html/template: only track brace depth when we are in a JS tmpl lit
The change that keeps on giving. Only track brace depth in tJS if we are
already inside of a template literal. If we start tracking depth outside
of nested literals it can cause the parser to think we're still in a JS
context when we've actually closed the string interp.
I believe this _mostly_ captures the expected parsing, but since the
JS parser does not implement proper lexical goal symbols, it may not
be entirely accurate. At some point in the future we may be able to
significantly reduce the complexity of this implementation by
implementing a lexical parser that more closely follows the ECMAScript
specification, and structuring escaping rules based on which symbol an
action appears in. This would also allow us to catch errors, which
we currently cannot reasonable do (although perhaps this is beyond the
scope of what html/template _should_ be doing).
Updates #61619
Change-Id: I56e1dbc0d0705ef8fb7a5454ebe2421d4e162ef6
Reviewed-on: https://go-review.googlesource.com/c/go/+/532595
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com> Reviewed-by: Damien Neil <dneil@google.com>