1 // Copyright 2009 The Go Authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style
3 // license that can be found in the LICENSE file.
5 // This file implements printing of AST nodes; specifically
6 // expressions, statements, declarations, and files. It uses
7 // the print functionality implemented in printer.go.
19 // - better comment formatting for /*-style comments at the end of a line (e.g. a declaration)
20 // when the comment spans multiple lines; if such a comment is just two lines, formatting is
22 // - formatting of expression lists
23 // - should use blank instead of tab to separate one-line function bodies from
24 // the function header unless there is a group of consecutive one-liners
26 // ----------------------------------------------------------------------------
29 // Print as many newlines as necessary (but at least min newlines) to get to
30 // the current line. ws is printed before the first line break. If newSection
31 // is set, the first line break is printed as formfeed. Returns true if any
32 // line break was printed; returns false otherwise.
34 // TODO(gri): linebreak may add too many lines if the next statement at "line"
35 // is preceded by comments because the computation of n assumes
36 // the current position before the comment and the target position
37 // after the comment. Thus, after interspersing such comments, the
38 // space taken up by them is not considered to reduce the number of
39 // linebreaks. At the moment there is no easy way to know about
40 // future (not yet interspersed) comments in this function.
42 func (p *printer) linebreak(line, min int, ws whiteSpace, newSection bool) (printedBreak bool) {
43 n := nlimit(line - p.pos.Line)
61 // setComment sets g as the next comment if g != nil and if node comments
62 // are enabled - this mode is used when printing source code fragments such
63 // as exports only. It assumes that there is no pending comment in p.comments
64 // and at most one pending comment in the p.comment cache.
65 func (p *printer) setComment(g *ast.CommentGroup) {
66 if g == nil || !p.useNodeComments {
69 if p.comments == nil {
70 // initialize p.comments lazily
71 p.comments = make([]*ast.CommentGroup, 1)
72 } else if p.cindex < len(p.comments) {
73 // for some reason there are pending comments; this
74 // should never happen - handle gracefully and flush
75 // all comments up to g, ignore anything after that
76 p.flush(p.posFor(g.List[0].Pos()), token.ILLEGAL)
77 p.comments = p.comments[0:1]
78 // in debug mode, report error
79 p.internalError("setComment found pending comments")
83 // don't overwrite any pending comment in the p.comment cache
84 // (there may be a pending comment when a line comment is
85 // immediately followed by a lead comment with no other
87 if p.commentOffset == infinity {
88 p.nextComment() // get comment ready for use
92 type exprListMode uint
95 commaTerm exprListMode = 1 << iota // list is optionally terminated by a comma
96 noIndent // no extra indentation in multi-line lists
99 // If indent is set, a multi-line identifier list is indented after the
100 // first linebreak encountered.
101 func (p *printer) identList(list []*ast.Ident, indent bool) {
102 // convert into an expression list so we can re-use exprList formatting
103 xlist := make([]ast.Expr, len(list))
104 for i, x := range list {
107 var mode exprListMode
111 p.exprList(token.NoPos, xlist, 1, mode, token.NoPos)
114 // Print a list of expressions. If the list spans multiple
115 // source lines, the original line breaks are respected between
118 // TODO(gri) Consider rewriting this to be independent of []ast.Expr
119 // so that we can use the algorithm for any kind of list
120 // (e.g., pass list via a channel over which to range).
