// Copyright 2009 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 implements printing of AST nodes; specifically
// expressions, statements, declarations, and files. It uses
// the print functionality implemented in printer.go.
package printer
import (
"bytes";
"go/ast";
"go/token";
)
// Disabled formatting - enable eventually and remove the flag.
const (
compositeLitBlank = false;
fewerSemis = true;
stringListMode = exprListMode(0); // previously: noIndent
)
// Other formatting issues:
// - replacement of expression spacing algorithm with rsc's algorithm
// - better comment formatting for /*-style comments at the end of a line (e.g. a declaration)
// when the comment spans multiple lines; if such a comment is just two lines, formatting is
// not idempotent
// - formatting of expression lists; especially for string lists (stringListMode)
// - blank after { and before } in one-line composite literals probably looks better
// - should use blank instead of tab to separate one-line function bodies from
// the function header unless there is a group of consecutive one-liners
// ----------------------------------------------------------------------------
// Common AST nodes.
// Print as many newlines as necessary (but at least min and and at most
// max newlines) to get to the current line. ws is printed before the first
// line break. If newSection is set, the first line break is printed as
// formfeed. Returns true if any line break was printed; returns false otherwise.
//
// TODO(gri): Reconsider signature (provide position instead of line)
//
func (p *printer) linebreak(line, min, max int, ws whiteSpace, newSection bool) (printedBreak bool) {
n := line - p.pos.Line;
switch {
case n < min:
n = min
case n > max:
n = max
}
if n > 0 {
p.print(ws);
if newSection {
p.print(formfeed);
n--;
printedBreak = true;
}
}
for ; n > 0; n-- {
p.print(newline);
printedBreak = true;
}
return;
}
// TODO(gri): The code for printing lead and line comments
// should be eliminated in favor of reusing the
// comment intersperse mechanism above somehow.
// Print a list of individual comments.
func (p *printer) commentList(list []*ast.Comment) {
for i, c := range list {
t := c.Text;
// TODO(gri): this needs to be styled like normal comments
p.print(c.Pos(), t);
if t[1] == '/' && i+1 < len(list) {
//-style comment which is not at the end; print a newline
p.print(newline)
}
}
}
// Print a lead comment followed by a newline.
func (p *printer) leadComment(d *ast.CommentGroup) {
// Ignore the comment if we have comments interspersed (p.comment != nil).
if p.comment == nil && d != nil {
p.commentList(d.List);
p.print(newline);
}
}
// Print a tab followed by a line comment.
// A newline must be printed afterwards since
// the comment may be a //-style comment.
func (p *printer) lineComment(d *ast.CommentGroup) {
// Ignore the comment if we have comments interspersed (p.comment != nil).
if p.comment == nil && d != nil {
p.print(vtab);
p.commentList(d.List);
}
}
// Sets multiLine to true if the identifier list spans multiple lines.
func (p *printer) identList(list []*ast.Ident, multiLine *bool) {
// convert into an expression list so we can re-use exprList formatting
xlist := make([]ast.Expr, len(list));
for i, x := range list {
xlist[i] = x
}
p.exprList(noPos, xlist, 1, commaSep, multiLine);
}
// Sets multiLine to true if the string list spans multiple lines.
func (p *printer) stringList(list []*ast.BasicLit, multiLine *bool) {
// convert into an expression list so we can re-use exprList formatting
xlist := make([]ast.Expr, len(list));
for i, x := range list {
xlist[i] = x
}
p.exprList(noPos, xlist, 1, stringListMode, multiLine);
}
type exprListMode uint
const (
blankStart exprListMode = 1 << iota; // print a blank before a non-empty list
blankEnd; // print a blank after a non-empty list
commaSep; // elements are separated by commas
commaTerm; // elements are terminated by comma
noIndent; // no extra indentation in multi-line lists
)
// Print a list of expressions. If the list spans multiple
// source lines, the original line breaks are respected between
// expressions. Sets multiLine to true if the list spans multiple
// lines.
func (p *printer) exprList(prev token.Position, list []ast.Expr, depth int, mode exprListMode, multiLine *bool) {
if len(list) == 0 {
return
}
if mode&blankStart != 0 {
p.print(blank)
}
// TODO(gri): endLine may be incorrect as it is really the beginning
// of the last list entry. There may be only one, very long
// entry in which case line == endLine.
