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75x 324x 324x 324x 324x 324x 324x 324x 324x | /**
* @file actions.js
* @description Compiles an `<action>` or `<resource>` body into a real function.
*
* ## What this replaces
*
* An action body is arbitrary JavaScript, so it could not take the expression
* generator's path — that implements the expression language templates use, and
* an action legitimately contains `if`, `for`, `try`, `const`, `await` and
* everything else. Anything with real statement syntax therefore fell through
* to:
*
* ```js
* new Function(`with(this) { ${source} }`)
* ```
*
* Two things followed from that line. The application needed `'unsafe-eval'`,
* which is what made "Avenx runs under a strict CSP" true of templates and
* false of most non-trivial actions. And the body ran against `AvenxSandbox`,
* the source-text sandbox the expression evaluator was written to replace.
*
* ## What happens instead
*
* The body is parsed at build time and the only thing rewritten is how *free
* identifiers* resolve. Everything else — control flow, declarations,
* destructuring, template literals, regular expressions, `await` — is copied
* through verbatim, because the engine that will run it understands it
* perfectly well and this compiler does not need to.
*
* ```text
* if (!text) { return; } if (!text) { return; }
* items.push({ label: text }); -> axGet($s,"items").push({ label: axGet($s,"text") });
* text = ''; $s.text = '';
* ```
*
* A read becomes `axGet`, which resolves scope-first and routes an allowed
* global through the tracer's substitution point, so `Date.now()` in an action
* is still recorded and replayed. A write becomes a plain property assignment
* on the scope, which is exactly what the interpreter's `writeIdentifier` did
* and what routes the value into reactive state.
*
* ## What this changes about security, precisely
*
* Nothing gets weaker, and one thing gets stronger.
*
* Action bodies never had the expression evaluator's guarantees: they went to
* `new Function` with a source-text sandbox around them, and a source-text
* check for `constructor` falls to string concatenation. That is unchanged
* here — a body's member accesses are the developer's own JavaScript, as they
* always were.
*
* What is new is that naming a restricted global (`window`, `fetch`,
* `localStorage`) or writing a forbidden static key (`__proto__`,
* `constructor`, `prototype`) is refused *at build time*, with the file and the
* offending name, rather than at the moment that branch happens to run. And
* there is no `eval`, no `new Function` and no `with` on this path at all.
*
* ## Why a real parser, and why only at build time
*
* Everything else in this compiler reads source with a purpose-built scanner,
* and for template expressions that is right: the language is small, closed and
* defined by Avenx. An action body is not — it is whatever JavaScript the
* developer wrote, including every feature the language gains next year. A
* hand-written parser would have permanent gaps, and each gap is either a
* silent miscompile or a body pushed back onto `new Function`, which is the
* thing being removed.
*
* So this uses `acorn`: MIT, no dependencies of its own, and the parser most of
* the ecosystem's tooling already trusts. It is a dependency of the *compiler*.
* Nothing under `lib/core` imports it, so the browser runtime keeps its zero
* dependencies, which was always the property worth protecting.
* @module lib/compiler/codegen/actions
*/
import { parse } from 'acorn';
import { RESTRICTED_GLOBALS, FORBIDDEN_KEYS, DYNAMIC_CODE_GLOBALS } from '../../core/expression/ops.js';
import { ExpressionCodegenError, RUNTIME_BINDINGS } from './expression.js';
/**
* Node types that introduce a function scope.
* @type {Set<string>}
*/
const FUNCTION_NODES = new Set([
'FunctionDeclaration',
'FunctionExpression',
'ArrowFunctionExpression',
]);
/**
* Node types that introduce a block scope.
* @type {Set<string>}
*/
const BLOCK_NODES = new Set([
'BlockStatement',
'ForStatement',
'ForInStatement',
'ForOfStatement',
'SwitchStatement',
'CatchClause',
]);
/**
* A lexical scope during analysis.
*/
class Scope {
/**
* @param {Scope|null} parent - The enclosing scope.
* @param {boolean} isFunction - Whether this is a function scope.
*/
constructor(parent, isFunction) {
this.parent = parent;
this.isFunction = isFunction;
/** @type {Set<string>} */
this.names = new Set();
}
/**
* @param {string} name - The name to test.
