Mapping a Wikimedia project URL to the corresponding Wikidata entity id

Question

I am looking for the best method to map a given Wikipedia/Wikisource/Wikibooks/... URL to the corresponding Wikidata entity id (similar to this question but via API calls instead of a full data dump). The URL can be in many forms, e.g.

• http://en.wikipedia.org/w/index.php?title=Element_18 is redirected (HTTP) to
• https://en.wikipedia.org/w/index.php?title=Element_18 is redirected (HTTP) to
• https://en.wikipedia.org/wiki/Element_18 is redirected (JavaScript/HTML) to
• https://en.wikipedia.org/wiki/Argon

Methods I tried so far:

• SPARQL query service - requires the URL to have a canonical form and seems to not know about redirects
• MediaWiki API at Wikidata, e.g. https://www.wikidata.org/w/api.php?action=wbgetentities&sites=enwiki&titles=Argon&languages=en&props=labels|descriptions&format=jsonfm requires to securely split URL into title and "site" key
• MediaWiki API at project site, e.g. https://en.wikipedia.org/w/api.php?action=query&prop=pageprops&titles=Argon requires to securely split URL into project and title
• Info page, e.g. https://en.wikipedia.org/w/index.php?title=Argon&action=info requires to modify URL and to parse resulting HTML

The most reliable (but nasty) method seems to enulate a browser to do a HTTP request to the URL, follow all redirects and parse the resulting HTML page to get the Wikidata ID.

Answer 1

As a general rule, Wikidata won't know about redirects - they're not part of the model there. They only record the canonical page title (leaving aside a few rare cases where the Wikidata sitelink is a redirect, which is deprecated but does occasionally happen). So any 'de-redirecting' will need to be done on the Wikipedia side.

If you use the local API with &redirects, you can get the Wikidata entity ID in a single query whether or not there's a redirect -

https://en.wikipedia.org/w/api.php?action=query&prop=pageprops&titles=Element_18&redirects

https://en.wikipedia.org/w/api.php?action=query&prop=pageprops&titles=Argon&redirects

both contain "wikibase_item": "Q696"

You'll still have to process the URL a bit to get the API call, though.