line := list[0].Pos().Line;
endLine := list[len(list)-1].Pos().Line;
if prev.IsValid() && prev.Line == line && line == endLine {
// all list entries on a single line
for i, x := range list {
if i > 0 {
if mode&commaSep != 0 {
p.print(token.COMMA)
}
p.print(blank);
}
p.expr0(x, depth, multiLine);
}
if mode&blankEnd != 0 {
p.print(blank)
}
return;
}
// list entries span multiple lines;
// use source code positions to guide line breaks
// don't add extra indentation if noIndent is set;
// i.e., pretend that the first line is already indented
ws := ignore;
if mode&noIndent == 0 {
ws = indent
}
if prev.IsValid() && prev.Line < line && p.linebreak(line, 1, 2, ws, true) {
ws = ignore;
*multiLine = true;
}
for i, x := range list {
prev := line;
line = x.Pos().Line;
if i > 0 {
if mode&commaSep != 0 {
p.print(token.COMMA)
}
if prev < line && prev > 0 && line > 0 {
if p.linebreak(line, 1, 2, ws, true) {
ws = ignore;
*multiLine = true;
}
} else {
p.print(blank)
}
}
p.expr0(x, depth, multiLine);
}
if mode&commaTerm != 0 {
p.print(token.COMMA);
if ws == ignore && mode&noIndent == 0 {
// unindent if we indented
p.print(unindent)
}
p.print(formfeed); // terminating comma needs a line break to look good
return;
}
if mode&blankEnd != 0 {
p.print(blank)
}
if ws == ignore && mode&noIndent == 0 {
// unindent if we indented
p.print(unindent)
}
}
// Sets multiLine to true if the the parameter list spans multiple lines.
func (p *printer) parameters(list []*ast.Field, multiLine *bool) {
p.print(token.LPAREN);
if len(list) > 0 {
for i, par := range list {
if i > 0 {
p.print(token.COMMA, blank)
}
if len(par.Names) > 0 {
p.identList(par.Names, multiLine);
p.print(blank);
}
p.expr(par.Type, multiLine);
}
}
p.print(token.RPAREN);
}
// Returns true if a separating semicolon is optional.
// Sets multiLine to true if the signature spans multiple lines.
func (p *printer) signature(params, result []*ast.Field, multiLine *bool) (optSemi bool) {
p.parameters(params, multiLine);
if result != nil {
p.print(blank);
if len(result) == 1 && result[0].Names == nil {
// single anonymous result; no ()'s unless it's a function type
f := result[0];
if _, isFtyp := f.Type.(*ast.FuncType); !isFtyp {
optSemi = p.expr(f.Type, multiLine);
return;
}
}
p.parameters(result, multiLine);
}
return;
}
func identListSize(list []*ast.Ident, maxSize int) (size int) {
for i, x := range list {
if i > 0 {
size += 2 // ", "
}
size += len(x.Value);
if size >= maxSize {
break
}
}
return;
}
func (p *printer) isOneLineFieldList(list []*ast.Field) bool {
if len(list) != 1 {
return false // allow only one field
}
f := list[0];
if f.Tag != nil || f.Comment != nil {
return false // don't allow tags or comments
}
// only name(s) and type
const maxSize = 30; // adjust as appropriate, this is an approximate value
namesSize := identListSize(f.Names, maxSize);
if namesSize > 0 {
namesSize = 1 // blank between names and types
}
typeSize := p.nodeSize(f.Type, maxSize);
return namesSize+typeSize <= maxSize;
}
func (p *printer) fieldList(lbrace token.Position, list []*ast.Field, rbrace token.Position, isIncomplete bool, ctxt exprContext) {
if !isIncomplete && !p.commentBefore(rbrace) {
// possibly a one-line struct/interface
if len(list) == 0 {
// no blank between keyword and {} in this case
p.print(lbrace, token.LBRACE, rbrace, token.RBRACE);
return;
} else if ctxt&(compositeLit|structType) == compositeLit|structType &&
p.isOneLineFieldList(list) { // for now ignore interfaces
// small enough - print on one line
// (don't use identList and ignore source line breaks)
p.print(lbrace, token.LBRACE, blank);
f := list[0];
for i, x := range f.Names {
if i > 0 {
p.print(token.COMMA, blank)
}
p.expr(x, ignoreMultiLine);
}
if len(f.Names) > 0 {
p.print(blank)
}
p.expr(f.Type, ignoreMultiLine);
p.print(blank, rbrace, token.RBRACE);
return;
}
}
// at least one entry or incomplete
p.print(blank, lbrace, token.LBRACE, indent, formfeed);
if ctxt&structType != 0 {
sep := vtab;
if len(list) == 1 {
sep = blank
}
var ml bool;
for i, f := range list {
