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// Copyright 2010 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// This file contains the printf-checker.
package printf
import (
"bytes"
"fmt"
"go/ast"
"go/constant"
"go/token"
"go/types"
"regexp"
"sort"
"strconv"
"strings"
"unicode/utf8"
"golang.org/x/tools/go/analysis"
"golang.org/x/tools/go/analysis/passes/inspect"
"golang.org/x/tools/go/analysis/passes/internal/analysisutil"
"golang.org/x/tools/go/ast/inspector"
"golang.org/x/tools/go/types/typeutil"
)
func init() {
Analyzer.Flags.Var(isPrint, "funcs", "comma-separated list of print function names to check")
}
var Analyzer = &analysis.Analyzer{
Name: "printf",
Doc: doc,
Requires: []*analysis.Analyzer{inspect.Analyzer},
Run: run,
FactTypes: []analysis.Fact{new(isWrapper)},
}
const doc = `check consistency of Printf format strings and arguments
The check applies to known functions (for example, those in package fmt)
as well as any detected wrappers of known functions.
A function that wants to avail itself of printf checking but is not
found by this analyzer's heuristics (for example, due to use of
dynamic calls) can insert a bogus call:
if false {
_ = fmt.Sprintf(format, args...) // enable printf checking
}
The -funcs flag specifies a comma-separated list of names of additional
known formatting functions or methods. If the name contains a period,
it must denote a specific function using one of the following forms:
dir/pkg.Function
dir/pkg.Type.Method
(*dir/pkg.Type).Method
Otherwise the name is interpreted as a case-insensitive unqualified
identifier such as "errorf". Either way, if a listed name ends in f, the
function is assumed to be Printf-like, taking a format string before the
argument list. Otherwise it is assumed to be Print-like, taking a list
of arguments with no format string.
`
// isWrapper is a fact indicating that a function is a print or printf wrapper.
type isWrapper struct{ Printf bool }
func (f *isWrapper) AFact() {}
func (f *isWrapper) String() string {
if f.Printf {
return "printfWrapper"
} else {
return "printWrapper"
}
}
func run(pass *analysis.Pass) (interface{}, error) {
findPrintfLike(pass)
checkCall(pass)
return nil, nil
}
type printfWrapper struct {
obj *types.Func
fdecl *ast.FuncDecl
format *types.Var
args *types.Var
callers []printfCaller
failed bool // if true, not a printf wrapper
}
type printfCaller struct {
w *printfWrapper
call *ast.CallExpr
}
// maybePrintfWrapper decides whether decl (a declared function) may be a wrapper
// around a fmt.Printf or fmt.Print function. If so it returns a printfWrapper
// function describing the declaration. Later processing will analyze the
// graph of potential printf wrappers to pick out the ones that are true wrappers.
// A function may be a Printf or Print wrapper if its last argument is ...interface{}.
// If the next-to-last argument is a string, then this may be a Printf wrapper.
// Otherwise it may be a Print wrapper.
func maybePrintfWrapper(info *types.Info, decl ast.Decl) *printfWrapper {
// Look for functions with final argument type ...interface{}.
fdecl, ok := decl.(*ast.FuncDecl)
if !ok || fdecl.Body == nil {
return nil
}
fn := info.Defs[fdecl.Name].(*types.Func)
sig := fn.Type().(*types.Signature)
if !sig.Variadic() {
return nil // not variadic
}
params := sig.Params()
nparams := params.Len() // variadic => nonzero
args := params.At(nparams - 1)
iface, ok := args.Type().(*types.Slice).Elem().(*types.Interface)
if !ok || !iface.Empty() {
return nil // final (args) param is not ...interface{}
}
// Is second last param 'format string'?
var format *types.Var
if nparams >= 2 {
if p := params.At(nparams - 2); p.Type() == types.Typ[types.String] {
format = p
}
}
return &printfWrapper{
obj: fn,
fdecl: fdecl,
format: format,
args: args,
}
}
// findPrintfLike scans the entire package to find printf-like functions.
