-
Russ Cox authored
All prior versions of Go have allowed redefining empty templates to become non-empty. Unfortunately, that has never consistently taken effect in html/template after the first execution: // define and execute t := template.New("root") t.Parse(`{{define "T"}}{{end}}<a href="{{template "T"}}">`) t.Execute(w, nil) // <a href=""> // redefine t.Parse(`{{define "T"}}my.url{{end}}`) // succeeds, but ignored t.Execute(w, nil) // <a href=""> When Go 1.6 added {{block...}} to text/template, that loosened the redefinition rules to allow redefinition at any time. The loosening was undone a bit in html/template, although inconsistently: // define and execute t := template.New("root") t.Parse(`{{define "T"}}body{{end}}`) t.Lookup("T").Execute(ioutil.Discard, nil) // attempt to redefine t.Parse(`{{define "T"}}body{{end}}`) // rejected in all Go versions t.Lookup("T").Parse("body") // OK as of Go 1.6, likely unintentionally Like in the empty->non-empty case, whether future execution takes notice of a redefinition basically can't be explained without going into the details of the template escape analysis. Address both the original inconsistencies in whether a redefinition would have any effect and the new inconsistencies about whether a redefinition is allowed by adopting a new rule: no parsing or modifying any templates after the first execution of any template in the same set. Template analysis begins at first execution, and once template analysis has begun, we simply don't have the right logic to update the analysis for incremental modifications (and never have). If this new rule breaks existing uses of templates that we decide need to be supported, we can try to invalidate all escape analysis for the entire set after any modifications. But let's wait on that until we know we need to and why. Also fix documentation of text/template redefinition policy (redefinition is always OK). Fixes #15761. Change-Id: I7d58d7c08a7d9df2440ee0d651a5b2ecaff3006c Reviewed-on: https://go-review.googlesource.com/31464 Run-TryBot: Russ Cox <rsc@golang.org> TryBot-Result: Gobot Gobot <gobot@golang.org> Reviewed-by:
Andrew Gerrand <adg@golang.org>
604146ce
Name |
Last commit
|
Last update |
---|---|---|
.github | ||
api | ||
doc | ||
lib/time | ||
misc | ||
src | ||
test | ||
.gitattributes | ||
.gitignore | ||
AUTHORS | ||
CONTRIBUTING.md | ||
CONTRIBUTORS | ||
LICENSE | ||
PATENTS | ||
README.md | ||
favicon.ico | ||
robots.txt |