[New Rule] Do not use setTemplate in Block classes

[lenaorobei]

Background

When creating a Block class, a Block class could set its PHTML template in multiple ways: Through XML layout, through a call to $this->setTemplate() and through a variable $_template. The new design of Block classes is to configure them at constructor time, meaning that configuration options (like the template) are added using constructor arguments. This allows for the XML layout to change the template. The template in the Block class is then only defined as a default value, if the XML layout is not overriding the template: This default value is best defined via a protected variable $_template.

Reason

If $this->setTemplate() is used instead, this could lead to potential issues: First of all, setters are deprecated in Block classes (because constructor arguments should be preferred instead). Second, if $this->setTemplate() is added to the constructor after calling upon the parent constructor, it would undo the configuration via XML layout. Simply put: It is outdated and leads to issues quickly.

Implementation

ExtDn SetTemplateInBlockSniff.

[lenaorobei]

Need to investigate and find Magento core use cases where this rule is not applicable.

[ldusan84]

Hi @lenaorobei

I investigated a bit, there might be 3 scenarios in core where the rule is not applicable.

1. Overriding setTemplate method.
2. setTemplate in tests.
3. setTemplate used in constructor.

All the other occurrences are rule violation and should be refactored.

Let me know what you think.

[lenaorobei]

Hi @ldusan84

I can raise this question during weekly architecture discussion magento/architecture#153
Would you be interested in attending? So we can cover this topic and move forward.

[ldusan84]

Hi @lenaorobei

Sorry for the late reply.

Yeah let's do it if it's still possible.

Thanks.

[lenaorobei]

@ldusan84, sure. I can be discussed during any upcoming meeting https://github.com/magento/architecture/issues?q=is%3Aissue+is%3Aopen+label%3A%22meeting+notes%22