if i > 0 {
p.linebreak(f.Pos().Line, 1, 2, ignore, ml)
}
ml = false;
extraTabs := 0;
p.leadComment(f.Doc);
if len(f.Names) > 0 {
// named fields
p.identList(f.Names, &ml);
p.print(sep);
p.expr(f.Type, &ml);
extraTabs = 1;
} else {
// anonymous field
p.expr(f.Type, &ml);
extraTabs = 2;
}
if f.Tag != nil {
if len(f.Names) > 0 && sep == vtab {
p.print(sep)
}
p.print(sep);
p.expr(&ast.StringList{f.Tag}, &ml);
extraTabs = 0;
}
p.print(token.SEMICOLON);
if f.Comment != nil {
for ; extraTabs > 0; extraTabs-- {
p.print(vtab)
}
p.lineComment(f.Comment);
}
}
if isIncomplete {
if len(list) > 0 {
p.print(formfeed)
}
// TODO(gri): this needs to be styled like normal comments
p.print("// contains unexported fields");
}
} else { // interface
var ml bool;
for i, f := range list {
if i > 0 {
p.linebreak(f.Pos().Line, 1, 2, ignore, ml)
}
ml = false;
p.leadComment(f.Doc);
if ftyp, isFtyp := f.Type.(*ast.FuncType); isFtyp {
// method
p.expr(f.Names[0], &ml);
p.signature(ftyp.Params, ftyp.Results, &ml);
} else {
// embedded interface
p.expr(f.Type, &ml)
}
p.print(token.SEMICOLON);
p.lineComment(f.Comment);
}
if isIncomplete {
if len(list) > 0 {
p.print(formfeed)
}
// TODO(gri): this needs to be styled like normal comments
p.print("// contains unexported methods");
}
}
p.print(unindent, formfeed, rbrace, token.RBRACE);
}
// ----------------------------------------------------------------------------
// Expressions
// exprContext describes the syntactic environment in which an expression node is printed.
type exprContext uint
const (
compositeLit = 1 << iota;
structType;
)
func walkBinary(e *ast.BinaryExpr) (has5, has6 bool, maxProblem int) {
switch e.Op.Precedence() {
case 5:
has5 = true
case 6:
has6 = true
}
switch l := e.X.(type) {
case *ast.BinaryExpr:
if l.Op.Precedence() < e.Op.Precedence() {
// parens will be inserted.
// pretend this is an *ast.ParenExpr and do nothing.
break
}
h5, h6, mp := walkBinary(l);
has5 = has5 || h5;
has6 = has6 || h6;
if maxProblem < mp {
maxProblem = mp
}
}
switch r := e.Y.(type) {
case *ast.BinaryExpr:
if r.Op.Precedence() <= e.Op.Precedence() {
// parens will be inserted.
// pretend this is an *ast.ParenExpr and do nothing.
break
}
h5, h6, mp := walkBinary(r);
has5 = has5 || h5;
has6 = has6 || h6;
if maxProblem < mp {
maxProblem = mp
}
case *ast.StarExpr:
if e.Op.String() == "/" {
maxProblem = 6
}
case *ast.UnaryExpr:
switch e.Op.String() + r.Op.String() {
case "/*":
maxProblem = 6
case "++", "--":
if maxProblem < 5 {
maxProblem = 5
}
}
}
return;
}
func cutoff(e *ast.BinaryExpr, depth int) int {
has5, has6, maxProblem := walkBinary(e);
if maxProblem > 0 {
return maxProblem + 1
}
if has5 && has6 {
if depth == 1 {
return 6
}
return 5;
}
if depth == 1 {
return 7
}
return 5;
}
func diffPrec(expr ast.Expr, prec int) int {
x, ok := expr.(*ast.BinaryExpr);
if !ok || prec != x.Op.Precedence() {
return 1
}
return 0;
}
// Format the binary expression: decide the cutoff and then format.
// Let's call depth == 1 Normal mode, and depth > 1 Compact mode.
// (Algorithm suggestion by Russ Cox.)
//
// The precedences are:
// 6 * / % << >> & &^
// 5 + - | ^
// 4 == != < <= > >=
// 3 <-
// 2 &&
// 1 ||
//
// The only decision is whether there will be spaces around levels 5 and 6.
// There are never spaces at level 7 (unary), and always spaces at levels 4 and below.
//
// To choose the cutoff, look at the whole expression but excluding primary
// expressions (function calls, parenthesized exprs), and apply these rules:
//
// 1) If there is a binary operator with a right side unary operand
// that would clash without a space, the cutoff must be (in order):
//
// &^ 7
// /* 7
// ++ 6
// -- 6
//
// 2) If there is a mix of level 6 and level 5 operators, then the cutoff
// is 6 (use spaces to distinguish precedence) in Normal mode
// and 5 (never use spaces) in Compact mode.
//
// 3) If there are no level 5 operators or no level 6 operators, then the
// cutoff is 7 (always use spaces) in Normal mode
// and 5 (never use spaces) in Compact mode.
