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.
22 // - better comment formatting for /*-style comments at the end of a line (e.g. a declaration)
23 // when the comment spans multiple lines; if such a comment is just two lines, formatting is
25 // - formatting of expression lists
26 // - should use blank instead of tab to separate one-line function bodies from
27 // the function header unless there is a group of consecutive one-liners
29 // ----------------------------------------------------------------------------
32 // Print as many newlines as necessary (but at least min newlines) to get to
33 // the current line. ws is printed before the first line break. If newSection
34 // is set, the first line break is printed as formfeed. Returns true if any
35 // line break was printed; returns false otherwise.
37 // TODO(gri): linebreak may add too many lines if the next statement at "line"
38 // is preceded by comments because the computation of n assumes
39 // the current position before the comment and the target position
40 // after the comment. Thus, after interspersing such comments, the
41 // space taken up by them is not considered to reduce the number of
42 // linebreaks. At the moment there is no easy way to know about
43 // future (not yet interspersed) comments in this function.
45 func (p
*printer
) linebreak(line
, min
int, ws whiteSpace
, newSection
bool) (printedBreak
bool) {
46 n
:= nlimit(line
- p
.pos
.Line
)
64 // setComment sets g as the next comment if g != nil and if node comments
65 // are enabled - this mode is used when printing source code fragments such
66 // as exports only. It assumes that there is no pending comment in p.comments
67 // and at most one pending comment in the p.comment cache.
68 func (p
*printer
) setComment(g
*ast
.CommentGroup
) {
69 if g
== nil ||
!p
.useNodeComments
{
72 if p
.comments
== nil {
73 // initialize p.comments lazily
74 p
.comments
= make([]*ast
.CommentGroup
, 1)
75 } else if p
.cindex
< len(p
.comments
) {
76 // for some reason there are pending comments; this
77 // should never happen - handle gracefully and flush
78 // all comments up to g, ignore anything after that
79 p
.flush(p
.posFor(g
.List
[0].Pos()), token
.ILLEGAL
)
80 p
.comments
= p
.comments
[0:1]
81 // in debug mode, report error
82 p
.internalError("setComment found pending comments")
86 // don't overwrite any pending comment in the p.comment cache
87 // (there may be a pending comment when a line comment is
88 // immediately followed by a lead comment with no other
90 if p
.commentOffset
== infinity
{
91 p
.nextComment() // get comment ready for use
95 type exprListMode
uint
98 commaTerm exprListMode
= 1 << iota // list is optionally terminated by a comma
99 noIndent
// no extra indentation in multi-line lists
102 // If indent is set, a multi-line identifier list is indented after the
103 // first linebreak encountered.
104 func (p
*printer
) identList(list
[]*ast
.Ident
, indent
bool) {
105 // convert into an expression list so we can re-use exprList formatting
106 xlist
:= make([]ast
.Expr
, len(list
))
107 for i
, x
:= range list
{
110 var mode exprListMode
114 p
.exprList(token
.NoPos
, xlist
, 1, mode
, token
.NoPos
)
117 // Print a list of expressions. If the list spans multiple
118 // source lines, the original line breaks are respected between
121 // TODO(gri) Consider rewriting this to be independent of []ast.Expr
122 // so that we can use the algorithm for any kind of list
123 // (e.g., pass list via a channel over which to range).
124 func (p
*printer
) exprList(prev0 token
.Pos
, list
[]ast
.Expr
, depth
int, mode exprListMode
, next0 token
.Pos
) {
129 prev
:= p
.posFor(prev0
)
130 next
:= p
.posFor(next0
)
131 line
:= p
.lineFor(list
[0].Pos())
132 endLine
:= p
.lineFor(list
[len(list
)-1].End())
134 if prev
.IsValid() && prev
.Line
== line
&& line
== endLine
{
135 // all list entries on a single line
136 for i
, x
:= range list
{
138 // use position of expression following the comma as
139 // comma position for correct comment placement
140 p
.print(x
.Pos(), token
.COMMA
, blank
)
147 // list entries span multiple lines;
148 // use source code positions to guide line breaks
150 // don't add extra indentation if noIndent is set;
151 // i.e., pretend that the first line is already indented
153 if mode
&noIndent
== 0 {
157 // the first linebreak is always a formfeed since this section must not
158 // depend on any previous formatting
159 prevBreak
:= -1 // index of last expression that was followed by a linebreak
160 if prev
.IsValid() && prev
.Line
< line
&& p
.linebreak(line
, 0, ws
, true) {
165 // initialize expression/key size: a zero value indicates expr/key doesn't fit on a single line
168 // print all list elements
169 prevLine
:= prev
.Line
170 for i
, x
:= range list
{
171 line
= p
.lineFor(x
.Pos())
173 // determine if the next linebreak, if any, needs to use formfeed:
174 // in general, use the entire node size to make the decision; for
175 // key:value expressions, use the key size
176 // TODO(gri) for a better result, should probably incorporate both
177 // the key and the node size into the decision process