func findPrintfLike(pass *analysis.Pass) (interface{}, error) {
// Gather potential wrappers and call graph between them.
byObj := make(map[*types.Func]*printfWrapper)
var wrappers []*printfWrapper
for _, file := range pass.Files {
for _, decl := range file.Decls {
w := maybePrintfWrapper(pass.TypesInfo, decl)
if w == nil {
continue
}
byObj[w.obj] = w
wrappers = append(wrappers, w)
}
}
// Walk the graph to figure out which are really printf wrappers.
for _, w := range wrappers {
// Scan function for calls that could be to other printf-like functions.
ast.Inspect(w.fdecl.Body, func(n ast.Node) bool {
if w.failed {
return false
}
// TODO: Relax these checks; issue 26555.
if assign, ok := n.(*ast.AssignStmt); ok {
for _, lhs := range assign.Lhs {
if match(pass.TypesInfo, lhs, w.format) ||
match(pass.TypesInfo, lhs, w.args) {
// Modifies the format
// string or args in
// some way, so not a
// simple wrapper.
w.failed = true
return false
}
}
}
if un, ok := n.(*ast.UnaryExpr); ok && un.Op == token.AND {
if match(pass.TypesInfo, un.X, w.format) ||
match(pass.TypesInfo, un.X, w.args) {
// Taking the address of the
// format string or args,
// so not a simple wrapper.
w.failed = true
return false
}
}
call, ok := n.(*ast.CallExpr)
if !ok || len(call.Args) == 0 || !match(pass.TypesInfo, call.Args[len(call.Args)-1], w.args) {
return true
}
fn, kind := printfNameAndKind(pass, call)
if kind != 0 {
checkPrintfFwd(pass, w, call, kind)
return true
}
// If the call is to another function in this package,
// maybe we will find out it is printf-like later.
// Remember this call for later checking.
if fn != nil && fn.Pkg() == pass.Pkg && byObj[fn] != nil {
callee := byObj[fn]
callee.callers = append(callee.callers, printfCaller{w, call})
}
return true
})
}
return nil, nil
}
func match(info *types.Info, arg ast.Expr, param *types.Var) bool {
id, ok := arg.(*ast.Ident)
return ok && info.ObjectOf(id) == param
}
const (
kindPrintf = 1
kindPrint = 2
)
// checkPrintfFwd checks that a printf-forwarding wrapper is forwarding correctly.
// It diagnoses writing fmt.Printf(format, args) instead of fmt.Printf(format, args...).
func checkPrintfFwd(pass *analysis.Pass, w *printfWrapper, call *ast.CallExpr, kind int) {
matched := kind == kindPrint ||
kind == kindPrintf && len(call.Args) >= 2 && match(pass.TypesInfo, call.Args[len(call.Args)-2], w.format)
if !matched {
return
}
if !call.Ellipsis.IsValid() {
typ, ok := pass.TypesInfo.Types[call.Fun].Type.(*types.Signature)
if !ok {
return
}
if len(call.Args) > typ.Params().Len() {
// If we're passing more arguments than what the
// print/printf function can take, adding an ellipsis
// would break the program. For example:
//
// func foo(arg1 string, arg2 ...interface{} {
// fmt.Printf("%s %v", arg1, arg2)
// }
return
}
desc := "printf"
if kind == kindPrint {
desc = "print"
}
pass.Reportf(call.Pos(), "missing ... in args forwarded to %s-like function", desc)
return
}
fn := w.obj
var fact isWrapper
if !pass.ImportObjectFact(fn, &fact) {
fact.Printf = kind == kindPrintf
pass.ExportObjectFact(fn, &fact)
for _, caller := range w.callers {
checkPrintfFwd(pass, caller.w, caller.call, kind)
}
}
}
// isPrint records the print functions.
// If a key ends in 'f' then it is assumed to be a formatted print.
