package check
import (
"bytes"
"go/ast"
"go/parser"
"go/printer"
"go/token"
"os"
)
func indent(s, with string) (r string) {
eol := true
for i := 0; i != len(s); i++ {
c := s[i]
switch {
case eol && c == '\n' || c == '\r':
case c == '\n' || c == '\r':
eol = true
case eol:
eol = false
s = s[:i] + with + s[i:]
i += len(with)
}
}
return s
}
func printLine(filename string, line int) (string, error) {
fset := token.NewFileSet()
file, err := os.Open(filename)
if err != nil {
return "", err
}
fnode, err := parser.ParseFile(fset, filename, file, parser.ParseComments)
if err != nil {
return "", err
}
config := &printer.Config{Mode: printer.UseSpaces, Tabwidth: 4}
lp := &linePrinter{fset: fset, fnode: fnode, line: line, config: config}
ast.Walk(lp, fnode)
result := lp.output.Bytes()
// Comments leave \n at the end.
n := len(result)
for n > 0 && result[n-1] == '\n' {
n--
}
return string(result[:n]), nil
}
type linePrinter struct {
config *printer.Config
fset *token.FileSet
fnode *ast.File
line int
output bytes.Buffer
stmt ast.Stmt
}
func (lp *linePrinter) emit() bool {
if lp.stmt != nil {
lp.trim(lp.stmt)
lp.printWithComments(lp.stmt)
lp.stmt = nil
return true
}
return false
}
func (lp *linePrinter) printWithComments(n ast.Node) {
nfirst := lp.fset.Position(n.Pos()).Line
nlast := lp.fset.Position(n.End()).Line
for _, g := range lp.fnode.Comments {
cfirst := lp.fset.Position(g.Pos()).Line
clast := lp.fset.Position(g.End()).Line
if clast == nfirst-1 && lp.fset.Position(n.Pos()).Column == lp.fset.Position(g.Pos()).Column {
for _, c := range g.List {
lp.output.WriteString(c.Text)
lp.output.WriteByte('\n')
}
}
if cfirst >= nfirst && cfirst <= nlast && n.End() <= g.List[0].Slash {
// The printer will not include the comment if it starts past
// the node itself. Trick it into printing by overlapping the
// slash with the end of the statement.
g.List[0].Slash = n.End() - 1
}
}
node := &printer.CommentedNode{n, lp.fnode.Comments}
lp.config.Fprint(&lp.output, lp.fset, node)
}
func (lp *linePrinter) Visit(n ast.Node) (w ast.Visitor) {
if n == nil {
if lp.output.Len() == 0 {
lp.emit()
}
return nil
}
first := lp.fset.Position(n.Pos()).Line
last := lp.fset.Position(n.End()).Line
if first <= lp.line && last >= lp.line {
// Print the innermost statement containing the line.
if stmt, ok := n.(ast.Stmt); ok {
if _, ok := n.(*ast.BlockStmt); !ok {
lp.stmt = stmt
}
}
if first == lp.line && lp.emit() {
return nil
}
return lp
}
return nil
}
func (lp *linePrinter) trim(n ast.Node) bool {
stmt, ok := n.(ast.Stmt)
if !ok {
return true
}
line := lp.fset.Position(n.Pos()).Line
if line != lp.line {
return false
}
switch stmt := stmt.(type) {
case *ast.IfStmt:
stmt.Body = lp.trimBlock(stmt.Body)
case *ast.SwitchStmt:
stmt.Body = lp.trimBlock(stmt.Body)
case *ast.TypeSwitchStmt:
stmt.Body = lp.trimBlock(stmt.Body)
case *ast.CaseClause:
stmt.Body = lp.trimList(stmt.Body)
case *ast.CommClause:
stmt.Body = lp.trimList(stmt.Body)
case *ast.BlockStmt:
stmt.List = lp.trimList(stmt.List)
}
return true
}
func (lp *linePrinter) trimBlock(stmt *ast.BlockStmt) *ast.BlockStmt {
if !lp.trim(stmt) {
return lp.emptyBlock(stmt)
}
stmt.Rbrace = stmt.Lbrace
return stmt
}
func (lp *linePrinter) trimList(stmts []ast.Stmt) []ast.Stmt {
for i := 0; i != len(stmts); i++ {
if !lp.trim(stmts[i]) {
stmts[i] = lp.emptyStmt(stmts[i])
break
}
}
return stmts
}
func (lp *linePrinter) emptyStmt(n ast.Node) *ast.ExprStmt {
return &ast.ExprStmt{&ast.Ellipsis{n.Pos(), nil}}
}
func (lp *linePrinter) emptyBlock(n ast.Node) *ast.BlockStmt {
p := n.Pos()
return &ast.BlockStmt{p, []ast.Stmt{lp.emptyStmt(n)}, p}
}