//
// Sets multiLine to true if the binary expression spans multiple lines.
func (p *printer) binaryExpr(x *ast.BinaryExpr, prec1, cutoff, depth int, multiLine *bool) {
prec := x.Op.Precedence();
if prec < prec1 {
// parenthesis needed
// Note: The parser inserts an ast.ParenExpr node; thus this case
// can only occur if the AST is created in a different way.
p.print(token.LPAREN);
p.expr0(x, depth-1, multiLine); // parentheses undo one level of depth
p.print(token.RPAREN);
return;
}
printBlank := prec < cutoff;
ws := indent;
p.expr1(x.X, prec, depth+diffPrec(x.X, prec), 0, multiLine);
if printBlank {
p.print(blank)
}
xline := p.pos.Line; // before the operator (it may be on the next line!)
yline := x.Y.Pos().Line;
p.print(x.OpPos, x.Op);
if xline != yline && xline > 0 && yline > 0 {
// at least one line break, but respect an extra empty line
// in the source
if p.linebreak(yline, 1, 2, ws, true) {
ws = ignore;
*multiLine = true;
printBlank = false; // no blank after line break
}
}
if printBlank {
p.print(blank)
}
p.expr1(x.Y, prec+1, depth+1, 0, multiLine);
if ws == ignore {
p.print(unindent)
}
}
func isBinary(expr ast.Expr) bool {
_, ok := expr.(*ast.BinaryExpr);
return ok;
}
// Returns true if a separating semicolon is optional.
// Sets multiLine to true if the expression spans multiple lines.
func (p *printer) expr1(expr ast.Expr, prec1, depth int, ctxt exprContext, multiLine *bool) (optSemi bool) {
p.print(expr.Pos());
switch x := expr.(type) {
case *ast.BadExpr:
p.print("BadExpr")
case *ast.Ident:
p.print(x)
case *ast.BinaryExpr:
if depth < 1 {
p.internalError("depth < 1:", depth);
depth = 1;
}
p.binaryExpr(x, prec1, cutoff(x, depth), depth, multiLine);
case *ast.KeyValueExpr:
p.expr(x.Key, multiLine);
p.print(x.Colon, token.COLON, blank);
p.expr(x.Value, multiLine);
case *ast.StarExpr:
const prec = token.UnaryPrec;
if prec < prec1 {
// parenthesis needed
p.print(token.LPAREN);
p.print(token.MUL);
optSemi = p.expr(x.X, multiLine);
p.print(token.RPAREN);
} else {
// no parenthesis needed
p.print(token.MUL);
optSemi = p.expr(x.X, multiLine);
}
case *ast.UnaryExpr:
const prec = token.UnaryPrec;
if prec < prec1 {
// parenthesis needed
p.print(token.LPAREN);
p.expr(x, multiLine);
p.print(token.RPAREN);
} else {
// no parenthesis needed
p.print(x.Op);
if x.Op == token.RANGE {
p.print(blank)
}
p.expr1(x.X, prec, depth, 0, multiLine);
}
case *ast.BasicLit:
p.print(x)
case *ast.StringList:
p.stringList(x.Strings, multiLine)
case *ast.FuncLit:
p.expr(x.Type, multiLine);
p.funcBody(x.Body, distance(x.Type.Pos(), p.pos), true, multiLine);
case *ast.ParenExpr:
p.print(token.LPAREN);
p.expr0(x.X, depth-1, multiLine); // parentheses undo one level of depth
p.print(x.Rparen, token.RPAREN);
case *ast.SelectorExpr:
p.expr1(x.X, token.HighestPrec, depth, 0, multiLine);
p.print(token.PERIOD);
p.expr1(x.Sel, token.HighestPrec, depth, 0, multiLine);
case *ast.TypeAssertExpr:
p.expr1(x.X, token.HighestPrec, depth, 0, multiLine);
p.print(token.PERIOD, token.LPAREN);
if x.Type != nil {
p.expr(x.Type, multiLine)
} else {
p.print(token.TYPE)
}
p.print(token.RPAREN);
case *ast.IndexExpr:
// TODO(gri): should treat[] like parentheses and undo one level of depth
p.expr1(x.X, token.HighestPrec, 1, 0, multiLine);
p.print(token.LBRACK);
p.expr0(x.Index, depth+1, multiLine);
p.print(token.RBRACK);
case *ast.SliceExpr:
// TODO(gri): should treat[] like parentheses and undo one level of depth
p.expr1(x.X, token.HighestPrec, 1, 0, multiLine);
p.print(token.LBRACK);
p.expr0(x.Index, depth+1, multiLine);
// blanks around ":" if both sides exist and either side is a binary expression
if depth <= 1 && x.End != nil && (isBinary(x.Index) || isBinary(x.End)) {
p.print(blank, token.COLON, blank)
} else {
