我是中国人" | substr 2 -1}};{{"我是中国人" | substr 2  2}}`
 		result, err = gview.ParseContent(context.TODO(), str, nil)
 		t.Assert(err != nil, false)
-		t.Assert(result, `中国人;中国`)
+		t.Assert(result, `中国;中国`)
 
 		str = `{{"我是中国人" | strlimit 2  "..."}}`
 		result, err = gview.ParseContent(context.TODO(), str, nil)

text/gstr/gstr_sub.go

@@ -55,24 +55,37 @@ func StrTillEx(haystack string, needle string) string {
 // The parameter `length` is optional, it uses the length of `str` in default.
 func SubStr(str string, start int, length ...int) (substr string) {
 	strLength := len(str)
-	// Simple border checks.
 	if start < 0 {
-		start = 0
-	}
-	if start >= strLength {
-		start = strLength
+		if -start > strLength {
+			start = 0
+		} else {
+			start = strLength + start
+		}
+	} else if start > strLength {
+		return ""
 	}
-	end := strLength
+	realLength := 0
 	if len(length) > 0 {
-		end = start + length[0]
-		if end < start {
-			end = strLength
+		realLength = length[0]
+		if realLength < 0 {
+			if -realLength > strLength-start {
+				realLength = 0
+			} else {
+				realLength = strLength - start + realLength
+			}
+		} else if realLength > strLength-start {
+			realLength = strLength - start
 		}
+	} else {
+		realLength = strLength - start
 	}
-	if end > strLength {
-		end = strLength
+
+	if realLength == strLength {
+		return str
+	} else {
+		end := start + realLength
+		return str[start:end]
 	}
-	return str[start:end]
 }
 
 // SubStrRune returns a portion of string `str` specified by the `start` and `length` parameters.
@@ -85,20 +98,32 @@ func SubStrRune(str string, start int, length ...int) (substr string) {
 		runesLength = len(runes)
 	)
 
-	// Simple border checks.
+	strLength := runesLength
 	if start < 0 {
-		start = 0
-	}
-	if start >= runesLength {
-		start = runesLength
+		if -start > strLength {
+			start = 0
+		} else {
+			start = strLength + start
+		}
+	} else if start > strLength {
+		return ""
 	}
-	end := runesLength
+	realLength := 0
 	if len(length) > 0 {
-		end = start + length[0]
-		if end < start {
-			end = runesLength
+		realLength = length[0]
+		if realLength < 0 {
+			if -realLength > strLength-start {
+				realLength = 0
+			} else {
+				realLength = strLength - start + realLength
+			}
+		} else if realLength > strLength-start {
+			realLength = strLength - start
 		}
+	} else {
+		realLength = strLength - start
 	}
+	end := start + realLength
 	if end > runesLength {
 		end = runesLength
 	}

text/gstr/gstr_z_unit_test.go

@@ -89,8 +89,12 @@ func Test_SubStr(t *testing.T) {
 		t.Assert(gstr.SubStr("我爱GoFrame", 0), "我爱GoFrame")
 		t.Assert(gstr.SubStr("我爱GoFrame", 6), "GoFrame")
 		t.Assert(gstr.SubStr("我爱GoFrame", 6, 2), "Go")
-		t.Assert(gstr.SubStr("我爱GoFrame", -1, 30), "我爱GoFrame")
+		t.Assert(gstr.SubStr("我爱GoFrame", -1, 30), "e")
 		t.Assert(gstr.SubStr("我爱GoFrame", 30, 30), "")
+		t.Assert(gstr.SubStr("abcdef", 0, -1), "abcde")
+		t.Assert(gstr.SubStr("abcdef", 2, -1), "cde")
+		t.Assert(gstr.SubStr("abcdef", 4, -4), "")
+		t.Assert(gstr.SubStr("abcdef", -3, -1), "de")
 	})
 }
 
@@ -99,8 +103,16 @@ func Test_SubStrRune(t *testing.T) {
 		t.Assert(gstr.SubStrRune("我爱GoFrame", 0), "我爱GoFrame")
 		t.Assert(gstr.SubStrRune("我爱GoFrame", 2), "GoFrame")
 		t.Assert(gstr.SubStrRune("我爱GoFrame", 2, 2), "Go")
-		t.Assert(gstr.SubStrRune("我爱GoFrame", -1, 30), "我爱GoFrame")
+		t.Assert(gstr.SubStrRune("我爱GoFrame", -1, 30), "e")
 		t.Assert(gstr.SubStrRune("我爱GoFrame", 30, 30), "")
+		t.Assert(gstr.SubStrRune("abcdef", 0, -1), "abcde")
+		t.Assert(gstr.SubStrRune("abcdef", 2, -1), "cde")
+		t.Assert(gstr.SubStrRune("abcdef", 4, -4), "")
+		t.Assert(gstr.SubStrRune("abcdef", -3, -1), "de")
+		t.Assert(gstr.SubStrRune("我爱GoFrame呵呵", -3, 100), "e呵呵")
+		t.Assert(gstr.SubStrRune("abcdef哈哈", -3, -1), "f哈")
+		t.Assert(gstr.SubStrRune("ab我爱GoFramecdef哈哈", -3, -1), "f哈")
+		t.Assert(gstr.SubStrRune("我爱GoFrame", 0, 3), "我爱G")
 	})
 }