WIP

packages/svelte/src/compiler/index.js

@@ -70,7 +70,7 @@ export function compileModule(source, options) {
 	const validated = validate_module_options(options, '');
 	state.reset(source, validated);
 
-	const analysis = analyze_module(parse_acorn(source, false), validated);
+	const analysis = analyze_module(source, validated);
 	return transform_module(analysis, source, validated);
 }
 

packages/svelte/src/compiler/phases/1-parse/acorn.js

@@ -5,14 +5,27 @@ import { tsPlugin } from '@sveltejs/acorn-typescript';
 
 const ParserWithTS = acorn.Parser.extend(tsPlugin());
 
+/**
+ * @typedef {Comment & {
+ *   start: number;
+ *   end: number;
+ * }} CommentWithLocation
+ */
+
 /**
  * @param {string} source
+ * @param {Comment[]} comments
  * @param {boolean} typescript
  * @param {boolean} [is_script]
  */
-export function parse(source, typescript, is_script) {
+export function parse(source, comments, typescript, is_script) {
 	const parser = typescript ? ParserWithTS : acorn.Parser;
-	const { onComment, add_comments } = get_comment_handlers(source);
+
+	const { onComment, add_comments } = get_comment_handlers(
+		source,
+		/** @type {CommentWithLocation[]} */ (comments)
+	);
+
 	// @ts-ignore
 	const parse_statement = parser.prototype.parseStatement;
 
@@ -53,13 +66,18 @@ export function parse(source, typescript, is_script) {
 
 /**
  * @param {string} source
+ * @param {Comment[]} comments
  * @param {boolean} typescript
  * @param {number} index
  * @returns {acorn.Expression & { leadingComments?: CommentWithLocation[]; trailingComments?: CommentWithLocation[]; }}
  */
-export function parse_expression_at(source, typescript, index) {
+export function parse_expression_at(source, comments, typescript, index) {
 	const parser = typescript ? ParserWithTS : acorn.Parser;
-	const { onComment, add_comments } = get_comment_handlers(source);
+
+	const { onComment, add_comments } = get_comment_handlers(
+		source,
+		/** @type {CommentWithLocation[]} */ (comments)
+	);
 
 	const ast = parser.parseExpressionAt(source, index, {
 		onComment,
@@ -78,18 +96,9 @@ export function parse_expression_at(source, typescript, index) {
  * to add them after the fact. They are needed in order to support `svelte-ignore` comments
  * in JS code and so that `prettier-plugin-svelte` doesn't remove all comments when formatting.
  * @param {string} source
+ * @param {CommentWithLocation[]} comments
  */
-function get_comment_handlers(source) {
-	/**
-	 * @typedef {Comment & {
-	 *   start: number;
-	 *   end: number;
-	 * }} CommentWithLocation
-	 */
-
-	/** @type {CommentWithLocation[]} */
-	const comments = [];
-
+function get_comment_handlers(source, comments) {
 	return {
 		/**
 		 * @param {boolean} block
@@ -97,7 +106,7 @@ function get_comment_handlers(source) {
 		 * @param {number} start
 		 * @param {number} end
 		 */
-		onComment: (block, value, start, end) => {
+		onComment: (block, value, start, end, start_loc, end_loc) => {
 			if (block && /\n/.test(value)) {
 				let a = start;
 				while (a > 0 && source[a - 1] !== '\n') a -= 1;
@@ -109,13 +118,21 @@ function get_comment_handlers(source) {
 				value = value.replace(new RegExp(`^${indentation}`, 'gm'), '');
 			}
 
-			comments.push({ type: block ? 'Block' : 'Line', value, start, end });
+			comments.push({
+				type: block ? 'Block' : 'Line',
+				value,
+				start,
+				end,
+				loc: { start: start_loc, end: end_loc }
+			});
 		},
 
 		/** @param {acorn.Node & { leadingComments?: CommentWithLocation[]; trailingComments?: CommentWithLocation[]; }} ast */
 		add_comments(ast) {
 			if (comments.length === 0) return;
 
