text/template: provide a mechanism for options
Add one option, which is the motivating example, a way to control
what happens when a map is indexed with a key that is not in the map.
Rather than do something specific for that case, we provide a simple
general option mechanism to avoid adding API if something else
comes up. This general approach also makes it easy for html/template
to track (and adapt, should that become important).
New method: Option(option string...). The option strings are key=value
pairs or just simple strings (no =).
New option:
missingkey: Control the behavior during execution if a map is
indexed with a key that is not present in the map.
"missingkey=default" or "missingkey=invalid"
The default behavior: Do nothing and continue execution.
If printed, the result of the index operation is the string
"<no value>".
"missingkey=zero"
The operation returns the zero value for the map type's element.
"missingkey=error"
Execution stops immediately with an error.
Fixes #6288.
Change-Id: Id811e2b99dc05aff324d517faac113ef3c25293a
Reviewed-on: https://go-review.googlesource.com/8462
Reviewed-by: Robert Griesemer <gri@golang.org>
diff --git a/src/html/template/template.go b/src/html/template/template.go
index 64c0041..bb9140a 100644
--- a/src/html/template/template.go
+++ b/src/html/template/template.go
@@ -51,6 +51,29 @@
return m
}
+// Option sets options for the template. Options are described by
+// strings, either a simple string or "key=value". There can be at
+// most one equals sign in an option string. If the option string
+// is unrecognized or otherwise invalid, Option panics.
+//
+// Known options:
+//
+// missingkey: Control the behavior during execution if a map is
+// indexed with a key that is not present in the map.
+// "missingkey=default" or "missingkey=invalid"
+// The default behavior: Do nothing and continue execution.
+// If printed, the result of the index operation is the string
+// "<no value>".
+// "missingkey=zero"
+// The operation returns the zero value for the map type's element.
+// "missingkey=error"
+// Execution stops immediately with an error.
+//
+func (t *Template) Option(opt ...string) *Template {
+ t.text.Option(opt...)
+ return t
+}
+
// escape escapes all associated templates.
func (t *Template) escape() error {
t.nameSpace.mu.Lock()
