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go.tools/cmd/vet: prepare print format checker for indexed arguments

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Rewrite the checker to be more flexible and better documented, being
more explicit about parsed format vs. checked arguments.
No attempt yet to do check indexed formats; this just paves the way.
All tests still pass.

R=gri
CC=golang-dev
https://golang.org/cl/9881044
This commit is contained in:
Rob Pike 2013-05-30 14:26:22 -04:00
parent 18f85da60d
commit 291b2c84b6
1 changed files with 95 additions and 33 deletions
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128
cmd/vet/print.go
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@ -104,6 +104,15 @@ func (f *File) literal(value ast.Expr) *ast.BasicLit {
return nil
}
// formatState holds the parsed representation of a printf directive such as "%3.*[4]d"
type formatState struct {
verb rune // the format verb: 'd' for "%d"
flags []byte // the list of # + etc.
argNums []int // the successive argument numbers that are consumed, adjusted to refer to actual arg in call
nbytes int // number of bytes of the format string consumed.
indexed bool // whether an indexing expression appears: %[1]d.
}
// checkPrintf checks a call to a formatted print routine such as Printf.
// call.Args[formatIndex] is (well, should be) the format argument.
func (f *File) checkPrintf(call *ast.CallExpr, name string, formatIndex int) {
@ -134,23 +143,29 @@ func (f *File) checkPrintf(call *ast.CallExpr, name string, formatIndex int) {
}
// Hard part: check formats against args.
argNum := firstArg
indexed := false
for i, w := 0, 0; i < len(format); i += w {
w = 1
if format[i] == '%' {
verb, flags, nbytes, nargs := f.parsePrintfVerb(call, format[i:])
w = nbytes
// If we've run out of args, print after loop will pick that up.
if argNum+nargs <= len(call.Args) {
f.checkPrintfArg(call, verb, flags, argNum, nargs)
state := f.parsePrintfVerb(call, format[i:], argNum)
w = state.nbytes
if state.indexed {
indexed = true
}
f.checkPrintfArg(call, state)
if len(state.argNums) > 0 {
// Continue with the next sequential argument.
argNum = state.argNums[len(state.argNums)-1] + 1
}
argNum += nargs
}
}
// TODO: Dotdotdot is hard.
if call.Ellipsis.IsValid() && argNum != len(call.Args) {
// Dotdotdot is hard.
if call.Ellipsis.IsValid() && argNum >= len(call.Args)-1 {
return
}
if argNum != len(call.Args) {
// If the arguments were direct indexed, we assume the programmer knows what's up.
// Otherwise, there should be no leftover arguments.
if !indexed && argNum != len(call.Args) {
expect := argNum - firstArg
numArgs := len(call.Args) - firstArg
f.Badf(call.Pos(), "wrong number of args for format in %s call: %d needed but %d args", name, expect, numArgs)
@ -159,11 +174,12 @@ func (f *File) checkPrintf(call *ast.CallExpr, name string, formatIndex int) {
// parsePrintfVerb returns the verb that begins the format string, along with its flags,
// the number of bytes to advance the format to step past the verb, and number of
// arguments it consumes.
func (f *File) parsePrintfVerb(call *ast.CallExpr, format string) (verb rune, flags []byte, nbytes, nargs int) {
// arguments it consumes. It returns a formatState that encodes what the formatting
// directive wants, without looking at the actual arguments present in the call.
func (f *File) parsePrintfVerb(call *ast.CallExpr, format string, argNum int) *formatState {
// There's guaranteed a percent sign.
flags = make([]byte, 0, 5)
nbytes = 1
flags := make([]byte, 0, 5)
nbytes := 1
end := len(format)
// There may be flags.
FlagLoop:
@ -176,10 +192,12 @@ FlagLoop:
break FlagLoop
}
}
argNums := make([]int, 0, 1)
getNum := func() {
if nbytes < end && format[nbytes] == '*' {
nbytes++
nargs++
argNums = append(argNums, argNum)
argNum++
} else {
for nbytes < end && '0' <= format[nbytes] && format[nbytes] <= '9' {
nbytes++
@ -195,13 +213,19 @@ FlagLoop:
getNum()
}
// Now a verb.
c, w := utf8.DecodeRuneInString(format[nbytes:])
verb, w := utf8.DecodeRuneInString(format[nbytes:])
nbytes += w
verb = c
if c != '%' {
nargs++
if verb != '%' {
argNums = append(argNums, argNum)
argNum++
}
return &formatState{
verb: verb,
flags: flags,
argNums: argNums,
nbytes: nbytes,
indexed: false, // TODO
}
return
}
// printfArgType encodes the types of expressions a printf verb accepts. It is a bitmask.