121 func (p *printer) exprList(prev0 token.Pos, list []ast.Expr, depth int, mode exprListMode, next0 token.Pos) {
126 prev := p.posFor(prev0)
127 next := p.posFor(next0)
128 line := p.lineFor(list[0].Pos())
129 endLine := p.lineFor(list[len(list)-1].End())
131 if prev.IsValid() && prev.Line == line && line == endLine {
132 // all list entries on a single line
133 for i, x := range list {
135 // use position of expression following the comma as
136 // comma position for correct comment placement
137 p.print(x.Pos(), token.COMMA, blank)
144 // list entries span multiple lines;
145 // use source code positions to guide line breaks
147 // don't add extra indentation if noIndent is set;
148 // i.e., pretend that the first line is already indented
150 if mode&noIndent == 0 {
154 // the first linebreak is always a formfeed since this section must not
155 // depend on any previous formatting
156 prevBreak := -1 // index of last expression that was followed by a linebreak
157 if prev.IsValid() && prev.Line < line && p.linebreak(line, 0, ws, true) {
162 // initialize expression/key size: a zero value indicates expr/key doesn't fit on a single line
165 // print all list elements
166 for i, x := range list {
168 line = p.lineFor(x.Pos())
170 // determine if the next linebreak, if any, needs to use formfeed:
171 // in general, use the entire node size to make the decision; for
172 // key:value expressions, use the key size
173 // TODO(gri) for a better result, should probably incorporate both
174 // the key and the node size into the decision process
177 // determine element size: all bets are off if we don't have
178 // position information for the previous and next token (likely
179 // generated code - simply ignore the size in this case by setting
182 const infinity = 1e6 // larger than any source line
183 size = p.nodeSize(x, infinity)
184 pair, isPair := x.(*ast.KeyValueExpr)
185 if size <= infinity && prev.IsValid() && next.IsValid() {
186 // x fits on a single line
188 size = p.nodeSize(pair.Key, infinity) // size <= infinity
191 // size too large or we don't have good layout information
195 // if the previous line and the current line had single-
196 // line-expressions and the key sizes are small or the
197 // the ratio between the key sizes does not exceed a
198 // threshold, align columns and do not use formfeed
199 if prevSize > 0 && size > 0 {
201 if prevSize <= smallSize && size <= smallSize {
204 const r = 4 // threshold
205 ratio := float64(size) / float64(prevSize)
206 useFF = ratio <= 1/r || r <= ratio
211 needsLinebreak := prevLine < line && prevLine > 0 && line > 0
212 // use position of expression following the comma as
213 // comma position for correct comment placement, but
214 // only if the expression is on the same line
221 // lines are broken using newlines so comments remain aligned
222 // unless forceFF is set or there are multiple expressions on
223 // the same line in which case formfeed is used
224 if p.linebreak(line, 0, ws, useFF || prevBreak+1 < i) {
227 needsBlank = false // we got a line break instead
235 if isPair && size > 0 && len(list) > 1 {
236 // we have a key:value expression that fits onto one line and
237 // is in a list with more then one entry: use a column for the
238 // key such that consecutive entries can align if possible
240 p.print(pair.Colon, token.COLON, vtab)
247 if mode&commaTerm != 0 && next.IsValid() && p.pos.Line < next.Line {
248 // print a terminating comma if the next token is on a new line
250 if ws == ignore && mode&noIndent == 0 {
251 // unindent if we indented
254 p.print(formfeed) // terminating comma needs a line break to look good
258 if ws == ignore && mode&noIndent == 0 {
259 // unindent if we indented
264 func (p *printer) parameters(fields *ast.FieldList) {
265 p.print(fields.Opening, token.LPAREN)
266 if len(fields.List) > 0 {
267 prevLine := p.lineFor(fields.Opening)
269 for i, par := range fields.List {
270 // determine par begin and end line (may be different
271 // if there are multiple parameter names for this par
272 // or the type is on a separate line)
274 var parLineEnd = p.lineFor(par.Type.Pos())
275 if len(par.Names) > 0 {
276 parLineBeg = p.lineFor(par.Names[0].Pos())
278 parLineBeg = parLineEnd
280 // separating "," if needed
281 needsLinebreak := 0 < prevLine && prevLine < parLineBeg
283 // use position of parameter following the comma as
284 // comma position for correct comma placement, but
285 // only if the next parameter is on the same line
291 // separator if needed (linebreak or blank)
292 if needsLinebreak && p.linebreak(parLineBeg, 0, ws, true) {
293 // break line if the opening "(" or previous parameter ended on a different line
299 if len(par.Names) > 0 {
300 // Very subtle: If we indented before (ws == ignore), identList
301 // won't indent again. If we didn't (ws == indent), identList will
302 // indent if the identList spans multiple lines, and it will outdent
303 // again at the end (and still ws == indent). Thus, a subsequent indent
304 // by a linebreak call after a type, or in the next multi-line identList
305 // will do the right thing.