180 // determine element size: all bets are off if we don't have
181 // position information for the previous and next token (likely
182 // generated code - simply ignore the size in this case by setting
185 const infinity
= 1e6
// larger than any source line
186 size
= p
.nodeSize(x
, infinity
)
187 pair
, isPair
:= x
.(*ast
.KeyValueExpr
)
188 if size
<= infinity
&& prev
.IsValid() && next
.IsValid() {
189 // x fits on a single line
191 size
= p
.nodeSize(pair
.Key
, infinity
) // size <= infinity
194 // size too large or we don't have good layout information
198 // if the previous line and the current line had single-
199 // line-expressions and the key sizes are small or the
200 // the ratio between the key sizes does not exceed a
201 // threshold, align columns and do not use formfeed
202 if prevSize
> 0 && size
> 0 {
204 if prevSize
<= smallSize
&& size
<= smallSize
{
207 const r
= 4 // threshold
208 ratio
:= float64(size
) / float64(prevSize
)
209 useFF
= ratio
<= 1.0/r || r
<= ratio
213 needsLinebreak
:= 0 < prevLine
&& prevLine
< line
215 // use position of expression following the comma as
216 // comma position for correct comment placement, but
217 // only if the expression is on the same line
224 // lines are broken using newlines so comments remain aligned
225 // unless forceFF is set or there are multiple expressions on
226 // the same line in which case formfeed is used
227 if p
.linebreak(line
, 0, ws
, useFF || prevBreak
+1 < i
) {
230 needsBlank
= false // we got a line break instead
238 if len(list
) > 1 && isPair
&& size
> 0 && needsLinebreak
{
239 // we have a key:value expression that fits onto one line
240 // and it's not on the same line as the prior expression:
241 // use a column for the key such that consecutive entries
242 // can align if possible
243 // (needsLinebreak is set if we started a new line before)
245 p
.print(pair
.Colon
, token
.COLON
, vtab
)
254 if mode
&commaTerm
!= 0 && next
.IsValid() && p
.pos
.Line
< next
.Line
{
255 // print a terminating comma if the next token is on a new line
257 if ws
== ignore
&& mode
&noIndent
== 0 {
258 // unindent if we indented
261 p
.print(formfeed
) // terminating comma needs a line break to look good
265 if ws
== ignore
&& mode
&noIndent
== 0 {
266 // unindent if we indented
271 func (p
*printer
) parameters(fields
*ast
.FieldList
) {
272 p
.print(fields
.Opening
, token
.LPAREN
)
273 if len(fields
.List
) > 0 {
274 prevLine
:= p
.lineFor(fields
.Opening
)
276 for i
, par
:= range fields
.List
{
277 // determine par begin and end line (may be different
278 // if there are multiple parameter names for this par
279 // or the type is on a separate line)
281 if len(par
.Names
) > 0 {
282 parLineBeg
= p
.lineFor(par
.Names
[0].Pos())
284 parLineBeg
= p
.lineFor(par
.Type
.Pos())
286 var parLineEnd
= p
.lineFor(par
.Type
.End())
287 // separating "," if needed
288 needsLinebreak
:= 0 < prevLine
&& prevLine
< parLineBeg
290 // use position of parameter following the comma as
291 // comma position for correct comma placement, but
292 // only if the next parameter is on the same line
298 // separator if needed (linebreak or blank)
299 if needsLinebreak
&& p
.linebreak(parLineBeg
, 0, ws
, true) {
300 // break line if the opening "(" or previous parameter ended on a different line
306 if len(par
.Names
) > 0 {
307 // Very subtle: If we indented before (ws == ignore), identList
308 // won't indent again. If we didn't (ws == indent), identList will
309 // indent if the identList spans multiple lines, and it will outdent
310 // again at the end (and still ws == indent). Thus, a subsequent indent
311 // by a linebreak call after a type, or in the next multi-line identList
312 // will do the right thing.
313 p
.identList(par
.Names
, ws
== indent
)
317 p
.expr(stripParensAlways(par
.Type
))
318 prevLine
= parLineEnd
320 // if the closing ")" is on a separate line from the last parameter,
321 // print an additional "," and line break
322 if closing
:= p
.lineFor(fields
.Closing
); 0 < prevLine
&& prevLine
< closing
{
324 p
.linebreak(closing
, 0, ignore
, true)
326 // unindent if we indented
331 p
.print(fields
.Closing
, token
.RPAREN
)
334 func (p
*printer
) signature(params
, result
*ast
.FieldList
) {
338 p
.print(token
.LPAREN
, token
.RPAREN
)
340 n
:= result
.NumFields()
344 if n
== 1 && result
.List
[0].Names
== nil {
345 // single anonymous result; no ()'s
346 p
.expr(stripParensAlways(result
.List
[0].Type
))
353 func identListSize(list
[]*ast
.Ident
, maxSize
int) (size
int) {
354 for i
, x
:= range list
{
358 size
+= utf8
.RuneCountInString(x
.Name
)
366 func (p
*printer
) isOneLineFieldList(list
[]*ast
.Field
) bool {
368 return false // allow only one field
371 if f
.Tag
!= nil || f
.Comment
!= nil {
372 return false // don't allow tags or comments
374 // only name(s) and type
375 const maxSize
= 30 // adjust as appropriate, this is an approximate value
376 namesSize
:= identListSize(f
.Names
, maxSize
)
378 namesSize
= 1 // blank between names and types
380 typeSize
:= p
.nodeSize(f
.Type
, maxSize
)
381 return namesSize
+typeSize
<= maxSize
384 func (p