//
// Keys are either values returned by (*types.Func).FullName,
// or case-insensitive identifiers such as "errorf".
//
// The -funcs flag adds to this set.
//
// The set below includes facts for many important standard library
// functions, even though the analysis is capable of deducing that, for
// example, fmt.Printf forwards to fmt.Fprintf. We avoid relying on the
// driver applying analyzers to standard packages because "go vet" does
// not do so with gccgo, and nor do some other build systems.
// TODO(adonovan): eliminate the redundant facts once this restriction
// is lifted.
//
var isPrint = stringSet{
"fmt.Errorf": true,
"fmt.Fprint": true,
"fmt.Fprintf": true,
"fmt.Fprintln": true,
"fmt.Print": true,
"fmt.Printf": true,
"fmt.Println": true,
"fmt.Sprint": true,
"fmt.Sprintf": true,
"fmt.Sprintln": true,
"runtime/trace.Logf": true,
"log.Print": true,
"log.Printf": true,
"log.Println": true,
"log.Fatal": true,
"log.Fatalf": true,
"log.Fatalln": true,
"log.Panic": true,
"log.Panicf": true,
"log.Panicln": true,
"(*log.Logger).Fatal": true,
"(*log.Logger).Fatalf": true,
"(*log.Logger).Fatalln": true,
"(*log.Logger).Panic": true,
"(*log.Logger).Panicf": true,
"(*log.Logger).Panicln": true,
"(*log.Logger).Print": true,
"(*log.Logger).Printf": true,
"(*log.Logger).Println": true,
"(*testing.common).Error": true,
"(*testing.common).Errorf": true,
"(*testing.common).Fatal": true,
"(*testing.common).Fatalf": true,
"(*testing.common).Log": true,
"(*testing.common).Logf": true,
"(*testing.common).Skip": true,
"(*testing.common).Skipf": true,
// *testing.T and B are detected by induction, but testing.TB is
// an interface and the inference can't follow dynamic calls.
"(testing.TB).Error": true,
"(testing.TB).Errorf": true,
"(testing.TB).Fatal": true,
"(testing.TB).Fatalf": true,
"(testing.TB).Log": true,
"(testing.TB).Logf": true,
"(testing.TB).Skip": true,
"(testing.TB).Skipf": true,
}
// formatString returns the format string argument and its index within
// the given printf-like call expression.
//
// The last parameter before variadic arguments is assumed to be
// a format string.
//
// The first string literal or string constant is assumed to be a format string
// if the call's signature cannot be determined.
//
// If it cannot find any format string parameter, it returns ("", -1).
func formatString(pass *analysis.Pass, call *ast.CallExpr) (format string, idx int) {
typ := pass.TypesInfo.Types[call.Fun].Type
if typ != nil {
if sig, ok := typ.(*types.Signature); ok {
if !sig.Variadic() {
// Skip checking non-variadic functions.
return "", -1
}
idx := sig.Params().Len() - 2
if idx < 0 {
// Skip checking variadic functions without
// fixed arguments.
return "", -1
}
s, ok := stringConstantArg(pass, call, idx)
if !ok {
// The last argument before variadic args isn't a string.
return "", -1
}
return s, idx
}
}
// Cannot determine call's signature. Fall back to scanning for the first
// string constant in the call.
for idx := range call.Args {
if s, ok := stringConstantArg(pass, call, idx); ok {
return s, idx
}
if pass.TypesInfo.Types[call.Args[idx]].Type == types.Typ[types.String] {
// Skip checking a call with a non-constant format
// string argument, since its contents are unavailable
// for validation.
return "", -1
}
}
return "", -1
}
// stringConstantArg returns call's string constant argument at the index idx.
