chore: modularize server code (#12596)

* start modularizing server code

* more

* more

* more

* more

* alphabetize

* start on JS visitors

* more

* more

* more

* more

* less

* more

* alphabetize

* lint

* combine into single visitors folder

* alphabetize

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

@@ -0,0 +1,11 @@
+/** @import { AssignmentExpression } from 'estree' */
+/** @import { Context } from '../types.js' */
+import { serialize_set_binding } from './shared/utils.js';
+
+/**
+ * @param {AssignmentExpression} node
+ * @param {Context} context
+ */
+export function AssignmentExpression(node, context) {
+	return serialize_set_binding(node, context, context.next);
+}

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

@@ -0,0 +1,33 @@
+/** @import { BlockStatement, Expression, Pattern } from 'estree' */
+/** @import { AwaitBlock } from '#compiler' */
+/** @import { ComponentContext } from '../types.js' */
+import * as b from '../../../../utils/builders.js';
+import { empty_comment } from './shared/utils.js';
+
+/**
+ * @param {AwaitBlock} node
+ * @param {ComponentContext} context
+ */
+export function AwaitBlock(node, context) {
+	context.state.template.push(
+		empty_comment,
+		b.stmt(
+			b.call(
+				'$.await',
+				/** @type {Expression} */ (context.visit(node.expression)),
+				b.thunk(
+					node.pending ? /** @type {BlockStatement} */ (context.visit(node.pending)) : b.block([])
+				),
+				b.arrow(
+					node.value ? [/** @type {Pattern} */ (context.visit(node.value))] : [],
+					node.then ? /** @type {BlockStatement} */ (context.visit(node.then)) : b.block([])
+				),
+				b.arrow(
+					node.error ? [/** @type {Pattern} */ (context.visit(node.error))] : [],
+					node.catch ? /** @type {BlockStatement} */ (context.visit(node.catch)) : b.block([])
+				)
+			)
+		),
+		empty_comment
+	);
+}

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

@@ -0,0 +1,44 @@
+/** @import { CallExpression, Expression } from 'estree' */
+/** @import { Context } from '../types.js' */
+import { get_rune } from '../../../scope.js';
+import * as b from '../../../../utils/builders.js';
+import { transform_inspect_rune } from '../../utils.js';
+
+/**
+ * @param {CallExpression} node
+ * @param {Context} context
+ */
+export function CallExpression(node, context) {
+	const rune = get_rune(node, context.state.scope);
+
+	if (rune === '$host') {
+		return b.id('undefined');
+	}
+
+	if (rune === '$effect.tracking') {
+		return b.literal(false);
+	}
+
+	if (rune === '$effect.root') {
+		// ignore $effect.root() calls, just return a noop which mimics the cleanup function
+		return b.arrow([], b.block([]));
+	}
+
+	if (rune === '$state.snapshot') {
+		return b.call('$.snapshot', /** @type {Expression} */ (context.visit(node.arguments[0])));
+	}
+
+	if (rune === '$state.is') {
+		return b.call(
+			'Object.is',
+			/** @type {Expression} */ (context.visit(node.arguments[0])),
+			/** @type {Expression} */ (context.visit(node.arguments[1]))
+		);
+	}
+
+	if (rune === '$inspect' || rune === '$inspect().with') {
+		return transform_inspect_rune(node, context);
+	}
+
+	context.next();
+}