306 p.identList(par.Names, ws == indent)
311 prevLine = parLineEnd
313 // if the closing ")" is on a separate line from the last parameter,
314 // print an additional "," and line break
315 if closing := p.lineFor(fields.Closing); 0 < prevLine && prevLine < closing {
317 p.linebreak(closing, 0, ignore, true)
319 // unindent if we indented
324 p.print(fields.Closing, token.RPAREN)
327 func (p *printer) signature(params, result *ast.FieldList) {
331 p.print(token.LPAREN, token.RPAREN)
333 n := result.NumFields()
337 if n == 1 && result.List[0].Names == nil {
338 // single anonymous result; no ()'s
339 p.expr(result.List[0].Type)
346 func identListSize(list []*ast.Ident, maxSize int) (size int) {
347 for i, x := range list {
351 size += utf8.RuneCountInString(x.Name)
359 func (p *printer) isOneLineFieldList(list []*ast.Field) bool {
361 return false // allow only one field
364 if f.Tag != nil || f.Comment != nil {
365 return false // don't allow tags or comments
367 // only name(s) and type
368 const maxSize = 30 // adjust as appropriate, this is an approximate value
369 namesSize := identListSize(f.Names, maxSize)
371 namesSize = 1 // blank between names and types
373 typeSize := p.nodeSize(f.Type, maxSize)
374 return namesSize+typeSize <= maxSize
377 func (p *printer) setLineComment(text string) {
378 p.setComment(&ast.CommentGroup{List: []*ast.Comment{{Slash: token.NoPos, Text: text}}})
381 func (p *printer) isMultiLine(n ast.Node) bool {
382 return p.lineFor(n.End())-p.lineFor(n.Pos()) > 0
385 func (p *printer) fieldList(fields *ast.FieldList, isStruct, isIncomplete bool) {
386 lbrace := fields.Opening
388 rbrace := fields.Closing
389 hasComments := isIncomplete || p.commentBefore(p.posFor(rbrace))
390 srcIsOneLine := lbrace.IsValid() && rbrace.IsValid() && p.lineFor(lbrace) == p.lineFor(rbrace)
392 if !hasComments && srcIsOneLine {
393 // possibly a one-line struct/interface
395 // no blank between keyword and {} in this case
396 p.print(lbrace, token.LBRACE, rbrace, token.RBRACE)
398 } else if isStruct && p.isOneLineFieldList(list) { // for now ignore interfaces
399 // small enough - print on one line
400 // (don't use identList and ignore source line breaks)
401 p.print(lbrace, token.LBRACE, blank)
403 for i, x := range f.Names {
405 // no comments so no need for comma position
406 p.print(token.COMMA, blank)
410 if len(f.Names) > 0 {
414 p.print(blank, rbrace, token.RBRACE)
418 // hasComments || !srcIsOneLine
420 p.print(blank, lbrace, token.LBRACE, indent)
421 if hasComments || len(list) > 0 {
432 for i, f := range list {
434 p.linebreak(p.lineFor(f.Pos()), 1, ignore, newSection)
438 if len(f.Names) > 0 {
440 p.identList(f.Names, false)
450 if len(f.Names) > 0 && sep == vtab {
457 if f.Comment != nil {
458 for ; extraTabs > 0; extraTabs-- {
461 p.setComment(f.Comment)
463 newSection = p.isMultiLine(f)
469 p.flush(p.posFor(rbrace), token.RBRACE) // make sure we don't lose the last line comment
470 p.setLineComment("// contains filtered or unexported fields")
473 } else { // interface
476 for i, f := range list {
478 p.linebreak(p.lineFor(f.Pos()), 1, ignore, newSection)
481 if ftyp, isFtyp := f.Type.(*ast.FuncType); isFtyp {
484 p.signature(ftyp.Params, ftyp.Results)
486 // embedded interface
489 p.setComment(f.Comment)
490 newSection = p.isMultiLine(f)
496 p.flush(p.posFor(rbrace), token.RBRACE) // make sure we don't lose the last line comment
497 p.setLineComment("// contains filtered or unexported methods")
501 p.print(unindent, formfeed, rbrace, token.RBRACE)
504 // ----------------------------------------------------------------------------
507 func walkBinary(e *ast.BinaryExpr) (has4, has5 bool, maxProblem int) {
508 switch e.Op.Precedence() {
515 switch l := e.X.(type) {
516 case *ast.BinaryExpr:
517 if l.Op.Precedence() < e.Op.Precedence() {
518 // parens will be inserted.
519 // pretend this is an *ast.ParenExpr and do nothing.
522 h4, h5, mp := walkBinary(l)
530 switch r := e.Y.(type) {
531 case *ast.BinaryExpr:
532 if r.Op.Precedence() <= e.Op.Precedence() {
533 // parens will be inserted.
534 // pretend this is an *ast.ParenExpr and do nothing.
537 h4, h5, mp := walkBinary(r)
545 if e.Op == token.QUO { // `*/`
550 switch e.Op.String() + r.Op.String() {
551 case "/*", "&&", "&^":
562 func cutoff(e *ast.BinaryExpr, depth int) int {
563 has4, has5, maxProblem := walkBinary(e)
565 return maxProblem + 1
579 func diffPrec(expr ast.Expr, prec int) int {
580 x, ok := expr.(*ast.BinaryExpr)
581 if !ok || prec != x.Op.Precedence() {
587 func reduceDepth(depth int) int {
595 // Format the binary expression: decide the cutoff and then format.
