Commit 7c7cecc1 authored by Dave Brophy's avatar Dave Brophy Committed by Rob Pike

fmt: fix incorrect format of whole-number floats when using %#v

This fixes the unwanted behaviour where printing a zero float with the
#v fmt verb outputs "0" - e.g. missing the trailing decimal. This means
that the output would be interpreted as an int rather than a float when
parsed as Go source. After this change the the output is "0.0".

Fixes #26363

Change-Id: Ic5c060522459cd5ce077675d47c848b22ddc34fa
GitHub-Last-Rev: adfb061363f0566acec134c81be9a3dcb1f4cac8
GitHub-Pull-Request: golang/go#26383
Reviewed-on: https://go-review.googlesource.com/123956Reviewed-by: default avatarDaniel Martí <mvdan@mvdan.cc>
Reviewed-by: default avatarRob Pike <r@golang.org>
Run-TryBot: Daniel Martí <mvdan@mvdan.cc>
TryBot-Result: Gobot Gobot <gobot@golang.org>
parent cb7f9ec4
...@@ -690,6 +690,14 @@ var fmtTests = []struct { ...@@ -690,6 +690,14 @@ var fmtTests = []struct {
{"%#v", []int32(nil), "[]int32(nil)"}, {"%#v", []int32(nil), "[]int32(nil)"},
{"%#v", 1.2345678, "1.2345678"}, {"%#v", 1.2345678, "1.2345678"},
{"%#v", float32(1.2345678), "1.2345678"}, {"%#v", float32(1.2345678), "1.2345678"},
// Whole number floats should have a single trailing zero added, but not
// for exponent notation.
{"%#v", 1.0, "1.0"},
{"%#v", 1000000.0, "1e+06"},
{"%#v", float32(1.0), "1.0"},
{"%#v", float32(1000000.0), "1e+06"},
// Only print []byte and []uint8 as type []byte if they appear at the top level. // Only print []byte and []uint8 as type []byte if they appear at the top level.
{"%#v", []byte(nil), "[]byte(nil)"}, {"%#v", []byte(nil), "[]byte(nil)"},
{"%#v", []uint8(nil), "[]byte(nil)"}, {"%#v", []uint8(nil), "[]byte(nil)"},
......
...@@ -481,36 +481,46 @@ func (f *fmt) fmtFloat(v float64, size int, verb rune, prec int) { ...@@ -481,36 +481,46 @@ func (f *fmt) fmtFloat(v float64, size int, verb rune, prec int) {
return return
} }
// The sharp flag forces printing a decimal point for non-binary formats // The sharp flag forces printing a decimal point for non-binary formats
// and retains trailing zeros, which we may need to restore. // and retains trailing zeros, which we may need to restore. For the sharpV
if f.sharp && verb != 'b' { // flag, we ensure a single trailing zero is present if the output is not
// in exponent notation.
if f.sharpV || (f.sharp && verb != 'b') {
digits := 0 digits := 0
if !f.sharpV {
switch verb { switch verb {
case 'v', 'g', 'G': case 'g', 'G':
digits = prec digits = prec
// If no precision is set explicitly use a precision of 6. // If no precision is set explicitly use a precision of 6.
if digits == -1 { if digits == -1 {
digits = 6 digits = 6
} }
} }
}
// Buffer pre-allocated with enough room for // Buffer pre-allocated with enough room for
// exponent notations of the form "e+123". // exponent notations of the form "e+123".
var tailBuf [5]byte var tailBuf [5]byte
tail := tailBuf[:0] tail := tailBuf[:0]
hasDecimalPoint := false var hasDecimalPoint, hasExponent bool
// Starting from i = 1 to skip sign at num[0]. // Starting from i = 1 to skip sign at num[0].
for i := 1; i < len(num); i++ { for i := 1; i < len(num); i++ {
switch num[i] { switch num[i] {
case '.': case '.':
hasDecimalPoint = true hasDecimalPoint = true
case 'e', 'E': case 'e', 'E':
hasExponent = true
tail = append(tail, num[i:]...) tail = append(tail, num[i:]...)
num = num[:i] num = num[:i]
default: default:
digits-- digits--
} }
} }
if f.sharpV {
if !hasDecimalPoint && !hasExponent {
num = append(num, '.', '0')
}
} else {
if !hasDecimalPoint { if !hasDecimalPoint {
num = append(num, '.') num = append(num, '.')
} }
...@@ -518,6 +528,7 @@ func (f *fmt) fmtFloat(v float64, size int, verb rune, prec int) { ...@@ -518,6 +528,7 @@ func (f *fmt) fmtFloat(v float64, size int, verb rune, prec int) {
num = append(num, '0') num = append(num, '0')
digits-- digits--
} }
}
num = append(num, tail...) num = append(num, tail...)
} }
// We want a sign if asked for and if the sign is not positive. // We want a sign if asked for and if the sign is not positive.
......
...@@ -24,8 +24,8 @@ func f0(x int) { ...@@ -24,8 +24,8 @@ func f0(x int) {
func f1(x float32) { func f1(x float32) {
switch x { switch x {
case 5: case 5:
case 5: // ERROR "duplicate case 5 in switch" case 5: // ERROR "duplicate case 5 .value 5\.0. in switch"
case 5.0: // ERROR "duplicate case 5 in switch" case 5.0: // ERROR "duplicate case 5 .value 5\.0. in switch"
} }
} }
...@@ -44,9 +44,9 @@ func f3(e interface{}) { ...@@ -44,9 +44,9 @@ func f3(e interface{}) {
case 0: // ERROR "duplicate case 0 in switch" case 0: // ERROR "duplicate case 0 in switch"
case int64(0): case int64(0):
case float32(10): case float32(10):
case float32(10): // ERROR "duplicate case float32\(10\) .value 10. in switch" case float32(10): // ERROR "duplicate case float32\(10\) .value 10\.0. in switch"
case float64(10): case float64(10):
case float64(10): // ERROR "duplicate case float64\(10\) .value 10. in switch" case float64(10): // ERROR "duplicate case float64\(10\) .value 10\.0. in switch"
} }
} }
......
Markdown is supported
0%
or
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment