Analysis: Map state down to the nodes that read it

[marcoroth]

This pull request takes dependency tracking from the file level to the node level.

affectedTemplates answers which templates a change invalidates. That is enough to decide what to re-render, but not enough to decide what to re-render within a template. dependencyIndex answers the finer question:

dependencyIndex(Herb, "app/views/posts/show.html.erb", source)
// {
//   "@post": [
//     { kind: "text_content", expression: "@post.title", location: "1:9",  nodePath: [0, 1, 1] },
//     { kind: "text_content", expression: "@post.body",  location: "1:35", nodePath: [0, 2, 1] },
//   ],
// }

Each entry records what kind of node reads the state, the expression that reads it, where it is, and a path of child indices leading back to it.

text_content for an ERB tag in the body, attribute_value for one inside an attribute, which also records which attribute:

<div class="<%= @active ? "on" : "off" %>">

render for a call that passes state to another template, and conditional for an if, unless or case. A conditional counts when anything inside it reads the state, not just its own condition, because the whole branch is what gets re-rendered:

<div><% if @admin %><%= @post.name %><% end %></div>

@admin is read by the condition, and @post by the body, so both map to the conditional, and @post maps to the inner tag as well.

[github-actions]

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_{🌱 Grown from commit 6580105}

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[pkg-pr-new]

npx https://pkg.pr.new/@herb-tools/formatter@2189

npx https://pkg.pr.new/@herb-tools/language-server@2189

npx https://pkg.pr.new/@herb-tools/linter@2189

commit: 6580105