596 // Let's call depth == 1 Normal mode, and depth > 1 Compact mode.
597 // (Algorithm suggestion by Russ Cox.)
599 // The precedences are:
600 // 5 * / % << >> & &^
606 // The only decision is whether there will be spaces around levels 4 and 5.
607 // There are never spaces at level 6 (unary), and always spaces at levels 3 and below.
609 // To choose the cutoff, look at the whole expression but excluding primary
610 // expressions (function calls, parenthesized exprs), and apply these rules:
612 // 1) If there is a binary operator with a right side unary operand
613 // that would clash without a space, the cutoff must be (in order):
621 // (Comparison operators always have spaces around them.)
623 // 2) If there is a mix of level 5 and level 4 operators, then the cutoff
624 // is 5 (use spaces to distinguish precedence) in Normal mode
625 // and 4 (never use spaces) in Compact mode.
627 // 3) If there are no level 4 operators or no level 5 operators, then the
628 // cutoff is 6 (always use spaces) in Normal mode
629 // and 4 (never use spaces) in Compact mode.
631 func (p *printer) binaryExpr(x *ast.BinaryExpr, prec1, cutoff, depth int) {
632 prec := x.Op.Precedence()
634 // parenthesis needed
635 // Note: The parser inserts an ast.ParenExpr node; thus this case
636 // can only occur if the AST is created in a different way.
637 p.print(token.LPAREN)
638 p.expr0(x, reduceDepth(depth)) // parentheses undo one level of depth
639 p.print(token.RPAREN)
643 printBlank := prec < cutoff
646 p.expr1(x.X, prec, depth+diffPrec(x.X, prec))
650 xline := p.pos.Line // before the operator (it may be on the next line!)
651 yline := p.lineFor(x.Y.Pos())
652 p.print(x.OpPos, x.Op)
653 if xline != yline && xline > 0 && yline > 0 {
654 // at least one line break, but respect an extra empty line
656 if p.linebreak(yline, 1, ws, true) {
658 printBlank = false // no blank after line break
664 p.expr1(x.Y, prec+1, depth+1)
670 func isBinary(expr ast.Expr) bool {
671 _, ok := expr.(*ast.BinaryExpr)
675 func (p *printer) expr1(expr ast.Expr, prec1, depth int) {
678 switch x := expr.(type) {
685 case *ast.BinaryExpr:
687 p.internalError("depth < 1:", depth)
690 p.binaryExpr(x, prec1, cutoff(x, depth), depth)
692 case *ast.KeyValueExpr:
694 p.print(x.Colon, token.COLON, blank)
698 const prec = token.UnaryPrec
700 // parenthesis needed
701 p.print(token.LPAREN)
704 p.print(token.RPAREN)
706 // no parenthesis needed
712 const prec = token.UnaryPrec
714 // parenthesis needed
715 p.print(token.LPAREN)
717 p.print(token.RPAREN)
719 // no parenthesis needed
721 if x.Op == token.RANGE {
722 // TODO(gri) Remove this code if it cannot be reached.
725 p.expr1(x.X, prec, depth)
733 p.funcBody(x.Body, p.distance(x.Type.Pos(), p.pos), true)
736 if _, hasParens := x.X.(*ast.ParenExpr); hasParens {
737 // don't print parentheses around an already parenthesized expression
738 // TODO(gri) consider making this more general and incorporate precedence levels
739 p.expr0(x.X, reduceDepth(depth)) // parentheses undo one level of depth
741 p.print(token.LPAREN)
742 p.expr0(x.X, reduceDepth(depth)) // parentheses undo one level of depth
743 p.print(x.Rparen, token.RPAREN)
746 case *ast.SelectorExpr:
747 p.expr1(x.X, token.HighestPrec, depth)
748 p.print(token.PERIOD)
749 if line := p.lineFor(x.Sel.Pos()); p.pos.IsValid() && p.pos.Line < line {
750 p.print(indent, newline, x.Sel.Pos(), x.Sel, unindent)
752 p.print(x.Sel.Pos(), x.Sel)
755 case *ast.TypeAssertExpr:
756 p.expr1(x.X, token.HighestPrec, depth)
757 p.print(token.PERIOD, token.LPAREN)
763 p.print(token.RPAREN)
766 // TODO(gri): should treat[] like parentheses and undo one level of depth
767 p.expr1(x.X, token.HighestPrec, 1)
768 p.print(x.Lbrack, token.LBRACK)
769 p.expr0(x.Index, depth+1)
770 p.print(x.Rbrack, token.RBRACK)
773 // TODO(gri): should treat[] like parentheses and undo one level of depth
774 p.expr1(x.X, token.HighestPrec, 1)
775 p.print(x.Lbrack, token.LBRACK)
777 p.expr0(x.Low, depth+1)
779 // blanks around ":" if both sides exist and either side is a binary expression