*printer
) setLineComment(text
string) {
385 p
.setComment(&ast
.CommentGroup
{List
: []*ast
.Comment
{{Slash
: token
.NoPos
, Text
: text
}}})
388 func (p
*printer
) fieldList(fields
*ast
.FieldList
, isStruct
, isIncomplete
bool) {
389 lbrace
:= fields
.Opening
391 rbrace
:= fields
.Closing
392 hasComments
:= isIncomplete || p
.commentBefore(p
.posFor(rbrace
))
393 srcIsOneLine
:= lbrace
.IsValid() && rbrace
.IsValid() && p
.lineFor(lbrace
) == p
.lineFor(rbrace
)
395 if !hasComments
&& srcIsOneLine
{
396 // possibly a one-line struct/interface
398 // no blank between keyword and {} in this case
399 p
.print(lbrace
, token
.LBRACE
, rbrace
, token
.RBRACE
)
401 } else if p
.isOneLineFieldList(list
) {
402 // small enough - print on one line
403 // (don't use identList and ignore source line breaks)
404 p
.print(lbrace
, token
.LBRACE
, blank
)
407 for i
, x
:= range f
.Names
{
409 // no comments so no need for comma position
410 p
.print(token
.COMMA
, blank
)
414 if len(f
.Names
) > 0 {
418 } else { // interface
419 if ftyp
, isFtyp
:= f
.Type
.(*ast
.FuncType
); isFtyp
{
422 p
.signature(ftyp
.Params
, ftyp
.Results
)
424 // embedded interface
428 p
.print(blank
, rbrace
, token
.RBRACE
)
432 // hasComments || !srcIsOneLine
434 p
.print(blank
, lbrace
, token
.LBRACE
, indent
)
435 if hasComments ||
len(list
) > 0 {
446 for i
, f
:= range list
{
448 p
.linebreak(p
.lineFor(f
.Pos()), 1, ignore
, p
.linesFrom(line
) > 0)
453 if len(f
.Names
) > 0 {
455 p
.identList(f
.Names
, false)
465 if len(f
.Names
) > 0 && sep
== vtab
{
472 if f
.Comment
!= nil {
473 for ; extraTabs
> 0; extraTabs
-- {
476 p
.setComment(f
.Comment
)
483 p
.flush(p
.posFor(rbrace
), token
.RBRACE
) // make sure we don't lose the last line comment
484 p
.setLineComment("// contains filtered or unexported fields")
487 } else { // interface
490 for i
, f
:= range list
{
492 p
.linebreak(p
.lineFor(f
.Pos()), 1, ignore
, p
.linesFrom(line
) > 0)
496 if ftyp
, isFtyp
:= f
.Type
.(*ast
.FuncType
); isFtyp
{
499 p
.signature(ftyp
.Params
, ftyp
.Results
)
501 // embedded interface
504 p
.setComment(f
.Comment
)
510 p
.flush(p
.posFor(rbrace
), token
.RBRACE
) // make sure we don't lose the last line comment
511 p
.setLineComment("// contains filtered or unexported methods")
515 p
.print(unindent
, formfeed
, rbrace
, token
.RBRACE
)
518 // ----------------------------------------------------------------------------
521 func walkBinary(e
*ast
.BinaryExpr
) (has4
, has5
bool, maxProblem
int) {
522 switch e
.Op
.Precedence() {
529 switch l
:= e
.X
.(type) {
530 case *ast
.BinaryExpr
:
531 if l
.Op
.Precedence() < e
.Op
.Precedence() {
532 // parens will be inserted.
533 // pretend this is an *ast.ParenExpr and do nothing.
536 h4
, h5
, mp
:= walkBinary(l
)
544 switch r
:= e
.Y
.(type) {
545 case *ast
.BinaryExpr
:
546 if r
.Op
.Precedence() <= e
.Op
.Precedence() {
547 // parens will be inserted.
548 // pretend this is an *ast.ParenExpr and do nothing.
551 h4
, h5
, mp
:= walkBinary(r
)
559 if e
.Op
== token
.QUO
{ // `*/`
564 switch e
.Op
.String() + r
.Op
.String() {
565 case "/*", "&&", "&^":
576 func cutoff(e
*ast
.BinaryExpr
, depth
int) int {
577 has4
, has5
, maxProblem
:= walkBinary(e
)
579 return maxProblem
+ 1
593 func diffPrec(expr ast
.Expr
, prec
int) int {
594 x
, ok
:= expr
.(*ast
.BinaryExpr
)
595 if !ok || prec
!= x
.Op
.Precedence() {
601 func reduceDepth(depth
int) int {
609 // Format the binary expression: decide the cutoff and then format.
610 // Let's call depth == 1 Normal mode, and depth > 1 Compact mode.
611 // (Algorithm suggestion by Russ Cox.)
613 // The precedences are:
614 // 5 * / % << >> & &^
620 // The only decision is whether there will be spaces around levels 4 and 5.
621 // There are never spaces at level 6 (unary), and always spaces at levels 3 and below.
623 // To choose the cutoff, look at the whole expression but excluding primary
624 // expressions (function calls, parenthesized exprs), and apply these rules:
626 // 1) If there is a binary operator with a right side unary operand
627 // that would clash without a space, the cutoff must be (in order):
635 // (Comparison operators always have spaces around them.)
637 // 2) If there is a mix of level 5 and level 4 operators, then the cutoff
638 // is 5 (use spaces to distinguish precedence) in Normal mode
639 // and 4 (never use spaces) in Compact mode.
641 // 3) If there are no level 4 operators or no level 5 operators, then the
642 // cutoff is 6 (always use spaces) in Normal mode
643 // and 4 (never use spaces) in Compact mode.
645 func (p
*printer
) binaryExpr(x
*ast
.BinaryExpr
, prec1
, cutoff
, depth
int) {
646 prec
:= x
.Op
.Precedence()
648 // parenthesis needed
649 // Note: The parser inserts an ast.ParenExpr node; thus this case
650 // can only occur if the AST is created in a different way.
651 p
.print(token
.LPAREN
)
652 p
.expr0(x
, reduceDepth(depth
)) // parentheses undo one level of depth
653 p
.print(token
.RPAREN
)
657 printBlank
:= prec
< cutoff
660 p
.expr1(x
.X
, prec
, depth
+diffPrec(x
.X
, prec
))
664 xline
:= p
.pos
.Line
// before the operator (it may be on the next line!)