//
// ("", false) is returned if call's argument at the index idx isn't a string
// constant.
func stringConstantArg(pass *analysis.Pass, call *ast.CallExpr, idx int) (string, bool) {
if idx >= len(call.Args) {
return "", false
}
arg := call.Args[idx]
lit := pass.TypesInfo.Types[arg].Value
if lit != nil && lit.Kind() == constant.String {
return constant.StringVal(lit), true
}
return "", false
}
// checkCall triggers the print-specific checks if the call invokes a print function.
func checkCall(pass *analysis.Pass) {
inspect := pass.ResultOf[inspect.Analyzer].(*inspector.Inspector)
nodeFilter := []ast.Node{
(*ast.CallExpr)(nil),
}
inspect.Preorder(nodeFilter, func(n ast.Node) {
call := n.(*ast.CallExpr)
fn, kind := printfNameAndKind(pass, call)
switch kind {
case kindPrintf:
checkPrintf(pass, call, fn)
case kindPrint:
checkPrint(pass, call, fn)
}
})
}
func printfNameAndKind(pass *analysis.Pass, call *ast.CallExpr) (fn *types.Func, kind int) {
fn, _ = typeutil.Callee(pass.TypesInfo, call).(*types.Func)
if fn == nil {
return nil, 0
}
var fact isWrapper
if pass.ImportObjectFact(fn, &fact) {
if fact.Printf {
return fn, kindPrintf
} else {
return fn, kindPrint
}
}
_, ok := isPrint[fn.FullName()]
if !ok {
// Next look up just "printf", for use with -printf.funcs.
_, ok = isPrint[strings.ToLower(fn.Name())]
}
if ok {
if strings.HasSuffix(fn.Name(), "f") {
kind = kindPrintf
} else {
kind = kindPrint
}
}
return fn, kind
}
// isFormatter reports whether t satisfies fmt.Formatter.
// Unlike fmt.Stringer, it's impossible to satisfy fmt.Formatter without importing fmt.
func isFormatter(pass *analysis.Pass, t types.Type) bool {
for _, imp := range pass.Pkg.Imports() {
if imp.Path() == "fmt" {
formatter := imp.Scope().Lookup("Formatter").Type().Underlying().(*types.Interface)
return types.Implements(t, formatter)
}
}
return false
}
// formatState holds the parsed representation of a printf directive such as "%3.*[4]d".
// It is constructed by parsePrintfVerb.
type formatState struct {
verb rune // the format verb: 'd' for "%d"
format string // the full format directive from % through verb, "%.3d".
name string // Printf, Sprintf etc.
flags []byte // the list of # + etc.
argNums []int // the successive argument numbers that are consumed, adjusted to refer to actual arg in call
firstArg int // Index of first argument after the format in the Printf call.
// Used only during parse.
pass *analysis.Pass
call *ast.CallExpr
argNum int // Which argument we're expecting to format now.
hasIndex bool // Whether the argument is indexed.
indexPending bool // Whether we have an indexed argument that has not resolved.
nbytes int // number of bytes of the format string consumed.
}
// checkPrintf checks a call to a formatted print routine such as Printf.
func checkPrintf(pass *analysis.Pass, call *ast.CallExpr, fn *types.Func) {
format, idx := formatString(pass, call)
if idx < 0 {
if false {
pass.Reportf(call.Lparen, "can't check non-constant format in call to %s", fn.Name())
}
return
}
firstArg := idx + 1 // Arguments are immediately after format string.
if !strings.Contains(format, "%") {
if len(call.Args) > firstArg {
pass.Reportf(call.Lparen, "%s call has arguments but no formatting directives", fn.Name())
}
return
}
// Hard part: check formats against args.
argNum := firstArg
maxArgNum := firstArg
anyIndex := false
for i, w := 0, 0; i < len(format); i += w {
w = 1
if format[i] != '%' {
continue
}
state := parsePrintfVerb(pass, call, fn.Name(), format[i:], firstArg, argNum)
if state == nil {
return
}
w = len(state.format)
if !okPrintfArg(pass, call, state) { // One error per format is enough.
return
}
if state.hasIndex {
anyIndex = true
}
if len(state.argNums) > 0 {
// Continue with the next sequential argument.