+			comments = comments.slice();
+
 			walk(ast, null, {
 				_(node, { next, path }) {
 					let comment;

packages/svelte/src/compiler/phases/1-parse/index.js

@@ -1,4 +1,5 @@
 /** @import { AST } from '#compiler' */
+/** @import { Comment } from 'estree' */
 // @ts-expect-error acorn type definitions are borked in the release we use
 import { isIdentifierStart, isIdentifierChar } from 'acorn';
 import fragment from './state/fragment.js';
@@ -87,6 +88,7 @@ export class Parser {
 			type: 'Root',
 			fragment: create_fragment(),
 			options: null,
+			comments: [],
 			metadata: {
 				ts: this.ts
 			}

packages/svelte/src/compiler/phases/1-parse/read/context.js

@@ -59,7 +59,12 @@ export default function read_pattern(parser) {
 			space_with_newline.slice(0, first_space) + space_with_newline.slice(first_space + 1);
 
 		const expression = /** @type {any} */ (
-			parse_expression_at(`${space_with_newline}(${pattern_string} = 1)`, parser.ts, start - 1)
+			parse_expression_at(
+				`${space_with_newline}(${pattern_string} = 1)`,
+				parser.root.comments,
+				parser.ts,
+				start - 1
+			)
 		).left;
 
 		expression.typeAnnotation = read_type_annotation(parser);
@@ -96,13 +101,13 @@ function read_type_annotation(parser) {
 		// parameters as part of a sequence expression instead, and will then error on optional
 		// parameters (`?:`). Therefore replace that sequence with something that will not error.
 		parser.template.slice(parser.index).replace(/\?\s*:/g, ':');
-	let expression = parse_expression_at(template, parser.ts, a);
+	let expression = parse_expression_at(template, parser.root.comments, parser.ts, a);
 
 	// `foo: bar = baz` gets mangled — fix it
 	if (expression.type === 'AssignmentExpression') {
 		let b = expression.right.start;
 		while (template[b] !== '=') b -= 1;
-		expression = parse_expression_at(template.slice(0, b), parser.ts, a);
+		expression = parse_expression_at(template.slice(0, b), parser.root.comments, parser.ts, a);
 	}
 
 	// `array as item: string, index` becomes `string, index`, which is mistaken as a sequence expression - fix that

packages/svelte/src/compiler/phases/1-parse/read/expression.js

@@ -34,7 +34,12 @@ export function get_loose_identifier(parser, opening_token) {
  */
 export default function read_expression(parser, opening_token, disallow_loose) {
 	try {
-		const node = parse_expression_at(parser.template, parser.ts, parser.index);
+		const node = parse_expression_at(
+			parser.template,
+			parser.root.comments,
+			parser.ts,
+			parser.index
+		);
 
 		let num_parens = 0;
 

packages/svelte/src/compiler/phases/1-parse/read/script.js

@@ -34,7 +34,7 @@ export function read_script(parser, start, attributes) {
 	let ast;
 
 	try {
-		ast = acorn.parse(source, parser.ts, true);
+		ast = acorn.parse(source, parser.root.comments, parser.ts, true);
 	} catch (err) {
 		parser.acorn_error(err);
 	}

packages/svelte/src/compiler/phases/1-parse/state/tag.js

@@ -389,7 +389,12 @@ function open(parser) {
 
 		let function_expression = matched
 			? /** @type {ArrowFunctionExpression} */ (
-					parse_expression_at(prelude + `${params} => {}`, parser.ts, params_start)
+					parse_expression_at(
+						prelude + `${params} => {}`,
+						parser.root.comments,
+						parser.ts,
+						params_start
+					)
 				)
 			: { params: [] };
 

packages/svelte/src/compiler/phases/2-analyze/index.js

@@ -1,8 +1,9 @@
-/** @import { Expression, Node, Program } from 'estree' */
+/** @import { Comment, Expression, Node, Program } from 'estree' */
 /** @import { Binding, AST, ValidatedCompileOptions, ValidatedModuleCompileOptions } from '#compiler' */
 /** @import { AnalysisState, Visitors } from './types' */
 /** @import { Analysis, ComponentAnalysis, Js, ReactiveStatement, Template } from '../types' */
 import { walk } from 'zimmerframe';
+import { parse } from '../1-parse/acorn.js';
 import * as e from '../../errors.js';
 import * as w from '../../warnings.js';
 import { extract_identifiers } from '../../utils/ast.js';
@@ -231,11 +232,16 @@ function get_component_name(filename) {
 const RESERVED = ['$$props', '$$restProps', '$$slots'];
 
 /**
- * @param {Program} ast
+ * @param {string} source
  * @param {ValidatedModuleCompileOptions} options
  * @returns {Analysis}
  */
-export function analyze_module(ast, options) {
+export function analyze_module(source, options) {
+	/** @type {Comment[]} */
+	const comments = [];
+
+	const ast = parse(source, comments, false, false);
+
 	const { scope, scopes } = create_scopes(ast, new ScopeRoot(), false, null);
 
 	for (const [name, references] of scope.references) {
@@ -259,6 +265,7 @@ export function analyze_module(ast, options) {
 		runes: true,
 		immutable: true,
 		tracing: false,
+		comments,
 		classes: new Map()
 	};
 
