Google does not correctly merge microdata and json+ld in the same page using same URI id

Question

I have a product page with \"microdata\" and \"json+ld\" codes. Both of the codes refers to the same @id URI object (http://www.example.org/product#this) so I would expect t

Answer 1

My guess would be that Google’s Structured Data Testing Tool doesn’t support this for different syntaxes, as it seems to work if using the same syntax. But as they still display the URIs correctly (http://www.example.org/product#this in both cases), you could argue that it’s just the tool’s interface that doesn’t merge them.
However, as far as I know Google does not document to support these subject URIs anyway (but this doesn’t necessarily mean that they don’t support it), so it might not matter for them.

Your example works fine if using http://linter.structured-data.org/: it creates one item with both brands and both offers.

Answer 2

While technically it is feasible to merge data coming from two different syntaxes (read microdata and json-ld) and the Structured Data Linter confirms so, Google does not support it, which means properties won't be merged (and won't satisfy Rich Snippets' requirements).

We have a final confirmation by several actors in the SEO World, including Dan Brickley and Jarno van Driel.

in general you can use both syntaxes side by side, but you won't get the fine-grained merging of triples by ID that a pure RDF application might expect (Dan Brickley on Twitter, Jan 14th, 2020, bold mine)

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I think @danbri already was pretty clear. Highly doubt you'll get a different answer from other Googlers. (Jarno van Driel on Twitter, Jan 14th, 2020)

The proposed solution so far is to parse the microdata and publish it as JSON-LD.