@ -218,7 +242,7 @@ const (
)
type printVerb struct {
verb rune
verb rune // User may provide verb through Formatter; could be a rune.
flags string // known flags are all ASCII
typ printfArgType
}
@ -262,50 +286,88 @@ var printVerbs = []printVerb{
{'X', sharpNumFlag, argRune | argInt | argString},
}
func (f *File) checkPrintfArg(call *ast.CallExpr, verb rune, flags []byte, argNum, nargs int) {
// checkPrintfArg compares the formatState to the arguments actually present,
// reporting any discrepancies it can discern. If the final argument is ellipsissed,
// there's little it can do for that.
func (f *File) checkPrintfArg(call *ast.CallExpr, state *formatState) {
var v printVerb
found := false
// Linear scan is fast enough for a small list.
for _, v = range printVerbs {
if v.verb == verb {
if v.verb == state.verb {
found = true
break
}
}
if !found {
f.Badf(call.Pos(), "unrecognized printf verb %q", verb)
f.Badf(call.Pos(), "unrecognized printf verb %q", state.verb)
return
}
for _, flag := range flags {
for _, flag := range state.flags {
if !strings.ContainsRune(v.flags, rune(flag)) {
f.Badf(call.Pos(), "unrecognized printf flag for verb %q: %q", verb, flag)
f.Badf(call.Pos(), "unrecognized printf flag for verb %q: %q", state.verb, flag)
return
}
}
// Verb is good. If nargs>trueArgs, we have something like %.*s and all but the final
// arg must be integer.
// Verb is good. If len(state.argNums)>trueArgs, we have something like %.*s and all
// but the final arg must be an integer.
trueArgs := 1
if verb == '%' {
if state.verb == '%' {
trueArgs = 0
}
nargs := len(state.argNums)
for i := 0; i < nargs-trueArgs; i++ {
if !f.matchArgType(argInt, call.Args[argNum+i]) {
f.Badf(call.Pos(), "arg %s for * in printf format not of type int", f.gofmt(call.Args[argNum+i]))
argNum := state.argNums[i]
if !f.argCanBeChecked(call, argNum, true, state.verb) {
continue
}
arg := call.Args[argNum]
if !f.matchArgType(argInt, arg) {
f.Badf(call.Pos(), "arg %s for * in printf format not of type int", f.gofmt(arg))
}
}
if verb == '%' {
if state.verb == '%' {
return
}
arg := call.Args[argNum+nargs-trueArgs]
argNum := state.argNums[len(state.argNums)-1]
if !f.argCanBeChecked(call, argNum, false, state.verb) {
return
}
arg := call.Args[argNum]
if !f.matchArgType(v.typ, arg) {
typeString := ""
if typ := f.pkg.types[arg]; typ != nil {
typeString = typ.String()
}
f.Badf(call.Pos(), "arg %s for printf verb %%%c of wrong type: %s", f.gofmt(arg), verb, typeString)
f.Badf(call.Pos(), "arg %s for printf verb %%%c of wrong type: %s", f.gofmt(arg), state.verb, typeString)
}
}
// argCanBeChecked reports whether the specified argument is statically present;
// it may be beyond the list of arguments or in a terminal slice... argument, which
// means we can't see it.
func (f *File) argCanBeChecked(call *ast.CallExpr, argNum int, isStar bool, verb rune) bool {
if argNum < 0 {
// Shouldn't happen, so catch it with prejudice.
panic("negative arg num")
}
if argNum < len(call.Args)-1 {
return true // Always OK.
}
if call.Ellipsis.IsValid() {
return false // We just can't tell; there could be many more arguments.
}
if argNum < len(call.Args) {
return true
}
if verb == '*' {
f.Badf(call.Pos(), "argument number %d for * for verb %%%c out of range", argNum, verb)
} else {
f.Badf(call.Pos(), "wrong number of args for format in Printf call")
}
return false
}
// checkPrint checks a call to an unformatted print routine such as Println.
// call.Args[firstArg] is the first argument to be printed.
func (f *File) checkPrint(call *ast.CallExpr, name string, firstArg int) {