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

@@ -0,0 +1,118 @@
+/** @import { ClassBody, Expression, MethodDefinition, PropertyDefinition } from 'estree' */
+/** @import { Context } from '../types.js' */
+/** @import { StateField } from '../../client/types.js' */
+import * as b from '../../../../utils/builders.js';
+import { get_rune } from '../../../scope.js';
+
+/**
+ * @param {ClassBody} node
+ * @param {Context} context
+ */
+export function ClassBodyRunes(node, context) {
+	/** @type {Map<string, StateField>} */
+	const public_derived = new Map();
+
+	/** @type {Map<string, StateField>} */
+	const private_derived = new Map();
+
+	/** @type {string[]} */
+	const private_ids = [];
+
+	for (const definition of node.body) {
+		if (
+			definition.type === 'PropertyDefinition' &&
+			(definition.key.type === 'Identifier' || definition.key.type === 'PrivateIdentifier')
+		) {
+			const { type, name } = definition.key;
+
+			const is_private = type === 'PrivateIdentifier';
+			if (is_private) private_ids.push(name);
+
+			if (definition.value?.type === 'CallExpression') {
+				const rune = get_rune(definition.value, context.state.scope);
+				if (rune === '$derived' || rune === '$derived.by') {
+					/** @type {StateField} */
+					const field = {
+						kind: rune === '$derived.by' ? 'derived_call' : 'derived',
+						// @ts-expect-error this is set in the next pass
+						id: is_private ? definition.key : null
+					};
+
+					if (is_private) {
+						private_derived.set(name, field);
+					} else {
+						public_derived.set(name, field);
+					}
+				}
+			}
+		}
+	}
+
+	// each `foo = $derived()` needs a backing `#foo` field
+	for (const [name, field] of public_derived) {
+		let deconflicted = name;
+		while (private_ids.includes(deconflicted)) {
+			deconflicted = '_' + deconflicted;
+		}
+
+		private_ids.push(deconflicted);
+		field.id = b.private_id(deconflicted);
+	}
+
+	/** @type {Array<MethodDefinition | PropertyDefinition>} */
+	const body = [];
+
+	const child_state = { ...context.state, private_derived };
+
+	// Replace parts of the class body
+	for (const definition of node.body) {
+		if (
+			definition.type === 'PropertyDefinition' &&
+			(definition.key.type === 'Identifier' || definition.key.type === 'PrivateIdentifier')
+		) {
+			const name = definition.key.name;
+
+			const is_private = definition.key.type === 'PrivateIdentifier';
+			const field = (is_private ? private_derived : public_derived).get(name);
+
+			if (definition.value?.type === 'CallExpression' && field !== undefined) {
+				const init = /** @type {Expression} **/ (
+					context.visit(definition.value.arguments[0], child_state)
+				);
+				const value =
+					field.kind === 'derived_call' ? b.call('$.once', init) : b.call('$.once', b.thunk(init));
+
+				if (is_private) {
+					body.push(b.prop_def(field.id, value));
+				} else {
+					// #foo;
+					const member = b.member(b.this, field.id);
+					body.push(b.prop_def(field.id, value));
+
+					// get foo() { return this.#foo; }
+					body.push(b.method('get', definition.key, [], [b.return(b.call(member))]));
+
+					if (
+						(field.kind === 'derived' || field.kind === 'derived_call') &&
+						context.state.options.dev
+					) {
+						body.push(
+							b.method(
+								'set',
+								definition.key,
+								[b.id('_')],
+								[b.throw_error(`Cannot update a derived property ('${name}')`)]
+							)
+						);
+					}
+				}
+
+				continue;
+			}
+		}
+
+		body.push(/** @type {MethodDefinition} **/ (context.visit(definition, child_state)));
+	}
+
+	return { ...node, body };
+}

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

@@ -0,0 +1,12 @@
+/** @import { Component } from '#compiler' */
+/** @import { ComponentContext } from '../types.js' */
+import * as b from '../../../../utils/builders.js';
+import { serialize_inline_component } from './shared/component.js';
+
+/**
+ * @param {Component} node
+ * @param {ComponentContext} context
+ */
+export function Component(node, context) {
+	serialize_inline_component(node, b.id(node.name), context);
+}

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

@@ -0,0 +1,16 @@
+/** @import { Expression, Pattern } from 'estree' */
+/** @import { ConstTag } from '#compiler' */
+/** @import { ComponentContext } from '../types.js' */
+import * as b from '../../../../utils/builders.js';
+
+/**
+ * @param {ConstTag} node
+ * @param {ComponentContext} context
+ */
+export function ConstTag(node, context) {
+	const declaration = node.declaration.declarations[0];
+	const id = /** @type {Pattern} */ (context.visit(declaration.id));
+	const init = /** @type {Expression} */ (context.visit(declaration.init));
+
+	context.state.init.push(b.const(id, init));
+}

