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Lit DevTools

All versions since 0.23.0

All versions

0.23.0

The Components panel now shows what a component keeps to itself: its #private fields, readable and editable under the dev server, and the custom states, form value and validity of a form-associated element. The tree no longer has a Live switch; it stays live, holds still under the pointer and paces itself on busy pages. The panel’s rows, colours and fields got easier to read and hit, and the docs run the examples live beside the panel. Nothing needs action to upgrade.

Added

  • The Components panel shows and edits a component’s #private fields. Under the dev server, a Private section after State lists each native #private field as #name with its live value. A string, number or boolean has the same edit button as a property, kept as an override you can switch off, pin across reloads or remove, and the component re-renders with it. Agents read them through lit_component-details and set them through lit_set-prop. They come from the hmr.privateFields rewrite, so turning that off hides them.
  • The Components details show custom states and form values. An element that calls attachInternals() gets an Internals section with the states :state() matches, the value it last passed to setFormValue(), and its validity and validation message, kept live as they change. Agents read the same through lit_component-details.
  • Try the examples live in the docs. The Demos page opens flame, Web Awesome, Fernhouse, CSS, Tailwind, Forms and the tutorial’s app running in your browser with the DevTools panel under them, with nothing to boot and a zoom control; StackBlitz is one switch away for editing their files.

Changed

  • The live component tree keeps up with busy pages without slowing them. A page that changes constantly still gets a fresh tree every so often, rebuilds space themselves out by how long the last one took, and none run while the Timeline is recording.
  • The Components toolbar sets Pick apart from the switches. Pick is a crosshair beside the tag filter, and Flash and Anatomy, which stay on until you turn them off, sit together as one group at the right.
  • Tree and list rows are easier to hit. Rows in the component tree and the timeline list are 24px tall, the minimum target size WCAG asks for.
  • Element references and functions no longer share a colour. Tags and element refs are teal, functions stay blue, in both colour schemes.

Fixed

  • A link to a component opens its details even before the page is ready. Opening the panel on #tab=components&component=N before the page connected, or before its components defined, no longer shows “This element is no longer in the page” for an element that is there.
  • Settings’ About shows the page’s Lit even when opened first. A panel opened on the Settings tab before the page connected said “lit: not detected” until the tab was reopened; it now lists the page’s Lit packages as soon as the page connects.
  • Disabled fields no longer pass for empty ones. A disabled select or input is dimmed, filled and dash-outlined with a not-allowed cursor, and the tags of a multi-select read as live rather than greyed out.
  • The Lit tab’s footer buttons work in a narrow panel. A long notice no longer covers its own “Don’t show again” or “Not now”: the text is cut short instead, and shows whole when you hover it.

Removed

  • The Components tab’s Live toggle is gone; the tree is always live. It stays still while the pointer is over it, so the row under the pointer does not move, and catches up when the pointer leaves. A tree paused in an earlier version comes back live.

0.24.0 Latest

Your components now describe themselves: the plugin writes a Custom Elements Manifest from your sources, in the build, the dev server or from lit-devtools manifest, and the details pane reads more of what a component declares, dispatches and inherits. A language server brings the same knowledge to your editor, and @oddsquad/lit-devtools installs the plugin, the server and its Oxlint rules as one package. Nothing needs action to upgrade.

Added

  • Generate a Custom Elements Manifest from your components. Set manifest: true and vite build emits custom-elements.json beside the bundle, the dev server serves it live, and write keeps a copy in the project for editors and Storybook, with no separate analyzer to set up.
  • lit-devtools manifest writes a Custom Elements Manifest from the command line. It reads every script under src and writes custom-elements.json, ready for a prepublishOnly script or CI. It uses your Vite config’s aliases, and in a project without one resolves imports the way Node and TypeScript do, tsconfig.json paths included.
  • A language server for Lit components. @oddsquad/lit-language-server completes your components’ tags, attributes, properties and events in templates, shows their docs on hover, types event handlers and reports one that doesn’t fit its event, in Zed or any LSP editor. Configure it with litPlugin({languageServer}).
  • Install everything as @oddsquad/lit-devtools. One package brings the plugin (@oddsquad/lit-devtools/vite, /astro), the language server and the Oxlint rules (/oxlint); the separate packages stay for a project that wants one part.
  • Components inherit docs from the library elements they extend. A component built on, say, Web Awesome’s badge now lists the badge’s properties, slots and events in the details pane, read from Web Awesome’s own Custom Elements Manifest.
  • Components show the events they dispatch, even without @fires. An event your class sends with this.dispatchEvent(new CustomEvent('pick')) now appears under Events in the details pane, typed CustomEvent.
  • The manifest says what each event carries. An event dispatched as new CustomEvent('add-to-cart', {detail: {id: this.productId}}) is listed as CustomEvent<{id: string}>, also when a @fires tag documents it without a type.
  • Component docs read @attr, @prop, @default and @tag. JSDoc written for the Custom Elements Manifest analyzer now shows in the details pane: attributes and properties the code doesn’t declare, defaults it doesn’t initialize, and the tag of a class registered elsewhere.
  • Components show the defaults their constructor sets. A this.variant = 'neutral' in the constructor now shows as the default of variant in the details pane, even when the property comes from a library base class such as Web Awesome’s.
  • Vanilla custom elements show their observed attributes. An element that lists static observedAttributes = ['mode'] now shows mode under Attributes in the details pane, described by an @attr tag if it has one.