665 yline
:= p
.lineFor(x
.Y
.Pos())
666 p
.print(x
.OpPos
, x
.Op
)
667 if xline
!= yline
&& xline
> 0 && yline
> 0 {
668 // at least one line break, but respect an extra empty line
670 if p
.linebreak(yline
, 1, ws
, true) {
672 printBlank
= false // no blank after line break
678 p
.expr1(x
.Y
, prec
+1, depth
+1)
684 func isBinary(expr ast
.Expr
) bool {
685 _
, ok
:= expr
.(*ast
.BinaryExpr
)
689 func (p
*printer
) expr1(expr ast
.Expr
, prec1
, depth
int) {
692 switch x
:= expr
.(type) {
699 case *ast
.BinaryExpr
:
701 p
.internalError("depth < 1:", depth
)
704 p
.binaryExpr(x
, prec1
, cutoff(x
, depth
), depth
)
706 case *ast
.KeyValueExpr
:
708 p
.print(x
.Colon
, token
.COLON
, blank
)
712 const prec
= token
.UnaryPrec
714 // parenthesis needed
715 p
.print(token
.LPAREN
)
718 p
.print(token
.RPAREN
)
720 // no parenthesis needed
726 const prec
= token
.UnaryPrec
728 // parenthesis needed
729 p
.print(token
.LPAREN
)
731 p
.print(token
.RPAREN
)
733 // no parenthesis needed
735 if x
.Op
== token
.RANGE
{
736 // TODO(gri) Remove this code if it cannot be reached.
739 p
.expr1(x
.X
, prec
, depth
)
747 p
.funcBody(p
.distanceFrom(x
.Type
.Pos()), blank
, x
.Body
)
750 if _
, hasParens
:= x
.X
.(*ast
.ParenExpr
); hasParens
{
751 // don't print parentheses around an already parenthesized expression
752 // TODO(gri) consider making this more general and incorporate precedence levels
755 p
.print(token
.LPAREN
)
756 p
.expr0(x
.X
, reduceDepth(depth
)) // parentheses undo one level of depth
757 p
.print(x
.Rparen
, token
.RPAREN
)
760 case *ast
.SelectorExpr
:
761 p
.selectorExpr(x
, depth
, false)
763 case *ast
.TypeAssertExpr
:
764 p
.expr1(x
.X
, token
.HighestPrec
, depth
)
765 p
.print(token
.PERIOD
, x
.Lparen
, token
.LPAREN
)
771 p
.print(x
.Rparen
, token
.RPAREN
)
774 // TODO(gri): should treat[] like parentheses and undo one level of depth
775 p
.expr1(x
.X
, token
.HighestPrec
, 1)
776 p
.print(x
.Lbrack
, token
.LBRACK
)
777 p
.expr0(x
.Index
, depth
+1)
778 p
.print(x
.Rbrack
, token
.RBRACK
)
781 // TODO(gri): should treat[] like parentheses and undo one level of depth
782 p
.expr1(x
.X
, token
.HighestPrec
, 1)
783 p
.print(x
.Lbrack
, token
.LBRACK
)
784 indices
:= []ast
.Expr
{x
.Low
, x
.High
}
786 indices
= append(indices
, x
.Max
)
788 // determine if we need extra blanks around ':'
793 for _
, x
:= range indices
{
801 if indexCount
> 1 && hasBinaries
{
805 for i
, x
:= range indices
{
807 if indices
[i
-1] != nil && needsBlanks
{
811 if x
!= nil && needsBlanks
{
819 p
.print(x
.Rbrack
, token
.RBRACK
)
826 if _
, ok
:= x
.Fun
.(*ast
.FuncType
); ok
{
827 // conversions to literal function types require parentheses around the type
828 p
.print(token
.LPAREN
)
829 wasIndented
= p
.possibleSelectorExpr(x
.Fun
, token
.HighestPrec
, depth
)
830 p
.print(token
.RPAREN
)
832 wasIndented
= p
.possibleSelectorExpr(x
.Fun
, token
.HighestPrec
, depth
)
834 p
.print(x
.Lparen
, token
.LPAREN
)
835 if x
.Ellipsis
.IsValid() {
836 p
.exprList(x
.Lparen
, x
.Args
, depth
, 0, x
.Ellipsis
)
837 p
.print(x
.Ellipsis
, token
.ELLIPSIS
)
838 if x
.Rparen
.IsValid() && p
.lineFor(x
.Ellipsis
) < p
.lineFor(x
.Rparen
) {
839 p
.print(token
.COMMA
, formfeed
)
842 p
.exprList(x
.Lparen
, x
.Args
, depth
, commaTerm
, x
.Rparen
)
844 p
.print(x
.Rparen
, token
.RPAREN
)
849 case *ast
.CompositeLit
:
850 // composite literal elements that are composite literals themselves may have the type omitted
852 p
.expr1(x
.Type
, token
.HighestPrec
, depth
)
855 p
.print(x
.Lbrace
, token
.LBRACE
)
856 p
.exprList(x
.Lbrace
, x
.Elts
, 1, commaTerm
, x
.Rbrace
)
857 // do not insert extra line break following a /*-style comment
858 // before the closing '}' as it might break the code if there
859 // is no trailing ','
860 mode
:= noExtraLinebreak
861 // do not insert extra blank following a /*-style comment
862 // before the closing '}' unless the literal is empty
866 // need the initial indent to print lone comments with
867 // the proper level of indentation
868 p
.print(indent
, unindent
, mode
, x
.Rbrace
, token
.RBRACE
, mode
)
872 p
.print(token
.ELLIPSIS
)
878 p
.print(token
.LBRACK
)
882 p
.print(token
.RBRACK
)
885 case *ast
.StructType
:
886 p
.print(token
.STRUCT
)
887 p
.fieldList(x
.Fields
, true, x
.Incomplete
)
891 p
.signature(x
.Params
, x
.Results
)
893 case *ast
.InterfaceType
:
894 p
.print(token
.INTERFACE
)
895 p
.fieldList(x
.Methods
, false, x
.Incomplete
)
898 p
.print(token
.MAP
, token
.LBRACK
)
900 p
.print(token
.RBRACK
)
905 case ast
.SEND | ast
.RECV
:
908 p
.print(token
.ARROW
, token
.CHAN
) // x.Arrow and x.Pos() are the same
910 p
.print(token
.CHAN
, x
.Arrow
, token
.ARROW
)
920 func (p
*printer
) possibleSelectorExpr(expr ast
.Expr
, prec1
, depth
int) bool {
921 if x
, ok
:= expr
.(*ast
.SelectorExpr
); ok
{
922 return p
.selectorExpr(x
, depth
, true)
924 p
.expr1(expr
, prec1
, depth
)
928 // selectorExpr handles an *ast.SelectorExpr node and returns whether x spans
930 func (p
*printer
) selectorExpr(x
*ast
.SelectorExpr
, depth
int, isMethod
bool) bool {
931 p
.expr1(x
.X
, token
.HighestPrec
, depth
)
932 p
.print(token
.PERIOD
)
933 if line
:= p
.lineFor(x
.Sel
.Pos()); p
.pos
.IsValid() && p
.pos
.Line
< line
{
934 p
.print(indent
, newline
, x
.Sel
.Pos(), x
.Sel
)
940 p
.print(x
.Sel
.Pos(), x
.Sel
)
944 func (p
*printer
) expr0(x ast
.Expr
, depth
int) {
945 p
.expr1(x
, token
.LowestPrec
, depth
)
948 func (p
*printer
) expr(x ast
.Expr
) {
950 p
.expr1(x
, token
.LowestPrec
, depth
)
953 // ----------------------------------------------------------------------------
956 // Print the statement list indented, but without a newline after the last statement.