@@ -429,6 +436,7 @@ export function analyze_component(root, source, options) {
 		module,
 		instance,
 		template,
+		comments: root.comments,
 		elements: [],
 		runes,
 		tracing: false,

packages/svelte/src/compiler/phases/3-transform/client/transform-client.js

@@ -362,6 +362,9 @@ export function client_component(analysis, options) {
 		.../** @type {ESTree.Statement[]} */ (template.body)
 	]);
 
+	// trick esrap into including comments
+	component_block.loc = instance.loc;
+
 	if (!analysis.runes) {
 		// Bind static exports to props so that people can access them with bind:x
 		for (const { name, alias } of analysis.exports) {

packages/svelte/src/compiler/phases/3-transform/index.js

@@ -36,7 +36,7 @@ export function transform_component(analysis, source, options) {
 	const js_source_name = get_source_name(options.filename, options.outputFilename, 'input.svelte');
 
 	// @ts-ignore TODO
-	const js = print(program, ts(), {
+	const js = print(program, ts({ comments: analysis.comments }), {
 		// include source content; makes it easier/more robust looking up the source map code
 		// (else esrap does return null for source and sourceMapContent which may trip up tooling)
 		sourceMapContent: source,
@@ -95,14 +95,20 @@ export function transform_module(analysis, source, options) {
 		];
 	}
 
-	return {
 	// @ts-expect-error
-		js: print(program, ts(), {
+	const js = print(program, ts({ comments: analysis.comments }), {
 		// include source content; makes it easier/more robust looking up the source map code
 		// (else esrap does return null for source and sourceMapContent which may trip up tooling)
 		sourceMapContent: source,
 		sourceMapSource: get_source_name(options.filename, undefined, 'input.svelte.js')
-		}),
+	});
+
+	// prepend comment
+	js.code = `/* ${basename} generated by Svelte v${VERSION} */\n${js.code}`;
+	js.map.mappings = ';' + js.map.mappings;
+
+	return {
+		js,
 		css: null,
 		metadata: {
 			runes: true

packages/svelte/src/compiler/phases/3-transform/server/transform-server.js

@@ -242,6 +242,9 @@ export function server_component(analysis, options) {
 		.../** @type {Statement[]} */ (template.body)
 	]);
 
+	// trick esrap into including comments
+	component_block.loc = instance.loc;
+
 	if (analysis.props_id) {
 		// need to be placed on first line of the component for hydration
 		component_block.body.unshift(

packages/svelte/src/compiler/phases/types.d.ts

@@ -2,6 +2,7 @@ import type { AST, Binding, StateField } from '#compiler';
 import type {
 	AssignmentExpression,
 	ClassBody,
+	Comment,
 	Identifier,
 	LabeledStatement,
 	Node,
@@ -37,6 +38,7 @@ export interface Analysis {
 	runes: boolean;
 	immutable: boolean;
 	tracing: boolean;
+	comments: Comment[];
 
 	classes: Map<ClassBody, Map<string, StateField>>;
 

packages/svelte/src/compiler/print/index.js

@@ -9,7 +9,8 @@ import ts from 'esrap/languages/ts';
 export function print(ast) {
 	// @ts-expect-error some bullshit
 	return esrap.print(ast, {
-		...ts(),
+		// @ts-expect-error some bullshit
+		...ts({ comments: ast.type === 'Root' ? ast.comments : [] }),
 		...visitors
 	});
 }
@@ -127,7 +128,13 @@ const visitors = {
 
 		context.write(`</${node.name}>`);
 	},
+	OnDirective(node, context) {
+		// TODO
+	},
 	TransitionDirective(node, context) {
 		// TODO
+	},
+	Comment(node, context) {
+		// TODO
 	}
 };

packages/svelte/src/compiler/types/template.d.ts

@@ -72,6 +72,8 @@ export namespace AST {
 		instance: Script | null;
 		/** The parsed `<script module>` element, if exists */
 		module: Script | null;
+		/** Comments found in <script> and {expressions} */
+		comments: import('estree').Comment[];
 		/** @internal */
 		metadata: {
 			/** Whether the component was parsed with typescript */

packages/svelte/tests/snapshot/samples/imports-in-modules/_expected/client/module.svelte.js

@@ -1,6 +1,5 @@
 /* module.svelte.js generated by Svelte VERSION */
 import * as $ from 'svelte/internal/client';
-
 import { random } from './export';
 
 export { random };

packages/svelte/tests/snapshot/samples/imports-in-modules/_expected/server/module.svelte.js

@@ -1,6 +1,5 @@
 /* module.svelte.js generated by Svelte VERSION */
 import * as $ from 'svelte/internal/server';
-
 import { random } from './export';
 
 export { random };