preact/debug/src/component-stack.js

import { options, Fragment } from 'preact';

/**
 * Get human readable name of the component/dom node
 * @param {import('./internal').VNode} vnode
 * @param {import('./internal').VNode} vnode
 * @returns {string}
 */
export function getDisplayName(vnode) {
	if (vnode.type === Fragment) {
		return 'Fragment';
	} else if (typeof vnode.type == 'function') {
		return vnode.type.displayName || vnode.type.name;
	} else if (typeof vnode.type == 'string') {
		return vnode.type;
	}

	return '#text';
}

/**
 * Used to keep track of the currently rendered `vnode` and print it
 * in debug messages.
 */
let renderStack = [];

/**
 * Keep track of the current owners. An owner describes a component
 * which was responsible to render a specific `vnode`. This exclude
 * children that are passed via `props.children`, because they belong
 * to the parent owner.
 *
 * ```jsx
 * const Foo = props => <div>{props.children}</div> // div's owner is Foo
 * const Bar = props => {
 *   return (
 *     <Foo><span /></Foo> // Foo's owner is Bar, span's owner is Bar
 *   )
 * }
 * ```
 *
 * Note: A `vnode` may be hoisted to the root scope due to compiler
 * optimiztions. In these cases the `_owner` will be different.
 */
let ownerStack = [];

/**
 * Get the currently rendered `vnode`
 * @returns {import('./internal').VNode | null}
 */
export function getCurrentVNode() {
	return renderStack.length > 0 ? renderStack[renderStack.length - 1] : null;
}

/**
 * If the user doesn't have `@babel/plugin-transform-react-jsx-source`
 * somewhere in his tool chain we can't print the filename and source
 * location of a component. In that case we just omit that, but we'll
 * print a helpful message to the console, notifying the user of it.
 */
let hasBabelPlugin = false;

/**
 * Check if a `vnode` is a possible owner.
 * @param {import('./internal').VNode} vnode
 */
function isPossibleOwner(vnode) {
	return typeof vnode.type == 'function' && vnode.type != Fragment;
}

/**
 * Return the component stack that was captured up to this point.
 * @param {import('./internal').VNode} vnode
 * @returns {string}
 */
export function getOwnerStack(vnode) {
	const stack = [vnode];
	let next = vnode;
	while (next._owner != null) {
		stack.push(next._owner);
		next = next._owner;
	}

	return stack.reduce((acc, owner) => {
		acc += `  in ${getDisplayName(owner)}`;

		const source = owner.__source;
		if (source) {
			acc += ` (at ${source.fileName}:${source.lineNumber})`;
		} else if (!hasBabelPlugin) {
			hasBabelPlugin = true;
			console.warn(
				'Add @babel/plugin-transform-react-jsx-source to get a more detailed component stack. Note that you should not add it to production builds of your App for bundle size reasons.'
			);
		}

		return (acc += '\n');
	}, '');
}

/**
 * Setup code to capture the component trace while rendering. Note that
 * we cannot simply traverse `vnode._parent` upwards, because we have some
 * debug messages for `this.setState` where the `vnode` is `undefined`.
 */
export function setupComponentStack() {
	let oldDiff = options._diff;
	let oldDiffed = options.diffed;
	let oldRoot = options._root;
	let oldVNode = options.vnode;
	let oldRender = options._render;

	options.diffed = vnode => {
		if (isPossibleOwner(vnode)) {
			ownerStack.pop();
		}
		renderStack.pop();
		if (oldDiffed) oldDiffed(vnode);
	};

	options._diff = vnode => {
		if (isPossibleOwner(vnode)) {
			renderStack.push(vnode);
		}
		if (oldDiff) oldDiff(vnode);
	};

	options._root = (vnode, parent) => {
		ownerStack = [];
		if (oldRoot) oldRoot(vnode, parent);
	};

	options.vnode = vnode => {
		vnode._owner =
			ownerStack.length > 0 ? ownerStack[ownerStack.length - 1] : null;
		if (oldVNode) oldVNode(vnode);
	};

	options._render = vnode => {
		if (isPossibleOwner(vnode)) {
			ownerStack.push(vnode);
		}

		if (oldRender) oldRender(vnode);
	};
}