godoc: don't convert multi-line functions into one-liners by default

- new heuristic: if both the opening { and closing } braces are on the
  same line, and the function body doesn't contain comments or is other-
  wise too long (e.g. signature too long), it is formatted as a one-line
  function

- related cleanups along the way

- gofmt -w src misc led to no additional changes as expected

R=rsc, rsc1
CC=golang-dev, ken2, r
https://golang.org/cl/758041

src/pkg/go/printer/nodes.go

@@ -74,7 +74,7 @@ func (p *printer) setComment(g *ast.CommentGroup) {
 		// for some reason there are pending comments; this
 		// should never happen - handle gracefully and flush
 		// all comments up to g, ignore anything after that
-		p.flush(g.List[0].Pos(), false)
+		p.flush(g.List[0].Pos(), token.ILLEGAL)
 	}
 	p.comments[0] = g
 	p.cindex = 0
@@ -112,7 +112,6 @@ func (p *printer) identList(list []*ast.Ident, indent bool, multiLine *bool) {
 // Compute the key size of a key:value expression.
 // Returns 0 if the expression doesn't fit onto a single line.
 func (p *printer) keySize(pair *ast.KeyValueExpr) int {
-	const infinity = 1e6 // larger than any source line
 	if p.nodeSize(pair, infinity) <= infinity {
 		// entire expression fits on one line - return key size
 		return p.nodeSize(pair.Key, infinity)
@@ -431,7 +430,7 @@ func (p *printer) fieldList(fields *ast.FieldList, isIncomplete bool, ctxt exprC
 			if len(list) > 0 {
 				p.print(formfeed)
 			}
-			p.flush(rbrace, false) // make sure we don't loose the last line comment
+			p.flush(rbrace, token.RBRACE) // make sure we don't loose the last line comment
 			p.setLineComment("// contains unexported fields")
 		}
 
@@ -458,7 +457,7 @@ func (p *printer) fieldList(fields *ast.FieldList, isIncomplete bool, ctxt exprC
 			if len(list) > 0 {
 				p.print(formfeed)
 			}
-			p.flush(rbrace, false) // make sure we don't loose the last line comment
+			p.flush(rbrace, token.RBRACE) // make sure we don't loose the last line comment
 			p.setLineComment("// contains unexported methods")
 		}
 
@@ -1224,16 +1223,26 @@ func (p *printer) nodeSize(n ast.Node, maxSize int) (size int) {
 
 
 func (p *printer) isOneLineFunc(b *ast.BlockStmt, headerSize int) bool {
-	const maxSize = 90 // adjust as appropriate, this is an approximate value
+	pos1 := b.Pos()
+	pos2 := b.Rbrace
+	if pos1.IsValid() && pos2.IsValid() && pos1.Line != pos2.Line {
+		// opening and closing brace are on different lines - don't make it a one-liner
+		return false
+	}
+	if len(b.List) > 5 || p.commentBefore(pos2) {
+		// too many statements or there is a comment inside - don't make it a one-liner
+		return false
+	}
+	// otherwise, estimate body size
+	const maxSize = 100
 	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)
+	for i, s := range b.List {
+		if i > 0 {
+			bodySize += 2 // space for a semicolon and blank
 		}
-	// require both headers and overall size to be not "too large"
-	return headerSize <= maxSize/2 && headerSize+bodySize <= maxSize
+		bodySize += p.nodeSize(s, maxSize)
+	}
+	return headerSize+bodySize <= maxSize
 }
 
 
@@ -1248,13 +1257,18 @@ func (p *printer) funcBody(b *ast.BlockStmt, headerSize int, isLit bool, multiLi
 		if isLit {
 			sep = blank
 		}
+		p.print(sep, b.Pos(), token.LBRACE)
 		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)
+			p.print(blank)
+			for i, s := range b.List {
+				if i > 0 {
+					p.print(token.SEMICOLON, blank)
+				}
+				p.stmt(s, ignoreMultiLine)
+			}
+			p.print(blank)
 		}
+		p.print(b.Rbrace, token.RBRACE)
 		return
 	}
 
@@ -1266,12 +1280,12 @@ func (p *printer) funcBody(b *ast.BlockStmt, headerSize int, isLit bool, multiLi
 
 // 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).
+// the result is infinity.
 func distance(from, to token.Position) int {
 	if from.IsValid() && to.IsValid() && from.Line == to.Line {
 		return to.Column - from.Column
 	}
-	return 1 << 30
+	return infinity
 }
 
 

src/pkg/go/printer/printer.go

@@ -54,7 +54,7 @@ var (
 
 // Special positions
 var noPos token.Position // use noPos when a position is needed but not known
-var infinity = token.Position{Offset: 1 << 30, Line: 1 << 30} // use infinity to indicate the end of the source
+var infinity = 1 << 30
 
 
 // Use ignoreMultiLine if the multiLine information is not important.
@@ -640,17 +640,16 @@ func (p *printer) writeCommentSuffix(needsLinebreak bool) (droppedFF bool) {
 