957 // Extra line breaks between statements in the source are respected but at most one
958 // empty line is printed between statements.
959 func (p
*printer
) stmtList(list
[]ast
.Stmt
, nindent
int, nextIsRBrace
bool) {
965 for _
, s
:= range list
{
966 // ignore empty statements (was issue 3466)
967 if _
, isEmpty
:= s
.(*ast
.EmptyStmt
); !isEmpty
{
968 // nindent == 0 only for lists of switch/select case clauses;
969 // in those cases each clause is a new section
970 if len(p
.output
) > 0 {
971 // only print line break if we are not at the beginning of the output
972 // (i.e., we are not printing only a partial program)
973 p
.linebreak(p
.lineFor(s
.Pos()), 1, ignore
, i
== 0 || nindent
== 0 || p
.linesFrom(line
) > 0)
976 p
.stmt(s
, nextIsRBrace
&& i
== len(list
)-1)
977 // labeled statements put labels on a separate line, but here
978 // we only care about the start line of the actual statement
979 // without label - correct line for each label
981 lt
, _
:= t
.(*ast
.LabeledStmt
)
996 // block prints an *ast.BlockStmt; it always spans at least two lines.
997 func (p
*printer
) block(b
*ast
.BlockStmt
, nindent
int) {
998 p
.print(b
.Lbrace
, token
.LBRACE
)
999 p
.stmtList(b
.List
, nindent
, true)
1000 p
.linebreak(p
.lineFor(b
.Rbrace
), 1, ignore
, true)
1001 p
.print(b
.Rbrace
, token
.RBRACE
)
1004 func isTypeName(x ast
.Expr
) bool {
1005 switch t
:= x
.(type) {
1008 case *ast
.SelectorExpr
:
1009 return isTypeName(t
.X
)
1014 func stripParens(x ast
.Expr
) ast
.Expr
{
1015 if px
, strip
:= x
.(*ast
.ParenExpr
); strip
{
1016 // parentheses must not be stripped if there are any
1017 // unparenthesized composite literals starting with
1019 ast
.Inspect(px
.X
, func(node ast
.Node
) bool {
1020 switch x
:= node
.(type) {
1021 case *ast
.ParenExpr
:
1022 // parentheses protect enclosed composite literals
1024 case *ast
.CompositeLit
:
1025 if isTypeName(x
.Type
) {
1026 strip
= false // do not strip parentheses
1030 // in all other cases, keep inspecting
1034 return stripParens(px
.X
)
1040 func stripParensAlways(x ast
.Expr
) ast
.Expr
{
1041 if x
, ok
:= x
.(*ast
.ParenExpr
); ok
{
1042 return stripParensAlways(x
.X
)
1047 func (p
*printer
) controlClause(isForStmt
bool, init ast
.Stmt
, expr ast
.Expr
, post ast
.Stmt
) {
1050 if init
== nil && post
== nil {
1051 // no semicolons required
1053 p
.expr(stripParens(expr
))
1057 // all semicolons required
1058 // (they are not separators, print them explicitly)
1062 p
.print(token
.SEMICOLON
, blank
)
1064 p
.expr(stripParens(expr
))
1068 p
.print(token
.SEMICOLON
, blank
)
1081 // indentList reports whether an expression list would look better if it
1082 // were indented wholesale (starting with the very first element, rather
1083 // than starting at the first line break).
1085 func (p
*printer
) indentList(list
[]ast
.Expr
) bool {
1086 // Heuristic: indentList returns true if there are more than one multi-
1087 // line element in the list, or if there is any element that is not
1088 // starting on the same line as the previous one ends.
