text/template: allow {{else if ... }} to simplify if chains
The method is simple: the parser just parses
{{if A}}a{{else if B}}b{{end}}
to the same tree that would be produced by
{{if A}}a{{else}}{{if B}}b{{end}}{{end}}
Thus no changes are required in text/template itself
or in html/template, only in text/template/parse.
Fixes #6085
R=golang-dev, adg
CC=golang-dev
https://golang.org/cl/13327043
diff --git a/src/pkg/text/template/parse/parse_test.go b/src/pkg/text/template/parse/parse_test.go
index 0e5c144..c35f4ac 100644
--- a/src/pkg/text/template/parse/parse_test.go
+++ b/src/pkg/text/template/parse/parse_test.go
@@ -194,6 +194,10 @@
`{{if .X}}"hello"{{end}}`},
{"if with else", "{{if .X}}true{{else}}false{{end}}", noError,
`{{if .X}}"true"{{else}}"false"{{end}}`},
+ {"if with else if", "{{if .X}}true{{else if .Y}}false{{end}}", noError,
+ `{{if .X}}"true"{{else}}{{if .Y}}"false"{{end}}{{end}}`},
+ {"if else chain", "+{{if .X}}X{{else if .Y}}Y{{else if .Z}}Z{{end}}+", noError,
+ `"+"{{if .X}}"X"{{else}}{{if .Y}}"Y"{{else}}{{if .Z}}"Z"{{end}}{{end}}{{end}}"+"`},
{"simple range", "{{range .X}}hello{{end}}", noError,
`{{range .X}}"hello"{{end}}`},
{"chained field range", "{{range .X.Y.Z}}hello{{end}}", noError,
@@ -238,6 +242,7 @@
{"dot applied to parentheses", "{{printf (printf .).}}", hasError, ""},
{"adjacent args", "{{printf 3`x`}}", hasError, ""},
{"adjacent args with .", "{{printf `x`.}}", hasError, ""},
+ {"extra end after if", "{{if .X}}a{{else if .Y}}b{{end}}{{end}}", hasError, ""},
// Equals (and other chars) do not assignments make (yet).
{"bug0a", "{{$x := 0}}{{$x}}", noError, "{{$x := 0}}{{$x}}"},
{"bug0b", "{{$x = 1}}{{$x}}", hasError, ""},