argNum = state.argNums[len(state.argNums)-1] + 1
}
for _, n := range state.argNums {
if n >= maxArgNum {
maxArgNum = n + 1
}
}
}
// Dotdotdot is hard.
if call.Ellipsis.IsValid() && maxArgNum >= len(call.Args)-1 {
return
}
// If any formats are indexed, extra arguments are ignored.
if anyIndex {
return
}
// There should be no leftover arguments.
if maxArgNum != len(call.Args) {
expect := maxArgNum - firstArg
numArgs := len(call.Args) - firstArg
pass.Reportf(call.Pos(), "%s call needs %v but has %v", fn.Name(), count(expect, "arg"), count(numArgs, "arg"))
}
}
// parseFlags accepts any printf flags.
func (s *formatState) parseFlags() {
for s.nbytes < len(s.format) {
switch c := s.format[s.nbytes]; c {
case '#', '0', '+', '-', ' ':
s.flags = append(s.flags, c)
s.nbytes++
default:
return
}
}
}
// scanNum advances through a decimal number if present.
func (s *formatState) scanNum() {
for ; s.nbytes < len(s.format); s.nbytes++ {
c := s.format[s.nbytes]
if c < '0' || '9' < c {
return
}
}
}
// parseIndex scans an index expression. It returns false if there is a syntax error.
func (s *formatState) parseIndex() bool {
if s.nbytes == len(s.format) || s.format[s.nbytes] != '[' {
return true
}
// Argument index present.
s.nbytes++ // skip '['
start := s.nbytes
s.scanNum()
ok := true
if s.nbytes == len(s.format) || s.nbytes == start || s.format[s.nbytes] != ']' {
ok = false
s.nbytes = strings.Index(s.format, "]")
if s.nbytes < 0 {
s.pass.Reportf(s.call.Pos(), "%s format %s is missing closing ]", s.name, s.format)
return false
}
}
arg32, err := strconv.ParseInt(s.format[start:s.nbytes], 10, 32)
if err != nil || !ok || arg32 <= 0 || arg32 > int64(len(s.call.Args)-s.firstArg) {
s.pass.Reportf(s.call.Pos(), "%s format has invalid argument index [%s]", s.name, s.format[start:s.nbytes])
return false
}
s.nbytes++ // skip ']'
arg := int(arg32)
arg += s.firstArg - 1 // We want to zero-index the actual arguments.
s.argNum = arg
s.hasIndex = true
s.indexPending = true
return true
}
// parseNum scans a width or precision (or *). It returns false if there's a bad index expression.
func (s *formatState) parseNum() bool {
if s.nbytes < len(s.format) && s.format[s.nbytes] == '*' {
if s.indexPending { // Absorb it.
s.indexPending = false
}
s.nbytes++
s.argNums = append(s.argNums, s.argNum)
s.argNum++
} else {
s.scanNum()
}
return true
}
// parsePrecision scans for a precision. It returns false if there's a bad index expression.
func (s *formatState) parsePrecision() bool {
// If there's a period, there may be a precision.
if s.nbytes < len(s.format) && s.format[s.nbytes] == '.' {
s.flags = append(s.flags, '.') // Treat precision as a flag.
s.nbytes++
if !s.parseIndex() {
return false
}
if !s.parseNum() {
return false
}
}
return true
}
// parsePrintfVerb looks the formatting directive that begins the format string
// and returns a formatState that encodes what the directive wants, without looking
// at the actual arguments present in the call. The result is nil if there is an error.
func parsePrintfVerb(pass *analysis.Pass, call *ast.CallExpr, name, format string, firstArg, argNum int) *formatState {
state := &formatState{
format: format,
name: name,
flags: make([]byte, 0, 5),
argNum: argNum,
argNums: make([]int, 0, 1),
nbytes: 1, // There's guaranteed to be a percent sign.
firstArg: firstArg,
pass: pass,
call: call,
}
// There may be flags.
state.parseFlags()
// There may be an index.
