[6.x] Legacy bridge

[brianjhanson]

Lets a Craft 5-era control panel screen render inside the Inertia shell without its author changing anything, and ports the form controls those screens rely on to web components.

A plugin that hasn't been updated for Craft 6 still returns asCpScreen() responses, calls renderTemplate(), and extends _layouts/cp. All three now arrive at BridgedScreen as server-rendered strings for the shell's slots, so the screens draw correctly instead of losing their tabs, assets and JS.

Screen bridge

• LegacyScreenFragments collects a legacy screen's fragments; BridgedScreen wraps them for cp/Screen.vue, which draws them into the shell's slots. RenderBridgedScreen middleware and _layouts/cp-fragments.twig cover the template and renderTemplate() routes into it.
• A bridged screen is always a hard visit. Legacy JS needs jQuery, Garnish and cp.js loaded in source order before anything that uses them, which a client-side visit can't offer, so the rule is total rather than partial.
• LegacyReadyShim holds ready-JS until the markup is mounted — Vue mounts a bridged screen after the document parses, so DOMContentLoaded has already fired. HtmlStack::deferInlineJs() wraps body-end inline JS to match.
• PageLifecycle no longer drops assets for a position with no placeholder in the output; they go back on the stack instead.
• Legacy admin tables render through LegacyAdminTable.vue.

Element index

• A screen that is just {% extends "_layouts/elementindex" %} gets the new Vue index. The layout declares it, since it's the one place that knows the element type; a child that replaces the content block opts back out via a sentinel.
• Its sources render into the secondary nav, with a Customize Sources item in an action menu at the foot of the subnav, matching Craft 5's sidebar. ContentIndexViewModel::sourceNavItems() builds them.
• Navigation::sourceSubnav() is now public, so a plugin building its own nav section can hang an element type's sources off it the way the core sections do.

Tabs

• LegacyTabsShim pairs a legacy screen's panes to <craft-tabs>, so a bridged screen gets the same tab component as the rest of the control panel. It returns null whenever it isn't certain, and the legacy strip covers that.
• <craft-tabs> mirrors the selected tab in the location hash and selects from it on load, enabled by default. Saving keeps the current hash.
• The tab strip is guttered with the content below it.

Form controls

• Autosuggest and selectize inputs render as <craft-combobox> rather than Vue 2 instances, through craft.cp.autosuggest()/craft.cp.selectize() and FormFields::autosuggestFromConfig()/selectizeFromConfig(). Craft 5's variable shapes are still accepted.
• Field toggles drive from a combobox, resolving data.boolean so an environment variable that parses to a boolean still toggles.
• Indicator options moved onto fill, with appearance and icon color alongside.
• An editable table initializes once it's actually laid out, rather than on the next window resize.

Plugin API and Yii adapter

• getVersion() stays out of the Craft 6 plugin API. The adapter keeps it, reading and writing $version and logging a deprecation, so a plugin author gets told rather than guessing.
• A legacy plugin's stored settings load in full, and a legacy CP URL rule for a plugin's settings path is honoured.
• Legacy type-registration events are deferred until first read.
• Craft::getAlias() returns a non-alias value unchanged; the Craft 6 utility base class extends the legacy one.

Note for review

The last commit pulls two commits from #19665 — Cp::sharedModules(), resources/js/vue.ts and resources/js/elements.ts — which publish the control panel's Vue runtime and element index to plugin bundles through an import map. A plugin that externalizes those specifiers (Commerce does) can't boot without them. They'll want dropping in favour of #19665 whenever that lands.

Testing

Exercised against Commerce and a Craft 5-era plugin on a 6.x install: plugin settings screens with tabs and editable tables, autosuggest and selectize fields, and a bridged product index with its sources in the subnav.

[github-actions]

📚 Storybook previews

@craftcms/ui — open Storybook

Changed components:

• Components/Tabs
• Components/Tabs
• Form Controls/Select Controls/Combobox
• Form Controls/Select Controls/Combobox

resources/js — open Storybook

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