p.print(token.COLON)
}
if x.End != nil {
p.expr0(x.End, depth+1, multiLine)
}
p.print(token.RBRACK);
case *ast.CallExpr:
if len(x.Args) > 1 {
depth++
}
p.expr1(x.Fun, token.HighestPrec, depth, 0, multiLine);
p.print(x.Lparen, token.LPAREN);
p.exprList(x.Lparen, x.Args, depth, commaSep, multiLine);
p.print(x.Rparen, token.RPAREN);
case *ast.CompositeLit:
p.expr1(x.Type, token.HighestPrec, depth, compositeLit, multiLine);
mode := commaSep | commaTerm;
if compositeLitBlank {
// add blank padding around composite literal
// contents for a less dense look
mode |= blankStart | blankEnd;
if x.Lbrace.Line < x.Rbrace.Line {
// add a blank before the opening { for multi-line composites
// TODO(gri): for now this decision is made by looking at the
// source code - it may not be correct if the source
// code was badly misformatted in the first place
p.print(blank)
}
}
p.print(x.Lbrace, token.LBRACE);
p.exprList(x.Lbrace, x.Elts, 1, mode, multiLine);
p.print(x.Rbrace, token.RBRACE);
case *ast.Ellipsis:
p.print(token.ELLIPSIS)
case *ast.ArrayType:
p.print(token.LBRACK);
if x.Len != nil {
p.expr(x.Len, multiLine)
}
p.print(token.RBRACK);
optSemi = p.expr(x.Elt, multiLine);
case *ast.StructType:
p.print(token.STRUCT);
p.fieldList(x.Lbrace, x.Fields, x.Rbrace, x.Incomplete, ctxt|structType);
optSemi = true;
case *ast.FuncType:
p.print(token.FUNC);
optSemi = p.signature(x.Params, x.Results, multiLine);
case *ast.InterfaceType:
p.print(token.INTERFACE);
p.fieldList(x.Lbrace, x.Methods, x.Rbrace, x.Incomplete, ctxt);
optSemi = true;
case *ast.MapType:
p.print(token.MAP, token.LBRACK);
p.expr(x.Key, multiLine);
p.print(token.RBRACK);
optSemi = p.expr(x.Value, multiLine);
case *ast.ChanType:
switch x.Dir {
case ast.SEND | ast.RECV:
p.print(token.CHAN)
case ast.RECV:
p.print(token.ARROW, token.CHAN)
case ast.SEND:
p.print(token.CHAN, token.ARROW)
}
p.print(blank);
optSemi = p.expr(x.Value, multiLine);
default:
panic("unreachable")
}
return;
}
func (p *printer) expr0(x ast.Expr, depth int, multiLine *bool) (optSemi bool) {
return p.expr1(x, token.LowestPrec, depth, 0, multiLine)
}
// Returns true if a separating semicolon is optional.
// Sets multiLine to true if the expression spans multiple lines.
func (p *printer) expr(x ast.Expr, multiLine *bool) (optSemi bool) {
const depth = 1;
return p.expr1(x, token.LowestPrec, depth, 0, multiLine);
}
// ----------------------------------------------------------------------------
// Statements
const maxStmtNewlines = 2 // maximum number of newlines between statements
// Print the statement list indented, but without a newline after the last statement.
// Extra line breaks between statements in the source are respected but at most one
// empty line is printed between statements.
func (p *printer) stmtList(list []ast.Stmt, _indent int) {
// TODO(gri): fix _indent code
if _indent > 0 {
p.print(indent)
}
var multiLine bool;
for i, s := range list {
// _indent == 0 only for lists of switch/select case clauses;
// in those cases each clause is a new section
p.linebreak(s.Pos().Line, 1, maxStmtNewlines, ignore, i == 0 || _indent == 0 || multiLine);
multiLine = false;
if !p.stmt(s, &multiLine) && (!fewerSemis || len(list) > 1) {
p.print(token.SEMICOLON)
}
}
if _indent > 0 {
p.print(unindent)
}
}
// block prints an *ast.BlockStmt; it always spans at least two lines.
func (p *printer) block(s *ast.BlockStmt, indent int) {
p.print(s.Pos(), token.LBRACE);
p.stmtList(s.List, indent);
p.linebreak(s.Rbrace.Line, 1, maxStmtNewlines, ignore, true);
p.print(s.Rbrace, token.RBRACE);
}
// TODO(gri): Decide if this should be used more broadly. The printing code
// knows when to insert parentheses for precedence reasons, but
// need to be careful to keep them around type expressions.