 
 // intersperseComments consumes all comments that appear before the next token
-// and prints it together with the buffered whitespace (i.e., the whitespace
+// tok and prints it together with the buffered whitespace (i.e., the whitespace
 // that needs to be written before the next token). A heuristic is used to mix
-// the comments and whitespace. The isKeyword parameter indicates if the next
-// token is a keyword or not. intersperseComments returns true if a pending
+// the comments and whitespace. intersperseComments returns true if a pending
 // formfeed was dropped from the whitespace buffer.
 //
-func (p *printer) intersperseComments(next token.Position, isKeyword bool) (droppedFF bool) {
+func (p *printer) intersperseComments(next token.Position, tok token.Token) (droppedFF bool) {
 	var last *ast.Comment
 	for ; p.commentBefore(next); p.cindex++ {
 		for _, c := range p.comments[p.cindex].List {
-			p.writeCommentPrefix(c.Pos(), next, last == nil, isKeyword)
+			p.writeCommentPrefix(c.Pos(), next, last == nil, tok.IsKeyword())
 			p.writeComment(c)
 			last = c
 		}
@@ -663,8 +662,8 @@ func (p *printer) intersperseComments(next token.Position, isKeyword bool) (drop
 			p.write([]byte{' '})
 		}
 		// ensure that there is a newline after a //-style comment
-		// or if we are at the end of a file after a /*-style comment
-		return p.writeCommentSuffix(last.Text[1] == '/' || next.Offset == infinity.Offset)
+		// or if we are before a closing '}' or at the end of a file
+		return p.writeCommentSuffix(last.Text[1] == '/' || tok == token.RBRACE || tok == token.EOF)
 	}
 
 	// no comment was written - we should never reach here since
@@ -743,7 +742,7 @@ func (p *printer) print(args ...interface{}) {
 		next := p.pos // estimated position of next item
 		var data []byte
 		var tag HTMLTag
-		isKeyword := false
+		var tok token.Token
 		switch x := f.(type) {
 		case whiteSpace:
 			if x == ignore {
@@ -785,7 +784,7 @@ func (p *printer) print(args ...interface{}) {
 			} else {
 				data = []byte(x.String())
 			}
-			isKeyword = x.IsKeyword()
+			tok = x
 		case token.Position:
 			if x.IsValid() {
 				next = x // accurate position of next item
@@ -797,7 +796,7 @@ func (p *printer) print(args ...interface{}) {
 		p.pos = next
 
 		if data != nil {
-			droppedFF := p.flush(next, isKeyword)
+			droppedFF := p.flush(next, tok)
 
 			// intersperse extra newlines if present in the source
 			// (don't do this in flush as it will cause extra newlines
@@ -820,14 +819,15 @@ func (p *printer) commentBefore(next token.Position) bool {
 
 
 // Flush prints any pending comments and whitespace occuring
-// textually before the position of the next item. Flush returns
-// true if a pending formfeed character was dropped from the
-// whitespace buffer as a result of interspersing comments.
+// textually before the position of the next token tok. Flush
+// returns true if a pending formfeed character was dropped
+// from the whitespace buffer as a result of interspersing
+// comments.
 //
-func (p *printer) flush(next token.Position, isKeyword bool) (droppedFF bool) {
+func (p *printer) flush(next token.Position, tok token.Token) (droppedFF bool) {
 	if p.commentBefore(next) {
 		// if there are comments before the next item, intersperse them
-		droppedFF = p.intersperseComments(next, isKeyword)
+		droppedFF = p.intersperseComments(next, tok)
 	} else {
 		// otherwise, write any leftover whitespace
 		p.writeWhitespace(len(p.buffer))
@@ -1026,7 +1026,7 @@ func (cfg *Config) Fprint(output io.Writer, node interface{}) (int, os.Error) {
 			p.errors <- os.NewError(fmt.Sprintf("printer.Fprint: unsupported node type %T", n))
 			runtime.Goexit()
 		}
-		p.flush(infinity, false)
+		p.flush(token.Position{Offset: infinity, Line: infinity}, token.EOF)
 		p.errors <- nil // no errors
 	}()
 	err := <-p.errors // wait for completion of goroutine

src/pkg/go/printer/testdata/comments.golden

@@ -411,7 +411,8 @@ func _() {
 
 
 // Some interesting interspersed comments
-func _( /* this */ x /* is */ /* an */ int)	{}
+func _( /* this */ x /* is */ /* an */ int) {
+}
 
 func _( /* no params */ )	{}
 
@@ -421,7 +422,13 @@ func _() {
 
 func ( /* comment1 */ T /* comment2 */ ) _()	{}
 
-func _() { /* one-liner */ }
+func _() { /* one-liner */
+}
+
+func _() {
+	_ = 0
+	/* closing curly brace should be on new line */
+}
 