1090 var b
= p
.lineFor(list
[0].Pos())
1091 var e
= p
.lineFor(list
[len(list
)-1].End())
1093 // list spans multiple lines
1094 n
:= 0 // multi-line element count
1096 for _
, x
:= range list
{
1097 xb
:= p
.lineFor(x
.Pos())
1098 xe
:= p
.lineFor(x
.End())
1100 // x is not starting on the same
1101 // line as the previous one ended
1105 // x is a multi-line element
1116 func (p
*printer
) stmt(stmt ast
.Stmt
, nextIsRBrace
bool) {
1119 switch s
:= stmt
.(type) {
1126 case *ast
.EmptyStmt
:
1129 case *ast
.LabeledStmt
:
1130 // a "correcting" unindent immediately following a line break
1131 // is applied before the line break if there is no comment
1132 // between (see writeWhitespace)
1135 p
.print(s
.Colon
, token
.COLON
, indent
)
1136 if e
, isEmpty
:= s
.Stmt
.(*ast
.EmptyStmt
); isEmpty
{
1138 p
.print(newline
, e
.Pos(), token
.SEMICOLON
)
1142 p
.linebreak(p
.lineFor(s
.Stmt
.Pos()), 1, ignore
, true)
1144 p
.stmt(s
.Stmt
, nextIsRBrace
)
1152 p
.expr0(s
.Chan
, depth
)
1153 p
.print(blank
, s
.Arrow
, token
.ARROW
, blank
)
1154 p
.expr0(s
.Value
, depth
)
1156 case *ast
.IncDecStmt
:
1158 p
.expr0(s
.X
, depth
+1)
1159 p
.print(s
.TokPos
, s
.Tok
)
1161 case *ast
.AssignStmt
:
1163 if len(s
.Lhs
) > 1 && len(s
.Rhs
) > 1 {
1166 p
.exprList(s
.Pos(), s
.Lhs
, depth
, 0, s
.TokPos
)
1167 p
.print(blank
, s
.TokPos
, s
.Tok
, blank
)
1168 p
.exprList(s
.TokPos
, s
.Rhs
, depth
, 0, token
.NoPos
)
1171 p
.print(token
.GO
, blank
)
1174 case *ast
.DeferStmt
:
1175 p
.print(token
.DEFER
, blank
)
1178 case *ast
.ReturnStmt
:
1179 p
.print(token
.RETURN
)
1180 if s
.Results
!= nil {
1182 // Use indentList heuristic to make corner cases look
1183 // better (issue 1207). A more systematic approach would
1184 // always indent, but this would cause significant
1185 // reformatting of the code base and not necessarily
1186 // lead to more nicely formatted code in general.
1187 if p
.indentList(s
.Results
) {
1189 p
.exprList(s
.Pos(), s
.Results
, 1, noIndent
, token
.NoPos
)
1192 p
.exprList(s
.Pos(), s
.Results
, 1, 0, token
.NoPos
)
1196 case *ast
.BranchStmt
:
1203 case *ast
.BlockStmt
:
1208 p
.controlClause(false, s
.Init
, s
.Cond
, nil)
1211 p
.print(blank
, token
.ELSE
, blank
)
1212 switch s
.Else
.(type) {
1213 case *ast
.BlockStmt
, *ast
.IfStmt
:
1214 p
.stmt(s
.Else
, nextIsRBrace
)
1216 // This can only happen with an incorrectly
1217 // constructed AST. Permit it but print so
1218 // that it can be parsed without errors.
1219 p
.print(token
.LBRACE
, indent
, formfeed
)
1220 p
.stmt(s
.Else
, true)
1221 p
.print(unindent
, formfeed
, token
.RBRACE
)
1225 case *ast
.CaseClause
:
1227 p
.print(token
.CASE
, blank
)
1228 p
.exprList(s
.Pos(), s
.List
, 1, 0, s
.Colon
)
1230 p
.print(token
.DEFAULT
)
1232 p
.print(s
.Colon
, token
.COLON
)
1233 p
.stmtList(s
.Body
, 1, nextIsRBrace
)
1235 case *ast
.SwitchStmt
:
1236 p
.print(token
.SWITCH
)
1237 p
.controlClause(false, s
.Init
, s
.Tag
, nil)
1240 case *ast
.TypeSwitchStmt
:
1241 p
.print(token
.SWITCH
)
1244 p
.stmt(s
.Init
, false)
1245 p
.print(token
.SEMICOLON
)
1248 p
.stmt(s
.Assign
, false)
1252 case *ast
.CommClause
:
1254 p
.print(token
.CASE
, blank
)
1255 p
.stmt(s
.Comm
, false)
1257 p
.print(token
.DEFAULT
)
1259 p
.print(s
.Colon
, token
.COLON
)
1260 p
.stmtList(s
.Body
, 1, nextIsRBrace
)
1262 case *ast
.SelectStmt
:
1263 p
.print(token
.SELECT
, blank
)
1265 if len(body
.List
) == 0 && !p
.commentBefore(p
.posFor(body
.Rbrace
)) {
1266 // print empty select statement w/o comments on one line
1267 p
.print(body
.Lbrace
, token
.LBRACE
, body
.Rbrace
, token
.RBRACE
)
1274 p
.controlClause(true, s
.Init
, s
.Cond
, s
.Post
)
1277 case *ast
.RangeStmt
:
1278 p
.print(token
.FOR
, blank
)
1282 // use position of value following the comma as
1283 // comma position for correct comment placement
1284 p
.print(s
.Value
.Pos(), token
.COMMA
, blank
)
1287 p
.print(blank
, s
.TokPos
, s
.Tok
, blank
)
1289 p
.print(token
.RANGE
, blank
)
1290 p
.expr(stripParens(s
.X
))
1295 panic("unreachable")
1299 // ----------------------------------------------------------------------------
1302 // The keepTypeColumn function determines if the type column of a series of
1303 // consecutive const or var declarations must be kept, or if initialization
1304 // values (V) can be placed in the type column (T) instead. The i'th entry
1305 // in the result slice is true if the type column in spec[i] must be kept.
1307 // For example, the declaration:
1310 // foobar int = 42 // comment
1316 // leads to the type/values matrix below. A run of value columns (V) can
1317 // be moved into the type column if there is no type for any of the values
1318 // in that column (we only move entire columns so that they align properly).
