Add an inspection for undefined attributes

Rationale

Add an inspection for undefined attributes. This will improve the quality of documentation by, e.g.:

• identifying typos in attributes,
• accidentally using attributes where the curly brace should be escaped, e.g. in API call /users/{id}.

Having an inspection allows to configure the severity level, and to ignore specific instances by annotations.

The feature complements the ability to generally treat warnings as errors (see https://github.com/asciidoctor/asciidoctor-intellij-plugin/issues/857) by handling this well-defined case explicitly. See also the related discussion on Zulip.

Proposed behavior

• Use an undefined attribute in an AsciiDoc file.
• The plugin currently does not detect this.
• With the new inspection, there will be an entry in the list of problems for the corresponding file/line in the source.

[mojavelinux]

I use a partial in the ROOT module to define component-wide shared attributes and settings. You are right, the playbook may be a better place to do this.

Also consider that you can set attributes in antora.yml. That’s usually better than putting them in the playbook because they stay with the content. It’s the closest thing to a shared attributes file.

[ahus1]

When I’m writing this, release 0.35.4 is the current release. This rule is enabled by default, and so far I haven’t heard complaints about too many false positive warnings, for example when people use internal, pre-defined attributes.

I now close this issue.