Should I worry about the output of html-validate on a default Quarto blog

[maelle]

Description

I used html-validate, a HTML5 validator, on a Quarto blog, and got errors.

I wonder whether some of those should be fixed on the Quarto side, or whether I should ignore them / tweak settings.

For the default Quarto blog (created via the RStudio IDE menu) I see

npx html-validate _site

/home/maelle/Documents/cynkra/quartotest/_site/about.html
   84:6   error  Attribute "target" has invalid value ""                   attribute-allowed-values
   86:8   error  Trailing whitespace                                       no-trailing-whitespace
   88:6   error  Attribute "target" has invalid value ""                   attribute-allowed-values
   88:6   error  Anchor link must have a text describing its purpose       wcag/h30
   89:5   error  Trailing whitespace                                       no-trailing-whitespace
   91:8   error  Trailing whitespace                                       no-trailing-whitespace
   93:6   error  Attribute "target" has invalid value ""                   attribute-allowed-values
   93:6   error  Anchor link must have a text describing its purpose       wcag/h30
   94:5   error  Trailing whitespace                                       no-trailing-whitespace
   96:8   error  Trailing whitespace                                       no-trailing-whitespace
  108:1   error  Trailing whitespace                                       no-trailing-whitespace
  111:4   error  <img> is missing required "alt" attribute                 wcag/h37
  112:11  error  Inline style is not allowed                               no-inline-style
  123:8   error  Trailing whitespace                                       no-trailing-whitespace
  126:4   error  Attribute "target" has invalid value ""                   attribute-allowed-values
  130:4   error  Attribute "target" has invalid value ""                   attribute-allowed-values
  134:4   error  Attribute "target" has invalid value ""                   attribute-allowed-values
  141:37  error  "type" attribute is unnecessary for javascript resources  script-type

/home/maelle/Documents/cynkra/quartotest/_site/index.html
   95:78   error  "type" attribute is unnecessary for javascript resources               script-type
  118:6    error  Attribute "target" has invalid value ""                                attribute-allowed-values
  120:8    error  Trailing whitespace                                                    no-trailing-whitespace
  122:6    error  Attribute "target" has invalid value ""                                attribute-allowed-values
  122:6    error  Anchor link must have a text describing its purpose                    wcag/h30
  123:5    error  Trailing whitespace                                                    no-trailing-whitespace
  125:8    error  Trailing whitespace                                                    no-trailing-whitespace
  127:6    error  Attribute "target" has invalid value ""                                attribute-allowed-values
  127:6    error  Anchor link must have a text describing its purpose                    wcag/h30
  128:5    error  Trailing whitespace                                                    no-trailing-whitespace
  130:8    error  Trailing whitespace                                                    no-trailing-whitespace
  145:1    error  Trailing whitespace                                                    no-trailing-whitespace
  146:1    error  Trailing whitespace                                                    no-trailing-whitespace
  149:1    error  Trailing whitespace                                                    no-trailing-whitespace
  150:1    error  Trailing whitespace                                                    no-trailing-whitespace
  151:1    error  Trailing whitespace                                                    no-trailing-whitespace
  153:1    error  Trailing whitespace                                                    no-trailing-whitespace
  154:1    error  Trailing whitespace                                                    no-trailing-whitespace
  159:1    error  Trailing whitespace                                                    no-trailing-whitespace
  175:5    error  Anchor link must have a text describing its purpose                    wcag/h30
  175:50   error  <img> is missing required "alt" attribute                              wcag/h37
  216:5    error  Anchor link must have a text describing its purpose                    wcag/h30
  216:43   error  <p> element is not permitted as content under <p>                      element-permitted-content
  216:67   error  <img> is missing required "alt" attribute                              wcag/h37
  216:138  error  Expected omitted end tag <img> instead of self-closing element <img/>  void-style
  254:37   error  "type" attribute is unnecessary for javascript resources               script-type

