[gmpassos]

The first UIRoot registers every component markup can create by tag (<ui-button>, <ui-document>, <ui-dialog>, <ui-svg>...). Whatever is registered is compiled in, so every app ships all of them; <ui-document> alone brings in the markdown package and its HTML-entity tables.

• New UIRoot(..., registerComponents: ...): the components to register. Without it all of them are, as before (new static UIRoot.registerAllComponents).
• An app that writes none of those tags passes () {}; one that uses a few passes those (UIDialog.register). Every UIRoot of the app must pass it.
• UIConsole.get() still runs unconditionally: it sets up logging, it is not a tag component.

Why a nullable parameter, not an overridable method or a default value: dart2js keeps a method that every instantiated subclass overrides, and keeps a default-value tear-off too; checked in a toy program and in the app. It does drop the registerComponents ?? registerAllComponents fallback once inference sees every call site passes one.

Measured in UnyCities (four roots, its only component a dialog created in code): main.dart.js went from 484,964 to 398,322 bytes gzipped, 18% smaller (1,608,618 to 1,335,230 raw). Its 500 browser tests pass on dart2js and dart2wasm.

Tests:

• bones_ui_root_register_components_test.dart (browser): a root registering only UIDialog has ui-dialog and none of the other built-in tags; the registration runs once, before the first render. In rendered markup, a registered <ui-dialog> becomes its component, an unregistered <ui-document> stays a plain element (its text as written, no <h1>), and a dialog created in code needs no registration.

• bones_ui_root_register_all_components_test.dart (browser): without registerComponents every tag component is registered, and <ui-document> renders its markdown. A separate file because registration happens once per app.

• register_components_tree_shaking_test.dart (VM, integration): compiles four minimal apps in test/register_components/ with dart compile js -O2 and checks what is in the output:

  app	gzipped	markdown	ui-document, ui-svg...
  registers all (default)	309,510	in	in
  registers none	218,698	out	out
  registers UIDialog only	221,439	out	only ui-dialog
  one root () {}, one default	309,722	in	in

  The last row is the documented caveat: every UIRoot must pass it.

Full suite passes locally: VM (34), Chrome dart2wasm (551) and dart2js (551); format, analyze (--fatal-infos --fatal-warnings) and dependency_validator are clean.

🤖 Generated with Claude Code

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 92.89%. Comparing base (5629f1c) to head (e2d756b).

Additional details and impacted files

@@           Coverage Diff           @@
##           master      #59   +/-   ##
=======================================
  Coverage   92.89%   92.89%           
=======================================
  Files          34       34           
  Lines        9420     9422    +2     
=======================================
+ Hits         8751     8753    +2     
  Misses        669      669           

Flag	Coverage Δ
unittests	92.89% <100.00%> (+<0.01%)	⬆️

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