locate_template does not check to see site has parent theme.

[spacedmonkey]

In locate_template, function checks to exist if a file exists in parent and child themes. But if the current theme is not a child theme, this check is pointless and checks if the same file exists twice per request.

So

if ( file_exists( STYLESHEETPATH . '/' . $template_name ) ) {
        $located = STYLESHEETPATH . '/' . $template_name;
        break;
} elseif ( file_exists( TEMPLATEPATH . '/' . $template_name ) ) {
        $located = TEMPLATEPATH . '/' . $template_name;
        break;
}

Should become

if ( file_exists( STYLESHEETPATH . '/' . $template_name ) ) {
        $located = STYLESHEETPATH . '/' . $template_name;
        break;
} elseif ( STYLESHEETPATH !== TEMPLATEPATH && file_exists( TEMPLATEPATH . '/' . $template_name ) ) {
        $located = TEMPLATEPATH . '/' . $template_name;
        break;
}

[nihar007]

Patch added

[thekt12]

Patch is tested and it works as expected. However, due to use of STYLESHEETPATH and TEMPLATEPATH in locate_template we are unable write testcase around here.
STYLESHEETPATH and TEMPLATEPATH are set to default theme path well before setup() function in a test file.

We generally use switch_theme() inside a testcase to switch to a parent or child test themes.
Unfortunately, this doesn't effect the constants and so locate_template gives out the initial default value irrespective of active theme.

[thekt12]

I have added a new ticket https://core.trac.wordpress.org/ticket/58866#ticket for the bug found during writing testcases here.

[flixos90]

@nihar007 The patch looks good, one recommendation though: Instead of manually checking the condition, I think we should use the is_child_theme() function instead which already contains that logic.

An additional small benefit from using that will be that if we implement #58866 we would not need to update this logic here, but only the used function internally.

[nihar007]

Replying to flixos90:

@nihar007 The patch looks good, one recommendation though: Instead of manually checking the condition, I think we should use the is_child_theme() function instead which already contains that logic.

An additional small benefit from using that will be that if we implement #58866 we would not need to update this logic here, but only the used function internally.

Hi @flixos90,
Thanks for your feedback. I am working on it

[nihar007]

Another patch added

[mukesh27]

Thank you, @spacedmonkey, for creating this ticket and also, thanks to @nihar007 for providing the patch.

@thekt12, you are absolutely right. We cannot test the functionality with a constant in the unit test. Great catch on issue #58866.

The changes made in the patch look good and appear to be ready for deployment.

Adding the commit keyword to request further consideration. Since Jonny is currently on vacation, @flixos90, could you please handle the commit process for this ticket?

[flixos90]

In 56357:

Themes: Avoid unnecessary check whether parent template file exists when not using a child theme.

Prior to this change, the locate_template() function would unconditionally check whether the relevant template file exists in the parent theme, which for sites not using a child theme is an exact duplicate of the previous check. This is wasteful and has a small impact on performance since file_exists() checks have a cost.

Props nihar007, thekt12, spacedmonkey, mukesh27.
Fixes #58576.

[spacedmonkey]

#58384 was marked as a duplicate.