if !state.parseIndex() {
return nil
}
// There may be a width.
if !state.parseNum() {
return nil
}
// There may be a precision.
if !state.parsePrecision() {
return nil
}
// Now a verb, possibly prefixed by an index (which we may already have).
if !state.indexPending && !state.parseIndex() {
return nil
}
if state.nbytes == len(state.format) {
pass.Reportf(call.Pos(), "%s format %s is missing verb at end of string", name, state.format)
return nil
}
verb, w := utf8.DecodeRuneInString(state.format[state.nbytes:])
state.verb = verb
state.nbytes += w
if verb != '%' {
state.argNums = append(state.argNums, state.argNum)
}
state.format = state.format[:state.nbytes]
return state
}
// printfArgType encodes the types of expressions a printf verb accepts. It is a bitmask.
type printfArgType int
const (
argBool printfArgType = 1 << iota
argInt
argRune
argString
argFloat
argComplex
argPointer
anyType printfArgType = ^0
)
type printVerb struct {
verb rune // User may provide verb through Formatter; could be a rune.
flags string // known flags are all ASCII
typ printfArgType
}
// Common flag sets for printf verbs.
const (
noFlag = ""
numFlag = " -+.0"
sharpNumFlag = " -+.0#"
allFlags = " -+.0#"
)
// printVerbs identifies which flags are known to printf for each verb.
var printVerbs = []printVerb{
// '-' is a width modifier, always valid.
// '.' is a precision for float, max width for strings.
// '+' is required sign for numbers, Go format for %v.
// '#' is alternate format for several verbs.
// ' ' is spacer for numbers
{'%', noFlag, 0},
{'b', numFlag, argInt | argFloat | argComplex | argPointer},
{'c', "-", argRune | argInt},
{'d', numFlag, argInt | argPointer},
{'e', sharpNumFlag, argFloat | argComplex},
{'E', sharpNumFlag, argFloat | argComplex},
{'f', sharpNumFlag, argFloat | argComplex},
{'F', sharpNumFlag, argFloat | argComplex},
{'g', sharpNumFlag, argFloat | argComplex},
{'G', sharpNumFlag, argFloat | argComplex},
{'o', sharpNumFlag, argInt | argPointer},
{'p', "-#", argPointer},
{'q', " -+.0#", argRune | argInt | argString},
{'s', " -+.0", argString},
{'t', "-", argBool},
{'T', "-", anyType},
{'U', "-#", argRune | argInt},
{'v', allFlags, anyType},
{'w', noFlag, anyType},
{'x', sharpNumFlag, argRune | argInt | argString | argPointer},
{'X', sharpNumFlag, argRune | argInt | argString | argPointer},
}
// okPrintfArg 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 okPrintfArg(pass *analysis.Pass, call *ast.CallExpr, state *formatState) (ok bool) {
var v printVerb
found := false
// Linear scan is fast enough for a small list.
for _, v = range printVerbs {
if v.verb == state.verb {
found = true
break
}
}
// Does current arg implement fmt.Formatter?
formatter := false
if state.argNum < len(call.Args) {
if tv, ok := pass.TypesInfo.Types[call.Args[state.argNum]]; ok {
formatter = isFormatter(pass, tv.Type)
}
}
if !formatter {
if !found {
pass.Reportf(call.Pos(), "%s format %s has unknown verb %c", state.name, state.format, state.verb)
return false
}
for _, flag := range state.flags {
// TODO: Disable complaint about '0' for Go 1.10. To be fixed properly in 1.11.