* @returns {boolean} Whether this scope or any enclosing one declares it.
*/
has(name) {
let scope = this;
while (scope) {
if (scope.names.has(name)) return true;
scope = scope.parent;
}
return false;
}
}
/**
* Collects the names a binding pattern declares.
* @param {object} node - A pattern node.
* @param {Set<string>} into - Where to collect them.
*/
function declaredByPattern(node, into) {
if (!node) return;
switch (node.type) {
case 'Identifier':
into.add(node.name);
return;
case 'ObjectPattern':
for (const property of node.properties) {
declaredByPattern(property.type === 'RestElement' ? property.argument : property.value, into);
}
return;
case 'ArrayPattern':
for (const element of node.elements) {
declaredByPattern(element, into);
}
return;
case 'AssignmentPattern':
declaredByPattern(node.left, into);
return;
case 'RestElement':
declaredByPattern(node.argument, into);
return;
default:
}
}
/**
* Hoists the declarations a scope's statements introduce.
*
* Run on entering a scope rather than as the walk reaches each statement, so a
* reference that appears before its declaration still resolves to the local —
* `count` in `count; let count = 1;` is a local in a temporal dead zone, not a
* free name to be routed to component state.
* @param {object[]} body - Statements in the scope.
* @param {Scope} scope - The scope to populate.
* @param {boolean} functionLevel - Whether to also take `var` from nested blocks.
*/
function hoist(body, scope, functionLevel) {
for (const statement of body || []) {
if (!statement) continue;
if (statement.type === 'VariableDeclaration') {
const isVar = statement.kind === 'var';
if (isVar === functionLevel || !isVar) {
for (const declarator of statement.declarations) {
declaredByPattern(declarator.id, scope.names);
}
}
continue;
}
if (statement.type === 'FunctionDeclaration' && statement.id) {
scope.names.add(statement.id.name);
continue;
}
if (statement.type === 'ClassDeclaration' && statement.id) {
scope.names.add(statement.id.name);
continue;
}
// `var` is function-scoped, so a declaration nested in a block belongs to
// the enclosing function and has to be found from here.
if (functionLevel) {
hoistVarsDeep(statement, scope);
}
}
}
/**
* Finds `var` and function declarations nested inside blocks.
* @param {object} node - The statement to search.
* @param {Scope} scope - The function scope to populate.
*/
function hoistVarsDeep(node, scope) {
if (!node || typeof node !== 'object') return;
if (FUNCTION_NODES.has(node.type)) return;
if (node.type === 'VariableDeclaration' && node.kind === 'var') {
for (const declarator of node.declarations) {
declaredByPattern(declarator.id, scope.names);
}
return;
}
if (node.type === 'FunctionDeclaration' && node.id) {
scope.names.add(node.id.name);
return;
}
for (const key of Object.keys(node)) {
if (key === 'type' || key === 'start' || key === 'end' || key === 'loc') continue;
const value = node[key];
if (Array.isArray(value)) {
for (const child of value) hoistVarsDeep(child, scope);
} else if (value && typeof value.type === 'string') {
hoistVarsDeep(value, scope);
}
}
}
/**
* Walks a parsed body, recording how each free identifier is used.
* @param {object} program - The acorn Program node.
* @param {string} source - The original source, for error messages.
* @param {boolean} [ambient] - Whether this is an `<action>` or `<resource>`
* body, where only `eval` and `Function` are refused.
* @returns {{reads: object[], writes: object[], thisNodes: object[], usesAwait: boolean,
* shorthand: Set<object>, parenthesised: Set<object>}} The identifier
* references to rewrite, and the positions that shape their rewrite.
*/
function analyse(program, source, ambient = false) {
/** @type {object[]} */
const reads = [];
/** @type {object[]} */
const writes = [];
/** @type {object[]} */
const thisNodes = [];
/**
* Identifiers written as shorthand properties, `{ count }`. Rewriting only
* the identifier would produce `{ axGet($s, "count") }`, which does not
* parse, so these keep their name as the key.
* @type {Set<object>}
*/
const shorthand = new Set();
/**
* Identifiers in a position where a call must be parenthesised: the callee
* of `new` and the tag of a tagged template. `new axGet($s, "Date")(0)`
* constructs `axGet` and then calls the result.
