text/template: allow .Field access to parenthesized expressions
Change the grammar so that field access is a proper operator.
This introduces a new node, ChainNode, into the public (but
actually internal) API of text/template/parse. For
compatibility, we only use the new node type for the specific
construct, which was not parseable before. Therefore this
should be backward-compatible.
Before, .X.Y was a token in the lexer; this CL breaks it out
into .Y applied to .X. But for compatibility we mush them
back together before delivering. One day we might remove
that hack; it's the simple TODO in parse.go/operand.
This change also provides grammatical distinction between
f
and
(f)
which might permit function values later, but not now.
Fixes #3999.
R=golang-dev, dsymonds, gri, rsc, mikesamuel
CC=golang-dev
https://golang.org/cl/6494119
diff --git a/src/pkg/text/template/exec_test.go b/src/pkg/text/template/exec_test.go
index 7f60dca..0835d31 100644
--- a/src/pkg/text/template/exec_test.go
+++ b/src/pkg/text/template/exec_test.go
@@ -340,6 +340,12 @@
// Parenthesized expressions
{"parens in pipeline", "{{printf `%d %d %d` (1) (2 | add 3) (add 4 (add 5 6))}}", "1 5 15", tVal, true},
+ // Parenthesized expressions with field accesses
+ {"parens: $ in paren", "{{($).X}}", "x", tVal, true},
+ {"parens: $.GetU in paren", "{{($.GetU).V}}", "v", tVal, true},
+ {"parens: $ in paren in pipe", "{{($ | echo).X}}", "x", tVal, true},
+ {"parens: spaces and args", `{{(makemap "up" "down" "left" "right").left}}`, "right", tVal, true},
+
// If.
{"if true", "{{if true}}TRUE{{end}}", "TRUE", tVal, true},
{"if false", "{{if false}}TRUE{{else}}FALSE{{end}}", "FALSE", tVal, true},
@@ -535,6 +541,21 @@
return sum
}
+func echo(arg interface{}) interface{} {
+ return arg
+}
+
+func makemap(arg ...string) map[string]string {
+ if len(arg)%2 != 0 {
+ panic("bad makemap")
+ }
+ m := make(map[string]string)
+ for i := 0; i < len(arg); i += 2 {
+ m[arg[i]] = arg[i+1]
+ }
+ return m
+}
+
func stringer(s fmt.Stringer) string {
return s.String()
}
@@ -545,6 +566,8 @@
"add": add,
"count": count,
"dddArg": dddArg,
+ "echo": echo,
+ "makemap": makemap,
"oneArg": oneArg,
"typeOf": typeOf,
"vfunc": vfunc,