/home/maelle/Documents/cynkra/quartotest/_site/posts/post-with-code/index.html
  121:6    error  Attribute "target" has invalid value ""                   attribute-allowed-values
  123:8    error  Trailing whitespace                                       no-trailing-whitespace
  125:6    error  Attribute "target" has invalid value ""                   attribute-allowed-values
  125:6    error  Anchor link must have a text describing its purpose       wcag/h30
  126:5    error  Trailing whitespace                                       no-trailing-whitespace
  128:8    error  Trailing whitespace                                       no-trailing-whitespace
  130:6    error  Attribute "target" has invalid value ""                   attribute-allowed-values
  130:6    error  Anchor link must have a text describing its purpose       wcag/h30
  131:5    error  Trailing whitespace                                       no-trailing-whitespace
  133:8    error  Trailing whitespace                                       no-trailing-whitespace
  153:1    error  Trailing whitespace                                       no-trailing-whitespace
  154:1    error  Trailing whitespace                                       no-trailing-whitespace
  163:1    error  Trailing whitespace                                       no-trailing-whitespace
  170:1    error  Trailing whitespace                                       no-trailing-whitespace
  171:1    error  Trailing whitespace                                       no-trailing-whitespace
  173:1    error  Trailing whitespace                                       no-trailing-whitespace
  174:1    error  Trailing whitespace                                       no-trailing-whitespace
  178:1    error  Trailing whitespace                                       no-trailing-whitespace
  187:275  error  <button> is missing required "type" attribute             no-implicit-button-type
  187:275  error  <button> must have accessible text                        text-content
  196:37   error  "type" attribute is unnecessary for javascript resources  script-type

/home/maelle/Documents/cynkra/quartotest/_site/posts/welcome/index.html
   87:6   error  Attribute "target" has invalid value ""                   attribute-allowed-values
   89:8   error  Trailing whitespace                                       no-trailing-whitespace
   91:6   error  Attribute "target" has invalid value ""                   attribute-allowed-values
   91:6   error  Anchor link must have a text describing its purpose       wcag/h30
   92:5   error  Trailing whitespace                                       no-trailing-whitespace
   94:8   error  Trailing whitespace                                       no-trailing-whitespace
   96:6   error  Attribute "target" has invalid value ""                   attribute-allowed-values
   96:6   error  Anchor link must have a text describing its purpose       wcag/h30
   97:5   error  Trailing whitespace                                       no-trailing-whitespace
   99:8   error  Trailing whitespace                                       no-trailing-whitespace
  117:1   error  Trailing whitespace                                       no-trailing-whitespace
  118:1   error  Trailing whitespace                                       no-trailing-whitespace
  127:1   error  Trailing whitespace                                       no-trailing-whitespace
  134:1   error  Trailing whitespace                                       no-trailing-whitespace
  135:1   error  Trailing whitespace                                       no-trailing-whitespace
  137:1   error  Trailing whitespace                                       no-trailing-whitespace
  138:1   error  Trailing whitespace                                       no-trailing-whitespace
  142:1   error  Trailing whitespace                                       no-trailing-whitespace
  150:5   error  <img> is missing required "alt" attribute                 wcag/h37
  156:37  error  "type" attribute is unnecessary for javascript resources  script-type

✖ 85 problems (85 errors, 0 warnings)

More information:
  https://html-validate.org/rules/attribute-allowed-values.html
  https://html-validate.org/rules/no-trailing-whitespace.html
  https://html-validate.org/rules/wcag/h30.html
  https://html-validate.org/rules/wcag/h37.html
  https://html-validate.org/rules/no-inline-style.html
  https://html-validate.org/rules/script-type.html
  https://html-validate.org/rules/element-permitted-content.html
  https://html-validate.org/rules/void-style.html
  https://html-validate.org/rules/no-implicit-button-type.html
  https://html-validate.org/rules/text-content.html

Thank you!

[maelle]

Related: #3831

[mcanouil]

Thanks!
Could you repost on the issue you just linked?

[maelle]

@mcanouil done!

[maelle]

I get more errors if I use different dark/light theme (I get it can be viewed as a false positive as in practice only one of the two elements with the same ID will be used 😅)

 error  Duplicate ID "quarto-text-highlighting-styles"            no-dup-id
error  Duplicate ID "quarto-bootstrap"                           no-dup-id

[cscheid]

112:11 error Inline style is not allowed no-inline-style

I'm not sure this validator is very good: https://developer.mozilla.org/en-US/docs/Web/HTML/Element/style

[krlmlr]

Thanks! The validator seems actively maintained, and the link you shared reads further below:

The <style> element must be included inside the of the document. In general, it is better to put your styles in external stylesheets and apply them using elements.

This means that the validation rule is actually a suggestion, and can be turned off.

Can you please expand on why this is an indicator of the validator's quality? Can you recommend a better alternative?

[cscheid]

This means that the validation rule is actually a suggestion, and can be turned off.

Defaults matter, especially when different people report bugs with different default opinions coming from different validators.

There's an official w3c validator. I'm reluctant to say "Quarto will always produce perfectly valid HTML under the validators", but we do make an effort not to emit broken HTML according to that one, and we consider it a bug to not be able to parse tables that it validates correctly.

[krlmlr]

Nice, thanks!

Seems there's an Ubuntu/Debian version: https://github.com/netresearch/docker-validator-w3c/blob/master/Dockerfile#L13C5-L13C25

[cscheid]

It also has an API.