* @type {Set<object>}
*/
const parenthesised = new Set();
let usesAwait = false;
const root = new Scope(null, true);
hoist(program.body, root, true);
/**
* Records a reference to a name that no enclosing scope declares.
* @param {object} node - The Identifier node.
* @param {Scope} scope - The scope it appears in.
* @param {boolean} write - Whether it is being assigned to.
*/
const reference = (node, scope, write) => {
if (scope.has(node.name)) return;
if (ambient ? DYNAMIC_CODE_GLOBALS.has(node.name) : RESTRICTED_GLOBALS.has(node.name)) {
throw new ExpressionCodegenError(
ambient
? `"${node.name}" constructs code from a string and cannot be used in an action body.`
: `"${node.name}" is a restricted global and cannot be used in an event handler. ` +
'Move the browser API into a component action and call that instead.',
source,
);
}
(write ? writes : reads).push(node);
};
/**
* Walks one node.
* @param {object} node - The node to walk.
* @param {Scope} scope - The scope it sits in.
* @param {boolean} inArrowChain - Whether `this` still means the caller's `this`.
*/
const walk = (node, scope, inArrowChain) => {
if (!node || typeof node.type !== 'string') return;
if (node.type === 'NewExpression' && node.callee.type === 'Identifier') {
parenthesised.add(node.callee);
} else if (node.type === 'TaggedTemplateExpression' && node.tag.type === 'Identifier') {
parenthesised.add(node.tag);
}
switch (node.type) {
case 'Identifier':
reference(node, scope, false);
return;
case 'ThisExpression':
// Only a `this` that is still the action's own `this` is rewritten. One
// inside a nested `function` means that function's receiver, which
// `with(this)` never changed either.
if (inArrowChain) thisNodes.push(node);
return;
case 'AwaitExpression':
usesAwait = true;
walk(node.argument, scope, inArrowChain);
return;
case 'MemberExpression':
walk(node.object, scope, inArrowChain);
if (node.computed) {
walk(node.property, scope, inArrowChain);
} else if (node.property.type === 'Identifier' && FORBIDDEN_KEYS.has(node.property.name)) {
throw new ExpressionCodegenError(
`Access to property "${node.property.name}" is blocked for security reasons.`,
source,
);
}
return;
case 'Property':
if (node.shorthand && node.value.type === 'Identifier') shorthand.add(node.value);
if (node.computed) walk(node.key, scope, inArrowChain);
else if (node.key.type === 'Identifier' && FORBIDDEN_KEYS.has(node.key.name)) {
throw new ExpressionCodegenError(
`Defining property "${node.key.name}" is blocked for security reasons.`,
source,
);
}
walk(node.value, scope, inArrowChain);
return;
case 'AssignmentExpression': {
if (node.left.type === 'Identifier') {
reference(node.left, scope, true);
} else if (node.left.type === 'ObjectPattern' || node.left.type === 'ArrayPattern') {
walkAssignmentTargets(node.left, scope, inArrowChain);
} else {
walk(node.left, scope, inArrowChain);
}
walk(node.right, scope, inArrowChain);
return;
}
case 'UpdateExpression':
if (node.argument.type === 'Identifier') {
reference(node.argument, scope, true);
} else {
walk(node.argument, scope, inArrowChain);
}
return;
case 'LabeledStatement':
walk(node.body, scope, inArrowChain);
return;
case 'BreakStatement':
case 'ContinueStatement':
return;
case 'VariableDeclaration':
for (const declarator of node.declarations) {
// The pattern's own names are declarations, not references; only a
// default value inside it is evaluated.
walkPatternDefaults(declarator.id, scope, inArrowChain);
walk(declarator.init, scope, inArrowChain);
}
return;
default:
break;
}
if (FUNCTION_NODES.has(node.type)) {
const inner = new Scope(scope, true);
if (node.id && node.type !== 'FunctionDeclaration') {
inner.names.add(node.id.name);
}
for (const param of node.params) {
declaredByPattern(param, inner.names);
}
if (node.body && node.body.type === 'BlockStatement') {
hoist(node.body.body, inner, true);
}
// An arrow keeps the enclosing `this`; a `function` introduces its own.