780 if depth <= 1 && x.Low != nil && x.High != nil && (isBinary(x.Low) || isBinary(x.High)) {
781 p.print(blank, token.COLON, blank)
786 p.expr0(x.High, depth+1)
788 p.print(x.Rbrack, token.RBRACK)
794 p.expr1(x.Fun, token.HighestPrec, depth)
795 p.print(x.Lparen, token.LPAREN)
796 if x.Ellipsis.IsValid() {
797 p.exprList(x.Lparen, x.Args, depth, 0, x.Ellipsis)
798 p.print(x.Ellipsis, token.ELLIPSIS)
799 if x.Rparen.IsValid() && p.lineFor(x.Ellipsis) < p.lineFor(x.Rparen) {
800 p.print(token.COMMA, formfeed)
803 p.exprList(x.Lparen, x.Args, depth, commaTerm, x.Rparen)
805 p.print(x.Rparen, token.RPAREN)
807 case *ast.CompositeLit:
808 // composite literal elements that are composite literals themselves may have the type omitted
810 p.expr1(x.Type, token.HighestPrec, depth)
812 p.print(x.Lbrace, token.LBRACE)
813 p.exprList(x.Lbrace, x.Elts, 1, commaTerm, x.Rbrace)
814 // do not insert extra line breaks because of comments before
815 // the closing '}' as it might break the code if there is no
817 p.print(noExtraLinebreak, x.Rbrace, token.RBRACE, noExtraLinebreak)
820 p.print(token.ELLIPSIS)
826 p.print(token.LBRACK)
830 p.print(token.RBRACK)
833 case *ast.StructType:
834 p.print(token.STRUCT)
835 p.fieldList(x.Fields, true, x.Incomplete)
839 p.signature(x.Params, x.Results)
841 case *ast.InterfaceType:
842 p.print(token.INTERFACE)
843 p.fieldList(x.Methods, false, x.Incomplete)
846 p.print(token.MAP, token.LBRACK)
848 p.print(token.RBRACK)
853 case ast.SEND | ast.RECV:
856 p.print(token.ARROW, token.CHAN)
858 p.print(token.CHAN, token.ARROW)
870 func (p *printer) expr0(x ast.Expr, depth int) {
871 p.expr1(x, token.LowestPrec, depth)
874 func (p *printer) expr(x ast.Expr) {
876 p.expr1(x, token.LowestPrec, depth)
879 // ----------------------------------------------------------------------------
882 // Print the statement list indented, but without a newline after the last statement.
883 // Extra line breaks between statements in the source are respected but at most one
884 // empty line is printed between statements.
885 func (p *printer) stmtList(list []ast.Stmt, _indent int, nextIsRBrace bool) {
886 // TODO(gri): fix _indent code
891 for i, s := range list {
892 // _indent == 0 only for lists of switch/select case clauses;
893 // in those cases each clause is a new section
894 p.linebreak(p.lineFor(s.Pos()), 1, ignore, i == 0 || _indent == 0 || multiLine)
895 p.stmt(s, nextIsRBrace && i == len(list)-1)
896 multiLine = p.isMultiLine(s)
903 // block prints an *ast.BlockStmt; it always spans at least two lines.
904 func (p *printer) block(s *ast.BlockStmt, indent int) {
905 p.print(s.Pos(), token.LBRACE)
906 p.stmtList(s.List, indent, true)
907 p.linebreak(p.lineFor(s.Rbrace), 1, ignore, true)
908 p.print(s.Rbrace, token.RBRACE)
911 func isTypeName(x ast.Expr) bool {
912 switch t := x.(type) {
915 case *ast.SelectorExpr:
916 return isTypeName(t.X)
921 func stripParens(x ast.Expr) ast.Expr {
922 if px, strip := x.(*ast.ParenExpr); strip {
923 // parentheses must not be stripped if there are any
924 // unparenthesized composite literals starting with
926 ast.Inspect(px.X, func(node ast.Node) bool {
927 switch x := node.(type) {
929 // parentheses protect enclosed composite literals
931 case *ast.CompositeLit:
932 if isTypeName(x.Type) {
933 strip = false // do not strip parentheses
937 // in all other cases, keep inspecting
941 return stripParens(px.X)
947 func (p *printer) controlClause(isForStmt bool, init ast.Stmt, expr ast.Expr, post ast.Stmt) {
950 if init == nil && post == nil {
951 // no semicolons required
953 p.expr(stripParens(expr))
957 // all semicolons required
958 // (they are not separators, print them explicitly)
962 p.print(token.SEMICOLON, blank)
964 p.expr(stripParens(expr))
968 p.print(token.SEMICOLON, blank)
981 // indentList reports whether an expression list would look better if it
982 // were indented wholesale (starting with the very first element, rather
983 // than starting at the first line break).
