From 98fd66808fafb6496caeb3e848ae277b734f8ed9 Mon Sep 17 00:00:00 2001
From: =?utf8?q?Daniel=20Mart=C3=AD?= <mvdan@mvdan.cc>
Date: Thu, 30 Aug 2018 11:02:41 -0600
Subject: [PATCH] text/template: simplify line tracking in the lexer
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First, move the strings.Count logic out of emit, since only itemText
requires that. Use it in those call sites. itemLeftDelim and
itemRightDelim cannot contain newlines, as they're the "{{" and "}}"
tokens.

Secondly, introduce a startLine lexer field so that we don't have to
keep track of it elsewhere. That's also a requirement to move the
strings.Count out of emit, as emit modifies the start position field.

Change-Id: I69175f403487607a8e5b561b3f1916ee9dc3c0c6
Reviewed-on: https://go-review.googlesource.com/132275
Run-TryBot: Daniel Martí <mvdan@mvdan.cc>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Rob Pike <r@golang.org>
---
 src/text/template/parse/lex.go | 22 +++++++++-------------
 1 file changed, 9 insertions(+), 13 deletions(-)

diff --git a/src/text/template/parse/lex.go b/src/text/template/parse/lex.go
index c0843af6ed..94a676c579 100644
--- a/src/text/template/parse/lex.go
+++ b/src/text/template/parse/lex.go
@@ -117,6 +117,7 @@ type lexer struct {
 	items      chan item // channel of scanned items
 	parenDepth int       // nesting depth of ( ) exprs
 	line       int       // 1+number of newlines seen
+	startLine  int       // start line of this item
 }
 
 // next returns the next rune in the input.
@@ -152,19 +153,16 @@ func (l *lexer) backup() {
 
 // emit passes an item back to the client.
 func (l *lexer) emit(t itemType) {
-	l.items <- item{t, l.start, l.input[l.start:l.pos], l.line}
-	// Some items contain text internally. If so, count their newlines.
-	switch t {
-	case itemText, itemLeftDelim, itemRightDelim:
-		l.line += strings.Count(l.input[l.start:l.pos], "\n")
-	}
+	l.items <- item{t, l.start, l.input[l.start:l.pos], l.startLine}
 	l.start = l.pos
+	l.startLine = l.line
 }
 
 // ignore skips over the pending input before this point.
 func (l *lexer) ignore() {
 	l.line += strings.Count(l.input[l.start:l.pos], "\n")
 	l.start = l.pos
+	l.startLine = l.line
 }
 
 // accept consumes the next rune if it's from the valid set.
@@ -186,7 +184,7 @@ func (l *lexer) acceptRun(valid string) {
 // errorf returns an error token and terminates the scan by passing
 // back a nil pointer that will be the next state, terminating l.nextItem.
 func (l *lexer) errorf(format string, args ...interface{}) stateFn {
-	l.items <- item{itemError, l.start, fmt.Sprintf(format, args...), l.line}
+	l.items <- item{itemError, l.start, fmt.Sprintf(format, args...), l.startLine}
 	return nil
 }
 
@@ -218,6 +216,7 @@ func lex(name, input, left, right string) *lexer {
 		rightDelim: right,
 		items:      make(chan item),
 		line:       1,
+		startLine:  1,
 	}
 	go l.run()
 	return l
@@ -252,16 +251,17 @@ func lexText(l *lexer) stateFn {
 		}
 		l.pos -= trimLength
 		if l.pos > l.start {
+			l.line += strings.Count(l.input[l.start:l.pos], "\n")
 			l.emit(itemText)
 		}
 		l.pos += trimLength
 		l.ignore()
 		return lexLeftDelim
-	} else {
-		l.pos = Pos(len(l.input))
 	}
+	l.pos = Pos(len(l.input))
 	// Correctly reached EOF.
 	if l.pos > l.start {
+		l.line += strings.Count(l.input[l.start:l.pos], "\n")
 		l.emit(itemText)
 	}
 	l.emit(itemEOF)
@@ -609,14 +609,10 @@ Loop:
 
 // lexRawQuote scans a raw quoted string.
 func lexRawQuote(l *lexer) stateFn {
-	startLine := l.line
 Loop:
 	for {
 		switch l.next() {
 		case eof:
-			// Restore line number to location of opening quote.
-			// We will error out so it's ok just to overwrite the field.
-			l.line = startLine
 			return l.errorf("unterminated raw quoted string")
 		case '`':
 			break Loop
-- 
2.50.0