func stripParens(x ast.Expr) ast.Expr {
if px, hasParens := x.(*ast.ParenExpr); hasParens {
return stripParens(px.X)
}
return x;
}
func (p *printer) controlClause(isForStmt bool, init ast.Stmt, expr ast.Expr, post ast.Stmt) {
p.print(blank);
needsBlank := false;
if init == nil && post == nil {
// no semicolons required
if expr != nil {
p.expr(stripParens(expr), ignoreMultiLine);
needsBlank = true;
}
} else {
// all semicolons required
// (they are not separators, print them explicitly)
if init != nil {
p.stmt(init, ignoreMultiLine)
}
p.print(token.SEMICOLON, blank);
if expr != nil {
p.expr(stripParens(expr), ignoreMultiLine);
needsBlank = true;
}
if isForStmt {
p.print(token.SEMICOLON, blank);
needsBlank = false;
if post != nil {
p.stmt(post, ignoreMultiLine);
needsBlank = true;
}
}
}
if needsBlank {
p.print(blank)
}
}
// Returns true if a separating semicolon is optional.
// Sets multiLine to true if the statements spans multiple lines.
func (p *printer) stmt(stmt ast.Stmt, multiLine *bool) (optSemi bool) {
p.print(stmt.Pos());
switch s := stmt.(type) {
case *ast.BadStmt:
p.print("BadStmt")
case *ast.DeclStmt:
p.decl(s.Decl, inStmtList, multiLine);
optSemi = true; // decl prints terminating semicolon if necessary
case *ast.EmptyStmt:
// nothing to do
case *ast.LabeledStmt:
// a "correcting" unindent immediately following a line break
// is applied before the line break if there is no comment
// between (see writeWhitespace)
p.print(unindent);
p.expr(s.Label, multiLine);
p.print(token.COLON, vtab, indent);
p.linebreak(s.Stmt.Pos().Line, 0, 1, ignore, true);
optSemi = p.stmt(s.Stmt, multiLine);
case *ast.ExprStmt:
const depth = 1;
p.expr0(s.X, depth, multiLine);
case *ast.IncDecStmt:
const depth = 1;
p.expr0(s.X, depth+1, multiLine);
p.print(s.Tok);
case *ast.AssignStmt:
var depth = 1;
if len(s.Lhs) > 1 && len(s.Rhs) > 1 {
depth++
}
p.exprList(s.Pos(), s.Lhs, depth, commaSep, multiLine);
p.print(blank, s.TokPos, s.Tok);
p.exprList(s.TokPos, s.Rhs, depth, blankStart|commaSep, multiLine);
case *ast.GoStmt:
p.print(token.GO, blank);
p.expr(s.Call, multiLine);
case *ast.DeferStmt:
p.print(token.DEFER, blank);
p.expr(s.Call, multiLine);
case *ast.ReturnStmt:
p.print(token.RETURN);
if s.Results != nil {
p.exprList(s.Pos(), s.Results, 1, blankStart|commaSep, multiLine)
}
case *ast.BranchStmt:
p.print(s.Tok);
if s.Label != nil {
p.print(blank);
p.expr(s.Label, multiLine);
}
case *ast.BlockStmt:
p.block(s, 1);
*multiLine = true;
optSemi = true;
case *ast.IfStmt:
p.print(token.IF);
p.controlClause(false, s.Init, s.Cond, nil);
p.block(s.Body, 1);
*multiLine = true;
optSemi = true;
if s.Else != nil {
p.print(blank, token.ELSE, blank);
switch s.Else.(type) {
case *ast.BlockStmt, *ast.IfStmt:
optSemi = p.stmt(s.Else, ignoreMultiLine)
default:
p.print(token.LBRACE, indent, formfeed);
p.stmt(s.Else, ignoreMultiLine);
p.print(unindent, formfeed, token.RBRACE);
}
}
case *ast.CaseClause:
if s.Values != nil {
p.print(token.CASE);
p.exprList(s.Pos(), s.Values, 1, blankStart|commaSep, multiLine);
} else {
p.print(token.DEFAULT)
}
p.print(s.Colon, token.COLON);
p.stmtList(s.Body, 1);
optSemi = true; // "block" without {}'s
case *ast.SwitchStmt:
p.print(token.SWITCH);
p.controlClause(false, s.Init, s.Tag, nil);
p.block(s.Body, 0);
*multiLine = true;
optSemi = true;
case *ast.TypeCaseClause:
if s.Types != nil {
p.print(token.CASE);
p.exprList(s.Pos(), s.Types, 1, blankStart|commaSep, multiLine);
} else {
p.print(token.DEFAULT)
}
p.print(s.Colon, token.COLON);
p.stmtList(s.Body, 1);
optSemi = true; // "block" without {}'s
case *ast.TypeSwitchStmt:
p.print(token.SWITCH);
if s.Init != nil {
p.print(blank);
p.stmt(s.Init, ignoreMultiLine);