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

@@ -0,0 +1,24 @@
+/** @import { Expression } from 'estree' */
+/** @import { DebugTag } from '#compiler' */
+/** @import { ComponentContext } from '../types.js' */
+import * as b from '../../../../utils/builders.js';
+
+/**
+ * @param {DebugTag} node
+ * @param {ComponentContext} context
+ */
+export function DebugTag(node, context) {
+	context.state.template.push(
+		b.stmt(
+			b.call(
+				'console.log',
+				b.object(
+					node.identifiers.map((identifier) =>
+						b.prop('init', identifier, /** @type {Expression} */ (context.visit(identifier)))
+					)
+				)
+			)
+		),
+		b.debugger
+	);
+}

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

@@ -0,0 +1,63 @@
+/** @import { BlockStatement, Expression, Pattern, Statement } from 'estree' */
+/** @import { EachBlock } from '#compiler' */
+/** @import { ComponentContext } from '../types.js' */
+import { BLOCK_OPEN_ELSE } from '../../../../../internal/server/hydration.js';
+import * as b from '../../../../utils/builders.js';
+import { block_close, block_open } from './shared/utils.js';
+
+/**
+ * @param {EachBlock} node
+ * @param {ComponentContext} context
+ */
+export function EachBlock(node, context) {
+	const state = context.state;
+
+	const each_node_meta = node.metadata;
+	const collection = /** @type {Expression} */ (context.visit(node.expression));
+	const item = each_node_meta.item;
+	const index =
+		each_node_meta.contains_group_binding || !node.index ? each_node_meta.index : b.id(node.index);
+
+	const array_id = state.scope.root.unique('each_array');
+	state.init.push(b.const(array_id, b.call('$.ensure_array_like', collection)));
+
+	/** @type {Statement[]} */
+	const each = [b.const(item, b.member(array_id, index, true))];
+
+	if (node.context.type !== 'Identifier') {
+		each.push(b.const(/** @type {Pattern} */ (node.context), item));
+	}
+	if (index.name !== node.index && node.index != null) {
+		each.push(b.let(node.index, index));
+	}
+
+	each.push(.../** @type {BlockStatement} */ (context.visit(node.body)).body);
+
+	const for_loop = b.for(
+		b.let(index, b.literal(0)),
+		b.binary('<', index, b.member(array_id, b.id('length'))),
+		b.update('++', index, false),
+		b.block(each)
+	);
+
+	if (node.fallback) {
+		const open = b.stmt(b.assignment('+=', b.id('$$payload.out'), block_open));
+
+		const fallback = /** @type {BlockStatement} */ (context.visit(node.fallback));
+
+		fallback.body.unshift(
+			b.stmt(b.assignment('+=', b.id('$$payload.out'), b.literal(BLOCK_OPEN_ELSE)))
+		);
+
+		state.template.push(
+			b.if(
+				b.binary('!==', b.member(array_id, b.id('length')), b.literal(0)),
+				b.block([open, for_loop]),
+				fallback
+			),
+			block_close
+		);
+	} else {
+		state.template.push(block_open, for_loop, block_close);
+	}
+}

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

@@ -0,0 +1,29 @@
+/** @import { ExpressionStatement } from 'estree' */
+/** @import { Context } from '../types.js' */
+import * as b from '../../../../utils/builders.js';
+
+/**
+ * @param {ExpressionStatement} node
+ * @param {Context} context
+ */
+export function ExpressionStatementRunes(node, context) {
+	const expression = node.expression;
+
+	if (expression.type === 'CallExpression') {
+		const callee = expression.callee;
+
+		if (callee.type === 'Identifier' && callee.name === '$effect') {
+			return b.empty;
+		}
+
+		if (
+			callee.type === 'MemberExpression' &&
+			callee.object.type === 'Identifier' &&
+			callee.object.name === '$effect'
+		) {
+			return b.empty;
+		}
+	}
+
+	context.next();
+}