// See issues 23598 and 23605.
if flag == '0' {
continue
}
if !strings.ContainsRune(v.flags, rune(flag)) {
pass.Reportf(call.Pos(), "%s format %s has unrecognized flag %c", state.name, state.format, flag)
return false
}
}
}
// 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 state.verb == '%' {
trueArgs = 0
}
nargs := len(state.argNums)
for i := 0; i < nargs-trueArgs; i++ {
argNum := state.argNums[i]
if !argCanBeChecked(pass, call, i, state) {
return
}
arg := call.Args[argNum]
if !matchArgType(pass, argInt, nil, arg) {
pass.Reportf(call.Pos(), "%s format %s uses non-int %s as argument of *", state.name, state.format, analysisutil.Format(pass.Fset, arg))
return false
}
}
if state.verb == '%' || formatter {
return true
}
argNum := state.argNums[len(state.argNums)-1]
if !argCanBeChecked(pass, call, len(state.argNums)-1, state) {
return false
}
arg := call.Args[argNum]
if isFunctionValue(pass, arg) && state.verb != 'p' && state.verb != 'T' {
pass.Reportf(call.Pos(), "%s format %s arg %s is a func value, not called", state.name, state.format, analysisutil.Format(pass.Fset, arg))
return false
}
if !matchArgType(pass, v.typ, nil, arg) {
typeString := ""
if typ := pass.TypesInfo.Types[arg].Type; typ != nil {
typeString = typ.String()
}
pass.Reportf(call.Pos(), "%s format %s has arg %s of wrong type %s", state.name, state.format, analysisutil.Format(pass.Fset, arg), typeString)
return false
}
if v.typ&argString != 0 && v.verb != 'T' && !bytes.Contains(state.flags, []byte{'#'}) && recursiveStringer(pass, arg) {
pass.Reportf(call.Pos(), "%s format %s with arg %s causes recursive String method call", state.name, state.format, analysisutil.Format(pass.Fset, arg))
return false
}
return true
}
// recursiveStringer reports whether the argument e is a potential
// recursive call to stringer, such as t and &t in these examples:
//
// func (t *T) String() string { printf("%s", t) }
// func (t T) String() string { printf("%s", t) }
// func (t T) String() string { printf("%s", &t) }
//
func recursiveStringer(pass *analysis.Pass, e ast.Expr) bool {
typ := pass.TypesInfo.Types[e].Type
// It's unlikely to be a recursive stringer if it has a Format method.
if isFormatter(pass, typ) {
return false
}
// Does e allow e.String()?
obj, _, _ := types.LookupFieldOrMethod(typ, false, pass.Pkg, "String")
stringMethod, ok := obj.(*types.Func)
if !ok {
return false
}
// Is the expression e within the body of that String method?
if stringMethod.Pkg() != pass.Pkg || !stringMethod.Scope().Contains(e.Pos()) {
return false
}
// Is it the receiver r, or &r?
recv := stringMethod.Type().(*types.Signature).Recv()
if recv == nil {
return false
}
if u, ok := e.(*ast.UnaryExpr); ok && u.Op == token.AND {
e = u.X // strip off & from &r
}
if id, ok := e.(*ast.Ident); ok {
return pass.TypesInfo.Uses[id] == recv
}
return false
}
// isFunctionValue reports whether the expression is a function as opposed to a function call.
// It is almost always a mistake to print a function value.
func isFunctionValue(pass *analysis.Pass, e ast.Expr) bool {
if typ := pass.TypesInfo.Types[e].Type; typ != nil {
_, ok := typ.(*types.Signature)
return ok
}
return false
}
// 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 argCanBeChecked(pass *analysis.Pass, call *ast.CallExpr, formatArg int, state *formatState) bool {
argNum := state.argNums[formatArg]
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
}
// There are bad indexes in the format or there are fewer arguments than the format needs.
// This is the argument number relative to the format: Printf("%s", "hi") will give 1 for the "hi".
arg := argNum - state.firstArg + 1 // People think of arguments as 1-indexed.
pass.Reportf(call.Pos(), "%s format %s reads arg #%d, but call has %v", state.name, state.format, arg, count(len(call.Args)-state.firstArg, "arg"))
return false
}
// printFormatRE is the regexp we match and report as a possible format string
// in the first argument to unformatted prints like fmt.Print.
