Haml 6 has
breaking changes
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regarding
boolean attributes
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. Only aria-, data- and a list of
select attributes
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(e.g. hidden, disabled) are considered "boolean".
"Boolean attributes" express meaning by their existence.
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. By this definition, Haml will, toggle boolean attributes by their value, and it will always assign a value to non-boolean attributes. E.g. %button{ disabled: !form.valid? } will render as <button></button> for a valid form, and as <button disabled></button> for an invalid form. In contrast, a non-boolean attribute %div{ 'form-valid': form.valid? } will render as either <div form-valid="true"></div> or . Attributes without a value must be written as %div(custom-boolean='')->`.
Interpretation of "boolean" attributes does not change
| Haml | HTML generated by Haml 5 & 6 |
|---|---|
| %button(disabled) | <button disabled></button> |
| %button(disabled=true) | <button disabled></button> |
| %button(disabled=false) | <button></button> |
| %button(disabled='true') | <button disabled="true"></button> |
| %button(disabled='false') | <button disabled="false"></button> |
| %button(disabled='') | <button disabled=''></button> |
| %button(data-test) | <button data-test></button> |
| %button(data-test=true) | <button data-test></button> |
| %button(data-test=false) | <button></button> |
| %button(data-test='true') | <button data-test="true"></button> |
| %button(data-test='false') | <button data-test="false"></button> |
| %button(data-test='') | <button data-test=''></button> |
Other attributes will be handled differently by Haml 6
| Haml | HTML generated by Haml 5 | HTML generated by Haml 6 |
|---|---|---|
| %button(up-test) | <button up-test></button> |
<button up-test="true"></button> |
| %button(up-test=true) | <button up-test></button> |
<button up-test="true"></button> |
| %button(up-test=false) | <button></button> |
<button up-test="false"></button> |
| %button(up-test='true') | <button up-test="true"></button> |
same |
| %button(up-test='false') | <button up-test="false"></button> |
same |
| %button(up-test='') | <button up-test=''></button> |
same |
Extending the list of attributes considered "boolean" (monkey patch)
In case you want to reconfigure the attributes that a recognized as boolean attributes, you can use a monkey patch in an initializer. For example, the following would consider all attributes prefixed with app- to be boolean attributes:
### Haml 6.3 and newer
Haml.class_eval do
remove_const(:BOOLEAN_ATTRIBUTES).tap do |boolean_attributes|
const_set(:BOOLEAN_ATTRIBUTES, [*boolean_attributes, /^app-/].freeze)
end
end
### Haml 6.0 - 6.2.x
Haml::AttributeBuilder.class_eval do
remove_const(:BOOLEAN_ATTRIBUTES).tap do |boolean_attributes|
const_set(:BOOLEAN_ATTRIBUTES, [*boolean_attributes, /^app-/].freeze)
end
end
Note: You might want to consider using data attributes for all your custom attributes e.g. scrollable => data-scrollable. It might still be legit to allow framework prefixes in case they do not support data attributes e.g. ng- (Angular) or up- (Unpoly).
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Be very selective about patching up- attributes so you can still use expressions like [up-follow=false] or [up-history=false].
Starting with
Unpoly 3.8
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, most Unpoly attributes can now be enabled with a value "true" and be disabled with a value "false". This pairs well with the default (unpatched) Haml 6 behavior.
A different approach is to create attributes from a ruby hash:
%tr{ { 'up-expand': ('' if superuser?) }.compact }
This will provide you with <tr up-expand=""> for a superuser and <tr> otherwise.