p.print(token.SEMICOLON);
}
p.print(blank);
p.stmt(s.Assign, ignoreMultiLine);
p.print(blank);
p.block(s.Body, 0);
*multiLine = true;
optSemi = true;
case *ast.CommClause:
if s.Rhs != nil {
p.print(token.CASE, blank);
if s.Lhs != nil {
p.expr(s.Lhs, multiLine);
p.print(blank, s.Tok, blank);
}
p.expr(s.Rhs, multiLine);
} else {
p.print(token.DEFAULT)
}
p.print(s.Colon, token.COLON);
p.stmtList(s.Body, 1);
optSemi = true; // "block" without {}'s
case *ast.SelectStmt:
p.print(token.SELECT, blank);
p.block(s.Body, 0);
*multiLine = true;
optSemi = true;
case *ast.ForStmt:
p.print(token.FOR);
p.controlClause(true, s.Init, s.Cond, s.Post);
p.block(s.Body, 1);
*multiLine = true;
optSemi = true;
case *ast.RangeStmt:
p.print(token.FOR, blank);
p.expr(s.Key, multiLine);
if s.Value != nil {
p.print(token.COMMA, blank);
p.expr(s.Value, multiLine);
}
p.print(blank, s.TokPos, s.Tok, blank, token.RANGE, blank);
p.expr(s.X, multiLine);
p.print(blank);
p.block(s.Body, 1);
*multiLine = true;
optSemi = true;
default:
panic("unreachable")
}
return;
}
// ----------------------------------------------------------------------------
// Declarations
type declContext uint
const (
atTop declContext = iota;
inGroup;
inStmtList;
)
// The parameter n is the number of specs in the group; context specifies
// the surroundings of the declaration. Separating semicolons are printed
// depending on the context. Sets multiLine to true if the spec spans
// multiple lines.
//
func (p *printer) spec(spec ast.Spec, n int, context declContext, multiLine *bool) {
var (
optSemi bool; // true if a semicolon is optional
comment *ast.CommentGroup; // a line comment, if any
extraTabs int; // number of extra tabs before comment, if any
)
switch s := spec.(type) {
case *ast.ImportSpec:
p.leadComment(s.Doc);
if s.Name != nil {
p.expr(s.Name, multiLine);
p.print(blank);
}
p.expr(&ast.StringList{s.Path}, multiLine);
comment = s.Comment;
case *ast.ValueSpec:
p.leadComment(s.Doc);
p.identList(s.Names, multiLine); // always present
if n == 1 {
if s.Type != nil {
p.print(blank);
optSemi = p.expr(s.Type, multiLine);
}
if s.Values != nil {
p.print(blank, token.ASSIGN);
p.exprList(noPos, s.Values, 1, blankStart|commaSep, multiLine);
optSemi = false;
}
} else {
extraTabs = 2;
if s.Type != nil || s.Values != nil {
p.print(vtab)
}
if s.Type != nil {
optSemi = p.expr(s.Type, multiLine);
extraTabs = 1;
}
if s.Values != nil {
p.print(vtab);
p.print(token.ASSIGN);
p.exprList(noPos, s.Values, 1, blankStart|commaSep, multiLine);
optSemi = false;
extraTabs = 0;
}
}
comment = s.Comment;
case *ast.TypeSpec:
p.leadComment(s.Doc);
p.expr(s.Name, multiLine);
if n == 1 {
p.print(blank)
} else {
p.print(vtab)
}
optSemi = p.expr(s.Type, multiLine);
comment = s.Comment;
default:
panic("unreachable")
}
if context == inGroup || context == inStmtList && !optSemi {
p.print(token.SEMICOLON)
}
if comment != nil {
for ; extraTabs > 0; extraTabs-- {
p.print(vtab)
}
p.lineComment(comment);
}
}
// Sets multiLine to true if the declaration spans multiple lines.
func (p *printer) genDecl(d *ast.GenDecl, context declContext, multiLine *bool) {
p.leadComment(d.Doc);
p.print(d.Pos(), d.Tok, blank);
if d.Lparen.IsValid() {
// group of parenthesized declarations
p.print(d.Lparen, token.LPAREN);
if len(d.Specs) > 0 {
p.print(indent, formfeed);
var ml bool;
for i, s := range d.Specs {
if i > 0 {
p.linebreak(s.Pos().Line, 1, 2, ignore, ml)
}
ml = false;
p.spec(s, len(d.Specs), inGroup, &ml);
}
p.print(unindent, formfeed);
*multiLine = true;
}
p.print(d.Rparen, token.RPAREN);
} else {
// single declaration
p.spec(d.Specs[0], 1, context, multiLine)
}
}
// nodeSize determines the size of n in chars after formatting.
