fmt: add flag "@" to format a verb "v" value with pretty style(indent…

…ed-multi-lines) string (#7) fmt: add flag "@" to format a verb "v" value with pretty style(indented-multi-lines) string #2 Current custom go data printing style "%#v" show all data in a single line, which is not easy to read, especially in a debugging process. I have made a patch to use "%@#v" "%@+v" to format a value with pretty style(indented-multi-lines) string to extends "%#v" "%+v".
vipally · Dec 23, 2017 · 55a970c · 55a970c
1 parent 5bbaec2
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diff --git a/README.md b/README.md
@@ -1,6 +1,6 @@
 # Ally master branch ![Version][version-img] [![Build status][travis-img]][travis-url]
 changlist from Official:
-- 
+- [#2: fmt: add flag "@" to format a verb "v" value with pretty style(indented-multi-lines) string](https://github.com/vipally/go/issues/2)
 - [#1: runtime, time: add API BuildTimestamp to report an application's build time](https://github.com/vipally/go/issues/1)
   - [func runtime.BuildTimestamp() int64](https://github.com/vipally/go/blob/ally_master/src/runtime/time.go#L21)
   - [func time.BuildTime() time.Time](https://github.com/vipally/go/blob/ally_master/src/time/time.go#L1517)

diff --git a/src/cmd/vet/print.go b/src/cmd/vet/print.go
@@ -356,7 +356,7 @@ func (f *File) checkPrintf(call *ast.CallExpr, name string) {
 func (s *formatState) parseFlags() {
 	for s.nbytes < len(s.format) {
 		switch c := s.format[s.nbytes]; c {
-		case '#', '0', '+', '-', ' ':
+		case '#', '0', '+', '-', ' ', '@':
 			s.flags = append(s.flags, c)
 			s.nbytes++
 		default:

diff --git a/src/fmt/doc.go b/src/fmt/doc.go
@@ -13,11 +13,15 @@
 	The verbs:
 
 	General:
-		%v	the value in a default format
-			when printing structs, the plus flag (%+v) adds field names
-		%#v	a Go-syntax representation of the value
-		%T	a Go-syntax representation of the type of the value
-		%%	a literal percent sign; consumes no value
+		%v		the value in a default format
+				when printing structs, the plus flag (%+v) adds field names
+		%@v		the value in a default pretty format
+		%#v		a Go-syntax representation of the value
+		%@#v	pretty style of Go-syntax representation of the value(an indented-multi-lines string)
+		%+v		when printing structs, the plus flag (%+v) adds field names.
+		%@+v	pretty style of struct-syntax representation of the value(an indented-multi-lines string)
+		%T		a Go-syntax representation of the type of the value
+		%%		a literal percent sign; consumes no value
 
 	Boolean:
 		%t	the word true or false
@@ -117,6 +121,7 @@
 			write e.g. U+0078 'x' if the character is printable for %U (%#U).
 		' '	(space) leave a space for elided sign in numbers (% d);
 			put spaces between bytes printing strings or slices in hex (% x, % X)
+		@   pretty style for verb %v, which will printing as an indented-multi-lines string.
 		0	pad with leading zeros rather than spaces;
 			for numbers, this moves the padding after the sign
 

diff --git a/src/fmt/example_test.go b/src/fmt/example_test.go
@@ -27,3 +27,140 @@ func ExampleStringer() {
 	fmt.Println(a)
 	// Output: Gopher (2)
 }
+
+func ExamplePrintf_flagV() {
+	type X struct {
+		A int
+		B string
+	}
+	type Y struct {
+		D X
+		E []int
+		F [2]string
+	}
+	type Z struct {
+		G Y
+		H string
+		I []string
+		J map[string]int
+	}
+	var z = Z{
+		G: Y{
+			D: X{
+				A: 123,
+				B: `"b" = 1`,
+			},
+			E: []int{1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12},
+			F: [2]string{
+				`aaa`,
+				`bbb`,
+			},
+		},
+		H: `zzz`,
+		I: []string{
+			`c:\x\y\z`,
+			`d:\a\b\c`,
+		},
+		J: map[string]int{
+			`abc`: 456,
+		},
+	}
+	fmt.Printf("-------\n\"%%v\":\n%v\n", z)
+	fmt.Printf("-------\n\"%%@v\":\n%@v\n", z)
+	fmt.Printf("-------\n\"%%#v\":\n%#v\n", z)
+	fmt.Printf("-------\n\"%%@#v\":\n%@#v\n", z)
+	fmt.Printf("-------\n\"%%+v\":\n%+v\n", z)
+	fmt.Printf("-------\n\"%%@+v\":\n%@+v\n", z)
+
+	// Output:
+	// -------
+	// "%v":
+	// {{{123 "b" = 1} [1 2 3 4 5 6 7 8 9 10 11 12] [aaa bbb]} zzz [c:\x\y\z d:\a\b\c] map[abc:456]}
+	// -------
+	// "%@v":
+	// {
+	//     {
+	//         {
+	//             123
+	//             "b" = 1
+	//         }
+	//         [
+	//             1 2 3 4 5 6 7 8 9 10
+	//             11 12
+	//         ]
+	//         [
+	//             aaa
+	//             bbb
+	//         ]
+	//     }
+	//     zzz
+	//     [
+	//         c:\x\y\z
+	//         d:\a\b\c
+	//     ]
+	//     map[
+	//         abc: 456
+	//     ]
+	// }
+	//
+	// -------
+	// "%#v":
+	// fmt_test.Z{G:fmt_test.Y{D:fmt_test.X{A:123, B:"\"b\" = 1"}, E:[]int{1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12}, F:[2]string{"aaa", "bbb"}}, H:"zzz", I:[]string{"c:\\x\\y\\z", "d:\\a\\b\\c"}, J:map[string]int{"abc":456}}
+	// -------
+	// "%@#v":
+	// fmt_test.Z{
+	//     G: fmt_test.Y{
+	//         D: fmt_test.X{
+	//             A: 123,
+	//             B: `"b" = 1`,
+	//         },
+	//         E: []int{
+	//             1, 2, 3, 4, 5, 6, 7, 8, 9, 10,
+	//             11, 12,
+	//         },
+	//         F: [2]string{
+	//             `aaa`,
+	//             `bbb`,
+	//         },
+	//     },
+	//     H: `zzz`,
+	//     I: []string{
+	//         `c:\x\y\z`,
+	//         `d:\a\b\c`,
+	//     },
+	//     J: map[string]int{
+	//         `abc`: 456,
+	//     },
+	// }
+	//
+	// -------
+	// "%+v":
+	// {G:{D:{A:123 B:"b" = 1} E:[1 2 3 4 5 6 7 8 9 10 11 12] F:[aaa bbb]} H:zzz I:[c:\x\y\z d:\a\b\c] J:map[abc:456]}
+	// -------
+	// "%@+v":
+	// {
+	//     G: {
+	//         D: {
+	//             A: 123
+	//             B: "b" = 1
+	//         }
+	//         E: [
+	//             1 2 3 4 5 6 7 8 9 10
+	//             11 12
+	//         ]
+	//         F: [
+	//             aaa
+	//             bbb
+	//         ]
+	//     }
+	//     H: zzz
+	//     I: [
+	//         c:\x\y\z
+	//         d:\a\b\c
+	//     ]
+	//     J: map[
+	//         abc: 456
+	//     ]
+	// }
+	//
+}