[ui/agg_response/tabify] -> TypeScript & Jest & Shim

[lukeelmers]

In the legacy world, we had multiple response handlers. Their job is basically to take the output from a request handler and convert the data into a shape that is useful for a visualization. Visualization developers could register their own request/response handlers, and specify which ones the vis should use.

With the move to an expressions-backed visualizations infrastructure, our internal usage of request/response handlers has been greatly simplified: everything uses the esaggs function, which comes with the courier (default) request handler baked in, and the tabify (default) response handler. Vis developers can still register custom request/response handlers, but there is no need for us to provide these out of the box in kibana anymore.

tabify (like courier) is just a legacy name for a response handler that transforms a response into tabular data. Something along these lines:

const tabified = {
  columns: [
    { id: 'name', name: 'Name' },
    { id: 'age', name: 'Age' }
  ],
  rows: [
    { name: 'Bob', age: 80 },
    { name: 'Sue', age: 50 },
    { name: 'Joe', age: 20 },
  ],
};

Steps to migrate src/legacy/ui/public/agg_response/tabify:

• convert remaining files to TS
• update old prototype based classes to use ES6 class syntax
• convert tests to Jest & TS
• relocate to data shim plugin src/legacy/core_plugins/data/public/search/aggs/agg_response
  • we only need to move the tabify portion, the rest can stay behind
• re-export contract from ui/agg_response/tabify (we can update imports later once it moves to NP along with the rest of agg_types)

[elasticmachine]

Pinging @elastic/kibana-app-arch (Team:AppArch)

[lizozom]

@lukeelmers @alexwizp Would you mind adding, for the record, a short description to this issue of what tabify is?

[lukeelmers]

@lizozom Sure thing, just updated the description -- let me know if this helps. Most people know what tabified data looks like, but perhaps just don't know that the name "tabify" was attached to it :)