 
 // Line comments with tabs

src/pkg/go/printer/testdata/comments.input

@@ -424,6 +424,10 @@ func (/* comment1 */ T /* comment2 */) _() {}
 
 func _() { /* one-liner */ }
 
+func _() {
+	_ = 0
+	/* closing curly brace should be on new line */ }
+
 
 // Line comments with tabs
 func _() {

src/pkg/go/printer/testdata/declarations.golden

@@ -356,7 +356,8 @@ func _() {
 // formatting of structs
 type _ struct{}
 
-type _ struct { /* this comment should be visible */ }
+type _ struct { /* this comment should be visible */
+}
 
 type _ struct {
 	// this comment should be visible and properly indented
@@ -588,15 +589,31 @@ func _()	{}
 func _()	{}
 
 func _()		{ f(1, 2, 3) }
-func _(x int) int	{ return x + 1 }
-func _() int		{ type T struct{} }
+func _(x int) int	{ y := x; return y + 1 }
+func _() int		{ type T struct{}; var x T; return x }
+
+// these must remain multi-line since they are multi-line in the source
+func _() {
+	f(1, 2, 3)
+}
+func _(x int) int {
+	y := x
+	return y + 1
+}
+func _() int {
+	type T struct{}
+	var x T
+	return x
+}
 
 
 // making function declarations safe for new semicolon rules
-func _() { /* one-line func */ }
+func _() { /* multi-line func because of comment */
+}
 
 func _() {
-	/* one-line func */ }
+	/* multi-line func because block is on multiple lines */
+}
 
 
 // ellipsis parameters

src/pkg/go/printer/testdata/declarations.input

@@ -581,22 +581,27 @@ func _() {}  // an empty line before this function
 func _() {}
 func _() {}
 
+func _() { f(1, 2, 3) }
+func _(x int) int { y := x; return y+1 }
+func _() int { type T struct{}; var x T; return x }
+
+// these must remain multi-line since they are multi-line in the source
 func _() {
 	f(1, 2, 3)
 }
 func _(x int) int {
-	return x+1
+	y := x; return y+1
 }
 func _() int {
-	type T struct{}
+	type T struct{}; var x T; return x
 }
 
 
 // making function declarations safe for new semicolon rules
-func _() { /* one-line func */ }
+func _() { /* multi-line func because of comment */ }
 
 func _() {
-/* one-line func */ }
+/* multi-line func because block is on multiple lines */ }
 
 
 // ellipsis parameters

src/pkg/go/printer/testdata/expressions.golden

@@ -210,14 +210,31 @@ func _() {
 
 
 func _() {
-	// one-line function literals
+	// one-line function literals (body is on a single line)
 	_ = func() {}
 	_ = func() int { return 0 }
-	_ = func(x, y int) bool { return x < y }
+	_ = func(x, y int) bool { m := (x + y) / 2; return m < 0 }
 
-	f(func() {})
-	f(func() int { return 0 })
-	f(func(x, y int) bool { return x < y })
+	// multi-line function literals (body is not on one line)
+	_ = func() {
+	}
+	_ = func() int {
+		return 0
+	}
+	_ = func(x, y int) bool {
+		m := (x + y) / 2
+		return x < y
+	}
+
+	f(func() {
+	})
+	f(func() int {
+		return 0
+	})
+	f(func(x, y int) bool {
+		m := (x + y) / 2
+		return x < y
+	})
 }
 
 

src/pkg/go/printer/testdata/expressions.input

@@ -206,22 +206,27 @@ _ = `foo
 
 
 func _() {
-	// one-line function literals
+	// one-line function literals (body is on a single line)
 	_ = func() {}
+	_ = func() int { return 0 }
+	_ = func(x, y int) bool { m := (x+y)/2; return m < 0 }
+
+	// multi-line function literals (body is not on one line)
+	_ = func() {
+	}
 	_ = func() int {
 		return 0
 	}
 	_ = func(x, y int) bool {
-		return x < y
-	}
+		m := (x+y)/2; return x < y }
 
-	f(func() {})
+	f(func() {
+	})
 	f(func() int {
 		return 0
 	})
 	f(func(x, y int) bool {
-		return x < y
-	})
+		m := (x+y)/2; return x < y })
 }
 
 

src/pkg/go/printer/testdata/expressions.raw

@@ -210,14 +210,31 @@ func _() {
 
 
 func _() {
-	// one-line function literals
+	// one-line function literals (body is on a single line)
 	_ = func() {}
 	_ = func() int { return 0 }
-	_ = func(x, y int) bool { return x < y }
+	_ = func(x, y int) bool { m := (x + y) / 2; return m < 0 }
 
-	f(func() {})
-	f(func() int { return 0 })
-	f(func(x, y int) bool { return x < y })
+	// multi-line function literals (body is not on one line)
+	_ = func() {
+	}
+	_ = func() int {
+		return 0
+	}
+	_ = func(x, y int) bool {
+		m := (x + y) / 2
+		return x < y
+	}
+
+	f(func() {
+	})
+	f(func() int {
+		return 0
+	})
+	f(func(x, y int) bool {
+		m := (x + y) / 2
+		return x < y
+	})
 }