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

1 files changed, 2 insertions, 0 deletions

diff --git a/src/pkg/text/template/exec_test.go b/src/pkg/text/template/exec_test.go
index be1a2d23d8..bc8aee6f3c 100644
--- a/src/pkg/text/template/exec_test.go
+++ b/src/pkg/text/template/exec_test.go
@@ -374,6 +374,8 @@ var execTests = []execTest{
 	{"if map not unset", "{{if not .MXI.none}}ZERO{{else}}NON-ZERO{{end}}", "ZERO", tVal, true},
 	{"if $x with $y int", "{{if $x := true}}{{with $y := .I}}{{$x}},{{$y}}{{end}}{{end}}", "true,17", tVal, true},
 	{"if $x with $x int", "{{if $x := true}}{{with $x := .I}}{{$x}},{{end}}{{$x}}{{end}}", "17,true", tVal, true},
+	{"if else if", "{{if false}}FALSE{{else if true}}TRUE{{end}}", "TRUE", tVal, true},
+	{"if else chain", "{{if eq 1 3}}1{{else if eq 2 3}}2{{else if eq 3 3}}3{{end}}", "3", tVal, true},
 
 	// Print etc.
 	{"print", `{{print "hello, print"}}`, "hello, print", tVal, true},