html/template: handle nil Error values in context.String
Add a special case to print a generic nil error when context.err is
nil.
Previously, this case was unchecked, leading to a call to (*Error).Error
with a nil receiver, which was triggering a nil pointer access. However,
this bug was masked by the panic-recovery code in package fmt.
I tested this change by running `dlv test` in src/html/template, running
the `continue` command, and verifying that no "bad access" errors are
returned.
Fixes #28854
Change-Id: I0b637b943de003d9efc294f6f1e49b793668d037
Reviewed-on: https://go-review.googlesource.com/c/go/+/181579
Reviewed-by: Dmitri Shuralyov <dmitshur@golang.org>
diff --git a/src/html/template/context.go b/src/html/template/context.go
index 7ab3d1f..f7d4849 100644
--- a/src/html/template/context.go
+++ b/src/html/template/context.go
@@ -26,7 +26,11 @@
}
func (c context) String() string {
- return fmt.Sprintf("{%v %v %v %v %v %v %v}", c.state, c.delim, c.urlPart, c.jsCtx, c.attr, c.element, c.err)
+ var err error
+ if c.err != nil {
+ err = c.err
+ }
+ return fmt.Sprintf("{%v %v %v %v %v %v %v}", c.state, c.delim, c.urlPart, c.jsCtx, c.attr, c.element, err)
}
// eq reports whether two contexts are equal.