985 func (p *printer) indentList(list []ast.Expr) bool {
986 // Heuristic: indentList returns true if there are more than one multi-
987 // line element in the list, or if there is any element that is not
988 // starting on the same line as the previous one ends.
990 var b = p.lineFor(list[0].Pos())
991 var e = p.lineFor(list[len(list)-1].End())
993 // list spans multiple lines
994 n := 0 // multi-line element count
996 for _, x := range list {
997 xb := p.lineFor(x.Pos())
998 xe := p.lineFor(x.End())
1000 // x is not starting on the same
1001 // line as the previous one ended
1005 // x is a multi-line element
1016 func (p *printer) stmt(stmt ast.Stmt, nextIsRBrace bool) {
1019 switch s := stmt.(type) {
1026 case *ast.EmptyStmt:
1029 case *ast.LabeledStmt:
1030 // a "correcting" unindent immediately following a line break
1031 // is applied before the line break if there is no comment
1032 // between (see writeWhitespace)
1035 p.print(s.Colon, token.COLON, indent)
1036 if e, isEmpty := s.Stmt.(*ast.EmptyStmt); isEmpty {
1038 p.print(newline, e.Pos(), token.SEMICOLON)
1042 p.linebreak(p.lineFor(s.Stmt.Pos()), 1, ignore, true)
1044 p.stmt(s.Stmt, nextIsRBrace)
1052 p.expr0(s.Chan, depth)
1053 p.print(blank, s.Arrow, token.ARROW, blank)
1054 p.expr0(s.Value, depth)
1056 case *ast.IncDecStmt:
1058 p.expr0(s.X, depth+1)
1059 p.print(s.TokPos, s.Tok)
1061 case *ast.AssignStmt:
1063 if len(s.Lhs) > 1 && len(s.Rhs) > 1 {
1066 p.exprList(s.Pos(), s.Lhs, depth, 0, s.TokPos)
1067 p.print(blank, s.TokPos, s.Tok, blank)
1068 p.exprList(s.TokPos, s.Rhs, depth, 0, token.NoPos)
1071 p.print(token.GO, blank)
1074 case *ast.DeferStmt:
1075 p.print(token.DEFER, blank)
1078 case *ast.ReturnStmt:
1079 p.print(token.RETURN)
1080 if s.Results != nil {
1082 // Use indentList heuristic to make corner cases look
1083 // better (issue 1207). A more systematic approach would
1084 // always indent, but this would cause significant
1085 // reformatting of the code base and not necessarily
1086 // lead to more nicely formatted code in general.
1087 if p.indentList(s.Results) {
1089 p.exprList(s.Pos(), s.Results, 1, noIndent, token.NoPos)
1092 p.exprList(s.Pos(), s.Results, 1, 0, token.NoPos)
1096 case *ast.BranchStmt:
1103 case *ast.BlockStmt:
1108 p.controlClause(false, s.Init, s.Cond, nil)
1111 p.print(blank, token.ELSE, blank)
1112 switch s.Else.(type) {
1113 case *ast.BlockStmt, *ast.IfStmt:
1114 p.stmt(s.Else, nextIsRBrace)
1116 p.print(token.LBRACE, indent, formfeed)
1117 p.stmt(s.Else, true)
1118 p.print(unindent, formfeed, token.RBRACE)
1122 case *ast.CaseClause:
1124 p.print(token.CASE, blank)
1125 p.exprList(s.Pos(), s.List, 1, 0, s.Colon)
1127 p.print(token.DEFAULT)
1129 p.print(s.Colon, token.COLON)
1130 p.stmtList(s.Body, 1, nextIsRBrace)
1132 case *ast.SwitchStmt:
1133 p.print(token.SWITCH)
1134 p.controlClause(false, s.Init, s.Tag, nil)
1137 case *ast.TypeSwitchStmt:
1138 p.print(token.SWITCH)
1141 p.stmt(s.Init, false)
1142 p.print(token.SEMICOLON)
1145 p.stmt(s.Assign, false)
1149 case *ast.CommClause:
1151 p.print(token.CASE, blank)
1152 p.stmt(s.Comm, false)
1154 p.print(token.DEFAULT)
1156 p.print(s.Colon, token.COLON)
1157 p.stmtList(s.Body, 1, nextIsRBrace)
1159 case *ast.SelectStmt:
1160 p.print(token.SELECT, blank)
1162 if len(body.List) == 0 && !p.commentBefore(p.posFor(body.Rbrace)) {
1163 // print empty select statement w/o comments on one line
1164 p.print(body.Lbrace, token.LBRACE, body.Rbrace, token.RBRACE)
1171 p.controlClause(true, s.Init, s.Cond, s.Post)
1174 case *ast.RangeStmt:
1175 p.print(token.FOR, blank)