const arrowChain = inArrowChain && node.type === 'ArrowFunctionExpression';
for (const param of node.params) {
walkPatternDefaults(param, inner, arrowChain);
}
if (node.body && node.body.type === 'BlockStatement') {
for (const statement of node.body.body) walk(statement, inner, arrowChain);
} else {
walk(node.body, inner, arrowChain);
}
return;
}
if (BLOCK_NODES.has(node.type)) {
const inner = new Scope(scope, false);
if (node.type === 'CatchClause') {
declaredByPattern(node.param, inner.names);
walk(node.body, inner, inArrowChain);
return;
}
if (node.type === 'BlockStatement') {
hoist(node.body, inner, false);
for (const statement of node.body) walk(statement, inner, inArrowChain);
return;
}
if (node.type === 'ForStatement') {
if (node.init && node.init.type === 'VariableDeclaration') {
hoist([node.init], inner, false);
}
walk(node.init, inner, inArrowChain);
walk(node.test, inner, inArrowChain);
walk(node.update, inner, inArrowChain);
walk(node.body, inner, inArrowChain);
return;
}
if (node.type === 'ForInStatement' || node.type === 'ForOfStatement') {
if (node.left.type === 'VariableDeclaration') {
hoist([node.left], inner, false);
walk(node.left, inner, inArrowChain);
} else if (node.left.type === 'Identifier') {
reference(node.left, inner, true);
} else {
walk(node.left, inner, inArrowChain);
}
walk(node.right, inner, inArrowChain);
walk(node.body, inner, inArrowChain);
return;
}
// SwitchStatement: the cases share one block scope.
hoist(node.cases.flatMap((entry) => entry.consequent), inner, false);
walk(node.discriminant, scope, inArrowChain);
for (const entry of node.cases) {
walk(entry.test, inner, inArrowChain);
for (const statement of entry.consequent) walk(statement, inner, inArrowChain);
}
return;
}
for (const key of Object.keys(node)) {
if (key === 'type' || key === 'start' || key === 'end' || key === 'loc') continue;
const value = node[key];
if (Array.isArray(value)) {
for (const child of value) walk(child, scope, inArrowChain);
} else if (value && typeof value.type === 'string') {
walk(value, scope, inArrowChain);
}
}
};
/**
* Walks a destructuring assignment target, `({ a, b: c } = value)`.
*
* Unlike a declaration pattern, its names are not new locals: each free one
* is a write to component scope, and a member target is evaluated.
* @param {object} node - The target pattern or element.
* @param {Scope} scope - The scope it appears in.
* @param {boolean} inArrowChain - Whether `this` is still the action's.
*/
const walkAssignmentTargets = (node, scope, inArrowChain) => {
if (!node) return;
switch (node.type) {
case 'Identifier':
reference(node, scope, true);
return;
case 'ObjectPattern':
for (const property of node.properties) {
if (property.type === 'RestElement') {
walkAssignmentTargets(property.argument, scope, inArrowChain);
continue;
}
if (property.shorthand && property.value.type === 'Identifier') shorthand.add(property.value);
if (property.computed) walk(property.key, scope, inArrowChain);
walkAssignmentTargets(property.value, scope, inArrowChain);
}
return;
case 'ArrayPattern':
for (const element of node.elements) walkAssignmentTargets(element, scope, inArrowChain);
return;
case 'RestElement':
walkAssignmentTargets(node.argument, scope, inArrowChain);
return;
case 'AssignmentPattern':
walkAssignmentTargets(node.left, scope, inArrowChain);
walk(node.right, scope, inArrowChain);
return;
default:
walk(node, scope, inArrowChain);
}
};
/**
* Walks only the default values inside a binding pattern.
* @param {object} node - The pattern.
* @param {Scope} scope - The scope defaults are evaluated in.
* @param {boolean} inArrowChain - Whether `this` is still the action's.
