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// Copyright 2022 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.
// Package timeformat defines an Analyzer that checks for the use
// of time.Format or time.Parse calls with a bad format.
package timeformat
import (
"go/ast"
"go/constant"
"go/token"
"go/types"
"strings"
"golang.org/x/tools/go/analysis"
"golang.org/x/tools/go/analysis/passes/inspect"
"golang.org/x/tools/go/ast/inspector"
"golang.org/x/tools/go/types/typeutil"
)
const badFormat = "2006-02-01"
const goodFormat = "2006-01-02"
const Doc = `check for calls of (time.Time).Format or time.Parse with 2006-02-01
The timeformat checker looks for time formats with the 2006-02-01 (yyyy-dd-mm)
format. Internationally, "yyyy-dd-mm" does not occur in common calendar date
standards, and so it is more likely that 2006-01-02 (yyyy-mm-dd) was intended.
`
var Analyzer = &analysis.Analyzer{
Name: "timeformat",
Doc: Doc,
Requires: []*analysis.Analyzer{inspect.Analyzer},
Run: run,
}
func run(pass *analysis.Pass) (interface{}, error) {
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, ok := typeutil.Callee(pass.TypesInfo, call).(*types.Func)
if !ok {
return
}
if !isTimeDotFormat(fn) && !isTimeDotParse(fn) {
return
}
if len(call.Args) > 0 {
arg := call.Args[0]
badAt := badFormatAt(pass.TypesInfo, arg)
if badAt > -1 {
// Check if it's a literal string, otherwise we can't suggest a fix.
if _, ok := arg.(*ast.BasicLit); ok {
pos := int(arg.Pos()) + badAt + 1 // +1 to skip the " or `
end := pos + len(badFormat)
pass.Report(analysis.Diagnostic{
Pos: token.Pos(pos),
End: token.Pos(end),
Message: badFormat + " should be " + goodFormat,
SuggestedFixes: []analysis.SuggestedFix{{
Message: "Replace " + badFormat + " with " + goodFormat,
TextEdits: []analysis.TextEdit{{
Pos: token.Pos(pos),
End: token.Pos(end),
NewText: []byte(goodFormat),
}},
}},
})
} else {
pass.Reportf(arg.Pos(), badFormat+" should be "+goodFormat)
}
}
}
})
return nil, nil
}
func isTimeDotFormat(f *types.Func) bool {
if f.Name() != "Format" || f.Pkg().Path() != "time" {
return false
}
sig, ok := f.Type().(*types.Signature)
if !ok {
return false
}
// Verify that the receiver is time.Time.
recv := sig.Recv()
if recv == nil {
return false
}
named, ok := recv.Type().(*types.Named)
return ok && named.Obj().Name() == "Time"
}
func isTimeDotParse(f *types.Func) bool {
if f.Name() != "Parse" || f.Pkg().Path() != "time" {
return false
}
// Verify that there is no receiver.
sig, ok := f.Type().(*types.Signature)
return ok && sig.Recv() == nil
}
// badFormatAt return the start of a bad format in e or -1 if no bad format is found.
func badFormatAt(info *types.Info, e ast.Expr) int {
tv, ok := info.Types[e]
if !ok { // no type info, assume good
return -1
}
t, ok := tv.Type.(*types.Basic)
if !ok || t.Info()&types.IsString == 0 {
return -1
}
if tv.Value == nil {
return -1
}
return strings.Index(constant.StringVal(tv.Value), badFormat)
}
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