1178 // use position of value following the comma as
1179 // comma position for correct comment placement
1180 p.print(s.Value.Pos(), token.COMMA, blank)
1183 p.print(blank, s.TokPos, s.Tok, blank, token.RANGE, blank)
1184 p.expr(stripParens(s.X))
1189 panic("unreachable")
1195 // ----------------------------------------------------------------------------
1198 // The keepTypeColumn function determines if the type column of a series of
1199 // consecutive const or var declarations must be kept, or if initialization
1200 // values (V) can be placed in the type column (T) instead. The i'th entry
1201 // in the result slice is true if the type column in spec[i] must be kept.
1203 // For example, the declaration:
1206 // foobar int = 42 // comment
1212 // leads to the type/values matrix below. A run of value columns (V) can
1213 // be moved into the type column if there is no type for any of the values
1214 // in that column (we only move entire columns so that they align properly).
1216 // matrix formatted result
1218 // T V -> T V -> true there is a T and so the type
1219 // - V - V true column must be kept
1221 // - V V - false V is moved into T column
1223 func keepTypeColumn(specs []ast.Spec) []bool {
1224 m := make([]bool, len(specs))
1226 populate := func(i, j int, keepType bool) {
1234 i0 := -1 // if i0 >= 0 we are in a run and i0 is the start of the run
1236 for i, s := range specs {
1237 t := s.(*ast.ValueSpec)
1238 if t.Values != nil {
1240 // start of a run of ValueSpecs with non-nil Values
1247 populate(i0, i, keepType)
1257 populate(i0, len(specs), keepType)
1263 func (p *printer) valueSpec(s *ast.ValueSpec, keepType bool) {
1265 p.identList(s.Names, false) // always present
1267 if s.Type != nil || keepType {
1274 if s.Values != nil {
1275 p.print(vtab, token.ASSIGN, blank)
1276 p.exprList(token.NoPos, s.Values, 1, 0, token.NoPos)
1279 if s.Comment != nil {
1280 for ; extraTabs > 0; extraTabs-- {
1283 p.setComment(s.Comment)
1287 // The parameter n is the number of specs in the group. If doIndent is set,
1288 // multi-line identifier lists in the spec are indented when the first
1289 // linebreak is encountered.
1291 func (p *printer) spec(spec ast.Spec, n int, doIndent bool) {
1292 switch s := spec.(type) {
1293 case *ast.ImportSpec:
1300 p.setComment(s.Comment)
1303 case *ast.ValueSpec:
1305 p.internalError("expected n = 1; got", n)
1308 p.identList(s.Names, doIndent) // always present
1313 if s.Values != nil {
1314 p.print(blank, token.ASSIGN, blank)
1315 p.exprList(token.NoPos, s.Values, 1, 0, token.NoPos)
1317 p.setComment(s.Comment)
1328 p.setComment(s.Comment)
1331 panic("unreachable")
1335 func (p *printer) genDecl(d *ast.GenDecl) {
1337 p.print(d.Pos(), d.Tok, blank)
1339 if d.Lparen.IsValid() {
1340 // group of parenthesized declarations
1341 p.print(d.Lparen, token.LPAREN)
1342 if n := len(d.Specs); n > 0 {
1343 p.print(indent, formfeed)
1344 if n > 1 && (d.Tok == token.CONST || d.Tok == token.VAR) {
1345 // two or more grouped const/var declarations:
1346 // determine if the type column must be kept
1347 keepType := keepTypeColumn(d.Specs)
1349 for i, s := range d.Specs {
1351 p.linebreak(p.lineFor(s.Pos()), 1, ignore, newSection)
1353 p.valueSpec(s.(*ast.ValueSpec), keepType[i])
1354 newSection = p.isMultiLine(s)
1358 for i, s := range d.Specs {
1360 p.linebreak(p.lineFor(s.Pos()), 1, ignore, newSection)
1363 newSection = p.isMultiLine(s)
1366 p.print(unindent, formfeed)
1368 p.print(d.Rparen, token.RPAREN)
1371 // single declaration
1372 p.spec(d.Specs[0], 1, true)
1376 // nodeSize determines the size of n in chars after formatting.
