text/template/parse: nicer error when comment ends before final delimiter

By separating finding the end of the comment from the end of the action,
we can diagnose malformed comments better.
Also tweak the documentation to make the comment syntax clearer.

Fixes #6022.

R=golang-dev, dsymonds
CC=golang-dev
https://golang.org/cl/12570044

diff --git a/src/pkg/text/template/doc.go b/src/pkg/text/template/doc.go
index 2da339ce8351d9b5a8be237b0b699bbf8a250d5c..c9121f74d3577728111ebd390913fa1fcb4dd356 100644 (file)
--- a/src/pkg/text/template/doc.go
+++ b/src/pkg/text/template/doc.go
@@ -44,7 +44,8 @@ data, defined in detail below.
 */
 //     {{/* a comment */}}
 //             A comment; discarded. May contain newlines.
-//             Comments do not nest.
+//             Comments do not nest and must start and end at the
+//             delimiters, as shown here.
 /*
 
        {{pipeline}}

diff --git a/src/pkg/text/template/parse/lex.go b/src/pkg/text/template/parse/lex.go
index 23c0cf0793c7d367bcc3f4758aa39b334633fecf..1674aaf9cd4bb63a42c0bee5aa833875bc5ec81a 100644 (file)
--- a/src/pkg/text/template/parse/lex.go
+++ b/src/pkg/text/template/parse/lex.go
@@ -243,11 +243,16 @@ func lexLeftDelim(l *lexer) stateFn {
 // lexComment scans a comment. The left comment marker is known to be present.
 func lexComment(l *lexer) stateFn {
        l.pos += Pos(len(leftComment))
-       i := strings.Index(l.input[l.pos:], rightComment+l.rightDelim)
+       i := strings.Index(l.input[l.pos:], rightComment)
        if i < 0 {
                return l.errorf("unclosed comment")
        }
-       l.pos += Pos(i + len(rightComment) + len(l.rightDelim))
+       l.pos += Pos(i + len(rightComment))
+       if !strings.HasPrefix(l.input[l.pos:], l.rightDelim) {
+               return l.errorf("comment ends before closing delimiter")
+
+       }
+       l.pos += Pos(len(l.rightDelim))
        l.ignore()
        return lexText
 }

diff --git a/src/pkg/text/template/parse/lex_test.go b/src/pkg/text/template/parse/lex_test.go
index d2264c991c989088e9a5afdb1f7fbbb150eb4d4f..ae90ae407b1e99fd5612cdb7b7f46b2f05fddfda 100644 (file)
--- a/src/pkg/text/template/parse/lex_test.go
+++ b/src/pkg/text/template/parse/lex_test.go
@@ -336,6 +336,10 @@ var lexTests = []lexTest{
                {itemText, 0, "hello-"},
                {itemError, 0, `unclosed comment`},
        }},
+       {"text with comment close separted from delim", "hello-{{/* */ }}-world", []item{
+               {itemText, 0, "hello-"},
+               {itemError, 0, `comment ends before closing delimiter`},
+       }},
 }
 
 // collect gathers the emitted items into a slice.