Check a document for conformance¶

The WHATWG parser recovers from bad markup and records its ParseError\s, but many authoring mistakes leave a perfectly parseable tree: an image with no alt text, an obsolete <font>, a duplicate id, an undefined ARIA role. check_html() parses a markup string and runs the HTML5 authoring rules over it, returning a ConformanceReport.

Read the verdict¶

A report is truthy when the document is valid – when nothing it found is an error. Warnings and info notes are advice and never change the verdict. Each ConformanceMessage carries a stable code, a severity, a description, and the source line and column of the node that triggered it:

from turbohtml.conformance import check_html

report = check_html(
    "<html><head></head><body><img src=logo.png><nav role=navigation><a href=/>Home</a></nav></body></html>"
)
print(report.valid)
for message in report.messages:
    print(message.severity, message.code, "--", message.message)

False
error img-missing-alt -- img element has no alt attribute
warning aria-redundant-role -- role navigation duplicates the element's implicit role
warning missing-lang -- html element has no lang attribute
error missing-title -- document has no non-empty title element

Split by severity¶

The report’s errors, warnings, and infos views partition the messages, so a gate can fail the build on errors while only logging the rest:

if not report:
    print("errors:", [message.code for message in report.errors])
    print("advice:", [message.code for message in report.warnings + report.infos])

errors: ['img-missing-alt', 'missing-title']
advice: ['aria-redundant-role', 'missing-lang']

Check an already-parsed tree¶

When you have already parsed the document, pass it to check() to skip a reparse. Handing check() a subtree runs only the per-element rules – the document-level title and language rules apply to a whole Document:

from turbohtml import parse
from turbohtml.conformance import check

document = parse("<html lang=en><head><title>Docs</title></head><body><h1>Hi</h1></body></html>")
print(check(document).valid)

fragment = parse("<section><img src=x></section>").find("section")
print([message.code for message in check(fragment).messages])

True
['section-no-heading', 'img-missing-alt']