1320 // matrix formatted result
1322 // T V -> T V -> true there is a T and so the type
1323 // - V - V true column must be kept
1325 // - V V - false V is moved into T column
1327 func keepTypeColumn(specs
[]ast
.Spec
) []bool {
1328 m
:= make([]bool, len(specs
))
1330 populate
:= func(i
, j
int, keepType
bool) {
1338 i0
:= -1 // if i0 >= 0 we are in a run and i0 is the start of the run
1340 for i
, s
:= range specs
{
1341 t
:= s
.(*ast
.ValueSpec
)
1342 if t
.Values
!= nil {
1344 // start of a run of ValueSpecs with non-nil Values
1351 populate(i0
, i
, keepType
)
1361 populate(i0
, len(specs
), keepType
)
1367 func (p
*printer
) valueSpec(s
*ast
.ValueSpec
, keepType
bool) {
1369 p
.identList(s
.Names
, false) // always present
1371 if s
.Type
!= nil || keepType
{
1378 if s
.Values
!= nil {
1379 p
.print(vtab
, token
.ASSIGN
, blank
)
1380 p
.exprList(token
.NoPos
, s
.Values
, 1, 0, token
.NoPos
)
1383 if s
.Comment
!= nil {
1384 for ; extraTabs
> 0; extraTabs
-- {
1387 p
.setComment(s
.Comment
)
1391 func sanitizeImportPath(lit
*ast
.BasicLit
) *ast
.BasicLit
{
1392 // Note: An unmodified AST generated by go/parser will already
1393 // contain a backward- or double-quoted path string that does
1394 // not contain any invalid characters, and most of the work
1395 // here is not needed. However, a modified or generated AST
1396 // may possibly contain non-canonical paths. Do the work in
1397 // all cases since it's not too hard and not speed-critical.
1399 // if we don't have a proper string, be conservative and return whatever we have
1400 if lit
.Kind
!= token
.STRING
{
1403 s
, err
:= strconv
.Unquote(lit
.Value
)
1408 // if the string is an invalid path, return whatever we have
1410 // spec: "Implementation restriction: A compiler may restrict
1411 // ImportPaths to non-empty strings using only characters belonging
1412 // to Unicode's L, M, N, P, and S general categories (the Graphic
1413 // characters without spaces) and may also exclude the characters
1414 // !"#$%&'()*,:;<=>?[\]^`{|} and the Unicode replacement character
1419 const illegalChars
= `!"#$%&'()*,:;<=>?[\]^{|}` + "`\uFFFD"
1420 for _
, r
:= range s
{
1421 if !unicode
.IsGraphic(r
) || unicode
.IsSpace(r
) || strings
.ContainsRune(illegalChars
, r
) {
1426 // otherwise, return the double-quoted path
1427 s
= strconv
.Quote(s
)
1429 return lit
// nothing wrong with lit
1431 return &ast
.BasicLit
{ValuePos
: lit
.ValuePos
, Kind
: token
.STRING
, Value
: s
}
1434 // The parameter n is the number of specs in the group. If doIndent is set,
1435 // multi-line identifier lists in the spec are indented when the first
1436 // linebreak is encountered.
1438 func (p
*printer
) spec(spec ast
.Spec
, n
int, doIndent
bool) {
1439 switch s
:= spec
.(type) {
1440 case *ast
.ImportSpec
:
1446 p
.expr(sanitizeImportPath(s
.Path
))
1447 p
.setComment(s
.Comment
)
1450 case *ast
.ValueSpec
:
1452 p
.internalError("expected n = 1; got", n
)
1455 p
.identList(s
.Names
, doIndent
) // always present
1460 if s
.Values
!= nil {
1461 p
.print(blank
, token
.ASSIGN
, blank
)
1462 p
.exprList(token
.NoPos
, s
.Values
, 1, 0, token
.NoPos
)
1464 p
.setComment(s
.Comment
)
1474 if s
.Assign
.IsValid() {
1475 p
.print(token
.ASSIGN
, blank
)
1478 p
.setComment(s
.Comment
)
1481 panic("unreachable")
1485 func (p
*printer
) genDecl(d
*ast
.GenDecl
) {
1487 p
.print(d
.Pos(), d
.Tok
, blank
)
1489 if d
.Lparen
.IsValid() {
1490 // group of parenthesized declarations
1491 p
.print(d
.Lparen
, token
.LPAREN
)
1492 if n
:= len(d
.Specs
); n
> 0 {
1493 p
.print(indent
, formfeed
)
1494 if n
> 1 && (d
.Tok
== token
.CONST || d
.Tok
== token
.VAR
) {
1495 // two or more grouped const/var declarations:
1496 // determine if the type column must be kept
1497 keepType
:= keepTypeColumn(d
.Specs
)
1499 for i
, s
:= range d
.Specs
{
1501 p
.linebreak(p
.lineFor(s
.Pos()), 1, ignore
, p
.linesFrom(line
) > 0)
1504 p
.valueSpec(s
.(*ast
.ValueSpec
), keepType
[i
])
1508 for i
, s
:= range d
.Specs
{
1510 p
.linebreak(p
.lineFor(s
.Pos()), 1, ignore
, p
.linesFrom(line
) > 0)
1516 p
.print(unindent
, formfeed
)
1518 p
.print(d
.Rparen
, token
.RPAREN
)
1521 // single declaration
1522 p
.spec(d
.Specs
[0], 1, true)
1526 // nodeSize determines the size of n in chars after formatting.
1527 // The result is <= maxSize if the node fits on one line with at
1528 // most maxSize chars and the formatted output doesn't contain
1529 // any control chars. Otherwise, the result is > maxSize.