// The result is <= maxSize if the node fits on one line with at
// most maxSize chars and the formatted output doesn't contain
// any control chars. Otherwise, the result is > maxSize.
//
func (p *printer) nodeSize(n ast.Node, maxSize int) (size int) {
size = maxSize + 1; // assume n doesn't fit
// nodeSize computation must be indendent of particular
// style so that we always get the same decision; print
// in RawFormat
cfg := Config{Mode: RawFormat};
var buf bytes.Buffer;
if _, err := cfg.Fprint(&buf, n); err != nil {
return
}
if buf.Len() <= maxSize {
for _, ch := range buf.Bytes() {
if ch < ' ' {
return
}
}
size = buf.Len(); // n fits
}
return;
}
func (p *printer) isOneLineFunc(b *ast.BlockStmt, headerSize int) bool {
const maxSize = 90; // adjust as appropriate, this is an approximate value
bodySize := 0;
switch {
case len(b.List) > 1 || p.commentBefore(b.Rbrace):
return false // too many statements or there is a comment - all bets are off
case len(b.List) == 1:
bodySize = p.nodeSize(b.List[0], maxSize)
}
// require both headers and overall size to be not "too large"
return headerSize <= maxSize/2 && headerSize+bodySize <= maxSize;
}
// Sets multiLine to true if the function body spans multiple lines.
func (p *printer) funcBody(b *ast.BlockStmt, headerSize int, isLit bool, multiLine *bool) {
if b == nil {
return
}
if p.isOneLineFunc(b, headerSize) {
sep := vtab;
if isLit {
sep = blank
}
if len(b.List) > 0 {
p.print(sep, b.Pos(), token.LBRACE, blank);
p.stmt(b.List[0], ignoreMultiLine);
p.print(blank, b.Rbrace, token.RBRACE);
} else {
p.print(sep, b.Pos(), token.LBRACE, b.Rbrace, token.RBRACE)
}
return;
}
p.print(blank);
p.block(b, 1);
*multiLine = true;
}
// distance returns the column difference between from and to if both
// are on the same line; if they are on different lines (or unknown)
// the result is infinity (1<<30).
func distance(from, to token.Position) int {
if from.IsValid() && to.IsValid() && from.Line == to.Line {
return to.Column - from.Column
}
return 1 << 30;
}
// Sets multiLine to true if the declaration spans multiple lines.
func (p *printer) funcDecl(d *ast.FuncDecl, multiLine *bool) {
p.leadComment(d.Doc);
p.print(d.Pos(), token.FUNC, blank);
if recv := d.Recv; recv != nil {
// method: print receiver
p.print(token.LPAREN);
if len(recv.Names) > 0 {
p.expr(recv.Names[0], multiLine);
p.print(blank);
}
p.expr(recv.Type, multiLine);
p.print(token.RPAREN, blank);
}
p.expr(d.Name, multiLine);
p.signature(d.Type.Params, d.Type.Results, multiLine);
p.funcBody(d.Body, distance(d.Pos(), p.pos), false, multiLine);
}
// Sets multiLine to true if the declaration spans multiple lines.
func (p *printer) decl(decl ast.Decl, context declContext, multiLine *bool) {
switch d := decl.(type) {
case *ast.BadDecl:
p.print(d.Pos(), "BadDecl")
case *ast.GenDecl:
p.genDecl(d, context, multiLine)
case *ast.FuncDecl:
p.funcDecl(d, multiLine)
default:
panic("unreachable")
}
}
// ----------------------------------------------------------------------------
// Files
const maxDeclNewlines = 3 // maximum number of newlines between declarations
func declToken(decl ast.Decl) (tok token.Token) {
tok = token.ILLEGAL;
switch d := decl.(type) {
case *ast.GenDecl:
tok = d.Tok
case *ast.FuncDecl:
tok = token.FUNC
}
return;
}
func (p *printer) file(src *ast.File) {
p.leadComment(src.Doc);
p.print(src.Pos(), token.PACKAGE, blank);
p.expr(src.Name, ignoreMultiLine);
if len(src.Decls) > 0 {
tok := token.ILLEGAL;
for _, d := range src.Decls {
prev := tok;
tok = declToken(d);
// if the declaration token changed (e.g., from CONST to TYPE)
// print an empty line between top-level declarations
min := 1;
if prev != tok {
min = 2
}
p.linebreak(d.Pos().Line, min, maxDeclNewlines, ignore, false);
p.decl(d, atTop, ignoreMultiLine);
}
}
p.print(newline);
}
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