1377 // The result is <= maxSize if the node fits on one line with at
1378 // most maxSize chars and the formatted output doesn't contain
1379 // any control chars. Otherwise, the result is > maxSize.
1381 func (p *printer) nodeSize(n ast.Node, maxSize int) (size int) {
1382 // nodeSize invokes the printer, which may invoke nodeSize
1383 // recursively. For deep composite literal nests, this can
1384 // lead to an exponential algorithm. Remember previous
1385 // results to prune the recursion (was issue 1628).
1386 if size, found := p.nodeSizes[n]; found {
1390 size = maxSize + 1 // assume n doesn't fit
1391 p.nodeSizes[n] = size
1393 // nodeSize computation must be independent of particular
1394 // style so that we always get the same decision; print
1396 cfg := Config{Mode: RawFormat}
1397 var buf bytes.Buffer
1398 if err := cfg.fprint(&buf, p.fset, n, p.nodeSizes); err != nil {
1401 if buf.Len() <= maxSize {
1402 for _, ch := range buf.Bytes() {
1407 size = buf.Len() // n fits
1408 p.nodeSizes[n] = size
1413 func (p *printer) isOneLineFunc(b *ast.BlockStmt, headerSize int) bool {
1416 if pos1.IsValid() && pos2.IsValid() && p.lineFor(pos1) != p.lineFor(pos2) {
1417 // opening and closing brace are on different lines - don't make it a one-liner
1420 if len(b.List) > 5 || p.commentBefore(p.posFor(pos2)) {
1421 // too many statements or there is a comment inside - don't make it a one-liner
1424 // otherwise, estimate body size
1427 for i, s := range b.List {
1429 bodySize += 2 // space for a semicolon and blank
1431 bodySize += p.nodeSize(s, maxSize)
1433 return headerSize+bodySize <= maxSize
1436 func (p *printer) funcBody(b *ast.BlockStmt, headerSize int, isLit bool) {
1441 if p.isOneLineFunc(b, headerSize) {
1446 p.print(sep, b.Lbrace, token.LBRACE)
1447 if len(b.List) > 0 {
1449 for i, s := range b.List {
1451 p.print(token.SEMICOLON, blank)
1453 p.stmt(s, i == len(b.List)-1)
1457 p.print(b.Rbrace, token.RBRACE)
1465 // distance returns the column difference between from and to if both
1466 // are on the same line; if they are on different lines (or unknown)
1467 // the result is infinity.
1468 func (p *printer) distance(from0 token.Pos, to token.Position) int {
1469 from := p.posFor(from0)
1470 if from.IsValid() && to.IsValid() && from.Line == to.Line {
1471 return to.Column - from.Column
1476 func (p *printer) funcDecl(d *ast.FuncDecl) {
1478 p.print(d.Pos(), token.FUNC, blank)
1480 p.parameters(d.Recv) // method: print receiver
1484 p.signature(d.Type.Params, d.Type.Results)
1485 p.funcBody(d.Body, p.distance(d.Pos(), p.pos), false)
1488 func (p *printer) decl(decl ast.Decl) {
1489 switch d := decl.(type) {
1491 p.print(d.Pos(), "BadDecl")
1497 panic("unreachable")
1501 // ----------------------------------------------------------------------------
1504 func declToken(decl ast.Decl) (tok token.Token) {
1506 switch d := decl.(type) {
1515 func (p *printer) file(src *ast.File) {
1516 p.setComment(src.Doc)
1517 p.print(src.Pos(), token.PACKAGE, blank)
1520 if len(src.Decls) > 0 {
1521 tok := token.ILLEGAL
1522 for _, d := range src.Decls {
1525 // if the declaration token changed (e.g., from CONST to TYPE)
1526 // or the next declaration has documentation associated with it,
1527 // print an empty line between top-level declarations
1528 // (because p.linebreak is called with the position of d, which
1529 // is past any documentation, the minimum requirement is satisfied
1530 // even w/o the extra getDoc(d) nil-check - leave it in case the
1531 // linebreak logic improves - there's already a TODO).
1533 if prev != tok || getDoc(d) != nil {
1536 p.linebreak(p.lineFor(d.Pos()), min, ignore, false)