1531 func (p
*printer
) nodeSize(n ast
.Node
, maxSize
int) (size
int) {
1532 // nodeSize invokes the printer, which may invoke nodeSize
1533 // recursively. For deep composite literal nests, this can
1534 // lead to an exponential algorithm. Remember previous
1535 // results to prune the recursion (was issue 1628).
1536 if size
, found
:= p
.nodeSizes
[n
]; found
{
1540 size
= maxSize
+ 1 // assume n doesn't fit
1541 p
.nodeSizes
[n
] = size
1543 // nodeSize computation must be independent of particular
1544 // style so that we always get the same decision; print
1546 cfg
:= Config
{Mode
: RawFormat
}
1547 var buf bytes
.Buffer
1548 if err
:= cfg
.fprint(&buf
, p
.fset
, n
, p
.nodeSizes
); err
!= nil {
1551 if buf
.Len() <= maxSize
{
1552 for _
, ch
:= range buf
.Bytes() {
1557 size
= buf
.Len() // n fits
1558 p
.nodeSizes
[n
] = size
1563 // numLines returns the number of lines spanned by node n in the original source.
1564 func (p
*printer
) numLines(n ast
.Node
) int {
1565 if from
:= n
.Pos(); from
.IsValid() {
1566 if to
:= n
.End(); to
.IsValid() {
1567 return p
.lineFor(to
) - p
.lineFor(from
) + 1
1573 // bodySize is like nodeSize but it is specialized for *ast.BlockStmt's.
1574 func (p
*printer
) bodySize(b
*ast
.BlockStmt
, maxSize
int) int {
1577 if pos1
.IsValid() && pos2
.IsValid() && p
.lineFor(pos1
) != p
.lineFor(pos2
) {
1578 // opening and closing brace are on different lines - don't make it a one-liner
1581 if len(b
.List
) > 5 {
1582 // too many statements - don't make it a one-liner
1585 // otherwise, estimate body size
1586 bodySize
:= p
.commentSizeBefore(p
.posFor(pos2
))
1587 for i
, s
:= range b
.List
{
1588 if bodySize
> maxSize
{
1589 break // no need to continue
1592 bodySize
+= 2 // space for a semicolon and blank
1594 bodySize
+= p
.nodeSize(s
, maxSize
)
1599 // funcBody prints a function body following a function header of given headerSize.
1600 // If the header's and block's size are "small enough" and the block is "simple enough",
1601 // the block is printed on the current line, without line breaks, spaced from the header
1602 // by sep. Otherwise the block's opening "{" is printed on the current line, followed by
1603 // lines for the block's statements and its closing "}".
1605 func (p
*printer
) funcBody(headerSize
int, sep whiteSpace
, b
*ast
.BlockStmt
) {
1610 // save/restore composite literal nesting level
1611 defer func(level
int) {
1617 if headerSize
+p
.bodySize(b
, maxSize
) <= maxSize
{
1618 p
.print(sep
, b
.Lbrace
, token
.LBRACE
)
1619 if len(b
.List
) > 0 {
1621 for i
, s
:= range b
.List
{
1623 p
.print(token
.SEMICOLON
, blank
)
1625 p
.stmt(s
, i
== len(b
.List
)-1)
1629 p
.print(noExtraLinebreak
, b
.Rbrace
, token
.RBRACE
, noExtraLinebreak
)
1634 p
.print(blank
) // always use blank
1639 // distanceFrom returns the column difference between from and p.pos (the current
1640 // estimated position) if both are on the same line; if they are on different lines
1641 // (or unknown) the result is infinity.
1642 func (p
*printer
) distanceFrom(from token
.Pos
) int {
1643 if from
.IsValid() && p
.pos
.IsValid() {
1644 if f
:= p
.posFor(from
); f
.Line
== p
.pos
.Line
{
1645 return p
.pos
.Column
- f
.Column
1651 func (p
*printer
) funcDecl(d
*ast
.FuncDecl
) {
1653 p
.print(d
.Pos(), token
.FUNC
, blank
)
1655 p
.parameters(d
.Recv
) // method: print receiver
1659 p
.signature(d
.Type
.Params
, d
.Type
.Results
)
1660 p
.funcBody(p
.distanceFrom(d
.Pos()), vtab
, d
.Body
)
1663 func (p
*printer
) decl(decl ast
.Decl
) {
1664 switch d
:= decl
.(type) {
1666 p
.print(d
.Pos(), "BadDecl")
1672 panic("unreachable")
1676 // ----------------------------------------------------------------------------
1679 func declToken(decl ast
.Decl
) (tok token
.Token
) {
1681 switch d
:= decl
.(type) {
1690 func (p
*printer
) declList(list
[]ast
.Decl
) {
1691 tok
:= token
.ILLEGAL
1692 for _
, d
:= range list
{
1695 // If the declaration token changed (e.g., from CONST to TYPE)
1696 // or the next declaration has documentation associated with it,
1697 // print an empty line between top-level declarations.
1698 // (because p.linebreak is called with the position of d, which
1699 // is past any documentation, the minimum requirement is satisfied
1700 // even w/o the extra getDoc(d) nil-check - leave it in case the
1701 // linebreak logic improves - there's already a TODO).
1702 if len(p
.output
) > 0 {
1703 // only print line break if we are not at the beginning of the output
1704 // (i.e., we are not printing only a partial program)
1706 if prev
!= tok ||
getDoc(d
) != nil {
1709 // start a new section if the next declaration is a function
1710 // that spans multiple lines (see also issue #19544)
1711 p
.linebreak(p
.lineFor(d
.Pos()), min
, ignore
, tok
== token
.FUNC
&& p
.numLines(d
) > 1)
1717 func (p
*printer
) file(src
*ast
.File
) {
1718 p
.setComment(src
.Doc
)
1719 p
.print(src
.Pos(), token
.PACKAGE
, blank
)
1721 p
.declList(src
.Decls
)