*/
function walkPatternDefaults(node, scope, inArrowChain) {
if (!node) return;
switch (node.type) {
case 'AssignmentPattern':
walkPatternDefaults(node.left, scope, inArrowChain);
walk(node.right, scope, inArrowChain);
return;
case 'ObjectPattern':
for (const property of node.properties) {
if (property.type === 'RestElement') {
walkPatternDefaults(property.argument, scope, inArrowChain);
continue;
}
if (property.computed) walk(property.key, scope, inArrowChain);
walkPatternDefaults(property.value, scope, inArrowChain);
}
return;
case 'ArrayPattern':
for (const element of node.elements) walkPatternDefaults(element, scope, inArrowChain);
return;
case 'RestElement':
walkPatternDefaults(node.argument, scope, inArrowChain);
return;
default:
}
}
for (const statement of program.body) {
walk(statement, root, true);
}
return { reads, writes, thisNodes, usesAwait, shorthand, parenthesised };
}
/**
* Applies a set of source edits, right to left.
* @param {string} source - The original source.
* @param {Array<{start: number, end: number, text: string}>} edits - The edits.
* @returns {string} The rewritten source.
*/
function applyEdits(source, edits) {
const ordered = [...edits].sort((a, b) => b.start - a.start);
let out = source;
for (const edit of ordered) {
out = out.slice(0, edit.start) + edit.text + out.slice(edit.end);
}
return out;
}
/**
* Compiles an action or resource body into a scope-taking function.
*
* `options.ambient` marks an `<action>` or `<resource>` body, which is ordinary
* JavaScript: a free name that is not component scope resolves to the page
* global (`fetch`, `window`, `setInterval`, …). Without it -- an inline event
* handler reaching this compiler because it uses statement syntax -- the
* template rule applies and browser globals are refused. `eval` and `Function`
* are refused in both.
* @param {string} source - The body as written.
* @param {{ambient?: boolean}} [options] - Compilation options.
* @returns {string} JavaScript source for the function.
* @throws {ExpressionCodegenError} When the body cannot be compiled.
*/
export function compileActionToSource(source, options = {}) {
const ambient = !!options.ambient;
const scopeName = RUNTIME_BINDINGS.scope;
let program;
try {
program = parse(source, {
ecmaVersion: 'latest',
sourceType: 'script',
// An action body is a function body, so both are legal in it even though
// neither is legal at the top level of a script.
allowAwaitOutsideFunction: true,
allowReturnOutsideFunction: true,
allowSuperOutsideMethod: false,
});
} catch (error) {
throw new ExpressionCodegenError(`could not be parsed: ${error.message}`, source);
}
const { reads, writes, thisNodes, usesAwait, shorthand, parenthesised } = analyse(program, source, ambient);
const readBinding = ambient ? RUNTIME_BINDINGS.ambientGet : RUNTIME_BINDINGS.get;
const edits = [];
for (const node of reads) {
let text = `${readBinding}(${scopeName}, ${JSON.stringify(node.name)})`;
if (parenthesised.has(node)) text = `(${text})`;
if (shorthand.has(node)) text = `${node.name}: ${text}`;
edits.push({ start: node.start, end: node.end, text });
}
for (const node of writes) {
// A write target has to stay assignable, so it becomes a property of the
// scope rather than a call. The scope's own `set` routes it into reactive
// state, which is exactly what the interpreter's writeIdentifier did. In an
// action body the holder is chosen at run time: component scope when it
// binds the name, the host global when it already defines it.
const name = JSON.stringify(node.name);
const holder = ambient ? `${RUNTIME_BINDINGS.ambientTarget}(${scopeName}, ${name})` : scopeName;
const target = `${holder}[${name}]`;
edits.push({ start: node.start, end: node.end, text: shorthand.has(node) ? `${node.name}: ${target}` : target });
}
for (const node of thisNodes) {
edits.push({ start: node.start, end: node.end, text: `${RUNTIME_BINDINGS.get}(${scopeName}, "this")` });
}
const body = applyEdits(source, edits);
const prefix = usesAwait ? 'async ' : '';
return `${prefix}(${scopeName}) => { ${body}\n}`;
}
/**
* Compiles an action body, returning the reason rather than throwing.
* @param {string} source - The body as written.
* @param {{ambient?: boolean}} [options] - Compilation options.
* @returns {{code: string}|{error: string}} The generated source, or the reason.
*/
export function tryCompileAction(source, options = {}) {
try {
return { code: compileActionToSource(source, options) };
} catch (error) {
return { error: error.message };
}
}
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