mirror of https://github.com/sveltejs/svelte
Rich Harris
2 days ago
parent
30b04a1e8c
commit
a77fab9d17
@ -0,0 +1,200 @@
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/** @import * as ESTree from 'estree' */
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/** @import { AwaitedStatement } from '../../types' */
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import * as b from '#compiler/builders';
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// TODO find a way to DRY out this and the corresponding server visitor
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/**
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* @param {ESTree.Program} program
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* @param {Map<ESTree.Node, AwaitedStatement>} awaited_statements
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* @param {ESTree.Expression} runner
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* @param {(node: ESTree.Node) => ESTree.Node} transform
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* @param {(node: ESTree.Statement | ESTree.ModuleDeclaration) => void} hoist
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*/
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export function transform_body(program, awaited_statements, runner, transform, hoist) {
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/** @type {ESTree.Statement[]} */
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const out = [];
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/** @type {AwaitedStatement[]} */
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const statements = [];
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/** @type {AwaitedStatement[]} */
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const deriveds = [];
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let awaited = false;
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/**
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* @param {ESTree.Statement | ESTree.VariableDeclarator | ESTree.ClassDeclaration | ESTree.FunctionDeclaration} node
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*/
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const push = (node) => {
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const statement = awaited_statements.get(node);
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awaited ||= !!statement?.has_await;
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if (!awaited || !statement || node.type === 'FunctionDeclaration') {
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if (node.type === 'VariableDeclarator') {
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out.push(/** @type {ESTree.VariableDeclaration} */ (transform(b.var(node.id, node.init))));
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} else {
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out.push(/** @type {ESTree.Statement} */ (transform(node)));
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}
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return;
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}
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// TODO put deriveds into a separate array, and group them immediately
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// after their latest dependency. for now, to avoid having to figure
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// out the intricacies of dependency tracking, just let 'em waterfall
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// if (node.type === 'VariableDeclarator') {
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// const rune = get_rune(node.init, context.state.scope);
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// if (rune === '$derived' || rune === '$derived.by') {
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// deriveds.push(statement);
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// return;
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// }
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// }
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statements.push(statement);
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};
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for (let node of program.body) {
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if (node.type === 'ImportDeclaration') {
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// TODO we can get rid of the visitor
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hoist(node);
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continue;
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}
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if (node.type === 'ExportDefaultDeclaration' || node.type === 'ExportAllDeclaration') {
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// this can't happen, but it's useful for TypeScript to understand that
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continue;
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}
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if (node.type === 'ExportNamedDeclaration') {
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if (node.declaration) {
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// TODO ditto — no visitor needed
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node = node.declaration;
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} else {
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continue;
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}
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}
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if (node.type === 'VariableDeclaration') {
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for (const declarator of node.declarations) {
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push(declarator);
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}
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} else {
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push(node);
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}
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}
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for (const derived of deriveds) {
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// find the earliest point we can insert this derived
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let index = -1;
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for (const binding of derived.reads) {
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index = Math.max(
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index,
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statements.findIndex((s) => s.declarations.includes(binding))
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);
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}
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if (index === -1 && !derived.has_await) {
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const node = /** @type {ESTree.VariableDeclarator} */ (derived.node);
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out.push(/** @type {ESTree.VariableDeclaration} */ (transform(b.var(node.id, node.init))));
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} else {
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// TODO combine deriveds with Promise.all where necessary
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statements.splice(index + 1, 0, derived);
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}
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}
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var promises = b.id('$$promises'); // TODO if we use this technique for fragments, need to deconflict
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if (statements.length > 0) {
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var declarations = statements.map((s) => s.declarations).flat();
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if (declarations.length > 0) {
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out.push(
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b.declaration(
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'var',
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declarations.map((d) => b.declarator(d.node))
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)
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);
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}
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const thunks = statements.map((s) => {
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if (s.node.type === 'VariableDeclarator') {
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const visited = /** @type {ESTree.VariableDeclaration} */ (
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transform(b.var(s.node.id, s.node.init))
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);
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if (visited.declarations.length === 1) {
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return b.thunk(
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b.assignment('=', s.node.id, visited.declarations[0].init ?? b.void0),
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s.has_await
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);
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}
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// if we have multiple declarations, it indicates destructuring
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return b.thunk(
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b.block([
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b.var(visited.declarations[0].id, visited.declarations[0].init),
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...visited.declarations
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.slice(1)
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.map((d) => b.stmt(b.assignment('=', d.id, d.init ?? b.void0)))
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]),
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s.has_await
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);
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}
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if (s.node.type === 'ClassDeclaration') {
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return b.thunk(
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b.assignment(
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'=',
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s.node.id,
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/** @type {ESTree.ClassExpression} */ ({ ...s.node, type: 'ClassExpression' })
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),
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s.has_await
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);
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}
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if (s.node.type === 'FunctionDeclaration') {
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return b.thunk(
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b.assignment(
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'=',
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s.node.id,
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/** @type {ESTree.FunctionExpression} */ ({ ...s.node, type: 'FunctionExpression' })
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),
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s.has_await
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);
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}
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if (s.node.type === 'ExpressionStatement') {
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const expression = /** @type {ESTree.Expression} */ (transform(s.node.expression));
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return expression.type === 'AwaitExpression'
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? b.thunk(expression, true)
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: b.thunk(b.unary('void', expression), s.has_await);
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}
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return b.thunk(b.block([/** @type {ESTree.Statement} */ (transform(s.node))]), s.has_await);
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});
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out.push(b.var(promises, b.call(runner, b.array(thunks))));
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for (let i = 0; i < statements.length; i += 1) {
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const s = statements[i];
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var blocker = b.member(promises, b.literal(i), true);
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for (const binding of s.declarations) {
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binding.blocker = blocker;
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}
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for (const binding of s.writes) {
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// if a statement writes to a binding, any reads of that
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// binding must wait for the statement
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binding.blocker = blocker;
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}
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}
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}
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return out;
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}
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