A field in a structure is sometimes protected by Mutex, but sometimes unprotected.

[BurtonQin]

What version of Hugo are you using (hugo version)?

master branch, commit c03ea2b

What happened:
A field in a structure is sometimes protected by Mutex, but sometimes unprotected.
This may lead to data race.
There are 2 such cases:

• templateStateMap.templates is not protected by t.mu on L754. But for all the other 3 places, it is protected by t.mu.
  

  hugo/tpl/tplimpl/template.go

  Lines 722 to 723 in c03ea2b

  	func (t *templateHandler) postTransform() error {
  	for _, v := range t.main.templates {

• t.text is not protected by t.nameSpace.mu on L35. But for all the other 3 places (https://github.com/gohugoio/hugo/blob/master/tpl/internal/go_templates/htmltemplate/template.go), it is protected by t.nameSpace.mu.
  

  hugo/tpl/internal/go_templates/htmltemplate/hugo_template.go

  Lines 31 to 35 in c03ea2b

  	func (t *Template) Prepare() (*template.Template, error) {
  	if err := t.escape(); err != nil {
  	return nil, err
  	}
  	return t.text, nil

What you expected to happen:
Data race

[paskal]

The only way to properly protect t.text (as it's used elsewhere after return) is to make a deep copy of it and return the pointer to that copy instead of the original: that's a cure worse than the disease, in my opinion, as it will complicate code for no clear benefit.

[bep]

This may lead to data race.

Only if it's read/write from multiple go routines at the same time.

1. postTransform is, to my knowledge, always done in 1 thread and before the templates gets used.
2. Any concurrency issue with t.text should be addressed in the source (Go stdlib).

Also, note that we have a fair amount of tests that run this code successfully with the -race flag enabled.