// We exclude the space flag, so that printing a string like "x % y" is not reported as a format.
var printFormatRE = regexp.MustCompile(`%` + flagsRE + numOptRE + `\.?` + numOptRE + indexOptRE + verbRE)
const (
flagsRE = `[+\-#]*`
indexOptRE = `(\[[0-9]+\])?`
numOptRE = `([0-9]+|` + indexOptRE + `\*)?`
verbRE = `[bcdefgopqstvxEFGTUX]`
)
// checkPrint checks a call to an unformatted print routine such as Println.
func checkPrint(pass *analysis.Pass, call *ast.CallExpr, fn *types.Func) {
firstArg := 0
typ := pass.TypesInfo.Types[call.Fun].Type
if typ == nil {
// Skip checking functions with unknown type.
return
}
if sig, ok := typ.(*types.Signature); ok {
if !sig.Variadic() {
// Skip checking non-variadic functions.
return
}
params := sig.Params()
firstArg = params.Len() - 1
typ := params.At(firstArg).Type()
typ = typ.(*types.Slice).Elem()
it, ok := typ.(*types.Interface)
if !ok || !it.Empty() {
// Skip variadic functions accepting non-interface{} args.
return
}
}
args := call.Args
if len(args) <= firstArg {
// Skip calls without variadic args.
return
}
args = args[firstArg:]
if firstArg == 0 {
if sel, ok := call.Args[0].(*ast.SelectorExpr); ok {
if x, ok := sel.X.(*ast.Ident); ok {
if x.Name == "os" && strings.HasPrefix(sel.Sel.Name, "Std") {
pass.Reportf(call.Pos(), "%s does not take io.Writer but has first arg %s", fn.Name(), analysisutil.Format(pass.Fset, call.Args[0]))
}
}
}
}
arg := args[0]
if lit, ok := arg.(*ast.BasicLit); ok && lit.Kind == token.STRING {
// Ignore trailing % character in lit.Value.
// The % in "abc 0.0%" couldn't be a formatting directive.
s := strings.TrimSuffix(lit.Value, `%"`)
if strings.Contains(s, "%") {
m := printFormatRE.FindStringSubmatch(s)
if m != nil {
pass.Reportf(call.Pos(), "%s call has possible formatting directive %s", fn.Name(), m[0])
}
}
}
if strings.HasSuffix(fn.Name(), "ln") {
// The last item, if a string, should not have a newline.
arg = args[len(args)-1]
if lit, ok := arg.(*ast.BasicLit); ok && lit.Kind == token.STRING {
str, _ := strconv.Unquote(lit.Value)
if strings.HasSuffix(str, "\n") {
pass.Reportf(call.Pos(), "%s arg list ends with redundant newline", fn.Name())
}
}
}
for _, arg := range args {
if isFunctionValue(pass, arg) {
pass.Reportf(call.Pos(), "%s arg %s is a func value, not called", fn.Name(), analysisutil.Format(pass.Fset, arg))
}
if recursiveStringer(pass, arg) {
pass.Reportf(call.Pos(), "%s arg %s causes recursive call to String method", fn.Name(), analysisutil.Format(pass.Fset, arg))
}
}
}
// count(n, what) returns "1 what" or "N whats"
// (assuming the plural of what is whats).
func count(n int, what string) string {
if n == 1 {
return "1 " + what
}
return fmt.Sprintf("%d %ss", n, what)
}
// stringSet is a set-of-nonempty-strings-valued flag.
// Note: elements without a '.' get lower-cased.
type stringSet map[string]bool
func (ss stringSet) String() string {
var list []string
for name := range ss {
list = append(list, name)
}
sort.Strings(list)
return strings.Join(list, ",")
}
func (ss stringSet) Set(flag string) error {
for _, name := range strings.Split(flag, ",") {
if len(name) == 0 {
return fmt.Errorf("empty string")
}
if !strings.Contains(name, ".") {
name = strings.ToLower(name)
}
ss[name] = true
}
return nil
}