fmt: normalize processing of format string

The old loop was a bit odd; change it to be more regular.
This also enables a diagnostic for Printf("%", 3): %!(NOVERB)

R=rsc, Kyle C
CC=golang-dev
https://golang.org/cl/3749044

diff --git a/src/pkg/fmt/fmt_test.go b/src/pkg/fmt/fmt_test.go
index d87b93a7956b1910bd68f68aed25aa988be81930..0234ad41d3dc460a9cc9769936897cffa4317f0c 100644 (file)
--- a/src/pkg/fmt/fmt_test.go
+++ b/src/pkg/fmt/fmt_test.go
@@ -381,11 +381,13 @@ var fmttests = []fmtTest{
        {"%p", 27, "%!p(int=27)"}, // not a pointer at all
 
        // erroneous things
+       {"%s %", "hello", "hello %!(NOVERB)"},
+       {"%s %.2", "hello", "hello %!(NOVERB)"},
        {"%d", "hello", "%!d(string=hello)"},
        {"no args", "hello", "no args%!(EXTRA string=hello)"},
        {"%s", nil, "%!s(<nil>)"},
        {"%T", nil, "<nil>"},
-       {"%-1", 100, "%!1(int=100)"},
+       {"%-1", 100, "%!(NOVERB)%!(EXTRA int=100)"},
 }
 
 func TestSprintf(t *testing.T) {
@@ -638,7 +640,7 @@ var startests = []starTest{
        {"%.*d", args(nil, 42), "%!(BADPREC)42"},
        {"%*d", args(5, "foo"), "%!d(string=  foo)"},
        {"%*% %d", args(20, 5), "% 5"},
-       {"%*", args(4), "%!(BADWIDTH)%!*(int=4)"},
+       {"%*", args(4), "%!(NOVERB)"},
        {"%*d", args(int32(4), 42), "%!(BADWIDTH)42"},
 }
 
@@ -655,7 +657,7 @@ func TestWidthAndPrecision(t *testing.T) {
        for _, tt := range startests {
                s := sprintf[len(tt.in)](tt.fmt, tt.in)
                if s != tt.out {
-                       t.Errorf("got %q expected %q", s, tt.out)
+                       t.Errorf("%q: got %q expected %q", tt.fmt, s, tt.out)
                }
        }
 }

diff --git a/src/pkg/fmt/print.go b/src/pkg/fmt/print.go
index 7ac6648c70c309fba44a7c44a5ff3e347980ba7a..8cc54ed8c61aeca129168b2e01111ea393a89061 100644 (file)
--- a/src/pkg/fmt/print.go
+++ b/src/pkg/fmt/print.go
@@ -26,6 +26,7 @@ var (
        bytesBytes      = []byte("[]byte{")
        widthBytes      = []byte("%!(BADWIDTH)")
        precBytes       = []byte("%!(BADPREC)")
+       noVerbBytes     = []byte("%!(NOVERB)")
 )
 
 // State represents the printer state passed to custom formatters.
@@ -821,19 +822,16 @@ func intFromArg(a []interface{}, end, i, fieldnum int) (num int, isInt bool, new
 }
 
 func (p *pp) doPrintf(format string, a []interface{}) {
-       end := len(format) - 1
+       end := len(format)
        fieldnum := 0 // we process one field per non-trivial format
-       for i := 0; i <= end; {
+       for i := 0; i < end; {
                c, w := utf8.DecodeRuneInString(format[i:])
-               if c != '%' || i == end {
-                       if w == 1 {
-                               p.buf.WriteByte(byte(c))
-                       } else {
-                               p.buf.WriteString(format[i : i+w])
-                       }
+               if c != '%' {
+                       p.buf.WriteRune(c)
                        i += w
                        continue
                }
+               // Process one verb
                i++
                // flags and widths
                p.fmt.clearflags()
@@ -855,7 +853,7 @@ func (p *pp) doPrintf(format string, a []interface{}) {
                        }
                }
                // do we have width?
-               if format[i] == '*' {
+               if i < end && format[i] == '*' {
                        p.fmt.wid, p.fmt.widPresent, i, fieldnum = intFromArg(a, end, i, fieldnum)
                        if !p.fmt.widPresent {
                                p.buf.Write(widthBytes)
@@ -874,6 +872,10 @@ func (p *pp) doPrintf(format string, a []interface{}) {
                                p.fmt.prec, p.fmt.precPresent, i = parsenum(format, i+1, end)
                        }
                }
+               if i >= end {
+                       p.buf.Write(noVerbBytes)
+                       continue
+               }
                c, w = utf8.DecodeRuneInString(format[i:])
                i += w
                // percent is special - absorbs no operand