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/parse/parse_test.go b/src/pkg/text/template/parse/parse_test.go
index 4be4ca0..0f75c33 100644
--- a/src/pkg/text/template/parse/parse_test.go
+++ b/src/pkg/text/template/parse/parse_test.go
@@ -188,6 +188,8 @@
`{{$x := .X | .Y}}`},
{"nested pipeline", "{{.X (.Y .Z) (.A | .B .C) (.E)}}", noError,
`{{.X (.Y .Z) (.A | .B .C) (.E)}}`},
+ {"field applied to parentheses", "{{(.Y .Z).Field}}", noError,
+ `{{(.Y .Z).Field}}`},
{"simple if", "{{if .X}}hello{{end}}", noError,
`{{if .X}}"hello"{{end}}`},
{"if with else", "{{if .X}}true{{else}}false{{end}}", noError,
@@ -370,8 +372,9 @@
"{{range .X}}",
hasError, `unexpected EOF`},
{"variable",
- "{{$a.b := 23}}",
- hasError, `illegal variable in declaration`},
+ // Declare $x so it's defined, to avoid that error, and then check we don't parse a declaration.
+ "{{$x := 23}}{{with $x.y := 3}}{{$x 23}}{{end}}",
+ hasError, `unexpected ":="`},
{"multidecl",
"{{$a,$b,$c := 23}}",
hasError, `too many declarations`},
