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node_modules/@sveltejs/vite-plugin-svelte/src/handle-hot-update.js

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+import { log, logCompilerWarnings } from './utils/log.js';
+import { toRollupError } from './utils/error.js';
+
+/**
+ * Vite-specific HMR handling
+ *
+ * @param {Function} compileSvelte
+ * @param {import('vite').HmrContext} ctx
+ * @param {import('./types/id.d.ts').SvelteRequest} svelteRequest
+ * @param {import('./utils/vite-plugin-svelte-cache.js').VitePluginSvelteCache} cache
+ * @param {import('./types/options.d.ts').ResolvedOptions} options
+ * @returns {Promise<import('vite').ModuleNode[] | void>}
+ */
+export async function handleHotUpdate(compileSvelte, ctx, svelteRequest, cache, options) {
+	if (!cache.has(svelteRequest)) {
+		// file hasn't been requested yet (e.g. async component)
+		log.debug(
+			`handleHotUpdate called before initial transform for ${svelteRequest.id}`,
+			undefined,
+			'hmr'
+		);
+		return;
+	}
+	const { read, server, modules } = ctx;
+
+	const cachedJS = cache.getJS(svelteRequest);
+	const cachedCss = cache.getCSS(svelteRequest);
+
+	const content = await read();
+	/** @type {import('./types/compile.d.ts').CompileData} */
+	let compileData;
+	try {
+		compileData = await compileSvelte(svelteRequest, content, options);
+		cache.update(compileData);
+	} catch (e) {
+		cache.setError(svelteRequest, e);
+		throw toRollupError(e, options);
+	}
+
+	const affectedModules = [...modules];
+
+	const cssIdx = modules.findIndex((m) => m.id === svelteRequest.cssId);
+	if (cssIdx > -1) {
+		const cssUpdated = cssChanged(cachedCss, compileData.compiled.css);
+		if (!cssUpdated) {
+			log.debug(`skipping unchanged css for ${svelteRequest.cssId}`, undefined, 'hmr');
+			affectedModules.splice(cssIdx, 1);
+		}
+	}
+	const jsIdx = modules.findIndex((m) => m.id === svelteRequest.id);
+	if (jsIdx > -1) {
+		const jsUpdated = jsChanged(cachedJS, compileData.compiled.js, svelteRequest.filename);
+		if (!jsUpdated) {
+			log.debug(`skipping unchanged js for ${svelteRequest.id}`, undefined, 'hmr');
+			affectedModules.splice(jsIdx, 1);
+			// transform won't be called, log warnings here
+			logCompilerWarnings(svelteRequest, compileData.compiled.warnings, options);
+		}
+	}
+
+	// TODO is this enough? see also: https://github.com/vitejs/vite/issues/2274
+	const ssrModulesToInvalidate = affectedModules.filter((m) => !!m.ssrTransformResult);
+	if (ssrModulesToInvalidate.length > 0) {
+		log.debug(
+			`invalidating modules ${ssrModulesToInvalidate.map((m) => m.id).join(', ')}`,
+			undefined,
+			'hmr'
+		);
+		ssrModulesToInvalidate.forEach((moduleNode) => server.moduleGraph.invalidateModule(moduleNode));
+	}
+	if (affectedModules.length > 0) {
+		log.debug(
+			`handleHotUpdate for ${svelteRequest.id} result: ${affectedModules
+				.map((m) => m.id)
+				.join(', ')}`,
+			undefined,
+			'hmr'
+		);
+	}
+	return affectedModules;
+}
+
+/**
+ * @param {import('./types/compile.d.ts').Code | null} [prev]
+ * @param {import('./types/compile.d.ts').Code | null} [next]
+ * @returns {boolean}
+ */
+function cssChanged(prev, next) {
+	return !isCodeEqual(prev?.code, next?.code);
+}
+
+/**
+ * @param {import('./types/compile.d.ts').Code | null} [prev]
+ * @param {import('./types/compile.d.ts').Code | null} [next]
+ * @param {string} [filename]
+ * @returns {boolean}
+ */
+function jsChanged(prev, next, filename) {
+	const prevJs = prev?.code;
+	const nextJs = next?.code;
+	const isStrictEqual = isCodeEqual(prevJs, nextJs);
+	if (isStrictEqual) {
+		return false;
+	}
+	const isLooseEqual = isCodeEqual(normalizeJsCode(prevJs), normalizeJsCode(nextJs));
+	if (!isStrictEqual && isLooseEqual) {
+		log.debug(
+			`ignoring compiler output js change for ${filename} as it is equal to previous output after normalization`,
+			undefined,
+			'hmr'
+		);
+	}
+	return !isLooseEqual;
+}
+
+/**
+ * @param {string} [prev]
+ * @param {string} [next]
+ * @returns {boolean}
+ */
+function isCodeEqual(prev, next) {
+	if (!prev && !next) {
+		return true;
+	}
+	if ((!prev && next) || (prev && !next)) {
+		return false;
+	}
+	return prev === next;
+}
+
+/**
+ * remove code that only changes metadata and does not require a js update for the component to keep working
+ *
+ * 1) add_location() calls. These add location metadata to elements, only used by some dev tools
+ * 2) ... maybe more (or less) in the future
+ *
+ * @param {string} [code]
+ * @returns {string | undefined}
+ */
+function normalizeJsCode(code) {
+	if (!code) {
+		return code;
+	}
+	return code.replace(/\s*\badd_location\s*\([^)]*\)\s*;?/g, '');
+}