Engine: Report template values as payload that names where they belong

[marcoroth]

This pull request turns what DynamicsCompiler produces from a bare Hash of indices into a payload that says which template, version and rendering the values came from, so a client can join them to the markers on the page.

{ template: "app/views/posts/index.html.erb", version: "aaaaaaaa", occurrence: 0, slots: { 0 => "Marco" } }

An index is a position in one template's numbering and means something else in the next, so a bare Hash of them cannot be joined to anything. Carrying the identifier and version SlotVisitor gave the markers lets a client tell the two were compiled together, and that a version no longer matching means the indices are not to be trusted.

That shape is also what a partial needs. <%= render "posts/card" %> evaluates to the partial's own values, and coercing them to a string flattened a whole payload into the markup it was meant to replace. A render keeps its value as it is, so a partial nests as a payload of its own, as deeply as the template does.

A template on the page more than once has one region per rendering, and counting them down the document holds only while render order and document order agree, which content_for and provide break by design. The region marker carries the number now, counted as the page renders, so the client reads the server's own answer instead of inferring one. The counter hangs off the view, which in Rails is the request, so every response starts at zero and a partial shares the count with the template that rendered it.

The round trip is what proves the two halves agree. It renders a template twice, hands the second rendering's values to the first rendering's markers, and asserts the page is byte for byte what the server would have sent. Nothing else says the numbering, the row keys, the attribute names and the collapsed conditional are all right at once, and each of them is wrong in a way that leaves the page looking plausible. Swapping two indices in the fixture fails the round trip, which is the check that the check is worth having.

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☁️ Nx Cloud last updated this comment at 2026-08-18 03:13:19 UTC

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commit: cd58803